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We present here a 16-channels ASIC for SiPMs readout in gamma-ray spectroscopy applications. Thanks to the automatic-gain-adjustment technique, the ASIC allows to achieve a high Dynamic Range (85dB). In gamma-ray measurements with SiPMs and LaBr3 scintillator, the ASIC allows to achieve PMT-like spectroscopy performances as well as capability to reconstuct the gamma photon point of interaction in scintillation crystals.

To observe the direct effect of molybdenum reinforcement on nuclear radiation shielding properties, a detailed investigation was performed with a group of bismuth borate glasses. Accordingly, glass samples with the nominal compositions (65-x)B2O3 + 20Bi(2)O(3) + 15Na(2)O + xMoO(3): x = 0, 1.5, 3, 4.5, 6 and 7.5 wt% have been synthesized by the solid state conventional method. The samples were named as M0 (x = 0), M1 (x = 1.5), M2 (x = 3), M3 (x = 4.5), M4 (x = 6) and M5 (x = 7.5). Physical characteristics and gamma-photon attenuation properties of (M0-M5) glasses have been investigated via MCNPX simulation code and XCOM program. XRD patterns confirmed that M0-M5 glasses were in amorphous nature. The density of the prepared glasses increased from 4.4104 for M0 glass sample to 5.3012 gm cm(-3), while molar volume decreased from 33.50083 to 28.92114 cm(3) mol(-1). The mass attenuation coefficient (mu(m)) increased with the increment of MoO3 concentration in mol% and followed the order: (M0)mu(m) < (M1)mu(m) < (M2)mu(m) < (M3)mu(m) < (M4)mu(m) < (M5)mu(m) at all photon energies. The mean free path (MFP), half value layer (HVL), and tenth value layer (TVL) for the prepared glasses M0-M5 have the same trend and follow the order: (M5)(MFP, HVL, TVL) < (M4) (MFP, HVL, TVL) < (M3) (MFP, HVL, TVL) < (M2) (MFP, HVL, TVL) < (M1) (MFP, HVL, TVL) < (M1) (MFP, HVL, TVL). The M5 glass sample (with maximum MoO3) achieved highest effective atomic number (Z(eff))and equivalent atomic numbers (Z(eq)) values for all photon energy ranges (low-medium-high). Among all the glass samples, the exposure build-up factor (EBF) and energy absorption build-up factor (EABF) values for M5 glass sample with the highest MoO3 additive are minimum due to the low amount of photons accumulated. These results indicate that M5 glass sample theoretically provides maximum protection for gamma-rays among all the samples.

In this paper we present the development of a modelling convention and a modelling environment, called PetDetSim, able to describe different PET detector block geometries. Using the developed simulation environment, the PET detector block designer can easily define different detector block configurations and test their optical behaviour regarding the characteristic features that determine the imaging quality of the device. In addition to the common optical behaviour of the detector block the developed modelling environment is also able to model gamma photon penetration. The PetDetSim environment is designed to use on a computer cluster and in a grid computing environment in order to reduce the computation time of the simulation. The validation of PetDetSim has been successfully done in the case of basic detector models, i.e. consisting of a single crystal needle.

In this paper we present the development of a modelling convention and a modelling environment, called PetDetSim, able to describe different PET detector block geometries. By the developed simulation environment the PET detector block designer can easily define different detector block configurations and test their optical behaviour regarding the characteristic features defining the imaging quality of the device. Beside the common optical behaviour of the detector block the developed modelling environment is also able to model gamma photon penetration. The PetDetSim environment is designed to use on a computer cluster and in a grid computing environment in order to reduce the computation time of the simulation. The validation of PetDetSim has been successfully done in the case of basic detector models, i.e. consisting of a single crystal needle.

The gamma photons continue to soften in energy as the number of scatterings increases in the target having finite dimensions both in depth and lateral dimensions. The number of multiply scattered photons increases with an increase in target thickness, and saturates at a particular value of the target thickness known as saturation thickness (depth). The present measurements are carried out to study the energy dependence of saturation thickness of multiply scattered gamma photons from targets of various thicknesses. The scattered photons are detected by a properly shielded NaI(Tl) gamma ray detector placed at 90° to the incident beam. We observe that the saturation thickness increases with increasing incident gamma photon energy. Monte Carlo calculations based upon the package developed by Bauer and Pattison [Compton scattering experiments at the HMI (1981), HMI-B 364, pp. 1–106] support the present experimental results.

A new approach to the observation of electromagnetic-induced transparency in gamma optics is proposed. For this purpose, the propagation of a resonant gamma photon in a 57Fe magnetic medium affected by an external radiofrequency (RF) field is considered. It is demonstrated that, in the case of crossing-anticrossing, a resonant RF field significantly transforms gamma-optical properties of the medium that become dependent on its parameters. This allows coherent control of the group velocity of gamma photons and controlled filtering of unpolarized gamma radiation in the sample to be realized.

Purpose: This preliminary study retrospectively evaluated the ability of intraoperative localization of recurrent melanoma using F-18 fluorodeoxyglucose (FDG) and a probe sensitive to both high-energy gamma rays and positrons to enable complete tumor resection and improved patient outcome. Materials and Methods: Three hours before surgery for resection of recurrent melanoma, 5 patients (mean age, 52 ± 22 years) with a history of local surgery, radiation therapy, and/or large habitus received 14.6 ± 3.2 mCi of F-18 FDG. Intraoperative tumor localization was performed with a radiation probe (PET-Probe; IntraMedical Imaging LLC, Los Angeles, CA). Intraoperative tumor tissue activities, background tissue activities, pathology results, and patient follow up (clinical/imaging) were recorded. Results: Eight of the 19 surgical specimens were identified by the probe as having increased FDG uptake when compared with the surrounding tissues before resection. All 8 specimens contained melanoma. Of the 11 specimens that were not identified using the probe, one contained melanoma, yielding a sensitivity of 89% (8 of 9) and a specificity of 100% (10 of 10). In 3 of the 5 cases, the probe allowed the identification of nonvisualized and nonpalpable tumor foci that were later confirmed pathologic. At an average follow up of 210 days (range, 30–515 days), 2 of 5 patients had no evidence of recurrent melanoma by clinical or radiographic evaluations. Conclusion: In the setting of recurrent melanoma, there appear to be potential benefits to intraoperative detection with FDG and a positron-detecting probe, particularly in cases with challenging or altered anatomy.

153Sm ( t 1 / 2 = 46 h ) emits a 103 keV gamma photon and two medium-energy beta particles. Five mCi of Samarium-153 ethylenediaminetetramethylenephosphonic acid (153Sm-EDTMP) were administered to a clinically normal dog and whole body scans were obtained at 15 min, 2 h, and 24 h post-injection (PI). Regions of interest (ROIs) were drawn representing abdomen, knee, rib, vertebral bodies, bladder, kidney, and liver, in each image. For each ROI, the mean intensity and standard deviation were computed, and a histogram was created. Clinically significant increased uptakes were found in liver and kidney.

Needs in medical diagnosis, especially for early and reliable breast cancer detection, lead us to consider developments in scintillation crystals and position sensitive photomultiplier tubes (PSPMT) in order to develop a high-resolution medium field γ -ray imaging device. However the ideal detector for γ -rays represents a compromise between many conflicting requirements. In order to optimize different parameters involved in the detection process, we have developed a Monte Carlo simulation software. Its aim was to study the light distribution produced by a gamma photon interacting with a pixellated scintillation crystal coupled to a PSPMT array. Several crystal properties were taken into account as well as the intrinsic response of PSPMTs. Images obtained by simulations are compared with experimental results. Agreement between simulation and experimental results validate our simulation model.

Background Intraoperative in situ identification of 18F-FDG-avid tissue sites during radioguided oncologic surgery remains a significant challenge for surgeons. The purpose of our study was to evaluate the 1.5-to-1 ratiometric threshold criteria method versus the three-sigma statistical threshold criteria method for determination of gamma detection probe positivity for intraoperative in situ identification of presumed abnormal 18F-FDG-avid tissue sites in a manner that was independent of the specific type of gamma detection probe used. Methods From among 52 patients undergoing appropriate in situ evaluation of presumed abnormal 18F-FDG-avid tissue sites during 18F-FDG-directed surgery using 6 available gamma detection probe systems, a total of 401 intraoperative gamma detection probe measurement sets of in situ counts per second measurements were cumulatively taken. Results For the 401 intraoperative gamma detection probe measurement sets, probe positivity was successfully met by the 1.5-to-1 ratiometric threshold criteria method in 150/401 instances (37.4%) and by the three-sigma statistical threshold criteria method in 259/401 instances (64.6%) (P

The progress in diagnostic nuclear medicine over the years since the discovery of 99m Tc is indeed phenomenal. Over 80% of the radiopharmaceuticals currently being used make use of this short-lived, metastable radionuclide, which has reigned as the workhorse of diagnostic nuclear medicine. The preeminence of 99m Tc is attributable to its optimal nuclear properties of a short half-life and a gamma photon emission of 140 keV, which is suitable for high-efficiency detection and which results in low radiation exposure to the patient. 99m TcO 4 − , which is readily available as a column eluate from a 99 Mo/ 99m Tc generator, is reduced in the presence of chelating agents. The versatile chemistry of technetium emerging from the 8 possible oxidation states, along with a proper understanding of the structure-biologic activity relationship, has been exploited to yield a plethora of products meant for morphologic and functional imaging of different organs. This article reviews the evolution of 99m Tc dating back to its discovery, the development of 99 Mo/ 99m Tc generators, and the efforts to exploit the diverse chemistry of the element to explore a spectrum of compounds for diagnostic imaging, planar, and single photon emission computed tomography. A brief outline of the 99m Tc radiopharmaceuticals currently being used has been categorically presented according to the organs being imaged. Newer methods of labeling involving bifunctional chelating agents (which encompass the "3+1" ligand system, Tc(CO) 3 +1 -containing chelates, hydrazinonicotinamide, water-soluble phosphines, and other Tc-carrying moieties) have added a new dimension for the preparation of novel technetium compounds. These developments in technetium chemistry have opened new avenues in the field of diagnostic imaging. These include fundamental aspects in the design and development of target-specific agents, including antibodies, peptides, steroids, and other small molecules that have specific receptor affinity.

Gamma-ray self-absorption in stainless steel samples has been studied with an experimental method based on fast neutron activation and a Monte Carlo calculation technique adapted to the experimental conditions. A relation between self-absorption and absorption of γ-photons inside stainless steel samples was found. The influence of the γ-ray energy and sample depth have been investigated. Agreement between the two methods has been found.

Positron emission tomography (PET) has been in existence since the 1970s due in large part to the pioneering work of Michael Phelps, PhD, Michel Ter-Pogossian, PhD, and others in the fields of medical physics and nuclear medicine [1]. Although initially a research tool, over the past 10 years PET has become increasingly used in the clinical setting, particularly after CMS (the Centers for Medicare and Medicaid Services, formerly known as the Health Care Financing Administration or HCFA) began reimbursing for PET evaluation of myocardial perfusion in 1995. Clinical utilization rose dramatically in 1998, when CMS began reimbursing for PET evaluation of solitary pulmonary nodules and initial staging of lung cancer. (CMS coverage as it relates to PET is covered in detail in Chapter 2.) 1998 also saw the creation of the first PET/computed tomography (CT) hybrid system, and in 2001, such systems became commercially available. Major manufacturers such as General Electric, Siemens, and Philips are now combining their latest CT technology with their latest PET technology to create very powerful hybrid systems that are the industry mainstay. PET/CT hybrids represent the state of the art in PET scanning, and it is estimated that PET/CT combination systems comprise 90% of sales in the current PET market [2]. The evolution of PET from its beginnings as an instrument of research to its present day wide and growing use in cancer, cardiac, and neurological imaging has resulted in instrumentation that is making a major impact in clinical care. Before launching an in-depth discussion of the clinical applications of PET, it is important to describe the fundamental basic scientific principles behind nuclear medicine imaging, of which PET is a part.

Technetium generators are loaded with molybdenum-99 (99Mo), that has a 66-h half life and decays to technetium-99 m (9mTc). 99Tc with a single 140 keV gamma photon emission and a 6-h half life is an ideal isotope for nuclear medicine imaging. Many nuclear medicine units receive generators and use the 99Tc elution to label a variety of prepared chemical species for the majority of the studies they perform. Other options are receiving bulk 99mTc and doing the same tagging or getting unit doses of already labeled pharmaceuticals. Units using generators must meet requirements spelled out in regulations of the Nuclear Regulatory Commission, Title 10, CFR, parts 20, 35, and 71 as well as the Department of Transportation, Title 49, CFR, part 173. The form described in this paper was an attempt to get all of the required records for each individual generator on a single sheet of paper.

A simple and economical passive graded shielding which is combination of low and high Z materials for HPGe detector for background radiation minimisation is developed for better identification of the peaks in acquired spectrum by reducing Compton continuum. The present paper discusses the design and advantages of the passive graded shielding (lead + copper + aluminium) which encloses the HPGe detector. The passive graded shielding improved sensitivity of the detector and reduced Minimum Detectable Activity (MDA) for planchet source from 19.6% to 11.7% for gamma photon energies in the range of 81–1408 keV and brought down the MDA, 35.25 GBq d –1 and 35.26 GBq d –1 for 133 Xe and 135 Xe respectively which was 72.31 GBq d –1 and 78.27 GBq d –1 for noble gases in gaseous effluents before shielding of the detector. The passive graded shielding as integral part is considerably very useful for radiological protection at nuclear power/research reactors by minimising background radiation.

Malignant melanoma is a highly metastatic tumor to the skin, liver, lung and especially the brain. Patients with brain metastases have a poor prognosis despite aggressive chemo-and radiotherapy. Many of these patients have disseminated melanoma but eventually succumb to their cerebral metastatic disease.

Radioisotope generator systems have traditionally played a central role in nuclear medicine in providing radioisotopes for both research and clinical applications. A resurgence of interest in generator development has been stimulated by advances in antibody technology, instrumentation development, and positron emission tomography (PET). Complementary advances in the development of new chelating agents and radiolabeling techniques for attachment of radioisotopes to various tissue-specific agents have given further impetus to generator research. Widespread interest in the use of antibodies for the radioimmunodetection and therapy of cancer requires readily available sources of radioisotopes with the optimal properties. In this paper, the development of several tungsten-188/rhenium-188 prototype generators which provide rhenium-188 for radioimmunotherapy (RAIT) is discussed. We have recently demonstrated that carrier-free iridium-194 can be obtained from the activated carbon system from decay of reactor-produced osmium-194 for potential RAIT applications. Instrumentation advances such as the new generation of high-count-rate (“fast”) gamma camera systems for first-pass technology require the availability of generator-produced ultra short-lived radioisotopes for radionuclide angiography (RNA). The activated carbon generator is an efficient system to obtain ultra short-lived iridium-191m from osmium-191 for RNA. In addition, the growing number of PET centers has stimulated research in generators which provide positron-emitting radioisotopes. Copper-62, obtained from the zinc-62 generator, is currently used for PET evaluation of organ perfusion. The availability of the parent radioisotopes, the fabrication and use of these generators, and the practical factors for use of these systems in the radiopharmacy are discussed.

Experimental data which demonstrate the potential of obtaining bearing information on gamma ray photon sources at ranges out to 1200 feet are presented. Collimation of multislit collimators was achieved with beamwidths of approximately 0.5° and 17°. Energy levels of 0.661 MeV from 137Cs and 1.17 and 1.33 MeV from 60Co sources were used with effective strengths up to 20 curie. The dependence of the parameters affecting angular accuracy was evaluated as a function of range, base energies and containments in the ray path.

The performance characteristics presented in this paper are: (1) the characteristics of gamma photon imaging with the Digital Autofluoroscope, (2) the resolution and efficiency of multihole and pinhole collimators, (3) a quantitative discussion of the image distortion inherent in pinhole collimators and of the penetration of the pinhole edges. In this discussion, it is pointed out that the various correction modes available, such as normalization of stored data and background suppression, are a means of removing the image distortion evident with pinhole collimators and of restoring image quality loss due to penetration of septa and pinhole edges. Also discussed is the use of the pinhole collimator as a means of magnifying small organs and minifying large ones.

In 1949 and 1950, Dudley and his associates (1, 2) showed that radiogallium 72 concentrated in areas of osteogenic activity, but Brucer et al. (3) subsequently demonstrated the impracticability of use of the isotope therapeutically because of toxicity of the non-radioactive carrier. Later, Desgrez et al. (4) investigated further the distribution of radioactive gallium in the skeleton and particularly in bone tumors. More recently Bauer and his co-workers (5, 6) found a high uptake of Sr85 by external counting over skeletal lesions such as fractures, metastatic carcinoma, eosinophilic granuloma, chondroma, osteomyelitis, and Paget's disease. In 1961, Fleming and his group first demonstrated the use of Sr85 for the photoscanning of bone lesions (7). Strontium 85 is admirably suited for photoscanning since, in its decay by electron capture to stable rubidium 85, a single gamma photon of 0.51 Mev is emitted. The material is administered intravenously, 50 µc to adults and 20 µc to patients under twenty years o...

Our knowledge of the pharmacokinetics of analgesics and antimigraine drugs in cranial structures is incomplete. This is mainly due to the difficulties of sampling blood or tissue from the region in question. However, the development of positron emission tomography (PET) has made it possible to obtain cross-sectional images of the distribution of 11C-labeled drugs and metabolites in the living animal. PET studies with 11C-labeled drugs make dynamic quantitative in vivo autoradiography of the head possible.

Although the role of blood platelets in health and disease may be assessed with in vitro methods such as platelet aggregometry, these have limited value and have been found wanting in the clinical situation, except in a few well-defined diseases. Recently investigators have relied increasingly on in vivo measurements of platelet behaviour. For many years the determination of platelet survival time was regarded as the best determinant of in vivo platelet behavior. It was also accepted that this was best done with sodium-dichromate as platelet label (1). In an important systematic investigation of alternative gamma-emitting radionuclides, Thakur(2) recommended In-111 as a suitable and preferable platelet label. The discovery of oxine and other chelates, has now established the superiority of In-111-complexes over Cr-51 as a platelet label.