technetium-tc-99m-tetrofosmin and Body-Weight

The decreasing image quality in heavier patients can be compensated by administration of a patient-specific dose in myocardial perfusion imaging (MPI) using a cadmium zinc telluride-based SPECT camera. Our aim was to determine if the same can be achieved when using a conventional SPECT camera.. 148 patients underwent SPECT stress MPI using a fixed Tc-99m tetrofosmin tracer dose. Measured photon counts were normalized to administered tracer dose and scan time and were correlated with body weight, body mass index, and mass per length to find the best predicting parameter. From these data, a protocol to provide constant image quality was derived, and subsequently validated in 125 new patients.. Body weight was found to be the best predicting parameter for image quality and was used to derive a new dose formula; A admin (MBq) = 223·body weight (kg)(0.65)/T scan (min). The measured photon counts decreased in heavier patients when using a fixed dose (P < .01) but this was no longer observed after applying a body-weight-dependent protocol (P = .20).. Application of a patient-specific protocol resulted in an image quality less depending on patient's weight. The results are most likely independent of the type of SPECT camera used, and, hence, adoption of patient-specific dose and scan time protocols is recommended.

Topics: Aged; Body Weight; Contrast Media; Coronary Artery Disease; Drug Administration Schedule; Equipment Design; Equipment Failure Analysis; Female; Gamma Cameras; Humans; Image Enhancement; Image Interpretation, Computer-Assisted; Male; Myocardial Perfusion Imaging; Organophosphorus Compounds; Organotechnetium Compounds; Patient-Centered Care; Patient-Specific Modeling; Radiopharmaceuticals; Reproducibility of Results; Sensitivity and Specificity; Tomography, Emission-Computed, Single-Photon

It is generally accepted that the quality of myocardial images deteriorates with increasing patient weight. This is attributed to a reduction of counts detected from the myocardium. In this paper we have looked at the count reduction in obese patients and suggest a workable algorithm to increase the injected activity to compensate for this loss of count. In this prospective study, 64 consecutive patients with normal myocardial images were selected to include a weight range of 50-120 kg. The height, weight and gender of patients were noted. Each patient had two studies (total of 128 studies), one at rest and one following stress with adenosine and 20-40 W bicycle exercise. Total myocardial counts were calculated from the back-projected views. The total myocardial counts per MBq of the injected activity were calculated. There was no significant difference in the injected activity and the size of the heart (pixel length of heart) between stress and rest, or gender of the patient. The normalized myocardial counts were not different between men and women, but the counts were slightly, although not significantly, higher ( P=NS) with adenosine and exercise (mean of 243 x 10(3) counts) compared to rest images (229 x 10(3) counts). There was a significant progressive loss of counts in patients with increasing weight, body mass index or body surface area ( P<0.001). There was no significant difference in the changes in counts with weight between male and female, or rest and stress studies. The combined data from all the studies were used to calculate the correlation coefficient and the slope of the line for reduction of cardiac counts with a patient's weight, body mass index, and body surface area. The best correlation was with patient weight ( r=0.58, P<0.001). This was used to calculate the increase in injection activity with increasing weight to maintain the same average counts as achieved in a 70 kg patient with a 400 MBq injection. We suggest that the injection activity should increase from 100% for a 70 kg patient to 140% for 110 kg, 200% for 140 kg, and 250% for a 150 kg patient.

Topics: Body Mass Index; Body Weight; Dose-Response Relationship, Drug; Exercise Test; Female; Heart; Humans; Injections, Intravenous; Male; Myocardium; Organophosphorus Compounds; Organotechnetium Compounds; Quality Control; Radiometry; Radionuclide Imaging; Radiopharmaceuticals

Nuclear medicine myocardial perfusion imaging (MPI) in obese patients requires the administration of higher amounts of radioactivity, to compensate for the loss of photons due to the increased attenuation and scatter. The aim of the present study was to investigate whether an administered activity escalation protocol, proposed to yield the same effective dose irrespective of patient's weight, can also lead to images of comparable count density for all patients.. 184 pharmacologically induced stress 99m-Tc MIBI and 99m-Tc tetrofosmin SPECT MPI examinations (123 males, 61 females) were included in this study. Body weight, BMI and chest circumference were collected for each patient. The administered activity was adjusted to body weight according to the IAEA protocol. Detector count rate (DCR) from the projection images and normal myocardial count rate (MCR) from the appropriately segmented reconstructed images, with and without attenuation correction, were recorded.. No statistically significant correlation was found between DCR and any anthropometric parameter. A weak correlation was observed between MCR and BMI and between MCR and chest circumference for male patients only, but even these correlations were eliminated after the application of attenuation correction. The anthropometric parameter that generally correlates more strongly with DCR/MBq and MCR/MBq was body weight for men and chest circumference for women.. The IAEA activity escalation protocol used in this study leads to comparable image count densities, irrespective of body weight, for both men and women.

Topics: Body Mass Index; Body Weight; Female; Humans; Male; Myocardial Perfusion Imaging; Organophosphorus Compounds; Organotechnetium Compounds; Technetium Tc 99m Sestamibi; Tomography, Emission-Computed, Single-Photon

Large body size can cause a higher proportion of emitted photons being attenuated within the patient. Therefore, clinical myocardial perfusion SPECT (MPS) protocols often include unproportionally higher radioisotope activity to obese patients. The aim was to evaluate if a linear weight-adjusted low-dose protocol can be applied to obese patients and thereby decrease radiation exposure.. Linear low-dose weight-adjusted protocol of 2.5 MBq/kg in MPS can be applied over a large weight span without loss of counts or image quality, resulting in a significant reduction in radiation exposure to obese patients.

Topics: Aged; Body Weight; Clinical Protocols; Female; Humans; Male; Middle Aged; Myocardial Perfusion Imaging; Organophosphorus Compounds; Organotechnetium Compounds; Overweight; Radiation Dosage; Radiation Exposure; Tomography, Emission-Computed, Single-Photon

For a 1-day myocardial perfusion SPECT (MPS) the recommendations for administered activity stated in the EANM guidelines results in an effective dose of up to 16 mSv per patient. Recently, a gamma camera system, based on cadmium zinc telluride (CZT) technology, was introduced. This technique has the potential to reduce the effective dose and scan time compared to the conventional NaI gamma camera. The aim of this study was to investigate if the effective dose can be reduced with a preserved image quality using CZT technology in MPS.. In total, 150 patients were included in the study. All underwent a 1-day (99m)Tc-tetrofosmin stress-rest protocol and were divided into three subgroups (n = 50 in each group) with 4, 3, and 2.5 MBq/kg body weight of administered activity in the stress examination, respectively. The acquisition time was increased in proportion to the decrease in administered activity. All examinations were analyzed for image quality by visual grading on a 4-point scale (1 = poor, 2 = adequate, 3 = good, 4 = excellent), by two expert readers.. The total effective dose (stress + rest) decreased from 9.3 to 5.8 mSv comparing 4 to 2.5 MBq/kg body weight. For the patients undergoing stress examination only (35%) the effective dose, administrating 2.5 MBq/kg, was 1.4 mSv. The image acquisition times for 2.5 MBq/kg body weight were 475 and 300 seconds (stress and rest) compared to 900 seconds for each when using conventional MPS. The average image quality was 3.7 ± 0.5, 3.8 ± 0.5, and 3.8 ± 0.4 for the stress images and 3.5 ± 0.6, 3.6 ± 0.6, and 3.5 ± 0.6 for the rest images and showed no statistically significant difference (P = .62) among the 4, 3, and 2.5 MBq/kg groups.. The new CZT technology can be used to considerably decrease the effective dose and acquisition time for MPS with preserved high image quality.

Topics: Aged; Body Weight; Cadmium; Coronary Artery Disease; Female; Gamma Cameras; Humans; Image Processing, Computer-Assisted; Likelihood Functions; Male; Middle Aged; Myocardial Perfusion Imaging; Organophosphorus Compounds; Organotechnetium Compounds; Perfusion; Radiation Dosage; Radiometry; Radiopharmaceuticals; Tellurium; Time Factors; Tomography, Emission-Computed, Single-Photon; Treatment Outcome; Zinc

The aim of this retrospective investigation was to devise a protocol for obtaining consistent myocardial counts for patients attending myocardial perfusion imaging.. A total of 229 patients were included in the study sample. For each rest single-photon emission computed tomography data set, a three-dimensional ellipse was manually defined to isolate the left ventricle. The count rate per voxel was measured from a threshold region of interest covering the normally perfused myocardium (70-100% of maximum counts). Data were normalized for net administered activity and plotted against patient weight. The correlation between the variables was used to derive a protocol for adjusting injected activity or scan time to obtain consistent counts from patient to patient.. There was a significant correlation between counts per second per voxel per MBq and patient weight. The best fit was achieved with an inverse model. A correlation equation was derived for patients weighing more than 60 kg (combined R=0.79): [CPS/voxel/MBq=(0.0163/weight(kg)]-3.68×10+A in which A, a sex-dependent constant, was 0 for men and -2.920×10 for women.. There was a significant inverse correlation between patient weight and CPS per voxel per MBq.

Topics: Body Weight; Female; Humans; Male; Myocardial Perfusion Imaging; Organophosphorus Compounds; Organotechnetium Compounds; Radiopharmaceuticals; Reference Values; Technetium Tc 99m Sestamibi; Tomography, Emission-Computed, Single-Photon; Ventricular Function, Left

The American Society of Nuclear Cardiology and the Society of Nuclear Medicine state that incorporation of attenuation-corrected (AC) images in myocardial perfusion scintigraphy (MPS) will improve image quality, interpretive certainty, and diagnostic accuracy. However, commonly used software packages for MPS usually include normal stress databases for non-attenuation corrected (NC) images but not for attenuation-corrected (AC) images. The aim of the study was to develop and compare different normal stress databases for MPS in relation to NC vs. AC images, male vs. female gender, and presence vs. absence of obesity. The principal hypothesis was that differences in mean count values between men and women would be smaller with AC than NC images, thereby allowing for construction and use of gender-independent AC stress database.. Normal stress perfusion databases were developed with data from 126 male and 205 female patients with normal MPS. The following comparisons were performed for all patients and separately for normal weight vs. obese patients: men vs. women for AC; men vs. women for NC; AC vs. NC for men; and AC vs. NC for women.. When comparing AC for men vs. women, only minor differences in mean count values were observed, and there were no differences for normal weight vs. obese patients. For all other analyses major differences were found, particularly for the inferior wall.. The results support the hypothesis that it is possible to use not only gender independent but also weight independent AC stress databases.

Topics: Adult; Aged; Aged, 80 and over; Body Weight; Coronary Artery Disease; Databases, Factual; Exercise Test; Female; Humans; Image Interpretation, Computer-Assisted; Male; Middle Aged; Obesity; Organophosphorus Compounds; Organotechnetium Compounds; Radiopharmaceuticals; Reference Values; Reproducibility of Results; Sex Factors; Software; Tomography, Emission-Computed, Single-Photon

In our previous publication, we proposed to increase the injection activity for overweight patients. We have now implemented this for our patients, i.e. increasing the activity for patients above 99 kg. In the present study, we audited whether this increased activity for overweight patients improved the myocardial counts effectively and also whether it improved the image quality for these patients. 125 consecutive normal myocardial perfusion studies were included into the study. The total left ventricular myocardial count was calculated, as was the total left ventricular myocardial volume using the Cedar Sinai QPS program. The myocardial count per millilitre of the myocardium (c ml(-1)) was correlated with patient weight using regression analysis. There was no significant difference (p = 0.120) among the mean myocardial counts for patients over 99 kg (n = 40, 1548 c ml(-1)) compared with patients in the 70-79 kg range (n = 26, 1746 c ml(-1)). This indicates that the previously proposed algorithm for adjusting injection activity maintains the count density in the myocardium and should be used for all patients over 99 kg. There was, however, a significant steady decrease with increased weight in the myocardial counts for patients under 100 kg (p<0.001), a range in which injection activity was not adjusted for weight. To correct for this, we now propose that the injection activity should be adjusted for all patients over 80 kg, using the previously proposed algorithm.

Topics: Algorithms; Artifacts; Body Weight; Clinical Protocols; Coronary Circulation; Female; Heart; Humans; Injections; Male; Organophosphorus Compounds; Organotechnetium Compounds; Overweight; Radiographic Image Enhancement; Radiopharmaceuticals; Reproducibility of Results; Tomography, Emission-Computed, Single-Photon; Ventricular Dysfunction