germanium and bismuth-germanium-oxide

We quantitatively and qualitatively investigated 2-dimensional (2D) and 3-dimensional (3D) imaging with scan-time reduction in 14 patients with 17 lesions, who had known or suspected head and neck cancer, using a bismuth germanate (BGO) crystal based PET/CT scanner with noise-matched images.. A 2D and 3D acquisition protocol using scan-time reduction on an axial single field of view resulted in a 2D 4-, 3D 4-, 3D 3-, 2D 3-, 2D 2-, and 3D 2-min scan sequence to minimize redistribution and decay bias. Tumor maximum standardized uptake values (SUVmax) and tumor mean standardized uptake values (SUV(mean)) were recorded, and two observers in consensus investigated lesion conspicuity between 2D and 3D paired 4-, 3-, and 2-min noise-matched images.. We found some minor advantages quantitatively in favor of 2D scanning, with higher mean SUVmax, and qualitatively in favor of 3D scanning, with lesion conspicuity preference. In our cohort, no great advantage or disadvantage to using either acquisition mode was observed, and all lesions were seen irrespective of acquisition mode and scan time.. In head and neck cancer patients, we can recommend a scan-time reduction from 4 to 3 min/bed position in 2D acquisitions with a BGO-based PET/CT scanner, using our imaging protocol and reconstruction defaults.

Topics: Bismuth; Female; Germanium; Head and Neck Neoplasms; Humans; Imaging, Three-Dimensional; Male; Middle Aged; Observer Variation; Positron-Emission Tomography; Time Factors; Tomography, X-Ray Computed

Topics: Bismuth; Germanium; Photons; Positron-Emission Tomography; Scintillation Counting

Dual-ended readout depth-encoding detectors based on bismuth germanate (BGO) scintillation crystal arrays are good candidates for high-sensitivity small animal positron emission tomography used for very-low-dose imaging. In this paper, the performance of three dual-ended readout detectors based on 15 × 15 BGO arrays with three different reflector arrangements and 8 × 8 silicon photomultiplier arrays were evaluated and compared.. The three BGO arrays, denoted wo-ILG (without internal light guide), wp-ILG (with partial internal light guide), and wf-ILG (with full internal light guide), share a pitch size of 1.6 mm and thickness of 20 mm. Toray E60 with a thickness of 50. The results showed that the detector based on the wo-ILG BGO array provided the best flood histogram. The energy, timing and DOI resolutions of the three detectors were similar. The energy resolutions full width at half maximum (FWHM value) based on the wo-ILG, wp-ILG and wf-ILG BGO arrays were 27.2 ± 3.9%, 28.7 ± 4.6%, and 29.5 ± 4.7%, respectively. The timing resolutions (FWHM value) were 4.7 ± 0.5 ns, 4.9 ± 0.5 ns, and 5.0 ± 0.6 ns, respectively. The DOI resolution (FWHM value) were 3.0 ± 0.2 mm, 2.9 ± 0.2 mm, and 3.0 ± 0.2 mm, respectively. Over all, the wo-ILG detector provided the best performance.

Topics: Animals; Bismuth; Germanium; Positron-Emission Tomography

Solid state photodetectors like silicon photomultipliers (SiPMs) are playing an important role in several fields of medical imaging, life sciences and high energy physics. They are able to sense optical photons with a single photon detection time precision below 100 ps, making them ideal candidates to read the photons generated by fast scintillators in time of flight positron emission tomography (TOF-PET). By implementing novel high-frequency readout electronics, it is possible to perform a completely new evaluation of the best timing performance achievable with state-of-the-art analog-SiPMs and scintillation materials. The intrinsic SiPM single photon time resolution (SPTR) was measured with Ketek, HPK, FBK, SensL and Broadcom devices. Also, the best achieved coincidence time resolution (CTR) for these devices was measured with LSO:Ce:Ca of [Formula: see text] mm

Topics: Bismuth; Germanium; Monte Carlo Method; Photons; Positron-Emission Tomography; Scintillation Counting; Silicon; Time Factors

Bismuth germanate (BGO) shows good properties for positron emission tomography (PET) applications, but was substituted by the development of faster crystals like lutetium oxyorthosilicate (LSO) for time-of-flight PET (TOF-PET). Recent improvements in silicon photomultipliers (SiPMs) and fast readout electronics make it possible to access the Cherenkov photon signal produced upon 511 keV interaction, which makes BGO a cost-effective candidate for TOF-PET. Tails in the time-delay distribution, however, remain a challenge. These are mainly caused by the high statistical fluctuation on the Cherenkov photons detected. To select fast events with a high detected Cherenkov photon number, the signal rise time of the SiPM was used for discrimination. The charge, time delay and signal rise time was measured for two different lengths of BGO crystals coupled to FBK NUV-HD SiPMs and high frequency readout in a coincidence time resolution setup. The recorded events were divided into 5 × 5 categories based on the signal rise time, and time resolutions of 200 ± 3 ps for 2 × 2 × 20 mm

Topics: Bismuth; Electronics; Germanium; Image Processing, Computer-Assisted; Lutetium; Photons; Positron-Emission Tomography; Scintillation Counting; Silicates

The performance of dual-ended readout depth-encoding positron emission tomography (PET) detectors based on bismuth germanate (BGO) coupled to silicon photomultipliers (SiPM) arrays was measured for the first time and compared to lutetium-yttrium oxyorthosilicate (LYSO)-based detectors using the same readout. The BGO and LYSO crystal arrays all had a crystal pitch of 2.2 mm and were coupled to 8 × 8 SiPM arrays with a matching pitch of 2.2 mm, using a one-to-one coupling configuration. Three types of crystals with Toray reflector were used: polished LYSO, polished BGO, and unpolished BGO, and for two different crystal thicknesses of 20 mm and 30 mm. All the crystal elements in the BGO arrays were clearly resolved in the flood histogram. Better flood histograms were obtained using the LYSO arrays for a selected crystal thickness, and better flood histograms were obtained using the 20 mm thick crystal arrays for a selected crystal type. The average crystal level energy resolution and timing resolution for 20 mm polished LYSO, polished BGO and unpolished BGO crystals at their optimal SiPM bias voltage were 18.6 ± 1.3% and 1.19 ± 0.20 ns, 17.8 ± 0.8% and 4.43 ± 0.47 ns, and 18.0 ± 1.0% and 4.68 ± 1.0 ns, respectively. Depth-of-interaction (DOI) resolution of the 20 mm polished LYSO array was 2.31 ± 0.17 mm and for the 20 mm unpolished BGO array was 3.53 ± 0.25 mm. However, polished BGO arrays with Toray reflector did not provide DOI information. Our key conclusion is that dual-ended readout depth-encoding 20 mm thick unpolished BGO detectors are good candidates for low-activity PET systems with small field-of-view and low timing performance requirements, such as preclinical or compact organ-dedicated PET systems, with the advantage over LYSO of having no background radiation and significantly lower cost.

Topics: Background Radiation; Bismuth; Germanium; Lutetium; Positron-Emission Tomography; Yttrium

Topics: Bismuth; Equipment Design; Germanium; Humans; Positron-Emission Tomography

Exploiting the moderate Cherenkov yield from 511 keV photoelectric interactions in bismuth germanate (BGO) scintillators enables one to achieve a level of coincidence time resolution (CTR) appropriate for time-of-flight positron emission tomography (TOF-PET). For this approach, owing to the low number of promptly emitted light photons, single photon time resolution (SPTR) can have a stronger influence on achievable CTR. We have previously shown readout techniques that reduce effective device capacitance of large area silicon photomultipliers (SiPMs) can yield improvements in single photon response shape that minimize the influence of electronic noise on SPTR. With these techniques, sub-100 ps FWHM SPTR can be achieved with [Formula: see text] mm

Topics: Bismuth; Electronics; Germanium; Photons; Positron-Emission Tomography; Scintillation Counting; Ultraviolet Rays

Range uncertainty is among the most formidable challenges associated with the treatment planning of proton therapy. Proton imaging, which includes proton radiography and proton computed tomography (pCT), is a useful verification tool. We have developed a pCT detection system that uses a thick bismuth germanium oxide (BGO) scintillator and a CCD camera. The current method is based on a previous detection system that used a plastic scintillator, and implements improved image processing techniques. In the new system, the scintillation light intensity is integrated along the proton beam path by the BGO scintillator, and acquired as a two-dimensional distribution with the CCD camera. The range of a penetrating proton is derived from the integrated light intensity using a light-to-range conversion table, and a pCT image can be reconstructed. The proton range in the BGO scintillator is shorter than in the plastic scintillator, so errors due to extended proton ranges can be reduced. To demonstrate the feasibility of the pCT system, an experiment was performed using a 70 MeV proton beam created by the AVF930 cyclotron at the National Institute of Radiological Sciences. The accuracy of the light-to-range conversion table, which is susceptible to errors due to its spatial dependence, was investigated, and the errors in the acquired pixel values were less than 0.5 mm. Images of various materials were acquired, and the pixel-value errors were within 3.1%, which represents an improvement over previous results. We also obtained a pCT image of an edible chicken piece, the first of its kind for a biological material, and internal structures approximately one millimeter in size were clearly observed. This pCT imaging system is fast and simple, and based on these findings, we anticipate that we can acquire 200 MeV pCT images using the BGO scintillator system.

Topics: Bismuth; Germanium; Humans; Image Processing, Computer-Assisted; Proton Therapy; Scintillation Counting; Tomography, X-Ray Computed

Due to detector developments in the last decade, the time-of-flight (TOF) method is now commonly used to improve the quality of positron emission tomography (PET) images. Clinical TOF-PET systems based on L(Y)SO:Ce crystals and silicon photomultipliers (SiPMs) with coincidence resolving times (CRT) between 325 ps and 400 ps FWHM have recently been developed. Before the introduction of L(Y)SO:Ce, BGO was used in many PET systems. In addition to a lower price, BGO offers a superior attenuation coefficient and a higher photoelectric fraction than L(Y)SO:Ce. However, BGO is generally considered an inferior TOF-PET scintillator. In recent years, TOF-PET detectors based on the Cherenkov effect have been proposed. However, the low Cherenkov photon yield in the order of  ∼10 photons per event complicates energy discrimination-a severe disadvantage in clinical PET. The optical characteristics of BGO, in particular its high transparency down to 310 nm and its high refractive index of  ∼2.15, are expected to make it a good Cherenkov radiator. Here, we study the feasibility of combining event timing based on Cherenkov emission with energy discrimination based on scintillation in BGO, as a potential approach towards a cost-effective TOF-PET detector. Rise time measurements were performed using a time-correlated single photon counting (TCSPC) setup implemented on a digital photon counter (DPC) array, revealing a prompt luminescent component likely to be due to Cherenkov emission. Coincidence timing measurements were performed using BGO crystals with a cross-section of 3 mm  ×  3 mm and five different lengths between 3 mm and 20 mm, coupled to DPC arrays. Non-Gaussian coincidence spectra with a FWHM of 200 ps were obtained with the 27 mm

Topics: Bismuth; Cost-Benefit Analysis; Germanium; Humans; Photons; Positron-Emission Tomography; Scintillation Counting; Silicon

Topics: Amplifiers, Electronic; Bismuth; Electrons; Germanium; Photometry; Photons; Positron-Emission Tomography; Silicon; Ultraviolet Rays

The use of positron emission tomography combined with computed tomography (PET/CT) has brought about significant technological advancement in diagnostic imaging, and a number of PET/CT scanners with bismuth germanate detectors can perform imaging in both 2D and 3D acquisition modes. Nevertheless, certain image acquisition parameters and physical features of patients have to be considered when designing low-dose protocols in the 3D mode.. The aim of this study was to compare images acquired in 2D and 3D modes and establish a low-dose protocol for use in PET/CT imaging, decreasing patient exposure to radiation without compromising results.. A total of 30 patients, aged 4-72 years, participated in this prospective study, which was conducted at Albert Einstein Hospital, São Paulo, Brazil. Images were evaluated for picture quality, presence/absence of lesions and the number of lesions that were detectable in both acquisition modes.. The results consistently showed that the loss in image quality in the 3D mode did not affect exam interpretation and lesion detection when compared with 2D at higher dose and for a longer time.. We therefore conclude that administration of 3.7 MBq [(18)F]-fluorodeoxyglucose (FDG)/kg for an acquisition time of 3 min per FOV (field of view) is optimal for image acquisition in the 3D mode. This protocol, which reduces the acquisition time and radiation dose, is quite beneficial, especially for children.

Topics: Adolescent; Adult; Aged; Bismuth; Child; Child, Preschool; Clinical Protocols; Germanium; Humans; Imaging, Three-Dimensional; Middle Aged; Positron-Emission Tomography; Prospective Studies; Radiation Dosage; Tomography, X-Ray Computed; Young Adult

In this study, a digital gamma-gamma coincidence/anticoincidence spectrometer was developed and examined for low-level cosmogenic (22)Na and (7)Be in air-filter sample monitoring. The spectrometer consists of two bismuth germanate scintillators (BGO) and an XIA LLC Digital Gamma Finder (DGF)/Pixie-4 software and card package. The spectrometer design allows a more selective measurement of (22)Na with a significant background reduction by gamma-gamma coincidence events processing. Hence, the system provides a more sensitive way to quantify trace amounts of (22)Na than normal high resolution gamma spectrometry providing a critical limit of 3 mBq within a 20 h count. The use of a list-mode data acquisition technique enabled simultaneous determination of (22)Na and (7)Be activity concentrations using a single measurement by coincidence and anticoincidence mode respectively.

Topics: Beryllium; Bismuth; Germanium; Limit of Detection; Radiation Monitoring; Radioisotopes; Scintillation Counting; Sodium; Sodium Radioisotopes; Spectrometry, Gamma

The present work is focused on the enhancement of network former environment in lead-germanate glasses by bismuth ions doping. A series of bismuth-lead-germanate glasses with the xBi2O3·(100-x)[7GeO2·3PbO] composition glass where 0≤x≤30 mol% Bi2O3 were synthesized by melt-quenching method. The FTIR, UV-VIS spectroscopy and cyclic voltammetry were conducted on these samples to evaluate the doping effect of structure of the host matrix network. Our results indicate that direct incorporation of Bi2O3 into the lead-germanate network modifies the lead-germanate network and the internal structure of glass network is rearranged. The structural flexibility of the lead-germanate network is possible due to its incapacity to accommodate with the excess of oxygen atoms and the creation of bridging oxygen ions. Optical gap energy and refractive index were obtained as a function of Bi2O3 content. Gap energy values decrease as Bi2O3 content increased from 0 to 10 mol%. Further increase of Bi2O3 concentration beyond 10 mol% increased the gap energy values. These behaviors of the glass system can be explained by two mechanisms: (i) for x≤10 mol% Bi2O3--increase of degree of disorder of the host matrix because Bi2O3 is network modifier and (ii) for x>10 mol%--Bi2O3 acts as a network former. Cyclic voltammetry measurements using the glass system with 10Bi2O3·90[7GeO2·3PbO] composition as working electrode show the mobility of the lead ions, in agreement with UV-VIS data.

Topics: Bismuth; Electrochemical Techniques; Germanium; Glass; Ions; Lead; Optical Phenomena; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; X-Ray Diffraction

An Er3+/Yb3+ co-doped bismuth germanate glass is synthesized and analyzed. The radiative characteristics and mid-infrared spectroscopic properties are investigated under excitation of a conventional 980 nm laser diode. The prepared glass possesses higher spontaneous transition probability (68.82 s(-1)) and larger calculated emission cross-section (7.73×10(-21) cm2) corresponding to the 4I11/2→4I13/2 transition. The calculated energy migration coefficient (CDD) among Yb3+ ions is larger than the energy transfer coefficient (CDA) from Yb3+ to Er3+, indicating the energy transfer process assisted with energy migration. The excellent spectroscopic properties along with the outstanding thermal stability suggest that this glass may become an attractive host for developing solid state lasers operating in the mid-infrared range.

Topics: Bismuth; Energy Transfer; Erbium; Germanium; Glass; Spectrophotometry, Infrared; Ytterbium

Tests of a large volume Bismuth Germinate (BGO) detector were carried out to detect low energy prompt gamma-rays from boron and cadmium-contaminated water samples using a portable neutron generator-based Prompt Gamma Neutron Activation Analysis (PGNAA) setup. Inspite of strong interference between the sample- and the detector-associated prompt gamma-rays, an excellent agreement has been observed between the experimental and calculated yields of the prompt gamma-rays, indicating successful application of the large volume BGO detector in the PGNAA analysis of bulk samples using low energy prompt gamma-rays.

Topics: Bismuth; Equipment Design; Equipment Failure Analysis; Gamma Rays; Germanium; Radiation Dosage; Radiometry; Reproducibility of Results; Sensitivity and Specificity; Transducers; Water Pollutants, Radioactive

In quantitative measurements of small animal PET studies, blood sampling is limited due to the small amounts of blood such animals can provide. In addition, injection doses are quite limited. In this situation, a high-sensitivity well counter would be useful for reducing the amount of the blood sample needed from small animals. Bismuth germinate (BGO) has a high stopping power for high-energy gamma rays compared to NaI(Tl), which is commonly used for conventional well counters. We have developed a BGO well counter and have tested it for blood-sampling measurements in small animals. The BGO well counter uses a square BGO block (59 × 59 × 50 mm) with a square open space (27 × 27 × 34 mm) in the center of the block. The BGO block was optically coupled to a 59-mm square-shaped photomultiplier tube (PMT). Signals from the PMT were digitally processed for the integration and energy window setting. The results showed that the energy spectrum of the BGO well counter measured with a Na-22 point source provided counts that were about 6 times higher for a 1022-keV (511 keV × 2) gamma peak than the spectrum of a 2-in. NaI(Tl) well counter. The relative sensitivity of the developed BGO well counter was 3.4 times higher than that of a NaI(Tl) well counter. The time activity curve of arterial blood was obtained successfully with the BGO well counter for a F-18-FDG study on rat. The BGO well counter will contribute to reducing the amount of sampled blood and to improving the throughput of quantitative measurements in small animal PET studies.

Topics: Animals; Bismuth; Fluorodeoxyglucose F18; Germanium; Male; Positron-Emission Tomography; Rats; Rats, Wistar; Scintillation Counting

We compared two treatment planning methods for stereotactic boost for treating nasopharyngeal carcinoma (NPC): the use of conventional whole-body bismuth germanate (BGO) scintillator positron emission tomography (PET(CONV)WB) versus the new brain (BR) PET system using semiconductor detectors (PET(NEW)BR).. Twelve patients with NPC were enrolled in this study. [(18)F]Fluorodeoxyglucose-PET images were acquired using both the PET(NEW)BR and the PET(CONV)WB system on the same day. Computed tomography (CT) and two PET data sets were transferred to a treatment planning system, and the PET(CONV)WB and PET(NEW)BR images were coregistered with the same set of CT images. Window width and level values for all PET images were fixed at 3000 and 300, respectively. The gross tumor volume (GTV) was visually delineated on PET images by using either PET(CONV)WB (GTV(CONV)) images or PET(NEW)BR (GTV(NEW)) images. Assuming a stereotactic radiotherapy boost of 7 ports, the prescribed dose delivered to 95% of the planning target volume (PTV) was set to 2000 cGy in 4 fractions.. The average absolute volume (±standard deviation [SD]) of GTV(NEW) was 15.7 ml (±9.9) ml, and that of GTV(CONV) was 34.0 (±20.5) ml. The average GTV(NEW) was significantly smaller than that of GTV(CONV) (p = 0.0006). There was no statistically significant difference between the maximum dose (p = 0.0585) and the mean dose (p = 0.2748) of PTV. The radiotherapy treatment plan based on the new gross tumor volume (PLAN(NEW)) significantly reduced maximum doses to the cerebrum and cerebellum (p = 0.0418) and to brain stem (p = 0.0041).. Results of the present study suggest that the new brain PET system using semiconductor detectors can provide more accurate tumor delineation than the conventional whole-body BGO PET system and may be an important tool for functional and molecular radiotherapy treatment planning.

Topics: Adult; Aged; Bismuth; Brain; Carcinoma; Female; Fluorodeoxyglucose F18; Germanium; Humans; Male; Middle Aged; Multimodal Imaging; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms; Positron-Emission Tomography; Radiopharmaceuticals; Radiotherapy Planning, Computer-Assisted; Tomography, X-Ray Computed; Tumor Burden

Megavoltage, cone-beam computed tomography (MV CBCT) employing an electronic portal imaging device (EPID) is a highly promising technique for providing soft-tissue visualization in image-guided radiotherapy. However, current EPIDs based on active matrix flat-panel imagers (AMFPIs), which are regarded as the gold standard for portal imaging and referred to as conventional MV AMFPIs, require high radiation doses to achieve this goal due to poor x-ray detection efficiency (∼2% at 6 MV). To overcome this limitation, the incorporation of thick, segmented, crystalline scintillators, as a replacement for the phosphor screens used in these AMFPIs, has been shown to significantly improve the detective quantum efficiency (DQE) performance, leading to improved image quality for projection imaging at low dose. Toward the realization of practical AMFPIs capable of low dose, soft-tissue visualization using MV CBCT imaging, two prototype AMFPIs incorporating segmented scintillators with ∼11 mm thick CsI:Tl and Bi(4)Ge(3)O(12) (BGO) crystals were evaluated. Each scintillator consists of 120 × 60 crystalline elements separated by reflective septal walls, with an element-to-element pitch of 1.016 mm. The prototypes were evaluated using a bench-top CBCT system, allowing the acquisition of 180 projection, 360° tomographic scans with a 6 MV radiotherapy photon beam. Reconstructed images of a spatial resolution phantom, as well as of a water-equivalent phantom, embedded with tissue equivalent objects having electron densities (relative to water) varying from ∼0.28 to ∼1.70, were obtained down to one beam pulse per projection image, corresponding to a scan dose of ∼4 cGy--a dose similar to that required for a single portal image obtained from a conventional MV AMFPI. By virtue of their significantly improved DQE, the prototypes provided low contrast visualization, allowing clear delineation of an object with an electron density difference of ∼2.76%. Results of contrast, noise and contrast-to-noise ratio are presented as a function of dose and compared to those from a conventional MV AMFPI.

Topics: Bismuth; Cesium; Cone-Beam Computed Tomography; Crystallization; Germanium; Humans; Organ Specificity; Phantoms, Imaging; Radiation Dosage; Scintillation Counting; Thallium

We investigated the relationship between noise equivalent count (NEC) and axial field of view (AFOV) for PET scanners with AFOVs ranging from one-half to twice those of current clinical scanners. PET scanners with longer or shorter AFOVs could fulfill different clinical needs depending on exam volumes and site economics. Using previously validated Monte Carlo simulations, we modeled true, scattered and random coincidence counting rates for a PET ring diameter of 88 cm with 2, 4, 6, and 8 rings of detector blocks (AFOV 7.8, 15.5, 23.3, and 31.0 cm). Fully 3D acquisition mode was compared to full collimation (2D) and partial collimation (2.5D) modes. Counting rates were estimated for a 200 cm long version of the 20 cm diameter NEMA count-rate phantom and for an anthropomorphic object based on a patient scan. We estimated the live-time characteristics of the scanner from measured count-rate data and applied that estimate to the simulated results to obtain NEC as a function of object activity. We found NEC increased as a quadratic function of AFOV for 3D mode, and linearly in 2D mode. Partial collimation provided the highest overall NEC on the 2-block system and fully 3D mode provided the highest NEC on the 8-block system for clinically relevant activities. On the 4-, and 6-block systems 3D mode NEC was highest up to ∼300 MBq in the anthropomorphic phantom, above which 3D NEC dropped rapidly, and 2.5D NEC was highest. Projected total scan time to achieve NEC-density that matches current clinical practice in a typical oncology exam averaged 9, 15, 24, and 61 min for the 8-, 6-, 4-, and 2-block ring systems, when using optimal collimation. Increasing the AFOV should provide a greater than proportional increase in NEC, potentially benefiting patient throughput-to-cost ratio. Conversely, by using appropriate collimation, a two-ring (7.8 cm AFOV) system could acquire whole-body scans achieving NEC-density levels comparable to current standards within long, but feasible, scan times.

Topics: Bismuth; Germanium; Humans; Kinetics; Monte Carlo Method; Positron-Emission Tomography; Whole Body Imaging

An autoradiography method revealed intratumoral inhomogeneity in various solid tumors. It is becoming increasingly important to estimate intratumoral inhomogeneity. However, with low spatial resolution and high scatter noise, it is difficult to detect intratumoral inhomogeneity in clinical settings. We developed a new PET system with CdTe semiconductor detectors to provide images with high spatial resolution and low scatter noise. Both phantom images and patients' images were analyzed to evaluate intratumoral inhomogeneity.. This study was performed with a cold spot phantom that had 6-mm-diameter cold sphenoid defects, a dual-cylinder phantom with an adjusted concentration of 1:2, and an "H"-shaped hot phantom. These were surrounded with water. Phantom images and (18)F-FDG PET images of patients with nasopharyngeal cancer were compared with conventional bismuth germanate PET images. Profile curves for the phantoms were measured as peak-to-valley ratios to define contrast. Intratumoral inhomogeneity and tumor edge sharpness were evaluated on the images of the patients.. The contrast obtained with the semiconductor PET scanner (1.53) was 28% higher than that obtained with the conventional scanner (1.20) for the 6-mm-diameter cold sphenoid phantom. The contrast obtained with the semiconductor PET scanner (1.43) was 27% higher than that obtained with the conventional scanner (1.13) for the dual-cylinder phantom. Similarly, the 2-mm cold region between 1-mm hot rods was identified only by the new PET scanner and not by the conventional scanner. The new PET scanner identified intratumoral inhomogeneity in more detail than the conventional scanner in 6 of 10 patients. The tumor edge was sharper on the images obtained with the new PET scanner than on those obtained with the conventional scanner.. These phantom and clinical studies suggested that this new PET scanner has the potential for better identification of intratumoral inhomogeneity, probably because of its high spatial resolution and low scatter noise.

Topics: Adult; Aged; Bismuth; Cadmium Compounds; Carcinoma, Squamous Cell; Female; Germanium; Glucose; Humans; Male; Nasopharyngeal Neoplasms; Neoplasms; Phantoms, Imaging; Positron-Emission Tomography; Semiconductors; Tellurium; Time Factors

We investigate the spectroscopic properties of the 1.5-microm emission from the (4)I(13/2)-->(4)I(15/2) transition of Er(3+) ions in bismuth-germanate-lead glasses for applications in broadband fiber amplifiers. The emission peak locates at 1532nm with a full width at half-maximum (FWHM) of approximately 65nm. The measured lifetime and the calculated emission cross-section of this transition are 3.3ms and 8.66x10(-21)cm(2), respectively. IR-to-green-upconversion occurs simultaneously upon excitation of the 1.5-microm emission with a commercially available 980nm laser diode. Effects of PbF(2) content on the thermal stability, structure and spectroscopic properties of Er(3+)-doped bismuth-germanate-lead glasses have been examined. We find that the substitution with PbF(2) provides a couple of potentials: shortening the UV cutoff band and decreasing the phonon energy of host glasses. Codoping of Yb(3+) significantly enhances both the green-upconversion and 1.5-microm emission intensity by means of a nonradiative Yb(3+)-->Er(3+) energy transfer. Energy transfer processes and nonradiative phonon-assisted decays could account for the population of the (2)H(11/2) level, which is an emitting level of the green-upconversion of Er(3+). The results indicate the possibility towards the development of bismuth-germanate-lead based glasses as photonics devices.

Topics: Bismuth; Electric Conductivity; Erbium; Germanium; Glass; Lasers, Semiconductor; Lead; Luminescence; Spectrometry, Fluorescence; Spectrum Analysis, Raman; Temperature; Thermodynamics; Time Factors

The present study is a comparative investigation of the luminescence properties of (Lu,Y)(2)SiO(5):Ce (LYSO:Ce), Lu(2)SiO(5):Ce (LSO:Ce), Gd(2)SiO(5):Ce (GSO:Ce) and (Bi(4)Ge(3)O(12)) BGO single crystal scintillators under medical X-ray excitation. All scintillating crystals have dimensions of 10 x 10 x 10 mm(3) are non-hygroscopic exhibiting high radiation absorption efficiency in the energy range used in medical imaging applications. The comparative investigation was performed by determining the absolute luminescence efficiency (emitted light flux over incident X-ray exposure) in X-ray energies employed in general X-ray imaging (40-140 kV) and in mammographic X-ray imaging (22-49 kV). Additionally, light emission spectra of crystals at various X-ray energies were measured, in order to determine the spectral compatibility to optical photon detectors incorporated in medical imaging systems and the overall efficiency (effective efficiency) of a scintillator-optical detector combination. The light emission performance of LYSO:Ce and LSO:Ce scintillators studied was found very high for X-ray imaging.

Topics: Biophysical Phenomena; Biophysics; Bismuth; Crystallization; Female; Gamma Cameras; Germanium; Humans; Luminescence; Lutetium; Mammography; Positron-Emission Tomography; Radiography; Radiopharmaceuticals; Silicates; Yttrium

The absorption and upconversion fluorescence spectra of a series of Er3+/Yb3+-codoped xBi(2)O(3)-(90-x)GeO2-10Na(2)O (BGN x, x=31, 36, 41, 46 and 51 mol%) glasses have been studied. Intense green and red emission bands at around 533, 548 and 659 nm, corresponding to the 2H(11/2)-->4I(15/2), 4S(3/2)-->4I(15/2) and 4F(9/2)-->4I(15/2) transitions of Er3+, respectively, were simultaneously observed at room temperature. The dependence of intensities of upconversion emission on excitation power and possible upconversion mechanisms were evaluated and analyzed. The important role of Bi(2)O(3) in upconversion intensity is observed and its influence on the green (533 and 548 nm) and red (659 nm) emissions is compared and discussed. The influence of Bi(2)O(3) on the upconversion emissions has been investigated based on the IR spectra.

Topics: Bismuth; Erbium; Germanium; Glass; Spectrometry, Fluorescence; Spectrophotometry, Infrared; Ytterbium

Arsenic is an extremely toxic metal, which poses a significant problem in many mining environments. Arsenic contamination is also a major problem in ground and surface waters. A feasibility study was conducted to determine if neutron-activation analysis is a practical method of measuring in situ arsenic levels. The response of hypothetical well-logging tools to arsenic was simulated using a readily available Monte Carlo simulation code (MCNP). Simulations were made for probes with both hyperpure germanium (HPGe) and bismuth germanate (BGO) detectors using accelerator and isotopic neutron sources. Both sources produce similar results; however, the BGO detector is much more susceptible to spectral interference than the HPGe detector. Spectral interference from copper can preclude low-level arsenic measurements when using the BGO detector. Results show that a borehole probe could be built that would measure arsenic concentrations of 100 ppm by weight to an uncertainty of 50 ppm in about 15 min.

Topics: Arsenic; Bismuth; Computer Simulation; Feasibility Studies; Germanium; Mining; Monte Carlo Method; Neutron Activation Analysis; Water Pollutants, Chemical

The capability of a recently developed BGO detector system featuring a "self-collimating" structure to locate a point source was established by Monte Carlo simulations and by laboratory scale experiments. The detector system's capability to determine the direction of a nuclear plume resulting from a PWR1 or PWR2 type accident in stable atmospheric conditions by airborne monitoring of the 2.4 MeV photons emitted by 88Kr was established by Monte Carlo simulations.

Topics: Bismuth; Cesium Radioisotopes; Germanium; Humans; Krypton Radioisotopes; Monte Carlo Method; Radiation Monitoring; Radiation Protection; Radioactive Hazard Release

A feasibility study is presented for a small, low-cost, dedicated device for positron emission mammography. Two detector arrays above and below the breast would be placed in a conventional mammography unit. These detectors are sensitive to positron annihilation radiation, and are connected to a coincidence circuit and a multiplane image memory. Images of the distribution of positron-emitting isotope are obtained in real time by incrementing the memory location at the intersection of each line of response. Monte Carlo simulations of a breast phantom are compared with actual scans of this phantom in a conventional PET scanner. The simulations and experimental data are used to predict the performance of the proposed system. Spatial resolution experiments using very narrow bismuth germanate BGO crystals suggest that spatial resolutions of about 2 mm should be possible. The efficiency of the proposed device is about ten times that of a conventional brain scanner. The scatter fraction is greater, but the scattered radiation has a very flat distribution. By designing the device to fit in an existing mammography unit, conventional mammograms can be taken after the injection of the radio-pharmaceutical allowing exact registration of the emission and conventional mammographic images.

Topics: Biophysical Phenomena; Biophysics; Bismuth; Evaluation Studies as Topic; Female; Germanium; Humans; Mammography; Models, Structural; Monte Carlo Method; Radiographic Image Enhancement; Tomography, Emission-Computed

Calculations to predict the radiation environment for spacecraft in low earth orbit sometimes ignore the contribution from secondary radiation products. However, the contribution of secondaries, particularly neutrons, on heavy spacecraft or in planetary bodies can be of concern for biological systems. The Shuttle Activation Monitor (SAM) and Cosmic Radiation Effects and Activation Monitor (CREAM) experiments provide valuable data on secondary (as well as primary) radiation effects. Comparisons have been made between induced activity from flight-exposed samples, induced activity in a ground-irradiated sample, and Monte Carlo-derived predictions with and without secondaries. These comparisons show that for a flight-exposed sample, predictions which omit the secondary contribution result in a spectrum that is too low by a factor of 2. The addition of the secondaries results in a predicted spectrum that closely matches the measured data.

Topics: Bismuth; Germanium; Models, Theoretical; Monte Carlo Method; Neutrons; Protons; Radiation Monitoring; Radiation Protection; Space Flight

Topics: Anorexia Nervosa; Bismuth; Body Composition; Chlorine; Evaluation Studies as Topic; Extracellular Space; Germanium; Humans; Hydrogen; Models, Structural; Neutron Activation Analysis; Whole-Body Counting

Topics: Adipose Tissue; Bismuth; Body Composition; Carbon; Germanium; Humans; Male; Neutrons; Nitrogen; Oxygen; Scattering, Radiation; Sodium Iodide; Triglycerides

Recent advances in fully three-dimensional reconstruction for multi-ring PET scanners have led us to explore the potential of a prototype scanner based on the rotation of two opposing arrays of BGO block detectors. The prototype contains only one-third of the number of detectors in the equivalent full ring scanner, resulting in reduced cost. With a lower energy threshold at 250 keV, the absolute efficiency of the scanner is 0.5% and the scatter fraction is 35% for a 20-cm cylinder. Transaxial and axial spatial resolution is about 6 mm. The maximum noise equivalent count rate estimated for a 15-cm diameter cylinder is 36,000 cps at a concentration of 26 kBq/ml. The minimum scan time for a 18F-fluoro-2-deoxyglucose (FDG) brain study is 55 sec. The camera has been validated for clinical applications using both FDG and 82Rb.

Topics: Algorithms; Bismuth; Equipment Design; Gamma Cameras; Germanium; Humans; Image Processing, Computer-Assisted; Technology, Radiologic; Tomography, Emission-Computed

An X2/2B level solar flare occurred on 12 August, 1989, during the last day of the flight of the Space Shuttle Columbia (STS-28). Detectors on the GOES 7 satellite observed increased X-ray fluxes at approximately 1400 GMT and a solar particle event (SPE) at approximately 1600 GMT. Measurements with the bismuth germanate (BGO) detector of the Shuttle Activation Monitor (SAM) experiment on STS-28 showed factors of two to three increases in count rates at high latitudes comparable to those seen during South Atlantic Anomaly (SAA) passages beginning at about 1100 GMT. That increased activity was observed at both north and south high latitudes in the 57 degrees, 300 kilometer orbit and continued until the detector was turned off at 1800 GMT. Measurements made earlier in the flight over the same geographic coordinates did not produce the same levels of activity. This increase in activity may not be entirely accounted for by observed geomagnetic phenomena which were not related to the solar flare.

Topics: Bismuth; Gamma Rays; Germanium; Magnetics; Protons; Radiation Monitoring; Radiation Protection; Radiometry; Sodium Iodide; Solar System; Space Flight; Spacecraft

A robust, highly sensitive system is described for monitoring the concentration of positron emitting radioisotopes contained within arterial blood continuously withdrawn during PET studies of the brain. Utilizing a specially designed flow-through bismuth germanate detector, gammas are more effectively counted, replacing the less efficient method of positron detection with plastic detectors. A polytetrafluoroethylene flow path system has been developed to overcome the problem of highly cohesive tracers adhering to the tubing material. Blood is drawn through the system from the radial artery by a medically approved peristaltic pump. Syringe samples of blood are extracted periodically downstream of the detector, for calibrations, plasma assays, metabolic analysis and physiological measurements. The complete system, including efficient heavy lead shielding is contained on a bedside trolley. Blood activity is continuously recorded throughout the PET investigations, and stored directly by the scanning computer, and additionally backed up on disc by a P.C.

Topics: Bismuth; Blood Specimen Collection; Brain; Crystallization; Equipment Design; Germanium; Humans; Polytetrafluoroethylene; Radioactive Tracers; Tomography, Emission-Computed; Wrist

Topics: Bismuth; Body Composition; Chlorine; Germanium; Humans; Neutron Activation Analysis; Neutrons; Oxygen; Scattering, Radiation

Bismuth germanate (BGO) and barium fluoride (BaF2) scintillators are presently used in positron emission tomegraphy (PET) cameras. This study evaluates the important PET performance parameters of image resolution, true sensitivity, scatter background, accidental background, and realistic maximum radioactivity in the field of view for both BGO and BaF2 in an identical non-time-of-flight, whole-body camera configuration. These performance parameters are evaluated for three phantoms simulating (a) the head, (b) whole-body cross-section and (c) heart/kidney. This study finds that the high stopping power of BGO yields higher sensitivity, higher resolution, less vignetting, better immunity from scattered gamma, and lower accident/true ratio at any dose level. The faster BaF2 timing acceptance window is traded off by its vulnerability to noncoincidental scatter-gamma which increases accidental coincidences. The BGO is found to be a better choice for non-time-of-flight systems especially with large objects which produce a lot of noncoincidental scatter-gammas. This study also found that the practical diminishing return maximum activity within the field-of-view is approximately 20-25 mCi for existing conventional cameras.

Topics: Barium; Barium Compounds; Bismuth; Equipment Design; Evaluation Studies as Topic; Fluorides; Germanium; Humans; Models, Structural; Scintillation Counting; Tomography, Emission-Computed

Accurate description of the arterial time-activity curve (ATAC) is of paramount importance in quantitative determination of the regional cerebral blood flow (rCBF) using positron tomography following bolus i.v. injection of 0-15 labeled water. Frequent manual sampling from an arterial catheter does not permit sampling in less than 5-sec intervals and runs the risk of missing the arrival time or the peak count. A continuous ATAC monitoring system has been developed. This system consists of a single bismuth germinate detector in a lead shield and a constant-flow aspirator. The arterial blood was drawn continuously from a catheter within the brachial artery into an extended tube and its activity was monitored by the detector as the detector time-activity curve (DTAC). Comparison with the manual sampling from the contralateral brachial artery in the same run revealed that the DTAC differed from the manual sampling not only in delayed arrival but also in the shape of the curve, which was dispersed because of viscosity and the width of the detector field of view. However, deconvolution of DTAC using the experimentally obtained system step response provided an accurate arterial time course, which successfully filled in the gaps of the manual sampling. Moreover, water and blood showed different dispersion in the step response, suggesting that the system function should be determined using blood or a fluid of similar hydrodynamic nature.

Topics: Arteries; Bismuth; Germanium; Humans; Monitoring, Physiologic; Regional Blood Flow; Time Factors

In order to increase the detection efficiency and also reduce the interdetector spillage, a new wedge-shaped BGO scintillation detector array is proposed. By shaping the front part of a detector as a wedge, the absorption path becomes longer, particularly for obliquely incident photons, thereby improving the uniformity in the sensitivity for the incident photons of different angles. To demonstrate the effectiveness of the proposed detector shape, a Monte Carlo simulation was performed and the results are presented.

Topics: Bismuth; Germanium; Scintillation Counting; Tomography, Emission-Computed