Gamma Camera System Research Articles

Feasibility study of real-time imaging of an Ir-192 source using compact gamma camera with curved diverging collimator for brachytherapy

Brachytherapy is a treatment method that requires the accurate positioning of a radioactive source to deliver high doses to a tumor while minimizing exposure to surrounding tissues. Herein, we propose a compact gamma camera system based on a diverging collimator for real-time source positioning during brachytherapy. In the process of developing and fabricating such a gamma camera system, Monte Carlo simulations for diverging and pinhole collimators are performed under conditions that are similar to the actual detection environment, with the camera-to-source distance set at 50 cm to verify the feasibility of the gamma camera. Full width at half maximum (FWHM) and signal-to-noise ratio (SNR) values are analyzed based on the horizontal and vertical profiles at each location as the source shifts stepwise from the center to the right and diagonal direction. On average, the diverging collimator had FWHM values of 18 and 13 mm and SNR values of 30 and 31, while the pinhole collimator had FWHM values of 26 and 25 mm and SNR values of 47 and 46 when profiled horizontally and vertically. The diverging collimator has a lower SNR than pinhole collimator but performs better in terms of spatial resolution. Additionally, to test the performance of the manufactured gamma camera, the distance between the camera and the source was set to 100 cm and an experiment was conducted. The experimental results exhibit a trend similar to the simulation. Numerically, the average FWHM value were 39 mm in the vertical direction and 71 mm in the horizontal direction. Additionally, the average SNR values were 27 for the vertical direction and 17 for the horizontal direction. Based on these results, we confirm the possibility of Ir-192 source imaging.

Research and manufacture of the mini gamma camera using multi-anode photo multiplier tube (Ma-PMT)

Gamma camera is an imaging technique that captures gamma radiation emitting from the radiation sources. In this paper, the authors built a Mini-Gamma camera system using a micro photomultiplier tube (µPMT) H12700, signal processing circuit, and control software as self-designed products. The Gamma camera system includes four parts: collimator, scintillator NaI(Tl), µPMT, processing, and controller boards. The electronic system had preamplifiers used to convert negative signals from the µPMT to positive signals, integrators used to sharpen the signal from the preamplifier, and an amplifier circuit to amplify the signal from the preamplifier, a position detection circuit to detect the location of radiation interaction in the crystal. All circuits in the Mini-Gamma camera system are optimized to achieve the best projection image quality. In this paper, the lab-built Mini-Gamma Camera has an energy resolution of 45% at 60 keV gamma rays, the affected field of the camera is 42×48.5 mm2, and the spatial resolution of the image is around 1 mm.

Energy window optimization in bremsstrahlung imaging after Yttrium-90 microsphere therapy

In imaging of Yttrium-90 patients treated hepatic primary and metastatic cancers, bremsstrahlung photons produced in a wide energy range is used. However, the image quality depends on acquisition energy window. This research aimed energy window optimization for Yttrium-90 bremsstrahlung imaging and 48 patients with various types of cancer received radioembolization therapy were investigated. Patients were imaged using a GE Healthcare Optima NM/CT 640 series gamma camera system with a medium energy general-purpose (MEGP) collimator and planar images were acquired with 8 different energy windows in the 55–400 keV energy range. The data set, formed with the % FOV, contrast, and spatial resolution of image quality parameters calculated from these images, was statistically examined with ANOVA and Tukey tests. According to the visual evaluations and ANOVA/Tukey test results, it was statistically concluded that energy window of 90–110 keV is the optimal energy window while 60–400 keV energy ranges show the lowest image quality for Y-90 bremsstrahlung imaging.

Assessment of infant gonadal dose irradiated from urine-contaminated diapers during diuretic renal scintigraphy.

To estimate the gonadal doses irradiated from urine- contaminated diapers during diuretic renal scintigraphy. Images of 31 patients (18 males and 13 females) with urine-contaminated diapers during 99mTc-MAG3 renal scintigraphy were analyzed. The count rate of the diapers was converted into a time-activity curve based on the calibrated factor of the gamma camera system. The cumulative activity was determined from the area under the curve. By incorporating dose per unit cumulative activity pre-calculated from Monte Carlo simulation with 0-year phantom, the gonadal dose irradiated from diaper was calculated. To assess the degree of this additionally introduced dose from diapers, the calculated gonadal dose was compared to the internal gonadal dose from injected radiotracer activity. The cumulative activities irradiated from urine-contaminated diapers were 1.12 E04 ± 1.29E04 MBq.s in male infants, which was nearly half of the 1.94 E04 ± 1.80E04 MBq.s (P = 0.15) in female infants. However, the absorbed doses for testes in male infants were 7.37E-01 ± 8.50E-01 mGy, which was approximately 10 times the 6.38E-02 ± 5.94E-02 mGy for ovaries in female infants (P < 0.01). The diaper-introduced dose for testes and ovaries was 91.7% and 3.9% of the gonadal doses from the injected activity in patients with normal renal function, and 99.0% and 4.3% of those in patients with abnormal renal function. Urine-contaminated diapers introduced additional radiation doses to infant patients during 99mTc-MAG3 renal scintigraphy. The gonadal doses were of significance in male infants who had nearly double the absorbed dose for the testes.

A study on energy window-based scatter correction methods in 99mTc and 123I imaging

Tc-99m and I-123 are radionuclides commonly used for diagnostic examination in nuclear medicine. Detection of the scattered photons by the Compton interactions in the photopeak energy window is a factor affecting the image quality. DEW and TEW scatter correction methods are used to improve the image quality degrade by Compton scattered photons. In the study, planar and SPECT images of sphere, rod and cardiac phantom containing different activities were acquired with a gamma camera system. DEW/TEW corrected and uncorrected images for Tc-99m/I-123 were evaluated qualitatively and quantitatively. Both for planar and SPECT images, the DEW and TEW scatter correction methods were found to improve the image quality at varying rates.

First clinical experience of a ring-configured cadmium zinc telluride camera: A comparative study versus conventional gamma camera systems.

A novel semiconductor cadmium zinc telluride (CZT) gamma camera system using a block sequential regularized expectation maximization (BSREM) reconstruction algorithm is now clinically available. Here we investigate how a multi-purpose ring-configurated CZT system can be safely applied in clinics and describe the initial optimization process. Seventy-six patients (bone-, cardiac- and lung scan) were scanned on a conventional gamma camera (planar and/or single-photon emission computed tomography [SPECT]/SPECT-CT) used in clinical routine and on the ring-configurated CZT camera Starguide (GE Healthcare). These data were used to validate and optimize the Starguide system for routine clinical use. Comparable image quality for the Starguide system, to that of the conventional gamma camera, was achieved for bone scan (4 min/bed position [BP] using a relative difference prior [RDP] with gamma 2 and beta 0.4, along with 10 iterations and 10 subsets), cardiac scan (8 min [stress] and 3 min 20 s [rest] using median root prior [MRP] with beta 0.07 non attenuation corrected and 0.008 attenuation corrected and 50 interations and 10 subsets for both stress and rest) and lung scan (10 min [vent] and 5 min [perf] using RDP with gamma 0.5 and beta 0.03 [vent] and 0.02 [perf] and 20 interations and 10 subsets for both vent and perf). It was possible to transition from a conventional gamma camera to the Starguide system as part of the clinical routine, with acceptable image quality. Images from the Starguide system were deemed to be at least as good as those from a conventional gamma camera.

Validation of a Monte Carlo simulated cardiac phantom for planar and SPECT studies

PurposeThis work aimed to validate Monte Carlo (MC) simulated cardiac phantoms for the evaluation of planar- and SPECT-gated-blood-pool (GBP-P and GBP-S) studies. MethodsA comparison of gamma camera system performance criteria measurements (energy resolution, spatial resolution, sensitivity) with MC simulations was conducted. Furthermore, the accuracy of measured and simulated volumes of two stereolithography-printed cardiac phantoms (based on 4D-XCAT phantoms) was assessed. Finally, the simulated GBP-P and GBP-S XCAT studies were validated by comparing calculated left ventricular ejection fraction (LVEF) and ventricle volume values with known parameters. ResultsThe simulated performance criteria compared well with measured values (energy resolution difference: 0.1 ± 0.10%; spatial resolution (full width at half maximum) difference ≤ 0.5 ± 0.8 mm and system sensitivity difference ≤ 6.2 ± 0.62cps/MBq). The measured and simulated cardiac phantoms were in good agreement; the left anterior oblique views compared well. This is supported by line profiles through these phantoms and on average, simulated counts were 5.8% lower than measured counts. The LVEF values calculated from the GBP-P and GBP-S simulated data differ from known values (2.8 ± 0.64% and 0.8 ± 0.52%). The differences between the known XCAT LV volumes and simulated GBP-S calculated volumes were −1.2 ± 1.91 ml and −1.5 ± 0.96 ml for the end-diastolic and end-systolic volumes. ConclusionThe MC-simulated cardiac phantom has been validated successfully. Stereolithography-printing allows researchers to create clinically realistic organ phantoms and is a valuable tool for validating MC simulations and clinical software. By conducting GBP simulation studies with various XCAT models, the user will be able to generate GBP-P and GBP-S databases for future software evaluation.

Spatial resolution and natural image quality assessment evaluation of gamma camera image using pinhole collimator in lutetium-yttrium oxyorthosilicate scintillation detector

Scintillator materials are widely used in the medical and industrial fields for imaging systems using gamma cameras. In this study, image evaluation is performed by modeling a gamma camera system based on a lutetium-yttrium oxyorthosilicate (LYSO) scintillation detector using a pinhole collimator that can improve the spatial resolution. A LYSO detector-based gamma camera system is modeled using a Monte Carlo simulation tool. The geometric concept of the pinhole collimator is designed using various magnification factors, and the spatial resolution is measured using the acquired source image. To evaluate the resolution, the full width at half maximum (FWHM) and natural image quality assessment (NIQE), a no-reference-based parameter, are used. We confirm that the FWHM and NIQE values decrease simultaneously when the diameter of the pinhole collimator increases. Additionally, we confirm that the spatial resolution improves as the magnification factor increases under the same pinhole diameter condition. Particularly, a 0.57 mm FWHM value is obtained using the modeled gamma camera system with a LYSO scintillation detector. In conclusion, our results demonstrate that a pinhole collimator with a LYSO scintillation detector is a promising gamma camera imaging system.

A Review on the Usage of Bone Single-Photon Emission Computed Tomography/Computed Tomography in Detecting Skeletal Metastases in the Post-COVID-19 Era: Is it Time to Ditch Planar and Single-Photon Emission Computed Tomography only Gamma Camera Systems?

Planar whole-body bone scanning (WBS) is widely used to evaluate skeletal lesions seen in cancer and noncancer cases. Frequently, degenerative, or other benign bony changes may give rise to indeterminate lesions that mimic bone metastases. In the post-COVID-19 era, there is an evolutionary phase that puts importance on global development and adaptability, which encompasses to include nuclear medicine practices worldwide. Single-photon emission computed tomography/computed tomography (SPECT/CT) can be used to improve the characterization of these lesions and help to resolve the diagnostic conundrum while reducing the need for patients to undergo multiple different examinations at various imaging departments. The fusion of SPECT and CT allows morphological characterization of functional abnormality detected by focal tracer uptake on planar scintigraphy, which provides a one-stop center imaging in nuclear medicine departments. The objective of this study was to review the diagnostic accuracy of SPECT/CT in diagnosing bone metastases in a variety of oncology and nononcology cases and to determine the feasibility of performing bone SPECT/CT in all suspected cancer cases, including cases of bone infection instead of planar imaging alone. The utilization of hybrid SPECT/CT in indeterminate bone lesions detected on planar WBS can significantly increase the diagnostic confidence and accuracy of image interpretation. Recognition of patterns of disease identified using hybrid imaging can improve the management of patients with potentially lower costs in the long term. Currently, hybrid SPECT/CT machines are becoming a norm in nuclear medicine departments, thus potentially making single planar application machines obsolete in the near future. We hypothesize that in the interest of providing a meaningful interpretation of isotope bone scans, the default protocol should involve the option of acquiring SPECT/CT images rather than relying on whole-body scans only. Departments choosing to upgrade existing equipment or those choosing to invest in only one gamma camera should proactively opt for hybrid SPECT/CT systems.

99m-Tc MDP Bone Scan Image Enhancement using Pipeline Application of Dynamic Stochastic Resonance Algorithm and Block-Matching 3D Filter.

In this pilot study, we have proposed and evaluated pipelined application of the dynamic stochastic resonance (DSR) algorithm and block-matching 3D (BM3D) filter for the enhancement of nuclear medicine images. The enhanced images out of the pipeline were compared with the corresponding enhanced images obtained using individual applications of DSR and BM3D algorithm. Twenty 99m-Tc MDP bone scan images acquired on SymbiaT6 SPECT/CT gamma camera system fitted with low-energy high-resolution collimators were exported in DICOM format to a personal computer and converted into PNG format. These PNG images were processed using the proposed algorithm in MATLAB. Two nuclear medicine physicians visually compared each input and its corresponding three enhanced images to select the best-enhanced image. The image quality metrics (Brightness, Global Contrast Factor (GCF), Contrast per pixel (CPP), and Blur) were used to assess the image quality objectively. The Wilcoxon signed test was applied to find a statistically significant difference in Brightness, GCF, CPP, and Blur of enhanced and its input images at a level of significance. Images enhanced using the pipelined application of SR and BM3D were selected as the best images by both nuclear medicine physicians. Based on Brightness, Global Contrast Factor (GCF), CPP, and Blur, the image quality of our proposed pipeline was significantly better than enhanced images obtained using individual applications of DSR and BM3D algorithm. The proposed method was found to be very successful in enhancing details in the low count region of input images. The enhanced images were bright, smooth, and had better target-to-background ratio compared to input images. The pipelined application of DSR and BM3D algorithm produced enhancement in nuclear medicine images having following characteristics: bright, smooth, better target-to-background ratio, and improved visibility of details in the low count regions of the input image, as compared to individual enhancements by application of DSR or BM3D algorithm.

An automatic segmentation framework for computer-assisted renal scintigraphy procedure.

One of the techniques for achieving unique and reliable information in medicine is renal scintigraphy. A key step for quantitative renal scintigraphy is segmentation of the kidneys. Here, an automatic segmentation framework was proposed for computer-aided renal scintigraphy procedures. To extract kidney boundary in dynamic renal scintigraphic images, a multi-step approach was proposed. This technique is featured with key steps, namely, localization and segmentation. At first, the ROI of each kidney was estimated using Otsu's thresholding, anatomical constraint, and integral projection, which is done in an automatic process. Afterwards, the ROI obtained for the kidneys was used as the initial contours to create the final counter of kidneys using geometric active contours. At this step and for the segmentation, an improved variational level set was utilized through Mumford-Shah formulation. Using e.cam gamma camera system (SIEMENS), 30 data sets were used to assess the proposed method. By comparing the manually outlined borders, the performance of the proposed method was shown. Different measures were used to examine the performance. It was found that the proposed segmentation method managed to extract the kidney boundary in renal scintigraphic images. The proposed technique achieved a sensitivity of 95.15% and a specificity of 95.33%. In addition, the section under the curve in the ROC analysis was equal to 0.974. The proposed technique successfully segmented the renal contour in dynamic renal scintigraphy. Using all the data sets, a correct segmentation of the kidney was performed. In addition, the technique was successful with noisy and low-resolution images and challenging cases with close interfering activities such as liver and spleen activities.

Use of radiolabeled hyaluronic acid for preclinical assessment of inflammatory injury and acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is accompanied by a dramatic increase in lung hyaluronic acid (HA), leading to a dose-dependent reduction of pulmonary oxygenation. This pattern is associated with severe infections, such as COVID-19, and other important lung injury etiologies. HA actively participates in molecular pathways involved in the cytokine storm of COVID-19-induced ARDS. The objective of this study was to evaluate an imaging approach of radiolabeled HA for assessment of dysregulated HA deposition in mouse models with skin inflammation and lipopolysaccharide (LPS)-induced ARDS using a novel portable intensified Quantum Imaging Detector (iQID) gamma camera system. MethodsHA of 10 kDa molecular weight (HA10) was radiolabeled with 125I and 99mTc respectively to produce [125I]I-HA10 and [99mTc]Tc-HA10, followed by comparative studies on stability, in vivo biodistribution, and uptake at inflammatory skin sites in mice with 12-O-tetradecanoylphorbol-13-acetate (TPA)-inflamed ears. [99mTc]Tc-HA10 was used for iQID in vivo dynamic imaging of mice with ARDS induced by intratracheal instillation of LPS. Results[99mTc]Tc-HA10 and [125I]I-HA10 had similar biodistribution and localization at inflammatory sites. [99mTc]Tc-HA10 was shown to be feasible in measuring skin injury and monitoring skin wound healing. [99mTc]Tc-HA10 dynamic pulmonary images yielded good visualization of radioactive uptake in the lungs. There was significantly increased lung uptake and slower lung washout in mice with LPS-induced ARDS than in control mice. Postmortem biodistribution measurement of [99mTc]TcHA10 (%ID/g) was 11.0 ± 3.9 vs. 1.3 ± 0.3 in the ARDS mice (n = 6) and controls (n = 6) (P < 0.001), consistent with upregulated HA expression as determined by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry (IHC) staining. Conclusions[99mTc]Tc-HA10 is promising as a biomarker for evaluating HA dysregulation that contributes to pulmonary injury in ARDS. Rapid iQID imaging of [99mTc]Tc-HA10 clearance from injured lungs may provide a functional template for timely assessment and quantitative monitoring of pulmonary pathophysiology and intervention in ARDS.

Optimization of the energy window setting in Ir-192 source imaging for high-dose-rate brachytherapy using a YAP(Ce) gamma camera

PurposeAlthough real-time imaging of the high-activity iridium-192 (Ir-192) source position during high-dose-rate (HDR) brachytherapy using a high-energy gamma camera system is a promising approach, the energy window was not optimized for spatial resolution or scatter fraction. MethodsBy using a list-mode data-acquisition system that can acquire energy information of a cerium-doped yttrium aluminum perovskite (YA1O3: YAP(Ce)) gamma camera, we tried to optimize the energy window’s setting to improve the spatial resolution and reduce scatter fraction. ResultsThe spatial resolution was highest for the central energy of the window at ∼300 keV. The scatter fraction was also smallest for the central energy of the window at ∼300 keV, and the scatter fraction was more than 48 % smaller than that for the full energy window. ConclusionsWe clarified that the spatial resolution can be improved and the scatter fraction can be reduced through optimizing the energy window of the YAP(Ce) gamma camera by setting the central energy of the window to ∼300 keV for HDR brachytherapy.

Technical note: Short-time sequential high-energy gamma photon imaging using list-mode data acquisition system for high-dose-rate brachytherapy.

Measurement of the dwell time and moving speed of a high-activity iridium-192 (Ir-192) source used for high-dose-rate (HDR) brachytherapy is important for estimating the precise dose delivery to a tumor. For this purpose, we used a cerium-doped yttrium aluminum perovskite (YA1O3 :YAP(Ce)) gamma camera system, combined with a list-mode data acquisition system that can acquire short-time sequential images, and measured the dwell times and moving speeds of the Ir-192 source. Gamma photon imaging was conducted using the gamma camera in list mode for the Ir-192 source of HDR brachytherapy with fixed dwell times and positions. The acquired list-mode images were sorted to millisecond-order interval time sequential images to evaluate the dwell time at each position. Time count rate curves were derived to calculate the dwell time at each source position and moving speed of the source. We could measure the millisecond-order time sequential images for the Ir-192 source. The measured times for the preset dwell times of 2 s and 10 s were 1.98 to 2.00 s full width at half maximum (FWHM) and 10.0 s FWHM, respectively. The dwell times at the first dwell position were larger than those at other positions. We also measured the moving speeds of the source after the dwells while moving back to the afterloader and found the speed increased with the distance from the edge of the field of view to the last dwell position. We conclude that millisecond-order time sequential imaging of the Ir-192 source is possible by using a gamma camera and is useful for evaluating the dwell times and moving speeds of the Ir-192 source.

Development of a diverging collimator for environmental radiation monitoring in the industrial fields

Environmental radiation monitoring is required to protect from the effects of radiation in industrial fields such as nuclear power plant (NPP) monitoring, and various gamma camera systems are being developed. The purpose of this study is to optimize parameters of a diverging collimator composed of pure tungsten for compactness and lightness through Monte Carlo simulation. We conducted the performance evaluation based on spatial resolution and signal-to-noise ratio for point source and obtained gamma images and profiles. As a result, optimization was determined at a collimator height of 60.0 mm, a hole size of 1.5 mm, and a septal thickness of 1.0 mm. Also, the full-width-at-half-maximum was 3.5 mm and the signal-to-noise ratio was 53.5. This study proposes a compact 45° diverging collimator structure that can quickly and accurately identify the location of the source for radiation monitoring.

Monte Carlo modelling of a compact CZT-based gamma camera with application to 177Lu imaging

BackgroundSemiconductor gamma-camera systems based on cadmium zinc telluride (CZT) detectors present new challenges due to an energy-response that includes effects of low-energy tailing. In particular, such energy tails produce effects that need to be considered when imaging radionuclides with multiple emissions such as ^{177}{mathrm {Lu}}. Monte Carlo simulation can be used to investigate the behaviour of such systems and optimise their use, provided that the detector model closely reflects the real physical detector. The aim of this work is to develop a CZT model applicable for simulation of CZT-based gamma cameras.MethodsThe equations describing the charge transport and signal induction are considered in three dimensions and are solved numerically, and the CZT model is then realised by coupling the detector-response to the photon-transport handled by the SIMIND Monte Carlo program. The CZT model is tuned to reproduce experimentally measured energy spectra of a hand-held gamma camera system for multiple radionuclides (^{99mathrm {m}}{mathrm {Tc}}, ^{123}{mathrm {I}} and ^{177}{mathrm {Lu}}) and parallel-hole collimators (MEGP, LEHR) as well as an uncollimated system.ResultsOverall, the model results agree well with measurements across the range of experimental conditions. The applicability of the model is demonstrated by separating energy spectra into components to investigate the interference of high-energy photons on lower energy-windows, where pronounced effects of low-energy tailing for ^{177}{mathrm {Lu}} are observed.ConclusionsThe developed model provides understanding of the specifics of the camera response and is expected to be helpful for future optimisation of gamma camera applications.

Quantification of SPECT Concentric Ring Artifacts by Radiomics and Radial Features

(1) Background: Concentric ring artifacts in reconstructed SPECT images indicate the presence of detector non-uniformity in gamma camera systems. The identification of these artifacts is generally visual and not quantitative. The aim of our study was to evaluate observer assessments of the presence of concentric rings in reconstructed SPECT phantom images and to verify whether quantitative texture analysis can detect such artifacts, which are detrimental to accurate tumor detection. (2) Methods: Test data were acquired as part of the quarterly quality assurance program using a standardized SPECT phantom containing solid spheres, solid rods, and a water solution of 99mTc. Forty separate SPECT acquisitions were analyzed to assess the presence of ring artifacts. Two experienced medical physicists independently reviewed transaxial images and graded the severity of artifacts on a five-point scale. Quantitative radiomic features were computed for volumes of interest located in the uniform phantom section. In addition to these, radial contrast (RContrast) and radial root-mean-square contrast (RRMSC) were also calculated and derived from the radial profile of summed slices transformed into polar coordinates. (3) Results: Artifacts were considered sufficiently severe to warrant camera re-tuning in 10 rod sections, 17 sphere sections, and 16 uniform sections. In the uniform sections, there was “good agreement” for inter-observer and intra-rater assessments (κ = 0.66, Fisher exact p &lt; 0.0001 and κ = 0.61, and Fisher exact p = 0.001, respectively). The two radial features agreed significantly (p &lt; 0.001) with visual severity judgment of ring artifacts in uniform sections and were selected as informative about the presence of ring artifacts by LASSO approach. The increased magnitude of RContrast and RRMSC correlated significantly with increasingly severe artifact scores (ρ = 0.65–0.66, p &lt; 0.0001). (4) Conclusions: There was good agreement between the physicists with respect to the presence of circular ring artifacts in uniform sections of SPECT quality assurance scans, with the artifacts accurately detected by radial contrast and noise-to-signal ratio measurements.

What validation tests can be done by the clinical medical physicist while waiting for the standardization of quantitative SPECT/CT imaging?

ObjectiveThe aim of the study was to assess the accuracy of quantitative SPECT/CT imaging in a clinical setting and to compare test results from two nuclear medicine departments.MethodsPhantom studies were carried out with two gamma cameras manufactured by GE Healthcare: Discovery NM/CT 670 and NM/CT 850, used in two nuclear medicine departments. The data were collected using a cylindrical uniform phantom and a NEMA/IEC NU2 Body Phantom, filled with 99mTc-pertechnetate.ResultsThe convergence of activity concentration recovery was validated for the two gamma cameras operating in two medical centers using the cylindrical uniform phantom. The comparison of results revealed a 5% difference in the background calibration factor Bg. cal; 6% difference in COV, and a 0.6% difference in total activity deviation ∆Atot. Recovery coefficients (RCmax) for activity concentration in spheres of the NEMA/IEC NU2 Body Phantom were measured for different image reconstruction techniques. RCmax was in the range of 0.2–0.4 for the smallest sphere (ϕ 10 mm), and 1.3–1.4 for the largest sphere (ϕ 37 mm). Conversion factors for SUVmax and SUVmean for the gamma camera systems used were 0.99 and 1.13, respectively.Conclusions(1) Measurements taken in our study confirmed the clinical suitability of 5 parameters of image quality (Bg. cal—background calibration factor, ∆Atot—total activity deviation, COV—coefficient of variation used for image noise assessment, QH—hot contrast, AM—accuracy of measurements, or RC—recovery coefficient) for the validation of SPECT/CT system performance in terms of correct quantitative acquisitions of images. (2) This work shows that absolute SPECT/CT quantification is achievable in clinical nuclear medicine centers. Results variation of quantitative analyses between centers is mainly related to the use of different reconstruction methods. (3) It is necessary to standardize the technique of measuring the SUV conversion factor obtained with different SPECT/CT scanners.

Assessment of Patient and Staff Annual Effective Doses at a Nuclear Medicine Department during Bone Scans

The current research aims to assess the staff and patients’ effective doses during Nuclear medicine (NM) bone scans procedures. The administered activity was utilized to quantify the patients’ effective doses, while personnel’s effective doses were quantified using thermoluminescent detectors (TLD-100). The average administered activity was 650 (440 to 1440) MBq procedures using SPECT gamma camera system. The average annual staff effective dose (mSv) was estimated to be 2.3 (0.1 to 4.9). The typical patient’s effective dose was 4.9 (3.6 to 6.0) mSv per procedure. Staff exposure within the yearly effective dose limits. Patients’ exposure optimization is required based on patient weight. Estimating staff eye lens doses is suggested to confirm that the yearly effective radiation doses are within the safety range.

Updates in Molecular Breast Imaging

Molecular breast imaging (MBI) is a nuclear medicine study performed with dedicated gamma camera systems optimized to image the uptake of Tc-99m sestamibi in the breast. MBI provides a relatively low-cost and simple functional breast imaging method that can identify breast cancers obscured by dense fibroglandular tissue on mammography. Recent studies have also found that background levels of uptake in benign dense tissue may provide breast cancer risk information. This article discusses the latest updates in MBI technology, recent evidence supporting its clinical use, and work in progress that may aid in wider adoption of MBI.