High-resolution Collimator Research Articles

SPECT findings on neuropsychiatric symptoms caused by nitrous oxide abuse.

The aim of the study was to investigate the clinical, neuropsychological, and regional cerebral blood flow (rCBF) perfusion changes in patients with neuropsychiatric symptoms caused by nitrous oxide (N2O) abuse. A total of 16 patients with neuropsychiatric symptoms caused by nitrous oxide abuse were recruited for this study. The study was carried out in the withdrawal phase of N2O abuse. A 925-1110 MBq 99mTc-ECD was administered intravenously. SPECT/CT images were collected with a low-energy and high-resolution collimator. The region uptake statistics of different brain regions of interest between patients with N2O abuse and normal people of the databases for younger subjects from the Scenium DB Comparison software were calculated automatically. The clinical manifestations of the 16 patients with neuropsychiatric symptoms were mood lability, anxiety, hallucination, delusion, agitation, confusion, and other psychiatric symptoms. In addition, 15 of the patients also complained of memory decline; 14 patients manifested numbness or paresthesia; 14 patients developed limb weakness, and their motor impairments were more severe in the lower limbs than in the upper limbs; and eight patients had urinary and defecation disturbances. In the neuropsychological examination, the BPRS score was 54.69 ± 11.48, the HAMD score was 30.00 ± 11.06, the HAMA score was 18.06 ± 5.77, the MMSE score was 28.06 ± 2.29, and the MoCA score was 25.06 ± 3.40. SPECT showed hypoperfusion in the frontal and temporal lobes, which is consistent with the clinical findings. This was the first study to demonstrate the obvious effect of N2O abuse on CBF in patients with neuropsychiatric symptoms. CBF perfusion imaging is helpful to detect the changes in the local brain functional activity in patients with N2O abuse.

Study of the diagnostic efficiency of single-photon emission computed tomography with [<sup>99m</sup>Tc]Tc-1-THIO-D-glucose in visualization of brain tumors

The aim of the study was to evaluate the feasibility of using single-photon emission computed tomography (SPECT) with [99mTc]Tc-1-THIO-D-glucose in the detection of brain tumor malignancy. Material and methods. The study included 70 patients diagnosed with grade II–Iv malignant brain tumors and 10 patients with benign brain tumors. The control group consisted of 20 patients who had no pathological changes in the brain at the time of diagnosis. All patients underwent single-photon emission computed tomography of the brain 40 minutes after intravenous injection of [99mTc]Tc-1-THIO-D-glucose at a dose of 500 MBq. The [[99mTc]Tc-1-THIO-D-glucose radiopharmaceutical was prepared directly in the nuclear medicine department in strict accordance with the instructions. The head and neck of the patient fell into the field of view of the detectors of the gamma camera, 32 projections were recorded in a matrix of 256×256 pixels without hardware magnification. High-resolution low-energy collimators were used. Results. In patients with verified diagnosis of malignant brain tumors, SPECT with [99mTc]Tc-1-THIO-D-glucose correctly visualized tumors in all cases. The tumor was visualized as a zone of increased accumulation of [99mTc]Tc-1-THIO-D-glucose of varying intensity and size. However, benign brain lesions did not show [99mTc]Tc-1-THIO-D-glucose uptake. Physiological accumulation of [99mTc]Tc-1-THIO-D-glucose was observed in soft tissues of the aponeurotic helmet, the choroid of the brain, the mucous membranes of the nasal cavity, and the sinuses of the skull bones. Pathological changes in the brain revealed by SPECT were confirmed by MRI with contrast enhancement. Conclusion. The study demonstrated a high efficiency of SPECT with [99mTc]Tc-1-THIO-D-glucose in visualization of malignant brain tumors. The sensitivity, specificity and accuracy of SPECT with [99mTc]Tc-1-THIO-D-glucose in the imaging of malignant brain tumors were 93–100 %, 65–100 %, 95–100 %, respectively. The data obtained suggest that [99mTc]Tc-1-THIO-D-glucose SPECT as an additional method for the detection of malignant brain tumors can increase access to radionuclides for this group of patients and improve the quality of cancer care.

Monte Carlo approach to comparison of parallel-hole collimators of clinical scintillation camera system for imaging astatine-211 (At-211)

Astatine-211 (At-211) is a promising alpha particle emitter for targeted radionuclide therapy. Since its daughter isotope (polonium-211(Po-211)) emits characteristic X-rays of about 80 keV, the distribution of At-211 in the body can be imaged by detecting the X-rays with a scintillation camera. However, the isotopes also emit high-energy gamma photons that are collimated with difficulty for a parallel-hole collimator of a clinical scintillation camera system, and thus the selection of a collimator is important. In this study, we compared the performances of low-energy high-resolution (LEHR), low-energy all-purpose (LEAP), medium-energy (ME), and high-energy (HE) parallel-hole collimators for At-211 using Monte Carlo simulation. We simulated a clinical scintillation camera system with the collimators using the Geant4 toolkit. The energy spectra, sensitivities, and spatial resolutions for the point source of At-211 were evaluated. Moreover, we simulated imaging of six sphere sources of At-211 in a 1-cm-thick cylindrical phantom filled with At-211 solution to evaluate image contrast. All of the results in this study are simulation data. The spatial resolution with LEHR was 7.6 mm full width at half maximum (FWHM) and the highest between collimators, while the sensitivity with LEAP was 85 cps/MBq and the highest. The image contrast acquired with the ME collimator was superior to those with the other collimators. We concluded that the LEHR, LEAP, and ME collimators had their advantages, so an optimum collimator should be selected depending on the purpose of imaging of At-211, although there was no advantage in using the HE collimator for the imaging of At-211.

First experience of SPECT-CT with the radiopharmaceutical Thallium-199 chloride in diagnosis and assessment of the metastatic spread of lung cancer

Introduction. The development and improvement of new tomographic technologies for highly sensitive imaging of lung cancer (LC) is crucial for the early detection of this disease, accurate staging and control of complex therapyThe purpose of the study. To study the possibility of using the radiopharmaceutical (rp) 199TlCl for SPECT-CT imaging of LC.Material and methods. 199TlCl in solution was obtained at the U-120 cyclotron (Efremov Institute of Physics and Technology, Rosatom, St. Petersburg) of the TPU Institute of Physics and Technology by the reaction of irradiation of a metal gold target with alpha particles 197Au(α,2n)199Tl, at an alpha particle energy of 28 MeV, with a 199Tl yield of over 95%, in saline solution. The injected dose of rp was 180–185 MBq in all cases, and the scan was performed in 12–20 minutes after the injection of 199TlCl. The chest SPECT was acquired as 64 planar scans per 360° rotation of the two-detector system, in a 64 × 64 matrix, with a field of view size of 40 × 40 cm, with acquisition of more than 50,000 pulses per frame, with a high-energy high-resolution collimator installed, with an energy peak of 70 keV set at a window width of 20% of the differential discriminator. The axial sections were reconstructed using the back-projection method, taking into account the depth absorption with an absorption constant of 0.12 1 / cm. The contour of the patient's body for this purpose was imported from the CT. CT of chest was carried out immediately after the SPECT, ro the 512 × 512 matrix, with a spatial resolution of 1 mm. No X-ray contrast enhancement was carried-out. All studies were performed using a combined SPECT-CT scanner Simbia T16 (Siemens Medical).We recruited 12 patients with an established diagnosis of non-small cell LC, in everybody the SPECT-CT with 199Tl-chloride was employed to stage the disease. The control group comprised 7 patients who underwent a study with 199Tl-chloride for non-oncological pathology, but the diagnosis was finally rejected.Results. Visually, in SPECT-CT with 199TlCl in patients without tumor pathology, the accumulation in the lungs was close to background, and the image of the mediastinum was due to the normal accumulation of rp to the heart muscle. Ratio “healthy lung/myocardium” was 0.23 ± 0.05 in the control group. For the primary node of LC, this index was 0.62 ± 0.14 (p < 0.02), and for metastatically involved lymph nodes, 0.59 ± 0.16 (p < 0.05). According to the results of the individual picture of SPECT-CT with 199TlCl in LC, 6 patients out of 12 had expanded radiation areas during external gamma therapy.Conclusion. 199TlCl has a high affinity to the LC tumor tissue and shows high accumulation both to the primary and to metastatic LC foci. Routine use of SPECT-CT with 199TlCl in LC makes sence, both in the primary diagnosis and for the staging of the disease. It is necessary to continue the study of 199TlCl as rp for both ptimary diafnostic imagung of LC and also for the follow-up control of therapy.

Critical Appraisal of Radionuclide Calibrators and Gamma Cameras Prior to Lutetium-177 Internal Dosimetry at Two South African Hospitals.

Introduction The functionality of radionuclide dose calibrator and nuclear medicine imaging systems hasa direct effect on the accuracy and preciseness of internal dosimetry evaluations. Our study, therefore, aimed to critically appraise the radionuclide calibrators and gamma cameras prior to Lutetium-177 ( 177 Lu) internal dosimetry in a developing country. Materials and Methods Two radionuclide calibrators' and three gamma cameras at two South African hospitals were critically appraised in preparation for internal dosimetry of 177 Lu. The radionuclide calibrators' accuracy, linearity, and sample volume abilities were appraised. For the three gamma cameras, the uniformity, energy resolution, center of rotation, and collimator sensitivity were appraised. These appraisals were performed between the years 2014 and 2019. Results The radionuclide calibrators' constancy, accuracy, linearity, and sample volume were within ± 5%. We also integrated a 177 Lu calibration factor into one radionuclide calibrator's library. The three gamma cameras' uniformity was within 2 to 5%, energy resolution within 11%, center of rotation within 2 mm, and the sensitivity recorded for all low energy high resolution collimator. Conclusion Our radionuclide calibrators passed the critical appraisal and may be confidently used for assaying 177 Lu. All three cameras also passed critical appraisal and may be used to assess organ absorbed dose.

First experience of SPECT-CT with the radiopharmaceutical Thallium-199 chloride in diagnosis and assessment of the metastatic spread of lung cancer

Introduction. The development and improvement of new tomographic technologies for highly sensitive imaging of lung cancer (LC) is crucial for the early detection of this disease, accurate staging and control of complex therapy.The purpose of the study. To study the possibility of using the radiopharmaceutical (rp) 199TlCl for SPECT-CT imaging of LC.Material and methods. 199TlCl in solution was obtained at the U-120 cyclotron (Efremov Institute of Physics and Technology, Rosatom, St. Petersburg) of the TPU Institute of Physics and Technology by the reaction of irradiation of a metal gold target with alpha particles 197Au(α,2n)199Tl, at an alpha particle energy of 28 MeV, with a 199Tl yield of over 95%, in saline solution. The injected dose of rp was 180–185 MBq in all cases, and the scan was performed in 12–20 minutes after the injection of 199TlCl. The chest SPECT was acquired as 64 planar scans per 360° rotation of the two-detector system, in a 64 × 64 matrix, with a field of view size of 40 × 40 cm, with acquisition of more than 50,000 pulses per frame, with a high-energy high-resolution collimator installed, with an energy peak of 70 keV set at a window width of 20% of the differential discriminator. The axial sections were reconstructed using the back-projection method, taking into account the depth absorption with an absorption constant of 0.12 1 / cm. The contour of the patient's body for this purpose was imported from the CT. CT of chest was carried out immediately after the SPECT, ro the 512 × 512 matrix, with a spatial resolution of 1 mm. No X-ray contrast enhancement was carried-out. All studies were performed using a combined SPECT-CT scanner Simbia T16 (Siemens Medical).We recruited 12 patients with an established diagnosis of non-small cell LC, in everybody the SPECT-CT with 199Tl-chloride was employed to stage the disease. The control group comprised 7 patients who underwent a study with 199Tl-chloride for non-oncological pathology, but the diagnosis was finally rejected.Results. Visually, in SPECT-CT with 199TlCl in patients without tumor pathology, the accumulation in the lungs was close to background, and the image of the mediastinum was due to the normal accumulation of rp to the heart muscle. Ratio “healthy lung/myocardium” was 0.23 ± 0.05 in the control group. For the primary node of LC, this index was 0.62 ± 0.14 (p < 0.02), and for metastatically involved lymph nodes, 0.59 ± 0.16 (p < 0.05). According to the results of the individual picture of SPECT-CT with 199TlCl in LC, 6 patients out of 12 had expanded radiation areas during external gamma therapy.Conclusion. 199TlCl has a high affinity to the LC tumor tissue and shows high accumulation both to the primary and to metastatic LC foci. Routine use of SPECT-CT with 199TlCl in LC makes sence, both in the primary diagnosis and for the staging of the disease. It is necessary to continue the study of 199TlCl as rp for both ptimary diafnostic imagung of LC and also for the follow-up control of therapy.

Technetium-99m methylene diphosphonate bone scan in evaluation of insufficiency fractures - A pictorial assay and experience from South India.

ABSTRACTInsufficiency fractures (IFs) can be challenging to diagnose due to varied presentations, and sometimes, it changes the course of treatment, as in cancer patients in whom it has to be differentiated with metastatic disease. We present the role of Technetium 99m methylene diphosphonate (99mTc-MDP) bone scan, which is a low-cost, simple to perform, whole body diagnostic investigation in the diagnosis of IFs. This is a retrospective analysis of all patients who underwent a 99mTc-MDP bone scan in a tertiary care teaching hospital during 2013–2017 and were diagnosed as having an IF on bone scan. The bone scans were performed on a dual-head gamma camera using low-energy high-resolution collimators. Of all the bone scan performed during 2013–2017, a total of 138 patients with a mean age of 57.5 ± 14.7 years were diagnosed as having IFs based on bone scan and final clinical diagnosis. Among them, the most common complaint was regional bony pain in 62% of patients, while the most common cause was osteoporosis in 47% of patients, both postmenopausal and senile osteoporosis. In all, 265 sites of fractures were identified with a fracture average of 1.9/patient, the most common site being dorsolumbar vertebrae, followed by ribs and lower limb bones. Many unusual sites were also identified such as talus, sternum, clavicle, and scapula. 99mTc-MDP bone scan, being noninvasive whole-body imaging, is a useful investigation for evaluation of IFs and in correlation with biochemical analysis and other imaging can be used to determine the etiology of IF.

Comparison of Low-Energy and Medium-Energy Collimators for Thyroid Scintigraphy with123I

CE credit: For CE credit, you can access the test for this article, as well as additional JNMT CE tests, online at https://www.snmmilearningcenter.org Complete the test online no later than March 2025. Your online test will be scored immediately. You may make 3 attempts to pass the test and must answer 75% of the questions correctly to receive Continuing Education Hour (CEH) credit. Credit amounts can be found in the SNMMI Learning Center Activity. SNMMI members will have their CEH credit added to their VOICE transcript automatically; nonmembers will be able to print out a CE certificate upon successfully completing the test. The online test is free to SNMMI members; nonmembers must pay $15.00 by credit card when logging onto the website to take the test.123I thyroid scintigraphy can be performed with either a low-energy or a medium-energy (ME) collimator. The high-energy photon emissions from 123I cause septal penetration with scattered photons, which deteriorate image quality. The aim of this study was to evaluate the impact of collimator choice on 123I thyroid scintigraphy in clinical practice. Methods: Forty-seven patients who underwent thyroid planar scintigraphy with both a low-energy, high-resolution (LEHR) collimator and a ME collimator were prospectively recruited using the same imaging protocol. Image quality, collimator sensitivity, and estimation of thyroid size were assessed between LEHR and ME collimators and were compared with thyroid ultrasonography as the gold standard. Results: Images acquired with the ME collimator demonstrated reduced scattered background noise, improved thyroid-to-background contrast, and increased sensitivity in the thyroid gland compared with images acquired by the LEHR collimator. Manual measurement of the thyroid length is more accurate using the ME collimator. Automatic estimation of the thyroid area using the same thyroid threshold is larger in ME collimator images than in LEHR collimator images. Conclusion: Compared with the LEHR collimator, the ME collimator generates cleaner 123I thyroid scintigraphy images with less background noise and has higher collimator sensitivity for thyroid imaging. Different thyroid thresholds should be used to estimate the thyroid area and volume between low and ME collimators.

Evaluation of Iodine-123 and Iodine-131 SPECT activity quantification: a Monte Carlo study

PurposeThe quantitative accuracy of Nuclear Medicine images, acquired for both planar and SPECT studies, is influenced by the isotope-collimator combination as well as image corrections incorporated in the iterative reconstruction process. These factors can be investigated and optimised using Monte Carlo simulations. This study aimed to evaluate SPECT quantification accuracy for 123I with both the low-energy high resolution (LEHR) and medium-energy (ME) collimators and 131I with the high-energy (HE) collimator.MethodsSimulated SPECT projection images were reconstructed using the OS-EM iterative algorithm, which was optimised for the number of updates, with appropriate corrections for scatter, attenuation and collimator detector response (CDR), including septal scatter and penetration compensation. An appropriate calibration factor (CF) was determined from four different source geometries (activity-filled: water-filled cylindrical phantom, sphere in water-filled (cold) cylindrical phantom, sphere in air and point-like source), investigated with different volume of interest (VOI) diameters. Recovery curves were constructed from recovery coefficients to correct for partial volume effects (PVEs). The quantitative method was evaluated for spheres in voxel-based digital cylindrical and patient phantoms.ResultsThe optimal number of OS-EM updates was 60 for all isotope-collimator combinations. The CFpoint with a VOI diameter equal to the physical size plus a 3.0-cm margin was selected, for all isotope-collimator geometries. The spheres’ quantification errors in the voxel-based digital cylindrical and patient phantoms were less than 3.2% and 5.4%, respectively, for all isotope-collimator combinations.ConclusionThe study showed that quantification errors of less than 6.0% could be attained, for all isotope-collimator combinations, if corrections for; scatter, attenuation, CDR (including septal scatter and penetration) and PVEs are performed. 123I LEHR and 123I ME quantification accuracies compared well when appropriate corrections for septal scatter and penetration were applied. This can be useful in departments that perform 123I studies and may not have access to ME collimators.

Lessons learned from 15-year of radionuclide bone scan in cancer context at Yaoundé General Hospital (Cameroon) (+ Running poster)

In our setting, patients come lately to cancer treatment centres. The introduction of radionuclide scan in 2004 has had a great contribution to the diagnosis of bone metastases. To take stock of fifteen years of bone exploration in cancer context in our setting. A 15-year retrospective study with 1278 patients who performed each a radionuclide bone scan for different cancers, from 2004 to 2019 in our national reference centre. All 99mTc-MDP bone scans were performed on a Siemens® gamma-camera with a low energy high-resolution collimator. Collected data were analysed using SPSS® software with significant P -value < 0.05. Ages ranged from 15 to 92 years with a mean of 55.9 ± 15.9 and a 1.34 sex ratio. The modal age group was 50 to 70 years (39.36%). The major cancers were prostate (49.68%), breast (31.77%) and cervix (5.16%) cancers. The average duration since the diagnosis of cancer was 25.7 months. Positive bone scans accounted for 40.77% and the presence of bone metastases revealed an unknown cancer in 9.79%. The main affected sites were chest (79.27%), spine (78.31%) and pelvis (71.01%). In 26.49% of positive cases, there was no clinical sign of bone disease. According to Soloway and SWOG's classifications, the prognosis was poor in 70.06% and 66.22%, respectively. Prostate cancer was the most pejorative and cervix cancer was the one with the best prognosis ( P = 0.0014). Bone metastases are present in almost half of cases of cancers, even in absence of clinical signs. Axial bones, mainly chest, spine and pelvis, are the preferential sites. Ten percent of cancers are revealed by bone metastases. In 2/3 of cases, the prognosis is pejorative, especially for prostate cancer. We recommend that clinicians become more aware of the systematic search of bone extension as soon as the cancer is diagnosed.

Evaluation of different CT maps for attenuation correction and segmentation in static 99m Tc-MAA SPECT/CT for 90 Y radioembolization treatment planning: A simulation study.

Conventional 99m Tc-macroaggregated albumin (99m Tc-MAA) planar scintigraphy overestimates lung shunt fraction (LSF) compared to SPECT/CT. However, the respiratory motion artifact due to the temporal mismatch between static SPECT and helical CT (HCT) may compromise the SPECT quantitation accuracy by incorrect attenuation correction (AC) and volume-of-interest (VOI) segmentation. This study aims to evaluate AC and VOI segmentation effects systematically and to propose a CT map for LSF and tumor-to-normal liver ratio (TNR) estimation in static 99m Tc-MAA SPECT/CT. The 4D XCAT phantom was used to simulate a phantom population of 120 phantoms, modeling 10 different anatomical variations, nine TNRs (2-13.2), nine tumor sizes (2-6.7cm diameter), eight tumor locations, three axial motion amplitudes of 1, 1.5, and 2 (cm), and four LSFs of 5%, 10%, 15%, and 20%. An analytical projector for low-energy high-resolution parallel-hole collimator was used to simulate 60 noisy projections over 360°, modeling attenuation and geometric collimator-detector response (GCDR). AC and VOI mismatch effects were investigated independently and together, using cine average CT (CACT), HCT at end-inspiration (HCT-IN), mid-respiration (HCT-MID), and end-expiration (HCT-EX) respectively as attenuation and segmentation maps. SPECT images without motion, AC, and VOI errors were also generated as reference. LSF and TNR errors were measured as compared to the ground truth. HCT-MID has slightly better performance for AC effect compared with other CT maps in LSF and TNR estimation, while HCT-EX and HCT-MID perform better for VOI effect. For a respiratory motion amplitude of 1.5cm and a LSF of 5%, the LSF errors are 19.56±4.58%, -6.79±1.74%, 77.29±14.74%, and 111.25±18.29% corresponding to HCT-MID, HCT-EX, HCT-IN, and CACT in static SPECT. The TNR errors are -12.38±6.42%, -20.55±11.25%, -20.89±9.98%, and -22.89±14.38% respectively. HCT-MID has the best performance for LSF estimation for LSF>10% and TNR estimation, followed by HCT-EX, HCT-IN, and CACT. The HCT-MID is recommended for AC and segmentation to alleviate respiratory artifacts and improve quantitation accuracy in 90 Y radioembolization treatment planning. HCT-EX would also be a recommended choice if HCT-MID is not available.

Diamond Detectors for Radiotherapy X-Ray Small Beam Dosimetry

Many new X-Ray treatment machines using small and/or non-standard radiation fields, e.g., Tomotherapy, Cyber-knife, and linear accelerators equipped with high-resolution multi-leaf collimators and on-board imaging system, have been introduced in the radiotherapy clinical routine within the last few years. The introduction of these new treatment modalities has led to the development of high conformal radiotherapy treatment techniques like Intensity Modulated photon Radiation Therapy, Volumetric Modulated Arc Therapy, and stereotactic radiotherapy. When using these treatment techniques, patients are exposed to non-uniform radiation fields, high dose gradients, time and space variation of dose rates, and beam energy spectrum. This makes reaching the required degree of accuracy in clinical dosimetry even more demanding. Continuing to use standard field procedures and detectors in fields smaller than 3 × 3 cm2, will generate a reduced accuracy of clinical dosimetry, running the risk to overshadowing the progress made so far in radiotherapy applications. These dosimetric issues represent a new challenge for medical physicists. To choose the most appropriate detector for small field dosimetry, different features must be considered. Short- and long-term stability, linear response to the absorbed dose and dose rate, no energy and angular dependence, are all needed but not sufficient. The two most sought-after attributes for small field dosimetry are water equivalence and small highly sensitive (high sensitivity) volumes. Both these requirements aim at minimizing perturbations of charged particle fluence approaching the Charged Particle Equilibrium condition as much as possible, while maintaining high spatial resolution by reducing the averaging effect for non-uniform radiation fields. A compromise between different features is necessary because no dosimeter currently fulfills all requirements, but diamond properties seem promising and could lead to a marked improvement. Diamonds have long been used as materials for dosimeters, but natural diamonds were only first used for medical applications in the 80 s. The availability of reproducible synthetic diamonds at a lower cost compared to natural ones made the diffusion of diamonds in dosimetry possible. This paper aims to review the use of synthetic poly and single-crystal diamond dosimeters in radiotherapy, focusing on their performance under MegaVoltage photon beams. Both commercial and prototype diamond dosimeters behaviour are described and analyzed. Moreover, this paper will report the main related results in literature, considering diamond development issues like growth modalities, electrical contacts, packaging, readout electronics, and how do they affect all the dosimetric parameters of interest such as signal linearity, energy dependence, dose-rate dependence, reproducibility, rise and decay times.

Performance of SwiftScan planar and SPECT technology using low-energy high-resolution and sensitivity collimator compared with Siemens SPECT system.

A new low-energy high-resolution-sensitivity (LEHRS) collimator was developed by General Electric (GE) Healthcare. SwiftScan planar and single photon emission computed tomography (SPECT) systems using LEHRS collimator were developed to achieve the low-dose and/or short-time acquisition. We demonstrated the performance of SwiftScan planar and SPECT system with LEHRS collimator using phantoms. Line source, cylindrical and flat plastic dish phantoms were used to evaluate the performance of planar and SPECT images for four patterns of Siemens LEHR, GE LEHR, GE LEHRS and SwiftScan using two SPECT-CT scanners. Each phantom was filled with 99mTc solution, and the spatial resolution, sensitivity and image uniformity were calculated from the planar and SPECT data. The full-width at half maximum (FWHM) values as a system spatial resolution of Siemens LEHR, GE LEHR and GE LEHRS were approximately 7.4 mm. GE LEHRS showed a lower FWHM value by increasing the blend ratio in Clarity2D processing. The system sensitivity of GE LEHRS increased by approximately 30% compared with that of GE LEHR and was similar to that of Siemens LEHR. The FWHM values of SPECT with an filtered back projection (FBP) method were approximately 10.3 mm. The FWHM values of the ordered subset expectation maximization (OSEM) method were better with an increase in iteration values. The differential uniformities of Siemens LEHR, GE LEHR, GE LEHRS and GE SwiftScan using the FBP method were approximately 15.1%. The differential uniformity of OSEM method was higher with an increase in the iteration value. The SwiftScan planar and SPECT have a high sensitivity while maintaining the spatial resolution compared with the conventional system.

Clinical validation of time reduction strategy in continuous step-and-shoot mode during SPECT acquisition

BackgroundThe SwiftScan solution (General Electric Healthcare) combines a new low-energy high-resolution sensitivity collimator and a tomographic step-and-shoot continuous (SSC) mode acquisition. The purpose of this study is to determine whether SSC mode can be used in clinical practice with shorter examination times, while preserving image quality and ensuring accurate semi-quantification. Twenty bone scan and 10 lung scan studies were randomly selected over a period of 2 months. Three sets of image datasets were produced: step-and-shoot (SS) acquisition, simulated 25% count reduction using the Poisson resampling method (SimSS), and SimSS continuous acquisition (SimSSC), where SimSS was summed with counts acquired during detector head rotation. Visual assessment (5-point Likert scale, 2 readers) and semi-quantitative evaluation (50 focal uptake from 10 bone studies), assessed by SUVmean, coefficient of variation (COV), and contrast-to-noise ratio (CNR), were performed using t test and Bland-Altman analysis.ResultsIntra-reader agreement was substantial for reader 1 (k = 0.71) and for reader 2 (k = 0.61). Inter-reader agreement was substantial for SS set (k = 0.93) and moderate for SimSSC (k = 0.52). Bland-Altman analysis showed a good interchangeability of SS and SimSSC SUV values. The mean CNR between SS and SimSSC was not significantly different: 42.9 ± 43.7 [23.7–62.1] vs. 43.1 ± 46 [22.9–63.3] (p = 0.46), respectively. COV values, assessing noise level, did not deviate significantly between SS and SimSSC: 0.20 ± 0.08 [0.18–0.23] vs. 0.21 ± 0.08, [0.18–0.23] (p = 0.15), respectively, whereas a significant difference was demonstrated between SS and SimSS: 0.20 ± 0.08 [0.18–0.23] vs. 0.23 ± 0.09 [0.20–0.25] (p < 0.0001), respectively.ConclusionsSSC mode acquisition decreases examination time by approximately 25% in bone and lung SPECT/CT studies compared to SS mode (~ 2 min per single-bed SPECT), without compromising image quality and signal quantification. This SPECT sensitivity improvement also offers the prospect of more comfortable exams, with less motion artifacts, especially in painful or dyspneic patients.

The usefulness of SwiftScan technology for bone scintigraphy using a novel anthropomorphic phantom

The aim of this study was to demonstrate the usefulness of SwiftScan with a low-energy high-resolution and sensitivity (LEHRS) collimator for bone scintigraphy using a novel bone phantom simulating the human body. SwiftScan planar image of lateral view was acquired in clinical condition; thereafter, each planar image of different blend ratio (0–80%) of Crality 2D processing were created. SwiftScan planar images with reduced acquisition time by 25–75% were created by Poisson’s resampling processing. SwiftScan single photon emission computed tomography (SPECT) was acquired with step-and-shoot and continuous mode, and SPECT images were reconstructed using a three-dimensional ordered subset expectation maximization incorporating attenuation, scatter and spatial resolution corrections. SwiftScan planar image showed a high contrast to noise ratio (CNR) and low percent of the coefficient of variance (%CV) compared with conventional planar image. The CNR of the tumor parts in SwiftScan SPECT was higher than that of the conventional SPECT image of step and shoot acquisition, while the %CV showed the lowest value in all systems. In conclusion, SwiftScan planar and SPECT images were able to reduce the image noise compared with planar and SPECT image with a low-energy high-resolution collimator, so that SwiftScan planar and SPECT images could be obtained a high CNR. Furthermore, the SwiftScan planar image was able to reduce the acquisition time by 25% when the blend ratio of Clarity 2D processing set to more than 40%.

Knowledge-Based Volumetric Modulated Arc Therapy Treatment Planning for Breast Cancer.

Purpose:To create and to validate knowledge-based volumetric modulated arc therapy (VMAT) models for breast cancer treatments without lymph node irradiation.Materials and Methods:One hundred VMAT-based breast plans (manual plans [MP]) were selected to create two knowledge-based VMAT models (breast left and breast right) using RapidPlan™. The plans were generated on Eclipse v15.5 (Varian Medical Systems, Palo Alto, CA) with 6 MV of a Novalis Tx equipped with a high-resolution multileaf collimator. The models were verified based on goodness-of-fit statistics using the coefficients of determination (R2) and Chi-square (χ2), and the goodness-of-estimation statistics through the mean square error (MSE). Geometrical and dosimetrical constraints were identified and removed from the RP models using statistical evaluation metrics and plots. For validation, 20 plans that integrate the models and 20 plans that do not were reoptimized with RP (closed and opened validation). Dosimetrical parameters of interest were used to compare MP versus RP plans for the Heart, Homolateral_Lung, Contralateral_Lung, and Contralateral_Breast. Optimization planning time and user independency were also analyzed.Results:The most unfavorable results of R2 in both models for the organs at risk were as follows: for Contralateral_Lung 0.51 in RP right breast (RP_RB) and for Heart 0.60 in RP left breast (RP_LB). The most unfavorable results of χ2 test were: for Contralateral_Breast 1.02 in RP_RB and for Heart 1.03 in RP_LB. These goodness-of-fit results show that no overfitting occurred in either of the models. There were no unfavorable results of mean square error (MSE, all < 0.05) in any of the two models. These goodness-of-estimation results show that the models have good estimation power. For closed validation, significant differences were found in RP_RB for Homolateral_Lung (all P ≤ 0.001), and in the RP_LB differences were found for the heart (all P ≤ 0.04) and for Homolateral_Lung (all P ≤ 0.022). For open validation, no statistically significant differences were obtained in either of the models. RP models had little impact on reducing optimization planning times for expert planners; nevertheless, the result showed a 30% reduction time for beginner planners. The use of RP models generates high-quality plans, without differences from the planner experience.Conclusion:Two RP models for breast cancer treatment using VMAT were successfully implemented. The use of RP models for breast cancer reduces the optimization planning time and improves the efficiency of the treatment planning process while ensuring high-quality plans.

Importance of Beam-Matching between TrueBeam STx and Novalis Tx in Pre-Treatment Quality Assurance Using Portal Dosimetry

Flexibility and efficiency in a radiotherapy department with different linear accelerators (linacs) can be improved if they are dosimetrically equivalent, and there is no need of plan or patient-specific quality assurance (PSQA) modification. From 2012 to 2017, our institution purchased three Novalis Tx and one TrueBeam STx beam-matched accelerators with the same high-resolution multileaf collimator (MLC). They are matched taking as reference dosimetric data from Novalis Tx SN-5479. We showed the importance of beam-matched dosimetric units by the use of electronic portal image device (EPID) and Delta4 PSQA. It was able to treat patients on a different machine than the machine used for PSQA. Depth dose, beam profiles, output factors, dosimetric leaf gap, and MLC transmission were compared for all energies and linacs. PSQA in all linacs for 30 volumetric-modulated arc therapy plans was also compared. Prostate, breast, and head-and-neck cases were selected to consider low, middle, and high plan complexity, respectively. The comparisons were evaluated using EPID and Delta4 phantom. Dosimetric differences between the three Novalis Tx and TrueBeam STx in all energies were lower than 1%. The only significant difference was observed in Novalis EPID in middle complexity when the criterion was tighter in distance. This result could be related with the nonsymmetric dose delivery of semi arcs. In all other cases, there were no differences in two different EPID evaluations. However, TrueBeam EPID values were slightly higher than Novalis EPID values. This could be associated with the high-resolution novel diode detector TrueBeam EPID. The dosimetric data indicated that the Novalis Tx and TrueBeam STx are equivalent. PSQA using EPID and Delta4 phantom showed that there are no dosimetric differences in any of the linacs. These results revealed the flexibility performance in PSQA by beam-matching.

SPECT performance evaluation on image of Yttrium 90 - Bremsstrahlung using Monte Carlo simulation

Yttrium-90 (90Y) is one of the most widely used radionuclides in Nuclear Medicine practice. However, characteristic energy of this beta emitter constitutes a difficulty for dose planning using SPECT imaging. This work aimed to study bremsstrahlung X-rays effects produced by 90Y beta particles during SPECT image acquisition using Monte Carlo code MCNPX. Several simulations were carried out to evaluate different aspects that could affect SPECT image quality, such as: collimator type, source-collimator distance and composition of each interacting material. Two configurations of 90Y sources were simulated: a point source in several spheres of different materials (soft tissue, water, articular cartilage, and bone) and dimensions with radius ranging from 1 to 20 mm; and a uniformly distributed source in a Lucite cylindrical phantom filled with water. It was evaluated the bremsstrahlung photon emission generated inside different materials; for this was considered the number photons that passing through every different sphere's surface for each radii and material. In case of cylindrical phantom filled with water, in order to obtain the energy deposited over NaI (Tl) crystal detector; there was considered Median Energy General Purpose (MEGP) and Low Energy High Resolution (LEHR) collimators. Moreover, using TMESH routine available in the MCNPX Monte Carlo code, energy distribution images according to the collimator type and the source-collimator distance were obtained. The simulation was validated by comparing with the spectral distribution of the 90Y bremsstrahlung X-rays obtained experimentally from an acrylic cylindrical phantom. Results corroborated the importance of Monte Carlo simulation method to evaluate a performance of SPECT image acquisition with 90Y. The best resolution was obtained with MEGP collimator independent of source-collimator distance.

Collimator and Energy Window Evaluation in Ga-67 Imaging by Monte Carlo Simulation

Objectives:Gallium-67 (Ga-67) imaging is affected by collimator penetration and scatter components owing to the high-energy (HE) gamma-ray emissions. The characterization of penetration and scatter distribution is essential for the optimization of low-energy high-resolution (LEHR), medium energy (ME), and HE collimators and for the development of an effective correction technique. We compared the image quality that can be achieved by 3 collimators for different energy windows using the SIMIND Monte Carlo code.Methods:Simulation experiments were conducted for LEHR, ME, and HE collimators for Ga-67 point source placed at 12-cm distance from the detector surface using the Monte Carlo SIMIND simulation code. Their spectra point spread functions as well as the original, penetration, scattering, and X-rays curves were drawn and analyzed. The parameters full-width at half maximum and full-width at tenth maximum were also investigated.Results:The original, penetration, and scatter curves within 10% for LEHR were 34.46%, 33.52%, 17.29%, and 14.72%, respectively. Similarly, the original, penetration, scatter, and X-rays within 10% for ME and HE were 83.06%, 10.25%, 6.69%, and 0% and 81.44%, 11.51%, 7.05%, and 0%, respectively. The trade-off between spatial resolution and sensitivity was achieved by using the ME collimator at 185 photopeak of Ga-67.Conclusion:The Monte Carlo simulation outcomes can be applied for optimal collimator designing and for the development of new correction method in Ga-67 imaging.

Generation of a high-resolution 3D-printed freeform collimator for VCSEL-based 3D-depth sensing

This Letter discusses the generation of 3D-printed micro-optics to obtain the desired beam profile from a multimode vertical-cavity surface-emitting laser (VCSEL) with a significantly reduced divergence angle via the usage of high-resolution two-photon polymerization. Due to the low cost and compact packaging, the VCSEL array is a novel light source for structured-light projection. Particularly for long-distance 3D sensing applications, a greatly reduced divergence angle ensures that a good signal with a sufficiently large number of photons can be recorded, and the projected illumination spots do not overlap. Therefore, exact laser beam characterization and appropriate physical modeling are required in accurate production of an optimal collimator lens. Furthermore, elliptical beam profiles with different orientations can solve the correspondence problem and improve the post-processing speed and robustness in structured light. To generate this special type of beam profile and verify the optical design process, this Letter describes thoroughly the optical prototyping process starting from the beam characterization, the optical design to the production of the two-photon polymerized optics, and its validation. The test of the beam profile and divergence confirm a good match of the produced optics with the physical optical simulation in Zemax. The collimator transforms the input laser beam divergence angle of 324 mrad to an output angle of 20 mrad only.