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Over the past decade, there has been intense interest in the modernization of scanners for cardiac SPECT imaging, with major changes in the design and functionality of hardware and software. This article aims at concisely reviewing recent developments in the field of detector materials, collimators, scanner configuration, and data acquisition strategies, as well as the new software reconstruction techniques typically associated with the new hardware. Since the new equipment and techniques can be employed either to reduce study acquisition time or to decrease radiation dose to the patient, the trade-off between these 2 desirable outcomes is also explored. [ABSTRACT FROM AUTHOR]

We studied the application of statistical reconstruction algorithms, namely maximum likelihood and least squares methods, to the problem of event reconstruction in a dual phase liquid xenon detector. An iterative method was developed for in-situ reconstruction of the PMT light response functions from calibration data taken with an uncollimated \gamma-ray source. Using the techniques described, the performance of the ZEPLIN-III dark matter detector was studied for 122 keV \gamma-rays. For the inner part of the detector (R<100\ \ mm), spatial resolutions of 13 mm and 1.6 mm FWHM were measured in the horizontal plane for primary and secondary scintillation, respectively. An energy resolution of 8.1% FWHM was achieved at that energy. The possibility of using this technique for improving performance and reducing cost of scintillation cameras for medical applications is currently under study. [ABSTRACT FROM AUTHOR]

Objective: Strontium-89 (Sr) chloride has been used to treat metastases in bone. A method to visualize the distribution of Sr chloride with a scintillation camera was developed in 1996. Studies using bremsstrahlung imaging have shown that Sr accumulates in bone and that the bremsstrahlung generated from biological tissue surrounding bone does not exceed 30 keV. However, it was not clear how low-energy bremsstrahlung from bone can produce peak energy levels of around 75 keV. We speculate that a different (unidentified) factor is involved. Methods: The energy spectrum of an Sr source was acquired with a scintillation camera with or without a low-to-medium-energy general-purpose collimator. The energy window was set at 20-650 keV for 4 windows. A 50-mm thick acrylic block was placed between the scintillation camera and the Sr source to exclude the effects of bremsstrahlung. The energy spectrum of Sr covered with lead was acquired using the scintillation camera without a collimator. Results: With the collimator the energy spectrum curve was similar to that without the 50 mm of acrylic. The energy spectrum curve showed peaks at about 75, 170, and 520 keV. Without the collimator the energy spectrum showed a similar curve but no peak at 75 keV peak. The curve was similar to that obtained with the scintillation camera and the collimator; however, the curve obtained when the Sr source had been placed in a lead container was similar to that obtained when the source was unshielded, and the collimator was not attached to the scintillation camera. Conclusion: If bremsstrahlung of Sr produces an image, a low-energy spectrum region should decrease when acrylic is placed between the Sr source and the scintillation camera. However, similar curves were obtained both with the acrylic in place and without the acrylic. Therefore, we believe that the radiation detected by the scintillation camera was not bremsstrahlung due to the beta rays of Sr. Most Sr preparations are contaminated by Sr, and most of the gamma ray energy of Sr is 514 keV. The scintillation camera detected the characteristic X-ray energy of about 75 keV from the materials of the collimator (lead and others) through interaction with the gamma rays of Sr. [ABSTRACT FROM AUTHOR]

Abstract: A position reconstruction algorithm was implemented for a liquid xenon scintillation camera aiming to reduce the uncertainty in the measurement of the energy of nuclear recoils from neutron scattering. The algorithm is based on the maximum likelihood (ML) technique. The performance of the algorithm was assessed both with simulated and experimental data. A resolution of σxy =6.7mm was measured with 122keV γ-rays at the bottom of the chamber. For 10keV γ-rays simulated events, a resolution of σxy ⩽20mm was obtained for 80% of the active volume of the detector. By means of the position reconstruction, the uncertainty of the nuclear recoil energy in the neutron scattering experiment was reduced by a factor of 2–3, depending on the energy. [Copyright &y& Elsevier]

Abstract: The principal limiting factor in the clinical acceptance of scintimammography is certainly its low sensitivity for cancers sized <1cm, mainly due to the lack of equipment specifically designed for breast imaging. The National Institute of Nuclear Physics (INFN) has been developing a new scintillation camera based on Lanthanum tri-Bromide Cerium-doped crystal (LaBr3:Ce), that demonstrating superior imaging performances with respect to the dedicated scintillation γ-camera that was previously developed. The proposed detector consists of continuous LaBr3:Ce scintillator crystal coupled to a Hamamatsu H8500 Flat Panel PMT. One centimeter thick crystal has been chosen to increase crystal detection efficiency. In this paper, we propose a comparison and evaluation between lanthanum γ-camera and a Multi PSPMT camera, NaI(Tl) discrete pixel based, previously developed under “IMI” Italian project for technological transfer of INFN. A phantom study has been developed to test both the cameras before introducing them in clinical trials. High resolution scans produced by LaBr3:Ce camera showed higher tumor contrast with a detailed imaging of uptake area than pixellated NaI(Tl) dedicated camera. Furthermore, with the lanthanum camera, the Signal-to-Noise Ratio (SNR) value was increased for a lesion as small as 5mm, with a consequent strong improvement in detectability. [Copyright &y& Elsevier]

Abstract: The aim of the present study was to investigate in detail the variation of the intrinsic spatial resolution across the useful field of view (UFOV) of γ-cameras and to explore whether this variation could lead to observable effects in clinical images. Two γ-cameras were used, without their collimators, to acquire 560 99mTc point source images at different points across their UFOVs, in order to measure the intrinsic spatial resolution at each point. Possible clinical effects of the resolution variation were examined on images of a thyroid phantom using a LEHR collimator, acquired at different locations on the UFOV and at various distances from the collimator. The γ-camera intrinsic resolution varied significantly across the UFOV, being generally lower at the central region and deteriorating at the edges. Pronounced local maxima and minima were found at points corresponding to the centers of the photomultiplier tubes (PMTs) and halfway in between. Maximum differences of more than 50% were observed between the points presenting the best and worst intrinsic resolution. Differences between neighboring points reached 17%. The effects of resolution variation were clearly observable on the thyroid phantom images. It was concluded that an appropriate correction algorithm might be necessary in order to correct for the variation of the intrinsic spatial resolution across the UFOV of γ-cameras. [Copyright &y& Elsevier]

In 153 children suffering from various renal or urological disease a total of 179 individual and regional renal clearance studies were performed using 123-I-hippuran and a scintillation camera. The clinical diagnoses and questions before and the therapeutic consequences after clearance determinations are analyzed. The dynamic information fo sequential scintigraphy combined with renal clearance determination allow a quantitative estimation of the individual and regional kidney function. The method is considerably helpful in cases of unilateral small kidneys, obstructive uropathies, duplication of the urinary tract, and segmental renal disease. [ABSTRACT FROM AUTHOR]

Cobalt-57 flood sources are often used for system flood-field uniformity checks of scintillation camera performance. Such sources are now available in large sizes and with high activities. Uniformity images using newCo sources have shown artefacts which are not present in uniformity images obtained from technetium-99m flood sources of the same activity. The high-energy photons emitted byCo and cobalt isotope impurities appear to influence the images obtained. This was investigated in three cameras using threeCo sources of different age. The flood-field images obtained with theCo sources showed non-uniformity patterns that were dependent on the age of the cobalt source, the distance of the source to the collimator, and the specific camera type. Quantification of the uniformity images reflected these findings. Energy spectra of a newCO source, obtained with an external 1024-channel analyser connected to the camera., showed a broad tail of high-energy photons above the 122-keV photopeak, due to Compton scatter and collimator penetration. This tail diminished with older sources and with increased source to collimator distance, indicating that in both situations fewer high-energy photons were being measured by the camera system. This tail of high-energy photons contributes to the total count rate, but because this is not obvious from the counts observed in the photopeak window, the camera can unsuspectingly be operated at too high a total countrate where pile-up effects become significant. Caution is therefore advised when usingCo sources. Problems may be minimized by purchasing low-activity sources (certainly no more than 370 MBq), by placing the source at a distance from the collimator, e.g. 50 cm, by allowing a new source to decay, and by manufacturers producingCo sources without detectable radioactive contaminants. [ABSTRACT FROM AUTHOR]

The purpose of this study was to describe the function of platelets throughout their life span by expressing their in vivo distribution and kinetic behaviour in mathematical terms by using multicompartmental analysis. The distribution of indium-111 labelled platelets in five normal subjects was imaged and quantified with a scintillation camera image processing system. Serial blood samples were also obtained. The data were modelled using the SAAM (Simulation Analysis and Modelling) compartmental computer program. Five models were entertained to evaluate the role of platelets that were either functional or injured during collection and their interaction with the liver, spleen and vascular endothelium. Models were evaluated by comparing F values calculated from the least squares estimate obtained from each model. The Dornhorst function was used to describe the sequestration of platelets in the compartmental model. Results indicated that the data could not be satisfactorily simulated when compartments were included that simulated only functional and sequestered platelets (model 1). It was necessary to include compartments that simulated the kinetics of collection-injured plateles in the liver (model 2) and spleen (model 3). The model that simulated the interaction with the vascular endothelium (model 5) showed a visual but not significant improvement in the fitting of the observed data compared to model 3. The mean organ uptake and range indicated in parentheses were calculated at equilibrium. There were 20% (15%-27%) of the injected platelets in the spleen, 10% (8%-11%) in the liver and 70% (64%-75%) in the circulation. The relatively high accumulation of activity in the spleen was as a result of the slow transit time of the functional platelets through the spleen of 5.1 (3.5-6.0) min compared with the transit time through the liver of 0.33 (0.19-0.50) min. The 9% (5%-12%) collection-injured platelets in the spleen and 10% (5%-16%) in the liver had longer transit times than functional platelets. Platelet sequestration was well simulated with the compartmental model. The mean platelet survival time estimated by the compartmental model and standard curve fitting techniques did not differ significantly. A multicompartmental model and reference range for platelet kinetics have been established and may prove to be clinically useful in platelet disease. [ABSTRACT FROM AUTHOR]

Characterization of the count-rate performance of scintillation cameras should include not only the specification of count losses. At high count rates, there is also an image distortion due to the mispositioning of pile-up events. In this paper a simple and clinically relevant procedure to quantify this distortion is presented. The images of a square uniform technetium-99m phantom at high and low count rates are used. The fraction of the total counts being correctly positioned is determined as the peripheral count density divided by the total average count density. This ratio, corrected for the camera non-uniformity at low count rates, is called the 'positioning ability'. According to the National Electrical Manufacturers' Association (NEMA), the 'system count rate performance with scatter' should be reported as the measured count rate giving 20% count losses. In this paper it is suggested that this measure be complemented by a measure of the fraction correct positioned events at this count rate. This fraction, the 'high count rate positioning ability', can be easily and accurately measured using our method. The method has been tested on two different scintillation cameras. For one of them the high count rate positioning ability was determined as 91% at a measured count rate of 30000 s with 20% count losses. For the other camera, the corresponding figures were 88% at 59000 s and close to 100% at 38000 s, before and after the installation of a new pile-up rejection circuit, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Ricerca in Clinica E in Laboratorio is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ricerca in Clinica E in Laboratorio is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ricerca in Clinica E in Laboratorio is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ricerca in Clinica E in Laboratorio is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose of this article is to introduce fundamental studies on improvement of count rate performance of scintillation detectors which Dr. Eiichi Tanaka dedicated himself to carrying out. He proposed a new technique based on the combination of pulse shortening and selective integration in which the integration period is not fixed but shortened by the arrival of the following pulse. Theoretical analysis of the degradation of the statistical component of resolution is made for the proposed system with delay line pulse shortening, and the factor of resolution loss is formulated as a function of the input pulse rate. A new method is also presented for determining the statistical component of resolution separately from the non-statistical system resolution. Preliminary experiments with a NaI (Tl) detector had been carried out, the results of which are consistent with the theoretical prediction. The related works are also introduced.

At present scintillation gamma camera plays key role in nuclear medicine as planner and tomographic single photon imaging modality. The basic technology of gamma camera made remarkable progress carried out by many researchers and engineers from around 1970 to 1980 and reached some matured stage as analog signal processing. Among them Dr. E. Tanaka made key contribution through the proposal of "Ideal arithmetics for position computer" (1969) and its implementation by the delay line time conversion (1970). These works triggered other unique position computing method applied to gamma camera products. This article reviews these technological progresses and outlines the next advances of gamma camera in the digital computer era.