sodium-pertechnetate-tc-99m and Pulmonary-Embolism

Technegas is a carbon-based nanoparticle developed in Australia in 1984 and has been in widespread clinical use, including SPECT imaging, since 1986. Although

Topics: Humans; Lung; Pulmonary Embolism; Respiration; Sodium Pertechnetate Tc 99m; Tomography, Emission-Computed, Single-Photon

Pulmonary embolism remains a major cause of morbidity and mortality, being responsible for an estimated 200,000 deaths per annum in the USA and 21,000 per annum in the UK. Lung scintigraphy is in many instances the investigation of choice in suspected pulmonary thromboembolism. A normal perfusion lung scan excludes pulmonary embolism. An abnormal perfusion scan, while being sensitive, is of low specificity for the diagnosis of pulmonary embolism and needs to be complemented with a ventilation study. Lung ventilation has been studied using inert gases of radiolabelled aerosols. The new radiopharmaceutical 99Tcm-Technegas is a suspension of 99Tcm-labelled, ultrafine, carbon particles produced in an atmosphere of high-purity argon. The size of the particles is of the order of 0.005-0.2 microns, which assures good peripheral penetration and alveolar deposition. After inhalation, static images in multiple projections may be acquired. The resultant images are of excellent technical quality and several publications have shown the value of Technegas images as an adjunct to perfusion imaging in suspected pulmonary thromboembolism. Studies comparing Technegas images with other ventilatory radiopharmaceuticals have in the majority of instances reported comparable diagnostic qualities.

Topics: Administration, Inhalation; Aerosols; Humans; Lung Diseases, Obstructive; Oximetry; Particle Size; Pulmonary Alveoli; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m

The contribution of isotope imaging to the investigation of respiratory disease has been primarily limited to the detection of ventilation and perfusion abnormalities and the investigation of inflammation or cancer. In recent years, there has been a growing interest in the metabolic function of the lung and in measurements of alveolar capillary permeability in a variety of conditions. This review will deal with these newer applications of isotope techniques in the lung in addition to developments in ventilation-perfusion imaging.

Topics: Capillary Permeability; Humans; Lung; Organotechnetium Compounds; Pulmonary Embolism; Radionuclide Imaging; Respiratory Function Tests; Sodium Pertechnetate Tc 99m

Lung scintigraphy is primarily used to diagnose pulmonary embolism. Ventilation imaging is often performed using (99m)Tc-DTPA or Technegas, an ultrafine dispersion of (99m)Tc-labeled carbon. Despite the common use of these radioaerosols, they have not been compared in an intraindividual study, and not with ventilation-perfusion (V/P) SPECT. The aim of the present head-to-head study was to systematically investigate differences in ventilation studies performed with (99m)Tc-diethylenetriaminepentaacetate (DTPA) and Technegas.. Sixty-three patients, 28 without and 35 with obstructive lung disease, were examined with V/P SPECT using both (99m)Tc-DTPA and Technegas. V/P SPECT images were randomized and assessed independently by 2 masked physicians according to a predefined scoring system. A paired comparison was performed using the Wilcoxon signed-rank test.. In both obstructive and nonobstructive disease, the overall unevenness of radiotracer deposition and the degree of central deposition were more pronounced in (99m)Tc-DTPA than Technegas studies. Because of better peripheral penetration, the extent of reverse mismatch was less when Technegas was used. Additionally, in obstructive disease, the degree of focal deposition in distal airways was more pronounced with (99m)Tc-DTPA. Mismatched perfusion defects were more frequently found with Technegas in obstructive disease.. This intraindividual comparative study shows that Technegas is the preferred radioaerosol, particularly in obstructive disease.

Topics: Aged; Female; Humans; Image Processing, Computer-Assisted; Lung; Lung Diseases; Lung Diseases, Obstructive; Male; Middle Aged; Pulmonary Disease, Chronic Obstructive; Pulmonary Embolism; Radiopharmaceuticals; Sodium Pertechnetate Tc 99m; Technetium Tc 99m Pentetate; Tomography, Emission-Computed, Single-Photon

To verify the negative predictive value of pulmonary ventilation/perfusion scintigraphy with single photon emission computed tomography (V/Q SPECT) in ruling out pulmonary thromboembolism.. V/Q SPECT using 99mTc-Technegas was performed on 584 patients to rule out pulmonary thromboembolism between October 2004 and July 2005. Pulmonary thromboembolism was defined as any clear-cut vascular mismatch, regardless of size. Indeterminate scans were defined as cases having matching vascular type defects with a corresponding X-ray abnormality, or cases with equivocal mismatches. Other patterns were considered negative for pulmonary thromboembolism. Outcome data was gathered >3 months after the scan. Absence of pulmonary thromboembolism was defined as any patient still alive at least 3 months after the scan, with no anticoagulation treatment and no proof of pulmonary thromboembolism by other techniques, either at the time of the scan or during follow-up, or death by other causes.. One hundred and eight patients (19%) had a positive pulmonary thromboembolism reading, 18 (3%) an indeterminate study, and 458 (78%) patients had a negative reading for pulmonary thromboembolism. There were 189 patients with an abnormal chest X-ray. The mean follow-up time was 165 days. Of the 458 patients classified as negative for pulmonary thromboembolism, patients receiving chronic anticoagulation for other causes were excluded from follow-up (n=53), which left 405 patients for final analysis. There were no pulmonary thromboembolism-related deaths in the negative group. Six patients were identified as false negatives. The negative predictive value is estimated at 98.5%.. SPECT pulmonary scintigraphy using 99mTc-Technegas demonstrates a high negative predictive value and a low indeterminate rate.

Topics: Female; Follow-Up Studies; Humans; Male; Middle Aged; Predictive Value of Tests; Prospective Studies; Pulmonary Embolism; Radiopharmaceuticals; Sodium Pertechnetate Tc 99m; Tomography, Emission-Computed, Single-Photon

Although ventilation/perfusion (V/Q) lung scintigraphy is a well-accepted and frequently performed procedure in the diagnosis of pulmonary embolism, there is growing controversy about its relevance, particularly due to the increasing competition between scintigraphy and CT. Even though comparative studies between both modalities have already been performed, their results were highly inconsistent. Remarkably, in most of those studies, conventional planar perfusion scans were compared with tomographic images acquired using state-of-the-art CT scanners-a study design that cannot give impartial results. Hence, the aim of our study was a balanced comparison between V/Q lung scintigraphy and CT angiography using advanced imaging techniques for both modalities.. A total of 83 patients with suspected pulmonary embolism were examined using V/Q lung scintigraphy in SPECT technique as well as 4-slice spiral CT. Ventilation scans were done using an ultrafine aerosol. Additionally, planar images in 8 views were extracted from the V/Q SPECT datasets. Two experienced referees assessed each of the 3 modalities. The final diagnosis was made at a consensus meeting while taking into account all of the imaging modalities, laboratory tests, clinical data, and evaluation of a follow-up period.. In the course of the consensus conference, pulmonary embolism was diagnosed in 37 of the 83 patients (44.6%). Compared with planar scintigraphy, SPECT raised the number of detectable defects at the segmental level by 12.8% (+11 defects; P = 0.401) and at the subsegmental level by 82.6% (+57 defects; P < 0.01). The sensitivity/specificity/accuracy of planar V/Q scintigraphy and V/Q SPECT was 0.76/0.85/0.81 and 0.97/0.91/0.94, respectively, compared with 0.86/0.98/0.93 for multislice CT.. SPECT and ultrafine aerosols are technical advancements that can substantially improve lung scintigraphy. Using advanced imaging techniques, V/Q scintigraphy and multislice spiral CT both yield an excellent and, in all aspects, comparable diagnostic accuracy, with CT leading in specificity while SPECT shows a superior sensitivity. Even though planar lung scintigraphy yields satisfactory results for a nontomographic modality, it does not compare with tomographic imaging.

Topics: Administration, Inhalation; Adolescent; Adult; Aged; Aged, 80 and over; False Negative Reactions; False Positive Reactions; Female; Humans; Image Interpretation, Computer-Assisted; Male; Middle Aged; Pulmonary Embolism; Radiopharmaceuticals; Reproducibility of Results; Sensitivity and Specificity; Sodium Pertechnetate Tc 99m; Tomography, Emission-Computed, Single-Photon; Tomography, Spiral Computed; Ventilation-Perfusion Ratio

We investigated the clinical significance of thyroid visualization on technegas (TcG) ventilation scintigraphy (TcGS) based on the hypothesis that this visualization may be correlated with thyroid disease with high radioactive thyroid uptake (RATU).. From a total of 1022 consecutive patients undergoing TcG/99mTc macroaggregated albumin ventilation/perfusion (V/Q) scintigraphy to exclude pulmonary embolism, 114 who underwent in vitro thyroid function tests (TFTs) within 2 weeks of the lung scintigraphy were included in the retrospective study. In addition, in 10 patients in whom high RATU was noted on [99mTc]pertechnetate thyroid scintigraphy, TcGS was performed prospectively. The degree of thyroid activity in each patient was graded on a scale of 0 to 2 (grade 0 = no or faint uptake; grade 1 = mild uptake, but less than the lung; and grade 2 = strong uptake, similar to, or more than, the lung).. Thyroid uptake was observed on TcGS in 17.5% of the patient group (20/114; 10 with grade 1, 10 with grade 2). Serum T3, T4 and TSH values differed significantly, depending on the grade of thyroid activity. All patients showing grade 2 thyroid uptake were clinically diagnosed as having Graves' disease. None of the 94 patients with grade 0 on TcGS had evidence of hyperthyroidism, although four patients had hypothyroidism. In the prospective group, all patients showed any visualization of the thyroid on TcGS (3 with grade 1, 7 with grade 2). The final diagnoses for these patients were Graves' disease in six, Hashimoto's thyroiditis in three and post-partum thyroiditis in one.. Thyroid visualization during TcGS appears to be correlated with thyroid disease with high RATU. Such a finding may also deserve further evaluation for additional irregularities in thyroid function.

Topics: Administration, Inhalation; Adult; Female; Humans; Male; Middle Aged; Pulmonary Embolism; Radionuclide Imaging; Radiopharmaceuticals; Reproducibility of Results; Sensitivity and Specificity; Sodium Pertechnetate Tc 99m; Thyroid Diseases; Thyroid Gland; Ventilation-Perfusion Ratio

A new Tc-99m labeled carbon particle aerosol ("Technegas") has been developed for lung ventilation scanning. This is the first reported clinical study of this agent in the United States. A total of 23 subjects were studied. Thirteen had comparative Xe-133 studies, and in seven patients pulmonary angiograms were available. The Technegas study agreed closely with the Xe-133 results in 10 out of 13 patients, while the pulmonary angiogram confirmed the Technegas and perfusion scan findings in seven out of seven cases. The Technegas scan was easily performed and well tolerated by all patients. If further clinical trials confirm these preliminary findings, Technegas may become the preferred agent for lung ventilation scanning.

Topics: Aerosols; Angiography; Clinical Trials as Topic; Humans; Lung; Pilot Projects; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Ventilation-Perfusion Ratio; Xenon Radioisotopes

A case of 99mTcO4 accumulation within the thorax is reported, consistent with septic emboli and thyroiditis during routine thyroid scintigraphy for subclinical hyperthyroidism. After antibiotic treatment, repeated 99mTcO4 imaging revealed complete resolution of foci of septic emboli.

Topics: Aged; Humans; Male; Pulmonary Embolism; Radionuclide Imaging; Sepsis; Sodium Pertechnetate Tc 99m; Thyroid Gland

Topics: Administration, Inhalation; Humans; Pulmonary Embolism; Sodium Pertechnetate Tc 99m; Tomography, Emission-Computed, Single-Photon

To develop a method of producing lung ventilation and perfusion (V/Q) planar images using forward projection of reconstructed single-photon emission computed tomography (SPECT) images through approximate attenuation (micro) maps generated from the lung emission scans alone, as transmission-based micro maps may not be routinely available.. Synthetic micro maps are derived from (99m)Tc photopeak and "scatter" windows for the attenuation correction of the SPECT images. The attenuation-corrected SPECT images are forward projected at appropriate angles to give the equivalent of planar images. This method allows high-count planar images, as well as the SPECT images, to be produced from a single SPECT acquisition. In addition, isolated "single lung" views of lateral and medial projections without "shine-through" from the contra-lateral lung, which have not been available previously, can be formed.. Comparison of reprojected images produced from CT-derived or synthetic micro maps displayed similar detail and radiopharmaceutical distribution. In a blinded comparison of "true" planar images with those from reprojecting the SPECT data using the synthetic micro maps, no difference in mismatched defect detection was found, and hence it was confirmed that the reprojected planar images could replace true planar images with no loss in planar diagnostic sensitivity.. The reprojected planar images provide high-count, high-quality images, which are comparable with conventional 2D images.

Topics: Administration, Inhalation; Humans; Lung; Pulmonary Embolism; Radiopharmaceuticals; Reproducibility of Results; Sensitivity and Specificity; Sodium Pertechnetate Tc 99m; Tomography, Emission-Computed, Single-Photon

Left heart failure (LHF) is a common and frequently overlooked condition owing to insufficient diagnostic methods. This can potentially delay onset of treatment. Our clinical experience with ventilation/perfusion single photon emission computed tomography (V/P SPECT) indicates that perfusion shows an antigravitational distribution pattern in LHF. The aim of the study was to test the hypothesis that LHF diagnosis can be made on the basis of V/P SPECT, and to develop and perform a first evaluation of objective parameters for LHF diagnostics in terms of perfusion gradients.. This retrospective study included 247 consecutive patients with clinical suspicion of pulmonary embolism (PE), who were examined with V/P SPECT. Perfusion gradients were developed and quantified in dorso-ventral and cranio-caudal directions. Quantitative results were compared with visual interpretation of patients with normal and heart failure patterns. Patients with LHF pattern were retrospectively followed up by review of medical records to confirm or discard heart failure diagnosis at the time of V/P SPECT examination.. LHF pattern on V/P SPECT was identified in 36 patients (15%), normal ventilation/perfusion pattern was found in 67 patients (27%), and PE in 62 patients (25%). The follow-up confirmed heart failure diagnosis in 32 of the 36 cases with LHF pattern, leading to a positive predictive value of 88% for LHF diagnosis based on V/P SPECT. Dorso-ventral perfusion gradients discriminated normal from LHF patients.. In patients with suspected PE, LHF is common. Appropriate V/P SPECT pattern recognition, supported by objectively determined dorso-ventral perfusion gradients, allows the diagnosis of LHF. A positive perfusion gradient in the dorso-ventral direction should lead to consideration of heart failure as a possible explanation for the symptoms in these patients.

Topics: Female; Heart Failure; Humans; Male; Middle Aged; Pulmonary Embolism; Radiopharmaceuticals; Retrospective Studies; Sodium Pertechnetate Tc 99m; Technetium Tc 99m Aggregated Albumin; Technetium Tc 99m Pentetate; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed; Ventilation-Perfusion Ratio

The objective of this study was to examine the feasibility of fusing ventilation and perfusion data from single-photon emission computed tomography (SPECT) ventilation perfusion (V/Q) scintigraphy together with computed tomographic pulmonary angiography (CTPA) data. We sought to determine the accuracy of this fusion process. In addition, we correlated the findings of this technique with the final clinical diagnosis.. Thirty consecutive patients (17 female, 13 male) who had undergone both CTPA and SPECT V/Q scintigraphy during their admission for investigation of potential pulmonary embolism were identified retrospectively. Image datasets from these two modalities were co-registered and fused using commercial software. Accuracy of the fusion process was determined subjectively by correlation between modalities of the anatomical boundaries and co-existent pleuro-parenchymal abnormalities.. In all 30 cases, SPECT V/Q images were accurately fused with CTPA images. An automated registration algorithm was sufficient alone in 23 cases (77%). Additional linear z-axis scaling was applied in seven cases. There was accurate topographical co-localisation of vascular, parenchymal and pleural disease on the fused images. Nine patients who had positive CTPA performed as an initial investigation had co-localised perfusion defects on the subsequent fused CTPA/SPECT images. Three of the 11 V/Q scans initially reported as intermediate could be reinterpreted as low probability owing to co-localisation of defects with parenchymal or pleural pathology.. Accurate fusion of SPECT V/Q scintigraphy to CTPA images is possible. This technique may be clinically useful in patients who have non-diagnostic initial investigations or in whom corroborative imaging is sought.

Topics: Administration, Inhalation; Adult; Aged; Aged, 80 and over; Angiography; Feasibility Studies; Female; Humans; Image Enhancement; Male; Middle Aged; Pilot Projects; Pulmonary Artery; Pulmonary Embolism; Reproducibility of Results; Sensitivity and Specificity; Sodium Pertechnetate Tc 99m; Subtraction Technique; Tomography, Emission-Computed, Single-Photon; Tomography, X-Ray Computed

To determine the optimal diagnostic cut-off point using a simplified criterion for the detection of pulmonary embolus (PE) and to evaluate the criterion's utility and reporter reproducibility.. Lung scintigraphy was carried out in 924 patients for the diagnosis of PE. This group consisted of 316 men and 608 women with median age of 63 years (range 18-94 years). Ventilation imaging was carried out with Tc-99m Technegas followed by perfusion imaging using 190 MBq Tc-99m macroaggregated albumin. Studies were classified using a 6-category probability criterion of incremental ventilation/perfusion (V/Q) mismatch: A, normal; B, low (minor matched V/Q defects or segmental matched V/Q defects without opacity on chest X-ray); C, low-moderate (a partial segment of V/Q mismatch); D, moderate (1 segment of mismatch); E, moderate-high (1-2 segments of V/Q mismatch) and F, high probability (=2 segments of V/Q mismatch). Clinical end-points at 3 and 6 months were death by PE or PE treated with anticoagulation therapy. Three-reporter reproducibility was determined by kappa statistic on a subgroup of patients (53/924).. A total of 122 patients (13%) had a confirmed diagnosis of PE at 3 months and no additional cases were registered at 6 months. The lung scintigraphy probability classification showed: normal 152 (16%), low 620 (67%), low-moderate 20 (2%), moderate 28 (3%), moderate-high 24 (3%) and high 80 (9%). The respective sensitivities and specificities, where the diagnostic cut-offs were established at F, high; E, moderate-high; D, moderate and C, low-moderate probability, were F, 64 and 100%; E, 82 and 99%; D, 95 and 98% and C, 98 and 96%. The respective false-negative cases for F, E, D and C cut-offs were 44, 22, 7 and 3. Using the revised Prospective Investigation of Pulmonary Embolism Diagnosis reporting classification reporter agreement showed kappa values of 0.31-0.48. Using a simplified 2-category (>0.5 segment of V/Q mismatch positive, all others negative) criterion resulted in a higher reporting agreement (kappa 0.74-0.83). There were only 3% of indeterminate cases if this was defined by the D category and a maximum of 8% if categories C, D and E were included.. Using a simplified diagnostic criterion where all studies showing >0.5 segments of V/Q mismatch are regarded as positive and all others as negative, lung scintigraphy, incorporating Tc-99m Technegas ventilation imaging or its equivalent, can achieve a very high diagnostic accuracy for the detection of PE. Using this technique, less than 5% of scans are indeterminate. A simplified, unambiguous approach to reporting is recommended.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Female; Humans; Lung; Male; Middle Aged; Prospective Studies; Pulmonary Embolism; Pulmonary Ventilation; Radionuclide Imaging; Radiopharmaceuticals; Reproducibility of Results; Sodium Pertechnetate Tc 99m; Technetium Tc 99m Aggregated Albumin; Ventilation-Perfusion Ratio

This study aimed to assess the feasibility of cardiac global function evaluation during a whole-chest multi-slice CT (MSCT) acquisition in patients referred for suspicion of pulmonary embolism (PE), and to compare the results with planar equilibrium radionuclide ventriculography (ERNA). Ten consecutive haemodynamically stable patients (six female, four male; mean age 69.7 years; heart rate 65-99 bpm) with suspicion of PE underwent an MSCT and ERNA within a 6 h period. CT acquisition was performed after contrast medium injection by using 16x1.5 mm collimation and retrospective ECG gating. Left ventricular (LVEF) and right ventricular (RVEF) ejection fractions were calculated using dedicated three-dimensional software. Relationships between measurements obtained with MSCT and ERNA were assessed using linear regression analysis and reliability of MSCT was assessed with intra-class correlation coefficient. Bland-Altman analysis was performed to calculate limits of agreement between MSCT and ERNA. MSCT was performed successfully in ten patients with a mean acquisition time of 16.5+/-2.8 s. Functional cardiac evaluation was possible on CT for all patients except for one due to poor opacification of right ventricle. Linear regression analysis showed a good correlation between MSCT and ERNA for the LVEF (R=0.91) and the RVEF (R=0.89) measurements. Intra-class correlation was superior for LVEF (0.92) than for the RVEF (0.68). Bland-Altman plots demonstrated that MSCT substantially overestimated the ERNA RVEF. Morphological CT data demonstrated PE in four of ten of patients and alternative diagnoses in five of ten patients. Our study reveals that MSCT with retrospective ECG gating may provide in one modality a morphological and a functional cardiopulmonary evaluation. Comparison with ERNA demonstrated a good correlation for both ventricular ejection fractions.

Topics: Aged; Contrast Media; Electrocardiography; Feasibility Studies; Female; Humans; Image Processing, Computer-Assisted; Imaging, Three-Dimensional; Male; Pulmonary Artery; Pulmonary Embolism; Radionuclide Ventriculography; Radiopharmaceuticals; Sodium Pertechnetate Tc 99m; Stroke Volume; Tomography, X-Ray Computed; Ventricular Function, Left; Ventricular Function, Right

Since the publication of the modified Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) criteria for the diagnosis of pulmonary embolism (PE), new clinical and scintigraphic diagnostic algorithms (the McMaster clinical criteria, the PisaPED simplified scintigraphic grading and the Miettinen logistic regression analysis) have been reported although the results have not been reproduced in other sites. Ventilation-perfusion lung scintigraphy was performed in 238 consecutive patients with a provisional diagnosis of PE. Scans were reported as normal/very low, low, intermediate or high probability for PE using standardized criteria. Each patient received a clinical grading of probability of PE as low, moderate or high using the McMaster clinical criteria. Using the PisaPED criteria (an alternate simplified scintigraphic grading system using the perfusion scan alone) each scan was also graded as normal/near normal, abnormal but not PE, or abnormal and PE. Using the logistic regression algorithm of Miettinen each scan received a numerical probability of PE. Frequencies for differing levels of probability of PE varied widely between the various algorithms. Cross tabulations revealed correlation of the standardized criteria with the Miettinen grading but not with the McMaster or the PisaPED gradings. We were unable to reproduce similar results using the McMaster clinical grading or the PisaPED simplified scintigraphic grading although the Miettinen logistic regression formula gave comparable results. New algorithms are not automatically transferable to new environments.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Algorithms; Female; Humans; Logistic Models; Male; Middle Aged; Pulmonary Embolism; Radionuclide Imaging; Reproducibility of Results; Severity of Illness Index; Sodium Pertechnetate Tc 99m; Technetium Tc 99m Aggregated Albumin

Topics: Acute Disease; Administration, Inhalation; Adult; Chagas Cardiomyopathy; Diagnosis, Differential; Diagnostic Errors; Female; Humans; Lupus Vulgaris; Pulmonary Embolism; Radionuclide Imaging; Radiopharmaceuticals; Rare Diseases; Respiratory Distress Syndrome; Sodium Pertechnetate Tc 99m; Ventilation-Perfusion Ratio

81mKr is widely used as a ventilation agent to diagnose pulmonary embolism (PE). However, (81m)Kr is expensive, which limits its continuous availability. Technegas can be an alternative ventilation agent with the advantage of being less expensive and available daily. The aim of this study was to compare the value of technegas with that of (81m)Kr in the detection of PE.. Ninety-two consecutive patients (29 men; mean +/- SD, 53 +/- 17 y old) with at least one segmental perfusion defect (Hull criteria) were studied prospectively. Perfusion and ventilation (V/Q) lung scintigraphy with both technegas and (81m)Kr were performed within 24 h on all patients. V/Q lung scan results were classified as high probability for PE (normal ventilation study) or nondiagnostic (abnormal ventilation study). All V/Q lung scans were read by two experienced nuclear physicians in consensus. For the intra- and interobserver variabilities, two experienced observers independently read the V/Q lung scans.. (81m)Kr and technegas showed a good agreement (kappa, 0.68; 95% confidence interval [CI], 0.53-0.82). However, technegas significantly increased the number of nondiagnostic V/Q lung scans (P: = 0.035). In 15 patients, a discrepancy was found between (81m)Kr and technegas. False-positive V/Q lung scan results occurred in 4 of 12 patients (33%) with (81m)Kr and in 2 of 3 patients (66%) with technegas. The intra- and interobserver variabilities were 0.71-0.88 (95% CI, 0.56-1.0) for perfusion/(81m)Kr and 0.74-0.96 (95% CI, 0.58-1.0) for perfusion/technegas.. In comparison with (81m)Kr, technegas does not result in more false-positive V/Q lung scan results. The use of technegas, however, increases the number of nondiagnostic V/Q lung scan results, which would increase the demand for further additional testing to confirm or refute PE.

Topics: Acute Disease; Angiography; False Positive Reactions; Female; Humans; Krypton Radioisotopes; Lung; Male; Middle Aged; Observer Variation; Pulmonary Artery; Pulmonary Embolism; Radionuclide Imaging; Radiopharmaceuticals; Sodium Pertechnetate Tc 99m; Tomography, X-Ray Computed; Ventilation-Perfusion Ratio

Radioactive gas or technetium-99m aerosols are used to perform pulmonary ventilation scintigraphy. The aim of this study was to compare three radiopharmaceuticals, Kryptoscan, Technegas and Venticis II, in terms of their costs and user preferences rather than on the basis of diagnostic efficacy. For each radiopharmaceutical agent, an analysis questionnaire was sent to nuclear medicine departments setting out the criteria (and subcriteria) to be assessed: diagnosis quality: imaging quality, distribution homogeneity, examination procedures and capacity to examine particular patients (e.g. smokers); safety: for patient, paramedical and medical staff and the environment; use: availability in cases of emergency, ergonomics of the apparatus, simplicity and time of preparation. A score, ranging from 0 to 5, and a weighting (importance of one criterion with regard to the others) were assigned to each criterion. The direct cost of a ventilation (drugs, generator systems, disposable materials) was calculated for each radiopharmaceutical agent according to the number of patients examined per day (1-6) and the number of examination days per week (2-5). Fourteen questionnaires concerning at least two of the products were returned out of the 30 mailed. A 'preference score' was calculated using Pharma Decision software. The mean score of Kryptoscan was significantly higher than that of Venticis II (444 vs. 286, P < 0.001) and higher than the mean score of Technegas (444 vs. 344, P < 0.01). For Venticis II and Technegas, the changes in patient direct costs were minor and depended on the number of patients per day and the number of examination days per week. Respectively, they were: $US 117.66 (5 patients.day-1; 5 days.week-1) to $US 147.74 (2 patients.day-1; 2 days.week-1) and $US 56.60 (6 patients.day-1; 5 days.week-1) to $US 132.08 (2 patients.day-1; 2 days.week-1). The direct cost of ventilation using Kryptoscan varied only according to the number of patients examined per day: $US 104.66 (6 patients.day-1) to $US 266.47 (2 patients.day-1). This study shows that Kryptoscan appears to be preferable for ventilation scintigraphy whenever at least four patients are examined daily.

Topics: Aerosols; Analysis of Variance; Costs and Cost Analysis; France; Humans; Pulmonary Embolism; Radionuclide Imaging; Radiopharmaceuticals; Rubidium Radioisotopes; Safety; Sodium Pertechnetate Tc 99m; Surveys and Questionnaires; Technetium

We evaluated selection bias in a prospective study of 1,162 consecutive patients with suspected pulmonary embolism. Of these, 983 were eligible, and 627 could actually be included. During two months extensive data were collected on all non-included patients. Finally, our patient characteristics were compared with those of the PIOPED study (1990) and the study of Hull et al. (1994). Compared with included patients, the non-included patients had more often non-diagnostic V/Q scans (50% vs. 36%, p <0.01) and were more often already hospitalized (31% vs. 22%, P = 0.04). The subgroup of patients not included due to refusal or inability to give informed consent (IC) was older (mean age 61 vs. 53 years, P <0.01), more often suffered from malignancies (26% vs. 11%, P <0.01) and frequently had non-diagnostic V/Q scans (57%) as compared to included patients. In our study, 54% of all patients screened was eventually included versus 27% in the PIOPED study. In the PIOPED study patients who had contra-indications for pulmonary angiography were excluded, while in the study of Hull et al. those with inadequate cardiorespiratory reserve were excluded. In studies on new diagnostic technologies, patient selection bias does occur. The potential for such a selection bias should be taken into account when diagnostic strategies are devised to improve their generalizability and acceptability.

Topics: Adult; Aged; Angiography; Comorbidity; Female; Humans; Incidence; Informed Consent; Male; Middle Aged; Patient Selection; Postoperative Complications; Predictive Value of Tests; Prospective Studies; Pulmonary Embolism; Radionuclide Imaging; Radiopharmaceuticals; Risk Factors; Selection Bias; Sensitivity and Specificity; Sodium Pertechnetate Tc 99m; Thrombophlebitis; Tomography, X-Ray Computed; Treatment Refusal; Ultrasonography; Ventilation-Perfusion Ratio

Conventional planar ventilation/perfusion (V/P)-imaging in those patients suspected of suffering from pulmonary thromboembolism (PTE) is of limited diagnostic value. It is the purpose of this retrospective study to determine whether the use of V/P-SPECT using Technegas might reduce the rate of those diagnostic uncertainties and might lead to better results.. 991 patients (660 female, 331 male, age 18-90, mean 60), referred to our laboratory with suspected PTE, were examined as follows: patients inhaled 37 MBq of Technegas in the supine position and a SPECT-acquisition was started. Following SPECT-completion, 185 MBq 99mTc-MAA was injected intravenously. SPECT was then repeated. Coronal and transverse ventilation and perfusion SPECT-slices were reconstructed and compared section by section. 85 patients underwent control scans by the same technique at a mean interval of 22 months after the original scans.. As the SPECT images in almost all cases made a clear match/mismatch decision possible, we categorized all patients as embolic (PTE+) if there was at least one mismatching defect, and as non embolic (PTE-) if there were none. Our results were: PTE+: 178 patients (18%), PTE-: 808 patients (81%), uncertain: 5 patients (0.5%), if 34 triple-match defects are included: 39 patients (3.9%). 46 patients, categorized as PTE+ underwent a control V/P scan after anticoagulant therapy. In 44 of these patients, PTE was confirmed by the controls. In a control group of 39 PTE- patients, control scans were unchanged in 38 cases. From these observations we can calculate a sensitivity of 96% and a specificity of 97%.. We conclude that V/P imaging can be improved significantly by V/P SPECT using Technegas.

Topics: Adult; Aged; Aged, 80 and over; Female; Humans; Lung; Male; Middle Aged; Patient Selection; Pulmonary Embolism; Radiopharmaceuticals; Retrospective Studies; Sodium Pertechnetate Tc 99m; Tomography, Emission-Computed, Single-Photon; Ventilation-Perfusion Ratio

Lung scintigraphy is used widely for diagnosis of pulmonary embolus (PE). Technegas ventilation imaging has many advantages over other methods, but little outcome data exists on this technique. The aims of this study were to better define the role of lung scintigraphy in the management of patients with suspected PE and to evaluate technegas ventilation imaging by following patient outcomes.. A group of 717 out of 834 consecutive patients, referred to a university teaching hospital for lung scintigraphy to confirm or refute the diagnosis of PE, was followed for 18-30 mo to determine clinical outcome. The follow-up endpoints were death as a result of PE, death as a result of hemorrhage after treatment for PE, uncomplicated survival, survival with subsequent PE, nonfatal hemorrhage after treatment for PE and recurrence of PE in treated patients. Ventilation imaging was performed using technegas, and perfusion imaging was performed using intravenous 99mTc macroaggregated albumin. The modified PIOPED (Prospective Investigation of Pulmonary Embolism Diagnosis) diagnostic criterion was used for interpretation of lung scintigraphy.. Diagnostic results included 3.5% normal studies, 67.4% assessed as low probability for PE, 10% as moderate probability for PE and 19.1% as high probability for PE. A total of 231 patents received therapy with heparin, followed by warfarin, including those receiving anticoagulation therapy for other conditions. Ninety-six percent of patients with normal and low probability studies (n = 508) had good outcomes, 6 patients died as a result of PE and 12 subsequently developed PE. The odds ratio for death by PE in this group was 0.2. Of the 72 moderate probability studies, 39 patients were untreated. In this group there was 1 death due to PE, and PE subsequently developed in 2 patients. None of the remaining 33 treated patients died, but 4 patients experienced bleeding complications. The odds ratio for death by PE in the moderate probability group was 0.7. In those patients with high-probability studies, there were 8 deaths by PE, 6 deaths by hemorrhage, 11 nonfatal hemorrhages and 7 patients who experienced recurrences of PE. The odds ratios in this group were 6 and 10 for death by PE, or death by PE and the treatment of PE, respectively.. The use of the modified PIOPED diagnostic classification is valid for technegas lung scintigraphy. Using technegas, normal/low-probability and high-probability results are highly predictive of respective outcomes. Technegas lung scintigraphy reduces the number of indeterminate studies.

Topics: Aged; Anticoagulants; Disease-Free Survival; Female; Follow-Up Studies; Graphite; Humans; Lung; Male; Pulmonary Embolism; Radionuclide Imaging; Radiopharmaceuticals; Sodium Pertechnetate Tc 99m; Technetium Tc 99m Aggregated Albumin; Time Factors; Treatment Outcome; Ventilation-Perfusion Ratio

Airborne contamination by 99Tcm has been monitored in the Nuclear Medicine Department in our hospital to assess the risk of internal contamination to occupational workers exposed to Technegas studies. An air sampler fitted with a membrane filter was used. The optimum time for air absorption for obtaining the maximum activity in the filter was calculated. Maximum activity in the membrane filter ensures minimum uncertainty, which is especially important when low-level activities are being measured. The optimum time depends on air absorption velocity, room volume and filter efficiency for isotope collection. It tends to 1/lambda (lambda = disintegration constant for 99Tcm) for large volume and low velocity. Room activity with the air pump switched on was related to filter activity, and its variation with time was studied. Free activity in air for each study was approximately 7 x 10(-4) the activity used, and the effective half-life of the isotope in the room was 13.9 min (decay and diffusion). For a typical study (630 MBq), the effective dose to staff was 0.01 microSv when in the room for 10 min.

Topics: Air Pollutants, Radioactive; Environmental Monitoring; Graphite; Humans; Microclimate; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Technetium

Topics: Adult; Breast; Female; Humans; Lung; Pregnancy; Pregnancy Complications, Cardiovascular; Pulmonary Embolism; Radionuclide Imaging; Radiopharmaceuticals; Sodium Pertechnetate Tc 99m

Pertechnegas, a variant of technegas, produces similar ventilation images with a much increased clearance rate. This work aims to determine the properties of pertechnegas and its use as a ventilatory agent.. Fourteen men and 11 women were scanned for PE, after pertechnegas ventilation. Six were reimaged with technegas within 1 wk. Studies were reported according to PIOPED criteria. Pertechnegas samples were analyzed by transmission electron microscopy (TEM), cascade impaction (CI), aerosol mobility analysis (AMA), Fourier transform mass spectrometry (FTMS), x-ray photoelectron spectroscopy (XPS), paper strip (PC) and gas chromatography (GC).. Post-test probabilities were normal in 5, low in 8, high in 5 and indeterminate in 7. There were 15 Grade 1, 6 Grade 2 and 4 Grade 3 studies. All Grade 3 patients had FEV1 < 1.5 liters, 3 with rates < 1.0 liter. Patients with high probability had proven deep venous thrombosis in three by venography and in one by doppler. TEM identified 0.3 micron salt particles. CI demonstrated a 7-min time to half clearance from the chamber for particles in the < 0.1 micron range. AMA indicated all particles were < 0.032 micron when salt was excluded. Pertechnegas behaves in PC as pertechnetate, GC demonstrated CO levels below 516 ppm. CO2 concentrations were 0.146 +/- 0.0009%. FTMS found molecular pertechnetate species including 99TcO3(OH)+, Na99TcO3(OH)3+ and Na99TcO3(OH)3+. XPS confirmed that these Tc species exist in oxidation state +7.. Comparison with technegas images in the follow-up group proved equivalent in the first five views, but indistinct lung boundaries and a high background activity characterized the final anterior images. The active component of pertechnegas is molecular pertechnetate.

Topics: Adult; Aged; Aged, 80 and over; Female; Humans; Lung; Male; Middle Aged; Prospective Studies; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m

D-dimer assay (DDA), measuring fibrin degradation products, was compared with lung scintigraphy (LS) in a prospective unselected series of 83 consecutive patients referred owing to suspicion of pulmonary embolism (PE). This patient series was also used to compare several methods of performing and interpreting LS images. The final diagnosis was established independently by a separate panel with all available information except for the result of DDA. D-dimer was determined by ELISA (threshold value 500 ng/ml). LS, including perfusion (.Q) and pseudo-ventilation (Technegas) (.V), was classified according to PIOPED, (1) immediately by the physician on duty, and (2) retrospectively by a blinded panel. A positive (19) or negative (61) diagnosis of PE was achieved in 80 patients, the prevalence of PE being 24%. Only one false-negative was noted on DDA (sensitivity=95%) but there were 42 false-positives (specificity=31%), resulting in a positive predictive value of 30% and a negative predictive value of 95%. Emergency and retrospective interpretations of LS were close (kappa=0.4). In a minority of patients, PE may be excluded with reasonable certainty if DDA is normal, resulting in a significant saving in terms of time and money.

Topics: Enzyme-Linked Immunosorbent Assay; Female; Fibrin Fibrinogen Degradation Products; Graphite; Humans; Lung; Male; Middle Aged; Predictive Value of Tests; Prospective Studies; Pulmonary Embolism; Radionuclide Imaging; Sensitivity and Specificity; Sodium Pertechnetate Tc 99m; Technetium

The objective was to study the 1-month outcome of patients who had a low probability ventilation/perfusion lung scan using Technegas radioaerosol as the inhalational agent and who did not receive anticoagulation. One hundred consecutive patients with suspected pulmonary embolism were studied retrospectively. Their Technegas lung scans were classified by two blinded and independent nuclear medicine physicians and the medical records of all patients with a low probability scan were reviewed. One hundred inpatients (42 males and 58 females) with a mean age of 63 years were studied. The three most common clinical presentations leading to lung scintigraphy were unexplained dyspnoea (30 cases), unexplained dyspnoea with pleuritic chest pain (26 cases) and pleuritic chest pain only (15 cases). Nine patients had been judged by their managing medical team to have a high clinical probability of true pulmonary embolism, 32 had an intermediate probability clinical presentation and 59 a low clinical probability of pulmonary embolism. None of the 100 patients experienced further episodes of suspected or proven pulmonary embolism during the follow-up period. Six patients died. In none of them was pulmonary embolism either the cause of or a major contributing factor to death. The finding of a low probability scan using Technegas as the ventilation scintigram agent of choice describes a group of patients who, even in the absence of therapeutic anticoagulation, have a favourable 1-month outcome free of either true or suspected clinical pulmonary embolism. Invasive, pulmonary angiography-based diagnostic strategies may not be needed in this group of patients.

Topics: Female; Graphite; Humans; Lung; Male; Medical Records; Middle Aged; Probability; Pulmonary Embolism; Radionuclide Imaging; Retrospective Studies; Sodium Pertechnetate Tc 99m; Time Factors; Treatment Outcome; Ventilation-Perfusion Ratio

In this preliminary study, four patients suspected of having pulmonary emboli underwent ventilation imaging after inhaling approximately 1 mCi (37 MBq) of Tc-99m Pertechnegas (micro aerosol carbon particles labeled with Tc-99m) in five breaths or less. Planar images in multiple projections were recorded for preset counts. A final posterior image was acquired to evaluate residual lung background activity. Immediately following ventilation imaging, perfusion imaging in the identical projections was performed using 4 mCi (148 MBq) of Tc-99m MAA. Two of the four patients demonstrated matched uniform ventilation and perfusion and two showed segmental ventilation-perfusion "mismatched" defects consistent with pulmonary emboli. In each case, residual Pertechnegas background lung activity (count rate) at the end of the last ventilation image was less than 10% of the initial Tc-99m MAA counts (count rate). The advantages of Pertechnegas, in comparison to aerosolized DTPA, include: less residual ventilation image activity superimposed on the MAA perfusion images, reduced demand for patient cooperation due to fewer required breaths (five or less), and lack of deposition of activity in the central airways. The authors conclude that Pertechnegas has properties that make it ideally suited for routine lung ventilation imaging.

Topics: Adult; Female; Graphite; Humans; Male; Middle Aged; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m

Topics: Humans; Infant; Infections; Male; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Technetium Tc 99m Aggregated Albumin

The image quality obtained with technetium-99mC aerosol (Technegas) was evaluated and compared with that obtained with 99mTc-phytate aerosol generated by a jet nebulizer. Fifty patients underwent ventilation scanning after inhalation of each aerosol (mean interval of 3 days). Four views (anterior, posterior, left and right posterior oblique) were recorded with 200 k precounts. Both sets of images were blindly compared for (i) qualitative evaluation of images, (ii) quantitation of penetration (PI) and heterogeneity (HI) indices and (iii) assessment of ventilation state. Peripheral penetration was the same in 64% of cases, greater with 99mTc-C in 27% and greater with 99mTc-phytate in 9%. The use of 99mTc-C led to fewer and less intense foci of bronchial or gastric activity. The differences for 99mTc-C and 99mTc-phytate, respectively, between mean PI (0.78 vs. 0.70) and HI (15 vs. 18) were not significant. Consideration of all the parameters indicates the overall superiority of 99mTc-C. The final interpretation of the lung ventilation scans was, however, similar with both tracers.

Topics: Administration, Inhalation; Female; Humans; Male; Middle Aged; Organotechnetium Compounds; Phytic Acid; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Ventilation-Perfusion Ratio

A ventilation agent that provides good quality lung images, which is cheap, easy to use and non-toxic, with a low radiation dose, has long been sought. Technegas, an ultrafine aerosol of technetium-99m-labelled carbon, was developed with these qualities in mind. We have studied Technegas in a clinical setting to evaluate some of these qualities. Twenty-five patients referred with a diagnosis of suspected pulmonary embolism were investigated during the same study using both krypton-81 m and Technegas as ventilation agents in conjunction with 99mTc-macroaggregated albumin as a perfusion agent. Technegas provided images which were of satisfactory quality. Images were obtained relatively easily and without discomfort to the patient, and Technegas has the advantage of always being available. A semi-quantitative regional assessment was employed which showed a good correlation (r = 0.499, P less than 0.001) between Technegas and krypton-81 m ventilation. We report on an effect not previously found to be significant, that is lung regions were better ventilated with Technegas than with krypton-81 m. This altered the diagnostic probability rating of pulmonary embolism in a number of patients (n = 3, 12%) compared with krypton-81 m. This effect was also noted in a further 8 patients (32%) without a change in the diagnostic probability. We offer possible explanations for this phenomenon.

Topics: Female; Graphite; Humans; Krypton Radioisotopes; Lung; Male; Middle Aged; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Ventilation-Perfusion Ratio

Clinical outcome analysis was carried out in 175 of 206 consecutive patients referred for a lung scan with clinical suspicion of pulmonary embolism (PE). The follow-up time period ranged from 4 to 18 months. High-quality ventilation images corresponding to the six standard perfusion images were obtained using Technegas as a ventilatory agent. Lung scan reports showed that 22% of the patients had a high, 14% indeterminate, 18% low and 9% very low probability for PE and 37% were normal lung scans. These reports usually supported the referring clinicians' provisional diagnosis and were confirmed by the clinical outcome analysis of these patients giving an apparent sensitivity for the lung scan of 96% and specificity 93%. A strategy for lung scanning in PE is proposed.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Female; Humans; Lung; Male; Middle Aged; Pulmonary Embolism; Radionuclide Imaging; Retrospective Studies; Sodium Pertechnetate Tc 99m; Treatment Outcome; Ventilation-Perfusion Ratio

The demand for high-quality ventilation imaging of the lungs has resulted in the advent of Technegas, which has proven its superiority to the more conventional agents in a number of clinical trials. Images of similar diagnostic quality have been difficult to obtain in patients who are uncooperative, intubated or very young. With this problem as the impetus, a ventilatory assistance device (VAD) was designed to exploit the superior imaging qualities of Technegas. The Technegas generator was interposed between the patient and the VAD, allowing the controlled movement of Technegas into the patient from the generator. Utilizing this device, the problems of increased dead space, turbulent gas flow and possible contamination were circumvented. Twenty patients, comprising nine children and eleven adults, were studied for various indications including assessment of pulmonary parenchymal disease, suspected pulmonary embolism and the lung clearance of modified Technegas. In all cases, images of diagnostic quality were obtained with ease, facilitating relevant clinical decision making. We conclude from this preliminary appraisal that the VAD is a simple, safe addition to the Technegas generator for imaging a group of patients in whom images of diagnostic quality have traditionally proven difficult to obtain.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Child; Child, Preschool; Female; Humans; Infant; Lung; Male; Middle Aged; Pulmonary Embolism; Radionuclide Imaging; Respiration, Artificial; Sodium Pertechnetate Tc 99m; Ventilation-Perfusion Ratio

Topics: Australia; Evaluation Studies as Topic; Humans; Lung Diseases; Lung Diseases, Obstructive; Pulmonary Embolism; Radionuclide Imaging; Respiratory Function Tests; Sodium Pertechnetate Tc 99m; Surveys and Questionnaires

Striking thyroidal uptake of Tc-99m pertechnetate was observed during the course of a perfusion lung scan performed with Tc-99m MAA to rule out pulmonary embolism in a 49-year-old man. There was no evidence of gastric pertechnetate activity. Radiochemical purity analysis of the Tc-MAA by chromatography in normal saline revealed 98.8% tagging, with 1.2% free pertechnetate. We estimate that a maximum of 60 microCi (2.2 MBq) of pertechnetate was available for thyroid trapping. This amount, given to a euthyroid volunteer studied with conventional gamma camera lung perfusion settings, failed to visualize the thyroid. A follow-up radioiodine thyroid uptake of the patient was markedly elevated, as was his thyroid function tests (T3,T7,T7). When diffuse intense thyroid gland radioactivity is seen during scintigraphy with a technetium radiopharmaceutical (e.g., bone and lung scans), consideration should be given to the possibility of hyperthyroidism. If gastric activity is not concomitantly seen, hyperthyroidism secondary to diffuse hyperplasia of the gland is probably present.

Topics: Humans; Hyperthyroidism; Male; Middle Aged; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Technetium Tc 99m Aggregated Albumin; Ventilation-Perfusion Ratio

In the diagnosis of pulmonary embolism, perfusion lung scintigraphy offers high sensitivity but low specificity. The specificity can be significantly increased by the use of combined ventilation and perfusion studies. Most aspects of perfusion lung scintigraphy are uniformly accepted but the technique of ventilation imaging varies from centre to centre. This study describes a new technique for the performance of ventilation scintigraphy using a suspension of ultrafine carbon particles labelled with 99Tcm ("Technegas"). The technique combines the ready availability of 99Tcm and its optimal imaging properties with an easily administered radiopharmaceutical of particle size sufficiently small to deposit in the alveoli. Of 63 patients studied by conventional perfusion scintigraphy plus Technegas ventilation scintigraphy, images of diagnostic quality were obtained in all. 31 of these patients also had a ventilation study using 81Krm gas and in only one instance did the two methods of ventilation imaging lead to differing interpretations. We conclude that high quality diagnostic images may be obtained using this new technique, which can be made available on both a routine and an emergency basis, thus improving the service provided for patients suspected of having pulmonary embolism.

Topics: Adult; Aged; Evaluation Studies as Topic; Female; Graphite; Humans; Krypton Radioisotopes; Lung; Male; Middle Aged; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Technetium

The potential of plasma measurement of D-dimer (DD), a specific derivative of crosslinked fibrin, for diagnosis or exclusion of pulmonary embolism was investigated in a prospective series of 171 consecutive patients who attended an emergency department with suspected pulmonary embolism. The diagnosis was made or excluded by means of a clinical decision-making process which included clinical evaluation, ventilation-perfusion (VQ) lung scan, and, as indicated, pulmonary angiography, venography, or non-invasive examination of the leg veins. Pulmonary embolism was diagnosed by this process in 55 (32%) of 170 patients with sufficient data. All but 1 of these 55 patients had a DD concentration of 500 micrograms/l or above. The sensitivity and specificity of this cutoff concentration for the presence of pulmonary embolism were 98% and 39%, respectively, which give positive and negative predictive values of 44% and 98%. Among the 115 patients (68%) who had inconclusive VQ scans, 31 were diagnosed as having pulmonary embolism. 29 of the remaining 84 patients without pulmonary embolism had DD concentrations below 500 micrograms/l, which means that further diagnostic procedures could have been avoided in a quarter of the patients with inconclusive VQ scans. The sensitivity of the plasma measurement of DD remained high even 3 and 7 days after presentation (96% and 93%). Plasma measurement of DD therefore has a definite place in the diagnostic procedure for suspected acute pulmonary embolism in attenders at emergency departments: a concentration below 500 micrograms/l rules out the diagnosis.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Emergencies; Evaluation Studies as Topic; Female; Fibrin Fibrinogen Degradation Products; Humans; Male; Middle Aged; Predictive Value of Tests; Prospective Studies; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Ventilation-Perfusion Ratio

A new method of producing aerosols (technegas) in which 99Tcm is bound to carbon atoms (99Tcm-C) was evaluated by comparing 99Tcm-C images with those obtained with 81Krm in the same patients. Twenty-five patients with suspected pulmonary embolism (PE) were studied. Immediately after the last 99Tcm-C view, the patients remained in supine position and inhaled 81Krm at tidal volume. Immediately after the 81Krm ventilation views were recorded, 4-7 mCi of MAA were injected IV. The same four views (ant, lop, rop, post) were recorded after inhalation of 99Tcm-C and 81Krm (200 kcounts) and 99Tcm MAA injection (400 kcounts). The mean penetration index of 99Tcm-C (0.91) was lower than that of 81Krm (1.04) (P less than 0.03). The apex to base lung distribution of 99Tcm-C and 81Krm appeared to be similar. The mean heterogeneity of 99Tcm distribution was 23, greater than that of 81Krm (14) (P = 10(-4)). The 99Tcm-C ventilation image quality was considered very good for 16 patients and good for 6 others. Significant foci of high bronchial uptake were infrequent. Interpretation of the examinations performed after inhalation of 99Tcm-C and 81Krm was concordant in all cases. No patient had an 81Krm/99Tcm MAA examination suggestive of PE when 99Tcm-C/99Tcm MAA indicated a low probability of PE, and vice versa. 99Tcm-C aerosols enable good quality ventilation images to be obtained in nearly all cases. Thus 99Tcm-C aerosols could be used in preference to 81Krm in ventilation studies for the diagnosis of PE.

Topics: Administration, Inhalation; Evaluation Studies as Topic; Humans; Krypton Radioisotopes; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m

Evaporation of 99mTc-pertechnetate at about 2500 degrees C on a carbon surface generates an ultrafine aerosol of labelled carbon clusters. Its particle size of about 2-5 nm enables the aerosol to behave similarly to a gas regarding the ability of penetration. After inhalation, the radioactive particles adhere to the walls of the respiratory bronchioli and alveoli. The high concentration of the radioactivity in the argon carrier gas makes it possible to record a scintigram after a single deep breath. We studied four healthy volunteers and 79 patients including 34 with a tentative diagnosis of pulmonary embolism, 20 with bronchus carcinoma, and 15 with various other lung diseases. Ten of these patients were infants, the youngest being nine months old. All patients also had a perfusion scintigraphy.

Topics: Administration, Inhalation; Adult; Aerosols; Aged; Bronchitis; Carcinoma, Bronchogenic; Female; Humans; Infant; Lung Diseases; Lung Neoplasms; Male; Middle Aged; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m

A comparison of "Technegas" and xenon-133 was performed in 50 patients presenting with a clinical diagnosis of pulmonary embolus. All patients underwent studies with xenon inhalation, Technegas inhalation, and macroaggregated albumin perfusion. Technegas is a new ultrafine ventilatory agent with a particle size of 50 to 200A produced from technetium pertechnetate and graphite in an argon environment. Although particulate in nature, Technegas is transported and diffuses like a gaseous agent. Its production results in a high specific activity yield with high efficiency. There is no significant deposition in the central airways, and good peripheral visualization of the lung is obtained. The study was designed to assess whether Technegas could be used as a ventilatory agent to obtain high-quality diagnostic images. All studies were reported as in normal clinical practice, and no statistical analysis was performed. The aim of the study was simply to see what role Technegas had in a busy clinical department and how well it reflected ventilation by comparison with xenon. Patient compliance with Technegas was 100 percent and for xenon was 94 percent. Technegas enables one to obtain high-quality ventilatory images and has an important role to play in the assessment of pulmonary ventilation.

Topics: Adult; Aged; Aged, 80 and over; Female; Humans; Male; Middle Aged; Probability; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m; Xenon Radioisotopes

Topics: Adult; Aged; Diagnosis, Differential; Female; Humans; Male; Middle Aged; Pulmonary Embolism; Radionuclide Angiography; Retrospective Studies; Sodium Pertechnetate Tc 99m; Technetium Tc 99m Aggregated Albumin; Thrombophlebitis

A simple process using technetium-99m generator eluate in a graphite crucible at 2500 degrees C, produces a structured ultra-fine dispersion of labelled carbon. Particle sizes are 5.0 nm (0.005 micron) and less and adhere to the walls of the alveoli on inhalation. Penetration characteristics are gas-like and the radioactivity per litre of carrier argon allows single breath inhalations of a diagnostic dose. Over 190 patients have been studied including 50 within a formal clinical trial with xenon-133. Results of tomography, dynamic inhalation, and image subtraction using this new agent-'Technegas'--are presented.

Topics: Carbon; Humans; Lung; Pulmonary Embolism; Radionuclide Imaging; Sodium Pertechnetate Tc 99m