Gamma Camera Research Articles

Resolution recovery on list mode MLEM reconstruction for dynamic cardiac SPECT system

The Dynamic Cardiac SPECT (DC-SPECT) system is being developed at the Massachusetts General Hospital, featuring a static cardio focus asymmetrical geometry enabling simultaneous high-resolution and high-sensitivity imaging. Among 14 design iterations of the DC-SPECT with varying number of detector heads, system sensitivity and resolution, the current version under development features 10 mm FWHM geometrical resolution (without resolution recovery) and 0.07% sensitivity at the center of the FOV, this is 1.5× resolution gain and 7× sensitivity gain compared to a conventional dual head gamma camera (0.01% sensitivity and 15-mm resolution). This work presents improvement in imaging resolution by implementing a spatially variant point spread function (SV-PSF) with list mode MLEM reconstruction. A resolution recovery method by PSF deconvolution is validated on list mode MLEM reconstruction for the DC-SPECT. A spatial invariant PSF is included as an additional test to show the influence of the PSF modelling accuracy on reconstructed image quality. We compare the MLEM reconstruction with and without PSF deconvolution; an analytic model is used for the calculation of system response, and the results are compared to the reconstruction with system modelling using Monte Carlo (MC) based methods. Results show that with PSF modelling applied, the quality of the reconstructed image is improved, and the DC-SPECT system can achieve a 4.5 mm central spatial resolution with average 795 counts/Mbq. Both the SV-PSF and the spatial-invariant PSF improve the image quality, and the reconstruction with SV-PSF generates line profiles closer to the ground truth. The results show substantial improvement over the GE Discovery 570c performance (7 mm spatial resolution with an average 460 counts/MBq, 5.8 mm resolution at the FOV center). The impact of PSF deconvolution is significant, improvement of the reconstructed image quality is evident in comparison to MC simulated system matrix with the same sampling size in the simulation.

The effects of kilovoltage (kV) and milliampere seconds (mAs) values for SPECT attenuation correction: An anthropomorphic phantom study

The purpose of SPECT/CT imaging to be used in dosimetric calculations is to perform accurate attenuation correction by giving the patient the minimum radiation dose. in accordance with ALARA principles (as low as reasonably achievable), it is critical to limit the amount of radiation given to the patient as far as possible in medical fields where radiation therapy is applied. The goal of this study is to determine the optimum kV and mAs values needed to keep the radiation dose that can be given to the patient in CT scans at a minimum level for attenuation correction, as well as to determine the CT-induced radiation doses on patients with different kV and mAs values using an anthropomorphic phantom.Radionuclides 177Lu and 131I were used in SPECT imaging. For CT-based attenuation correction, images were taken with various values between 80 kV × 30 mAs and 140 kV × 300 mAs using the anthropomorphic phantom. After that attenuation correction was performed with the obtained CT images for SPECT images. Then, CT-derived radiation doses were calculated.Our results showed that 80 kV × 30 mAs values can be used in scans after radionuclide treatment for CT attenuation correction. It was determined that the patient was exposed to a radiation dose of 0.432 mSv as a result of the CT scanning with the full detector width area of gamma camera detector. Thus, scanning with these values (80 kV × 30 mAs) resulted in approximately 95% less radiation exposure (0,432 mSv) than the value (9,38 mSv) with scanning of the manufacturer's recommended value (120 kV × 200 mAs).

Estimating blurless and noise-free Ir-192 source images from gamma camera images for high-dose-rate brachytherapy using a deep-learning approach

Objective. Precise monitoring of the position and dwell time of iridium-192 (Ir-192) during high-dose-rate (HDR) brachytherapy is crucial to avoid serious damage to normal tissues. Source imaging using a compact gamma camera is a potential approach for monitoring. However, images from the gamma camera are affected by blurring and statistical noise, which impact the accuracy of source position monitoring. This study aimed to develop a deep-learning approach for estimating ideal source images that reduce the effect of blurring and statistical noise from experimental images captured using a compact gamma camera. Approach. A double pix2pix model was trained using the simulated gamma camera images of an Ir-192 source. The first model was responsible for denoising the Ir-192 images, whereas the second model performed super resolution. Trained models were then applied to the experimental images to estimate the ideal images. Main results. At a distance of 100 mm between the compact gamma camera and the Ir-192 source, the difference in full width at half maximum (FWHM) between the estimated and actual source sizes was approximately 0.5 mm for a measurement time of 1.5 s. This difference has been improved from approximately 2.7 mm without the use of DL. Even with a measurement time of 0.1 s, the ideal images could be estimated as accurately as in the 1.5 s measurements. This method consistently achieved accurate estimations of the source images at any position within the field of view; however, the difference increased with the distance between the Ir-192 source and the compact gamma camera. Significance. The proposed method successfully provided estimated images from the experimental images within errors smaller than 0.5 mm at 100 mm. This method is promising for reducing blurring and statistical noise from the experimental images, enabling precise real-time monitoring of Ir-192 sources during HDR brachytherapy.

Speckle tracking echocardiography allows for the detection of subclinical myocardial dysfunction resulting from perfusion abnormalities confirmed by SPECT-based CFR measurement

Abstract Background Speckle tracking echocardiography (STE) is helpful for the detection of subclinical systolic function abnormalities. Coronary flow reserve (CFR) measured by dynamic 99mTc-MIBI SPECT-CZT gamma camera allows the diagnosis of myocardial perfusion defects in patients with suspected coronary artery disease (CAD). Purpose The aim of our study is to assess the diagnostic value of STE and SPECT-based CFR in patients with suspected coronary artery disease (CAD). Methods 85 patients (pts) (37.6% females, mean age 65.4 ± 8.5 years) with suspected CAD underwent 2D and 3D STE, as well as myocardial perfusion study with novel solid-state CZT nuclear camera (dipyridamole stress protocol). We calculated global longitudinal left ventricular strain (GLS), as well as LS of individual coronary artery territories (LAD LS, Cx LS and RCA LS). Total CFR and CFR in three coronary territories were also measured. The presence of CAD (coronary artery stenosis > 70%) was assessed by coronary angiography. Results Significant CAD was confirmed in 50 patients. Mean total CFR (1.71 ± 0.61 vs 2.1 ± 0.52, p = 0.002), as well as CFR in LAD territories (1.54 ± 0.68 vs 1.91 ± 0.56, p = 0.02), RCA territories (1.58 ± 0.82 vs 1.95 ± 0.68, p = 0.048) and Cx territories (1.58 ± 0.78 vs 2.08 ±0.76, p = 0.01) were lower in pts with CAD. In the ROC curve analysis of total CFR for the diagnosis of CAD the AUC was found to be 0.7 (p = 0.001). Mean absolute 2D GLS in pts with total CFR < 2.0 was significantly lower than in pts with CFR >= 2.0 (-14.5 ± 4.3 vs -16.9 ± 3.4, p = 0.005). Similar differences were observed in all three coronary territories (p ≤ 0.05). The same results were not observed in case of 3D GLS . Modest but significant correlations were detected between total CFR and 2D GLS values (r = -0.38; p < 0.001), LAD CFR and 2D LAD LS (r = -0.33; p = 0.002), LCx CFR and 2 D LCx LS (r = -0.39; p < 0.001), total CFR and EF (r = 0.36; p < 0.001). GLS at rest had good diagnostic value for detecting total CFR < 2 (AUC= 0.7; p = 0.004). The criterion with the highest diagnostic accuracy was GLS > (- 18.5) – its sensitivity was 84%, specificity 42%, positive predictive value 0.7, negative predictive value 0.7 and overall accuracy 66%. Conclusions CFR assessed by SPECT provides acceptable diagnostic accuracy for the detection of significant CAD. STE allows for identification of patients with subclinical dysfunction resulting from perfusion abnormalities confirmed by SPECT-based CFR measurement.

Sub-millimeter resolution SiPM-based neutron anger camera

Thermal and cold neutron beamlines require detector systems that have a high neutron efficiency, large active area, and good spatial resolution. One type of detector that has been implemented at beamlines at the Spallation Neutron Source (SNS) is a scintillator-based Anger camera that utilizes photomultiplier tubes (PMTs) as photodetectors. In this work, we present a new Anger camera design that replaces PMTs with silicon photomultipliers (SiPMs). This new design offers better resolution, less distortion, and more compactness than the previous cameras. A camera with active area of ∼100 cm2 was shown to have a spatial resolution better than 0.5 mm. Additionally, the use of SiPMs allows for use in strong magnetic fields, opening the possibility of additional experimental capabilities. A prototype has been built that demonstrates vacuum-compatibility, as required for a proposed beamline for the Second Target Station at SNS.

Design, development and bio-evaluation of a novel radio-ligand 99mTc-THQ-DTPA as a sigma 2 receptor specific breast tumor imaging agent

Over-expression of sigma-2 receptor in cancer cells provides an opportunity to develop molecular probes for diagnosis, even for non-receptor specific malignancies like triple negative breast cancers. In this work, a novel sigma-2 receptor ligand [THQ-DTPA] has been synthesized and characterized using 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (THQ) and diethylenetriaminepentaacetic acid (DTPA). The ligand is further chelated with 99mTc for application as metal based radiotracer [99mTc-THQ-DTPA]. Radiolabelling with 99mTc was achieved in an excellent yield of 98.0 ± 0.5% using stannous chloride as a reducing agent. The radioligand was found to be stable in human serum up-to 24 h, bio-compatible with less than 4% hemolysis, and exhibited high binding with sigma receptors isolated from rat liver membrane (Kd of 16.32 ± 4.93 nM and Bmax of 0.5232 ± 0.06 pmol/mg). Bio-distribution studies in triple-negative breast tumor bearing nude mice showed high tumor uptake after 30 min of injection with tumor/muscle (T/M) ratio of 3.58 ± 0.09. At 240 min, the T/M ratio (2.84 ± 0.20) decreased by 35% when administered in sigma blocked tumor bearing mice (1.81 ± 0.16) suggesting the selectivity of the ligand. Tumor imaging in gamma camera indicated a contrast of 3.56 at 30 min p.i. The above findings indicate that the ligand 99mTc-THQ-DTPA binds to sigma-2 receptors with high affinity and has potential for triple-negative breast tumor 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.

IMPLEMENTASI INDONESIAN DIAGNOSTIC REFERENCE LEVEL (I-DRL) PADA PELAYANAN DIAGNOSTIK IN VIVO KEDOKTERAN NUKLIR DI RSUP DR. SARDJITO TAHUN 2022-2023

The Indonesian Diagnostic Reference Level (I-DRL) value in nuclear medicine was only published in November 2022 by the Nuclear Energy Regulatory Agency (BAPETEN). Implementing I-DRL in in-vivo diagnostic services in nuclear medicine at Sardjito Hospital, which has been running so far, needs ongoing evaluation to help realize an increase in the ratio of benefits to risks of radiation to patients. This research aims to apply I-DRL nuclear medicine at Dr. Sardjito Hospital while still applying the principles of optimizing medical exposure. Optimization focuses on maintaining guaranteed image quality, namely images that are readable or not readable by nuclear medicine specialists, while still implementing radiation protection against medical exposure. The research is a retrospective descriptive method from bone scan patient data from 2022-2023. The selection of 299 bone scan data was based on the most frequently performed examinations. The bone scan imaging tool used was a GE brand single-photon emission computed tomography (SPECT-CT) gamma camera type NM/CT 870 DR. Image processing uses a comparison of region of interest (ROI) values from the target and background on the femur bone using Xeleris software. Based on the image analysis results, the target and background's lowest, average, and highest comparison values were respectively 1.15, 2.1, and 3.75. Spearman statistical testing was also carried out between the dose per Body Mass Index (BMI) and the target/background value ratio, obtaining an R-value of -0.046, which means the two variables have a weak relationship. This research provides information that I-DRL Bone scan can be implemented without affecting the image quality results. Implementing I-DRL is a form of optimizing radiation protection for patients, preventing unnecessary radiation exposure, and ensuring the quality of nuclear medicine services will improve in the future. Keywords: I-DRL, in vivo diagnostics, optimization, radiation protection, bone scan.

Deep Learned Segmentations of Inflammation for Novel ⁹⁹mTc-maraciclatide Imaging of Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is an autoimmune disease that causes joint pain, stiffness, and erosion. Power Doppler ultrasound and MRI are imaging modalities used in detecting and monitoring the disease, but they have limitations. ⁹⁹mTc-maraciclatide gamma camera imaging is a novel technique that can detect joint inflammation at all sites in a single examination and has been shown to correlate with power Doppler ultrasound. In this work, we investigate if machine learning models can be used to automatically segment regions of normal, low, and highly inflamed tissue from 192 ⁹⁹mTc-maraciclatide scans of the hands and wrists from 48 patients. Two models were trained: a thresholding model that learns lower and upper threshold values and a neural-network-based nnU-Net model that uses a convolutional neural network (CNN). The nnU-Net model showed 0.94 ± 0.01, 0.51 ± 0.14, and 0.76 ± 0.16 modified Dice scores for segmenting the normal, low, and highly inflamed tissue, respectively, when compared to clinical segmented labels. This outperforms the thresholding model, which achieved modified Dice scores of 0.92 ± 0.01, 0.14 ± 0.07, and 0.35 ± 0.21, respectively. This is an important first step in developing artificial intelligence (AI) tools to assist clinicians' workflow in the use of this new radiopharmaceutical.

Validation Calibration Factor of Single Photon Emission Computed Tomography for Iodine-131 using Non-Spherical Targeted Volume

Absolute quantification of Iodine-131 (131I) on Single Photon Emission Computed Tomography (SPECT) imaging is extremely necessary for the lesion dose per administrative differentiated thyroid cancer procedure. However, non-quantitative SPECT imaging makes determining the dose required for a tumour to be treated is challenging. This multi-vendor and multi-centre research uses phantom measures to assess the quantitative accuracy and inter-system variability of various SPECT/CT systems. Hence, this study aims to determine the calibration factor (CF) for 131I activity quantification using the National Electrical Manufacturer Association (NEMA) phantom uptake for the Philips BrightView XCT modality. The accuracy activity concentration for a non-spherical targeted volume is less than 15% compared to a spherical targeted volume (&lt;9%). Furthermore, the CF has no significant difference in the value between the matrix sizes of 64×64, 128×128, and 256×256. Therefore, the gamma camera CF must be precisely determined to convert the reconstructed images' counts into activity values for quantitative imaging. However, the NEMA phantom with spherical geometrical is the standard tool for determining CF, the various geometrical shapes other than spherical should be considered for determining CF because the effect of photon distribution contribution is different for any different lesion geometrical.

SAT510 I-131 Therapy with Dosimetry for Advanced Thyroid Carcinoma: Recombinant TSH vs Thyroid Hormone Withdrawal

Abstract Disclosure: D. Awad: None. J. Hamsa: None. A. Fingeret: None. C. Johnson: None. F. Rutar: None. C. Carson: None. A. Kotwal: None. A. Patel: None. A. Thornburg: None. W.S. Goldner: None. Background: Dosimetry can be used to calculate an optimal and safe dose of Iodine-131 (I-131) for treatment of advanced differentiated thyroid cancer (DTC). Thyroid hormone withdrawal (THW) is the preferred method of TSH elevation for I-131 therapy with dosimetry. At our institution, Recombinant TSH (RhTSH) is used in patients in whom prolonged hypothyroidism is deemed clinically unsafe or cannot tolerate THW. We aim to evaluate if RhTSH and THW are equivalent methods of preparation for I-131 therapy using dosimetry (I-131D). Methods: This is a single institution retrospective cohort study evaluating all patients who received I-131D from 2010-2022. Demographic, clinical variables were assessed and dosimetric calculations were obtained. Statistical analysis was performed with Mann Whitney U, Kruskal Wallis, Chi-squared and Fisher’s exact testing. Results: Fifty-one unique patients were included with a total of fifty-five I-131D treatments, with 55% being female. Median (IQR) age at time of treatment was 60.3 years (42.8-70.4), and BMI kg/m2 was 29.3 (24-33.8). Of these patients 13% were stage I, 18.5% stage II, and 68.5% stage III/IV AJCC 7th ed. Sixty percent underwent THW and 40% received RhTSH. Gamma camera and blood activity measurements, at several time points following the pre-therapeutic I-131 dose, were taken to calculate the residence times and effective half-lives in whole body and blood. All patients demonstrated a monophasic elimination of I-131 activity in both the whole body and blood. Patients receiving RhTSH exhibited a slower elimination of the I-131 in the whole body than THW patients (effective half-life of 22 hrs vs 17 hrs) resulting in a higher fraction of I-131 activity remaining in the whole body 48 hours post-dose (25% vs 16%, p= 0.025). The effective half-life in the blood was also higher in the RhTSH group (p=0.025) resulting in a higher amount of activity remaining in the blood. As a result, the median (IQR) RAI dose was lower for those who received RhTSH (187.5 mCi (167-198)) vs those who underwent THW (260 mCi (202-306)) (p&amp;lt;0.001). As expected, TSH at the time of treatment was higher in the RhTSH group (p=0.0038). Thyroglobulin was higher at the time of treatment in the RhTSH group (p=0.031), but thyroglobulin drop at three months was not statistically different (p=0.0682) between groups. Conclusion: RhTSH administration is non-inferior to THW as a method of TSH elevation and preparation for I-131D for patients with advanced DTC. RhTSH, in comparison to THW, results in a significantly longer half-life in the whole-body and blood resulting in a lower calculated RAI dose. More studies are needed to confirm these findings. Presentation Date: Saturday, June 17, 2023

Diagnostic accuracy for CZT gamma camera compared to conventional gamma camera technique with myocardial perfusion single-photon emission computed tomography: Assessment of myocardial infarction and function

BackgroundThe solid-state cadmium-zinc-telluride (CZT) gamma camera for myocardial perfusion single-photon emission computed tomography (MPS) has theoretical advantages compared to the conventional gamma camera technique. This includes more sensitive detectors and better energy resolution. We aimed to explore the diagnostic performance of gated MPS with a CZT gamma camera compared to a conventional gamma camera for detection of myocardial infarct (MI) and assessment of left ventricular (LV) volumes and ejection fraction (LVEF), using cardiac magnetic resonance (CMR) as the reference method. MethodsSeventy-three patients (26% female) with known or suspected chronic coronary syndrome were examined with gated MPS using both a CZT gamma camera and a conventional gamma camera as well as with CMR. Presence and extent of MI on MPS and late gadolinium enhancement (LGE) CMR was evaluated. For LV volumes, LVEF and LV mass, gated MPS images and cine CMR images were evaluated. ResultsMI was found in 42 patients on CMR. The overall sensitivity, specificity, positive and negative predictive values for the CZT and the conventional gamma camera were the same (67%, 100%, 100% and 69%). For infarct size > 3% on CMR, the sensitivity was 82% for the CZT and 73% for the conventional gamma camera, respectively. LV volumes were significantly underestimated by MPS compared to CMR (P ≤ .002 for all measures). The underestimation was slightly less pronounced for the CZT compared to the conventional gamma camera (2-10 mL, P ≤ .03 for all measures). For LVEF, however, accuracy was high for both gamma cameras. ConclusionDifferences between a CZT and a conventional gamma camera for detection of MI and assessment of LV volumes and LVEF are small and do not appear to be clinically significant.

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.

Lung-to-heart ratio analysis using virtual planar images obtained from myocardial perfusion SPECT data: A phantom and clinical studies

BackgroundsThe lung-to-heart ratio (L/H ratio) in myocardial perfusion scintigraphy (MPS) is a useful marker that complements the sensitivity of ischemia detection. However, it requires planar imaging acquired following a separate protocol in addition to single-photon emission computed tomography (SPECT). We developed a novel method for constructing virtual planar image (VPI) from SPECT data. MethodsMyocardial phantoms using Tl-201 were built with different amounts of radioactivity in the lungs. SPECT data and conventional planar images of these phantoms were collected with an Anger-type gamma camera. VPIs were constructed by adding all coronal images reconstructed from SPECT data. The clinical utility of VPIs obtained from 52 patients who underwent MPS with Tc-99m sestamibi was evaluated. ResultsThe radioactivity linearity of VPIs was satisfactory, with a correlation coefficient of r ≥ .99 between the measured amounts of radioactivity and image counts. The L/H ratios obtained from VPI analysis were strongly correlated with those of conventional planar images with a correlation coefficient of r ≥ .99 in the phantom study and r = .929 in clinical application. ConclusionThe accuracy of VPI-based L/H ratio analysis was comparable to that of conventional planar image-based analysis. VPIs could be used as an alternative method of obtaining planar images in clinical settings.

Advantages of multi-target scintigraphy in the diagnosis of kidney cancer

Background. There has been a recent increase in the incidence of kidney cancer, which is explained not only by the improvement in the diagnosis of neoplasms but also by a true increase in the incidence of renal cell cancer. This led to the need for in-depth study and solution of the following problem: to prove the benefits of multi-target scintigraphy for the assessment of the functional capacity of kidneys in establishing the diagnosis of kidney cancer and early detection of secondary lesion of the skeleton during the primary full examination of the patient, as well as in monitoring of the disease.&#x0D; Purpose. For the first time to prove diagnostic significance of a multi-target scintigraphic examination with a radiopharmaceutical drug with renal and osteotropic kinetics, in the form of a sequential combination of dynamic renal scintigraphy and osteoscintigraphy (as one diagnostic examination) in the early detection of secondary lesion of the bones of the skeleton and simultaneous determination of the functional capacity of kidneys in the pre-treatment period and in monitoring of the course of kidney cancer.&#x0D; Materials and methods. Dynamic renal scintigraphy and subsequent (within the next 3 hours) osteoscintigraphy with 99mTc-methylenediphosphonic acid (99mТс-MDP) (activity of 370–740 MBq) were performed on the SPECT-1 gamma camera «AMCRIS-H Limited» (Ukrainian-American enterprise) with computer software «Spect Work» (Ukraine) at the premises of the Department of Radiology and Radiation Medicine of Bogomolets National Medical University in the Department of Radionuclide Diagnostics of communal non-commercial enterprise&#x0D; «Kyiv City Clinical Hospital No.18». 20 patients with a morphologically established diagnosis of kidney cancer, aged from 38 to 68 years, were examined before the full diagnosis was established according to TNMx. As a control group, 8 patients with ultrasonography-confirmed cystic lesions of the kidneys were examined.&#x0D; Results. Using a radiopharmaceutical drug with renal and osteotropic kinetics in the form of a simultaneous sequential combination of dynamic renal scintigraphy and osteoscintigraphy (as one diagnostic examination) allowed us to assess the degree of deterioration of the filtering and excretory capacity of the kidneys regardless of the origin of the expansive process. The results of dynamic renal scintigraphy with 99mТс-MDP made it possible to assess functional capacity of the kidneys no worse than specific renal imaging agents in subsequently given possibility to determine secondary lesion of the bones of the skeleton in osteoscintigraphy. We established indicators of development of renal compensation process and subsequent decompensation process of the contralateral kidney. It was especially noticeable when analyzing the asymmetry of the fixation of the radiopharmaceutical in the functioning kidney parenchyma, depending on the degree of the disease progression.&#x0D; 20 patients with kidney cancer underwent osteoscintigraphy for the complete diagnosis to be established according to TNM. The following changes were detected: the presence of heterogeneous focal (17,8% of the cases) and multifocal (7,1% of the cases) distribution of the radiopharmaceutical.&#x0D; Conclusions. Performing a multi-target scintigraphy with 99mТс-MDP (phosphates) in malignant process in the kidney allows the functional capacity of the kidneys and the presence of the secondary lesion of the bones to be assessed in one exami- nation. Besides reducing radiation burden on the patient (one examination instead of two), it is also economically beneficial.

Developing an Analytical Model for Knife-Edge Slit Collimator Optimization for Prompt Gamma Imaging in Proton Therapy

Purpose: Gamma cameras are one of the most promising technologies for in-vivo range monitoring in proton therapy. Monte Carlo (MC) simulation is a common calculation-based technique to design and optimize gamma cameras. However, it is prohibitively time-consuming. Analytical modeling speeds up the process of finding the optimal design.&#x0D; Materials and Methods: We proposed an analytical method using the efficiency-resolution trade-off for optimizing a knife-edge collimator based on the range retrieval precision of protons. Monte Carlo simulation was used for validation of obtained collimator efficiencies.&#x0D; Results: The model predicts that for the optimal range retrieval precision, the ratio of the source-to-detector distance to the source-to-collimator distance should be ranging from . For a special case, it was found that assuming an ideal detector , the falloff retrieval precision is optimal at independent of the collimator resolution. Moreover, using the optimized camera, the difference between the MC calculated range and the absolute range was 0.5 cm (the relative error is about 3%).&#x0D; Conclusion: It was found that the collimator parameters are in good agreement in comparison with that of the MC results reported in the literature. The analytical method studied in this work can be used to design and optimize imaging systems based on KE collimators in combination with new detectors in a fast and reliable way.

Use of intraoperative bone scintigraphy for resection of spinal osteoid osteoma.

The location and proximity to the spinal cord in spinal osteoid osteoma can increase the likelihood of an incomplete resection. Intraoperative bone scintigraphy (IOBS) can be used to verify location and complete surgical resection. To review our experience using IOBS for resection of intraspinal osteoid osteoma. IRB approved, retrospective review of IOBS-guided resection over 10years. Patients underwent injection of 200 uCi/kg (1-20mCi) 99mTc-MDP 3-4h prior surgery. Portable single-headed gamma camera equipped with a pinhole collimator (3- or 4-mm aperture) was used. Images were obtained pre-operatively, at the start of the procedure, and intraoperatively. Operative notes were reviewed. Evaluation of recurrence and clinical follow-up was performed. Twenty IOBS-guided resections were performed in 18 patients (median age 13.5years, 6-22years, 12 males). Size ranged 5-16mm, with 38.9% (7/18) cervical, 22.2% (4/18) thoracic, 22.2% (4/18) lumbar, and 16.7% (3/18) sacral. In all cases, IOBS was able to localize the lesion. After suspected total excision, IOBS altered the surgical plan in 75% of cases (15/20), showing residual activity prompting further resection. Median length of follow-up was 6months (range 1-156months) with 90% (18/20) showing complete resection without recurrence. Two patients had osteoid osteoma recurrence at 7 and 10months following the original resection, requiring re-intervention. IOBS is a useful tool for real-time localization and assessment of spinal osteoid osteoma resection. In all cases, IOBS was able to localize the lesion and changed surgical planning in 75% of cases. Ninety percent of patients achieved complete resection and remain recurrence free.

Development of a real-time gamma camera for high radiation fields

In high radiation fields, gamma cameras suffer from pulse pile-up, resulting in poor energy resolution, count losses, and image distortion. To overcome this problem, various methods have been introduced to reduce the size of the aperture or pixel, reject the pile-up events, and correct the pile-up events, but these technologies have limitations in terms of mechanical design and real-time processing. The purpose of this study is to develop a real-time gamma camera to evaluate the radioactive contamination in high radiation fields. The gamma camera is composed of a pinhole collimator, NaI(Tl) scintillator, position sensitive photomultiplier (PSPMT), signal processing board, and data acquisition (DAQ). The pulse pile-up is corrected in real-time with a field programmable gate array (FPGA) using the start time correction (STC) method. The STC method corrects the amplitude of the pile-up event by correcting the time at the start point of the pile-up event. The performance of the gamma camera was evaluated using a high dose rate 137Cs source. For pulse pile-up ratios (PPRs) of 0.45 and 0.30, the energy resolution improved by 61.5 and 20.3%, respectively. In addition, the image artifacts in the 137Cs radioisotope image due to pile-up were reduced.

Multiple scatter correction for single plane Compton camera imaging in nuclear decommissioning

AbstractThis paper focuses on the application of Compton cameras in nuclear decommissioning, aiming to develop efficient and affordable radiological characterization methods. Compton cameras offer advantages over traditional Anger cameras, including increased sensitivity and a larger field of view. We showcase the use of monolithic scintillation detectors in a Compton camera setup to compute two‐dimensional reconstructions of the source location of incident gamma rays. The presence of multiple scattering effects in the large, spatially non‐resolved detectors can lead to spatial artifacts in the reconstructed source activity. To address this, the paper proposes an extended forward model that accounts for double scattering interactions within a single detector element. Experimental and simulation results demonstrate the effectiveness of the proposed approach.

Gamma camera-specific reference standards for radioactive iodine uptake measurements

BackgroundCurrent guidelines of the radioiodine uptake (RAIU) test allow the use of different equipment, isotopes, activity and region-of-interest (ROI). We evaluated presence and extent of these differences in clinical practice and evaluated the effect of some of these variations on RAIU outcomes. Also, gamma camera-specific reference standards were calculated and retrospectively compared with measurements obtained during clinical RAIU tests.Materials and methodsFirst, questionnaires were sent to Dutch nuclear medicine departments requesting information about equipment usage, isotope, isotope formulation, activity and measurement techniques. Secondly, a neck phantom containing a range of activities in capsule or water-dissolved formulation was scanned. Counts were measured using automatic ROI, square box ROI or all counts in the image. Thirdly, clinical RAIU data were collected during 2015–2018 using three different gamma cameras. Reference standards for each scanner were calculated using regression analysis between reference activity and measured counts. Uptake measurements using this gamma camera-specific reference standard were compared with original measurements.ResultsThe survey demonstrated significant differences in isotope, isotope formulation, activity, use of neck phantoms, frequency and duration of reference measurements, distance to collimator, use of background measurements and ROI delineation. The phantom study demonstrated higher counts for the water-dissolved formulation than capsules using both automatic and square box ROI. Also, higher counts were found using a square box ROI than an automatic ROI. The retrospective study showed feasibility of RAIU calculations using camera-specific reference standards and good correlation with the original RAIU measurements.ConclusionsThis study demonstrated considerable technical variation in RAIU measurement in clinical practice. The phantom study demonstrated that these differences could result in differences in count measurements, potentially resulting in different dose calculations for radioactive iodine therapy. Retrospective data suggest that camera-specific reference standards may be used instead of individual reference measurements using separate activity sources, which may thus eliminate some sources of variation.