Dosis efectivas asociadas a estudios híbridos SPECT-CT en pacientes adultos / Effective dose associated to hybrid SPECT-CT imaging in adult patients / Doses eficazes associadas a estudos de SPECT-CT híbridos em pacientes adultos

Introducción: la técnica de imagen híbrida de SPECT-CT combina la imagen de la tomografía por emisión de fotón único (SPECT) con el estudio de tomografía computada (TC), obteniendo información funcional y anatómica en un mismo estudio. La dosis efectiva total de radiación ionizante recibida en los estudios SPECT-CT puede ser estimada a partir de la dosis efectiva atribuible a la actividad administrada del radiofármaco y la dosis efectiva del componente de tomografía computada (TC). Objetivos: estimar la dosis efectiva total en los protocolos SPECT-CT utilizados en población adulta y determinar el aporte adicional del estudio TC sobre la dosis efectiva total. Método: se evaluaron 258 estudios SPECT-CT para estimar la dosis efectiva total aportada por la administración de los radiofármacos y los estudios de TC de baja dosis. Para estimar el aporte de ambos componentes se utilizaron factores de conversión específicos de cada radiofármaco y región explorada mediante TC. Resultados: la dosis efectiva total (media ± DS) en los estudios SPECT-CT fueron: 12,4 ± 1,44 mSv en el estudio de perfusión miocárdica, 1,14 ± 0,25 mSv en ganglio centinela de mama, 8,6 ± 0,6 mSv paratiroides, 1,48 ± 1,02 mSv tiroides y los estudios óseos de las regiones de cuello 4,5 ± 0,3, tórax 6,07 ± 0,3 mSv, abdomen y pelvis 6,1 ± 0,3 mSv. La dosis de radiación aportada por el estudio TC se encuentra entre 0,46 mSv para la región del tórax en el estudio de ganglio centinela de mama y 2,3 mSv para el SPECT-CT óseo en la región de abdomen y pelvis. Conclusión: se logró estimar la dosis efectiva en los protocolos SPECT-CT de uso clínico más frecuente en población adulta y el aporte de los estudios TC a la dosis efectiva total siendo relativamente baja comparado con la dosis aportada por los radiofármacos administrados con la excepción del estudio de ganglio centinela donde la contribución del componente TC es aproximadamente la mitad de la dosis efectiva total.

Introduction: SPECT-CT Hybrid image technique combines the SPECT (single-photon emission computed tomography) image with the CT (computerized tomography) image to obtain both functional and anatomical images in the same study. The total effective ionizing radiation dose received in SPECT-CT studies may be estimated based on the effective dose from the radiopharmaceutical administered and the effective dose from the CT (computerized tomography) component. Objectives: the study aims to estimate the total effective dose in SPECT-CT protocols applied for the adult population, and to determine the additional contribution from the CT component to the total effective dose. Method: 258 SPECT-CT studies were evaluated to estimate the total effective dose from the administration of radiopharmaceuticals and low dose CT studies. Specific conversion factors for each radiopharmaceutical and area of the body explored with the CT were used to estimate radiation doses from both components. Results: total effective dose (average ± SD) in the SPECT-CT studies was: 12.4 ± 1.44 mSv in the myocardial perfusion study, 1.14 ± 0.25 mSv in the breast sentinel lymph node study, 8.6 ± 0.6 mSv in the parathyroid study, 1.48 ± 1.02 mSv in the thyroid study. As to bone studies, doses found were: 4.5 ± 0.3, in neck studies, 6.07 ± 0.3 mSv in thoracic studies and 6.1 ± 0.3 mSv in abdominal and pelvic studies. The radiation dose from the CT study ranges from 0.46 mSv for the thoracic region on the breast sentinel lymph node study to 2.3 mSv for the bone SPECT-CT study of the abdominal and pelvic region. Conclusions: we managed to estimate the effective dose in the the most frequently used SPECT-CT protocols for the adult population and the contribution of CT studies to the total effective dose. It was found to be relatively low when compared to the dose contributed by the radiopharmaceuticals administered, with the exception of the sentinel lymph node study for which the contribution from the CT study is approximately half the total effective dose.

Introdução: a técnica de imagem híbrida SPECT-CT combina a imagem de tomografia por emissão de fóton único (SPECT) com o estudo de tomografia computadorizada (TC), obtendo informações funcionais e anatômicas no mesmo estudo. A dose efetiva total de radiação ionizante recebida em estudos SPECT-CT pode ser estimada a partir da dose efetiva atribuível à atividade administrada do radiofármaco e da dose efetiva do componente de tomografia computadorizada (TC). Objetivos: estimar a dose efetiva total nos protocolos SPECT-CT utilizados na população adulta e determinar a contribuição adicional do estudo de TC na dose efetiva total. Método : 258 estudos SPECT-CT foram avaliados para estimar a dose efetiva total fornecida pela administração de radiofármacos e estudos de TC de baixa dose. Para estimar a contribuição de ambos os componentes, foram utilizados fatores de conversão específicos para cada radiofármaco e região explorada pela TC. ⁠ Resultados: a dose efetiva total (média ± DP) nos estudos SPECT-CT foi: 12,4 ± 1,44 mSv no estudo de perfusão miocárdica, 1,14 ± 0,25 mSv no linfonodo sentinela mamário, 8,6 ± 0,6 mSv paratireoide, 1,48 ± 1,02 mSv estudos de tireoide e ossos das regiões do pescoço 4,5 ± 0,3, tórax 6,07 ± 0,3 mSv, abdômen e pelve 6,1 ±0,3mSv. A dose de radiação fornecida pelo estudo de TC está entre 0,46 mSv para a região do tórax no estudo do linfonodo sentinela da mama e 2,3 mSv para o SPECT-CT ósseo na região do abdome e pelve. Conclusão: foi possível estimar a dose efetiva nos protocolos de SPECT-CT mais utilizados clinicamente na população adulta e a contribuição dos estudos de TC para a dose efetiva total, sendo relativamente baixa em relação à dose fornecida pelos radiofármacos administrados com a exceção do estudo do linfonodo sentinela onde a contribuição do componente TC é aproximadamente metade da dose efetiva total.

Nuclear Medicine Imaging Procedures in Oncology.

Nuclear medicine radionuclide imaging is a quantitative imaging modality based on radioisotope-labeled tracers which emit radiation in the form of photons used for image reconstruction. Single photon emission computed tomography (SPECT) and positron emission tomography (PET) are the two noninvasive tomographic three-dimensional radionuclide imaging procedures for both clinical and preclinical settings. In this review on nuclear medicine imaging procedures in oncology, a variety of standard SPECT and PET tracers including radioiodine, 18Fluorine fluorodeoxyglucose (18F-FDG), and 68Gallium-labeled small proteins like Prostate Specific Membrane Antigen (PSMA) or somatostatin analogues and their application as targeted molecular imaging probes for improved tumor diagnosis and tumor phenotype characterization are described. Absolute and semiquantitative approaches for calculation of tracer uptake in tumors during the course of disease and during treatment allow further insight into tumor biology, and the combination of SPECT and PET with anatomical imaging procedures like computed tomography (CT) or magnetic resonance imaging (MRI) by hybrid SPECT/CT, PET/CT, and PET/MRI scanners provides both anatomical information and tumor functional characterization within one imaging session. With the recent establishment of novel molecular radiolabeled probes for specific tumor diagnosis, prognosis, and treatment monitoring, nuclear medicine has been able to establish itself as a distinct imaging modality with increased sensitivity and specificity.

Sestamibi Single-Positron Emission Computed Tomography/Diagnostic-quality Computed Tomography for the localization of abnormal parathyroid glands in patients with primary hyperparathyroidism: What clinicopathologic factors affect its accuracy?

PURPOSE: Sestamibi Single-Positron Emission Computed Tomography/Diagnostic-quality Computed Tomography (MIBI-SPECT/CT) is a common technology used for primary hyperparathyroidism (PHPT) localization in clinical practice. However, the clinicopathologic factors affecting the accuracy of MIBI-SPECT/CT and the potential limitations remain unclear. METHODS: Retrospectively enrolled PHPT patients (n = 280) were analyzed from August 2017 to December 2019. RESULTS: Of 96 patients with PHPT (mean age, 54 years; 63 females), 17 had discordance between MIBI-SPECT/CT and intraoperative findings. Among the 17 patients with discordance, 58.8% had major discordance, which occurred in most patients with multigland disease (MGD). Compared with concordant patients, discordant patients exhibited increased frequencies of autoimmune thyroid disease (29.4% vs 10.1%, p = 0.035), MDG (41.2% vs 3.8%, p = 0.035), higher PTH (296 pg/mL vs 146 pg/mL; p = 0.012),and lower phosphorus levels (0.77 mmol/L vs 0.90 mmol/L; p = 0.024). MDG (odds ratio [OR], 16.95; 95% CI 2.10-142.86), parathyroid lesion size of 12 mm or less (OR, 6.93; 95% CI 1.41-34.10), and a PTH level higher than 192.5 pg/mL (OR, 12.66; 95% CI 2.17-71.43) were independently associated with discordant MIBI-SPECT/CT results. CONCLUSION: MGD was most strongly associated with discordance between MIBI-SPECT/CT and intraoperative findings followed by a PTH level higher than 192.5 pg/mL and parathyroid lesion size of 12 mm or less. Surgeons should recognize these potential limitations, which may improve the preoperative procedure by encouraging further localization imaging and promptly facilitate intraoperative troubleshooting.

Head-to-Head Comparison of 68Ga-PSMA-11 and 131I in the Follow-Up of Well-Differentiated Metastatic Thyroid Cancer: A New Potential Theragnostic Agent.

Introduction: Thyroid cancer is the main endocrine neoplasia worldwide, for which 131I therapy is the cornerstone treatment. One of the main problems of follow up in patients with this type of cancer, is the need for thyroglobulin stimulation, not to mention the poor availability of 123I or 124I, to perform studies with a higher degree of sensitivity. Prostatic Specific Membrane Antigen (PSMA) PET/CT has demonstrated to be quite useful in a diversified number of neoplasms, on behalf of its capacity of evaluating the extent of type II carboxypeptidase expression in vascular endothelium. The end point of this article is to assess whether this novel image method possesses applicability in thyroid neoplasms follow up, for diagnostic and potentially therapeutic purposes. Methods: We retrospectively evaluated well differentiated metastatic thyroid cancer patients, who underwent a post therapeutic 131I dose whole body scan (WBS) and complementary SPECT/CT, as well as 68Ga-PSMA-11 PET/CT. Results: Ten patients with differentiated thyroid cancer were included, of whom 80% were women and 20% men, mean age was 58 years old (± 11.6). Sixty-four metastatic lesions were analyzed, 67.19% had papillary histology and 32.81% were follicular type, the most affected site of metastases was bone in 57.81%, followed by lung 17.19%, lymph nodes 7.81%, postoperative thyroid bed 4.69%, brain 4.69% and others 7.81%. 68Ga PSMA-11 PET/CT detected 64/64 lesions, all of them also identified by computed tomography (CT), whereas 131I SPECT/CT detected 55/64 lesions. Discrepant lesions were localized in lung 44.4%, brain 22.2%, postoperative thyroid bed 11.1%, lymph nodes 11.1% and bone 11.1%. The degree of correspondence among observers was outstanding for both radiotracers, but close upon perfect for PSMA-11 (κ = 0.98; 95% CI, 0.80 - 0.91), as opposed to 131 I (κ = 0.86; 95% CI, 0.71 - 0.76). Conclusions: 68Ga-PSMA PET/CT showed an utterly superior capability for metastatic lesion detection when compared to 131I SPECT/CT. These findings suggest that PSMA PET/CT could possibly and precociously identify radioiodine refractoriness. PSMA uptake values not only expedite diagnosis, but also award it the ability to be used for therapeutic intents.

The additional prognostic value of myocardial perfusion SPECT in patients with known coronary artery disease with high exercise capacity.

BACKGROUND: The prognostic value of myocardial perfusion imaging (MPI) in patients with known coronary artery disease (CAD) and high exercise capacity is still unknown. We sought to determine the MPI additional prognostic value over electrocardiography (ECG) stress testing alone in patients with known CAD who achieved ≥ 10 metabolic equivalents (METs). METHODS AND RESULTS: We evaluated 926 patients with known CAD referred for MPI with exercise stress. Patients were followed for a mean of 32.4 ± 9.7 months for the occurrence of all-cause death or nonfatal myocardial infarction (MI). Those achieving ≥ 10 METs were younger, predominantly male, and had lower prevalence of cardiovascular risk factors. Patients reaching ≥ 10 METs had a lower annualized rate of hard events compared to their counterparts achieving < 10 METs (1.13%/year vs 3.95%/year, P < .001). Patients who achieved ≥ 10 METs with abnormal scans had a higher rate of hard events compared to those with normal scans (3.37%/year vs 0.57%/year, P = .023). Cardiac workload < 10 METs and an abnormal MPI scan were independent predictors of hard events. CONCLUSIONS: MPI is able to stratify patients with known CAD achieving ≥ 10 METs for the occurrence of all-cause death and nonfatal MI, with incremental prognostic value over ECG stress test alone.

The value of skeletal standardized uptake values obtained by quantitative single-photon emission computed tomography-computed tomography in differential diagnosis of bone metastases.

PURPOSE: The aim of this study was to explore the value of skeletal standardized uptake value (SUV) obtained by quantitative single-photon emission computed tomography-computed tomography (SPECT/CT) in differential diagnosis of bone metastases from benign lesions. MATERIALS AND METHODS: Retrospective analysis has been conducted to 51 patients with extraskeletal malignant tumors who underwent whole-body bone scan with quantitative SPECT/CT imaging, and there are no more than three hotspots that were visually detected in the SPECT/CT imaging range. Fifty-one patients were enrolled, including 28 men and 23 women with an average age of 58.8 ± 9.5 (37-77) years. A total of 88 hotspots, including 40 benign lesions and 48 metastatic lesions, and corresponding normal sites were obtained. The region of interest (ROI) of the hotspots was sketched. The ROI of the normal bone of the spinal vertebral body adjacent to the lesions or normal bone of the symmetric side of the lesions of other locations was delineated to obtain the maximum SUV (SUVmax) and the average SUV (SUVave). RESULTS: The SUVmax value of all lesions was 20.73 ± 14.01 (3.90-92.61), and the SUVmax value of the corresponding normal parts was 5.88 ± 2.36 (2.08-12.52). The difference between the two groups was statistically significant (t = 10.343, P < 0.01). The SUVave of all lesions was 8.42 ± 4.81 (37-77), and the SUVave of the corresponding normal sites was 3.10 ± 1.51 (0.65-7.54). The difference between the two groups was statistically significant (t = 11.342, P < 0.01). The SUVmax of metastases was 24.77 ± 16.32 (3.90-92.61), and the SUVmax of benign lesions was 15.89 ± 8.51 (4.68-42.32). The difference between the two groups was statistically significant (t = 3.273, P = 0.002). The SUVave of metastases was 9.09 ± 5.59 (0.81-29.08), and the SUVave of benign lesions was 7.61 ± 3.57 (1.66-17.48). There was no significant difference between the two groups (t = 1.44, P = 0.154). The area under the curve (AUC) values of the SUVmax curves was greater than that of the SUVave curve. AUCs of the SUVmax and SUVave were 0.687 (P = 0.03) and 0.576 (P = 0.223), respectively. SUVmax had greater accuracy for discriminating bone metastasis from benign lesions. Hotspots of the patients with malignant neoplasms in bone SPECT/CT may be discriminated using SUVmax with certain accuracy, and the optimal cutoff value was 17.705. CONCLUSION: The SUVmax of bone metastases was significantly larger than that of benign lesions, and there was no significant difference in SUVave between the two groups. Therefore, the SUVmax has a certain value for the differential diagnosis of metastases from benign lesions.

Uniformity of cardiac 123I-MIBG uptake on SPECT images in older adults with normal cognition and patients with dementia.

INTRODUCTION: Some studies report that assessing regional 123I-cardiac MIBG uptake can aid in the diagnosis of Lewy body disease, but others report heterogeneity in healthy controls. We aimed to evaluate regional cardiac MIBG uptake patterns in healthy older adults and patients with dementia. METHODS: 31 older adults with normal cognition, 15 Alzheimer's disease (AD), and 17 Dementia with Lewy bodies (DLB) patients were recruited. 5 individuals had previous myocardial infarction. Participants with sufficient cardiac uptake for regional SPECT analysis (29/31 controls, 15/15 AD, 5/17 DLB) had relative uptake pattern recorded. Controls were assessed for risk of future cardiovascular events using QRISK2, a validated online tool. RESULTS: In controls uptake was reduced in the inferior wall (85%), apex (23%), septum (15%), and lateral wall (8%). AD and DLB showed similar patterns to controls. Lung or liver interference was present in 61% of cases. Myocardial infarction cases showed regional reductions in uptake, but normal/borderline planar uptake. In controls, there was no relationship between cardiovascular risk score and uptake pattern. CONCLUSIONS: Significant variability of regional cardiac 123I-MIBG uptake is common in cases with normal planar cardiac uptake. Heterogeneity of regional uptake appears non-specific and unlikely to aid in the diagnosis of Lewy body disease.

Does whole-body bone SPECT/CT provide additional diagnostic information over [18F]-FCH PET/CT for the detection of bone metastases in the setting of prostate cancer biochemical recurrence?

BACKGROUND: To assess whether whole-body (WB) bone SPECT/CT provides additional diagnostic information over [18F]-FCH PET/CT for the detection of bone metastases in the setting of prostate cancer biochemical recurrence (PC-BR). METHODS: Patients referred for a PC-BR and whom benefited from a WB bone SPECT/CT and FCH PET/CT were retrospectively included. Tests were classified as positive, equivocal, or negative for bone metastases. A best valuable comparator (BVC) strategy including imaging and follow-up data was used to determine the metastatic status in the absence of systematic histological evaluation. RESULTS: Between January 2011 and November 2017, 115 consecutive patients with a PC-BR were evaluated. According to the BVC, 30 patients had bone metastases and 85 patients did not present with bone lesions. The sensitivity, specificity, positive and negative predictive values were respectively 86.7% [69.3-96.2], 98.8% [93.6-100.0], 96.3% [78.7-99.5], and 95.5% [89.4-98.1] for WB bone SPECT/CT and 93.3% [77.9-99.2], 100.0% [95.8-100.0], 100.0 and 97.7% [91.8-99.4] for FCH PET/CT. There was no significant difference in diagnostic accuracy of bone metastases between WB Bone SPECT/CT (AUC 0.824 [0.74-0.90]) and FCH PET/CT (AUC 0.829 [0.75-0.90], p = 0.41). CONCLUSION: Despite good performances for the diagnosis of bone metastases in PC-BR, WB bone SPECT/CT does not provide additive diagnostic information over concomitant FCH PET/CT.

Inter- and intraobserver agreement in standard and ultra-fast single-photon emission computed tomography/computed tomography for the assessment of bone metastases.

OBJECTIVE: To investigate inter- and intraobserver agreement using standard (std)-single-photon emission computed tomography/computed tomography (SPECT/CT) or ultra-fast acquisition (UF)-SPECT/CT as an add-on to planar whole-body bone scintigraphy (WB-BS) for the detection of bone metastases in patients with known cancer. METHODS: Images from patients (n = 104) participating in a prospective trial comparing SPECT/CT as an add-on to WB-BS with two different acquisition methods (std-SPECT/CT; 20 s per view, 32 views and UF-SPECT/CT; 16 views of 10 s per view) were included. The combinations of WB-BS with the two different SPECT/CT acquisition methods were independently evaluated by two experienced observers using a three-point scale (M0: no metastases, Me: equivocal for bone metastases and M1: bone metastases). The observers re-evaluated the scans 6 months later. Inter- and intraobserver agreement was calculated using linear weighted kappa. RESULTS: The linear weighted kappa for the interobserver agreement was 0.78 [95% confidence interval (CI) 0.61-0.94] for WB-BS with std-SPECT/CT and 0.84 (95% CI 0.67-1.00) for WB-BS with UF-SPECT/CT. Similar values were observed for the intraobserver agreement, in which the linear weighted kappa was 0.76 (95% CI 0.60-0.92) and 0.73 (95% CI 0.57-0.90) for std-SPECT/CT and UF-SPECT/CT, respectively. CONCLUSION: Satisfactory inter- and intraobserver agreement was seen for both acquisition methods, emphasizing that the use of SPECT/CT as an add-on to WB-BS is a robust method for the detection of bone metastases even when conducted with a very short acquisition time.

Incidental CT Findings Suspicious for COVID-19-Associated Pneumonia on Nuclear Medicine Examinations: Recognition and Management Plan.

Some patients undergoing routine SPECT/CT and PET/CT examinations during the COVID-19 pandemic may incidentally reveal findings of COVID-19-associated pneumonia (C-19AP) on localizing CT. It is critical for nuclear medicine physicians to develop diagnostic skills for timely recognition of typical findings of C-19AP on a localizing CT. Furthermore, it is our responsibility to know the optimal practices for safely isolating and managing such patients while protecting the staff, other patients at the facility, family and/or friend accompanying the patients, and the public in general from risky exposure to COVID-19 sources. We offer several steps following an encounter suspicious of C-19AP.

SCreg: a registration-based platform to compare unicondylar knee arthroplasty SPECT/CT scans.

BACKGROUND: A combination of conventional computed tomography and single photon emitted computed tomography (SPECT/CT) provides simultaneous data on the intensity and location of osteoblastic activity. Currently, since SPECT/CT scans are not spatially aligned, scans following knee arthroplasty are compared by extracting average and maximal values of osteoblastic activity intensity from large subregions of the structure of interest, which leads to a loss of resolution, and hence, information. Therefore, this paper describes the SPECT/CT registration platform (SCreg) based on the principle of image registration to spatially align SPECT/CT scans following unicondylar knee arthroplasty (UKA) and allow full resolution intra-subject and inter-subject comparisons. METHODS: SPECT-CT scans of 20 patients were acquired before and 1 year after UKA. Firstly, scans were pre-processed to account for differences in voxel sizes and divided in volumes of interest. This was followed by optimization of registration parameters according to their volumetric agreement, and alignment using a combination of rigid, affine and non-rigid registration. Finally, radiotracer uptakes were normalized, and differences between pre-operative and post-operative activity were computed for each voxel. Wilcoxon signed rank sum test was performed to compare Dice similarity coefficients pre- and post-registration. RESULTS: Qualitative and quantitative validation of the platform assessing the correct alignment of SPECT/CT scans resulted in Dice similarity coefficient values over 80% and distances between predefined anatomical landmarks below the fixed threshold of (2;2;0) voxels. Locations of increased and decreased osteoblastic activity obtained during comparisons of osteoblastic activity before and after UKA were mainly consistent with literature. CONCLUSIONS: Thus, a full resolution comparison performed on the platform could assist surgeons and engineers in optimizing surgical parameters in view of bone remodeling, thereby improving UKA survivorship.

FASpecT/CT, A New SPECT/CT Acquisition With Higher Sensitivity and Efficiency in Radioiodine Thyroid Cancer Imaging.

PURPOSE: This article demonstrates the use of a new SPECT/CT acquisition protocol in patients with differentiated thyroid cancer (DTC). METHODS: SPECT/CT scans (FASpecT/CT) with fewer angle acquisitions were retrospectively reviewed in 30 DTC patients treated with radioiodine at University Hospital, San Antonio, Tex, from July 2017 to March 2019. This FASpecT/CT of 12 versus 60 to 64 sampled views for convention SPECT was made possible by iterative reconstruction. RESULTS: The FASpecT/CT protocol was judged to increase lesion detection in patients with low count rates. Furthermore, in patients with higher count rates, this technique reduced the acquisition time. FASpecT/CT patient images are shown as case examples in 4 of the 30 patients reviewed. CONCLUSIONS: This FASpecT/CT acquisition in radioiodine-treated DTC offers the potential of higher sensitivity for metastatic lymph node detection in low count rates and a significant decrease in imaging time in high count rates. These advantages make SPECT/CT imaging more acceptable for patients who have difficulty with longer imaging times, to include the pediatric population.

Standardised quantitative radioiodine SPECT/CT Imaging for multicentre dosimetry trials in molecular radiotherapy.

The SEL-I-METRY trial (EudraCT No 2015-002269-47) is the first multicentre trial to investigate the role of 123I and 131I SPECT/CT-based tumour dosimetry to predict response to radioiodine therapy. Standardised dosimetry methodology is essential to provide a robust evidence-base for absorbed dose-response thresholds for molecular radiotherapy (MRT). In this paper a practical standardised protocol is used to establish the first network of centres with consistent methods of radioiodine activity quantification. Nine SPECT/CT systems at eight centres were set-up for quantitative radioiodine imaging. The dead-time of the systems was characterised for up to 2.8 GBq 131I. Volume dependent calibration factors were measured on centrally reconstructed images of 123I and 131I in six (0.8-196 ml) cylinders. Validation of image quantification using these calibration factors was performed on three systems, by imaging a 3D-printed phantom mimicking a patient's activity distribution. The percentage differences between the activities measured in the SPECT/CT image and those measured by the radionuclide calibrator were calculated. Additionally uncertainties on the SPECT/CT-based activities were calculated to indicate the limit on the quantitative accuracy of this method. For systems set-up to image high 131I count rates, the count rate versus activity did not peak below 2.8 GBq and fit a non-paralysable model. The dead-times and volume-dependent calibration factors were comparable between systems of the same model and crystal thickness. Therefore a global calibration curve could be fitted to each. The errors on the validation phantom activities' were comparable to the measurement uncertainties derived from uncertainty analysis, at 10% and 16% on average for 123I and 131I respectively in a 5 cm sphere. In conclusion, the dead-time and calibration factors varied between centres, with different models of system. However, global calibration factors may be applied to the same system model with the same crystal thickness, to simplify set-up of future multi-centre MRT studies.

Two decades of SPECT/CT - the coming of age of a technology: An updated review of literature evidence.

PURPOSE: Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) was introduced as a hybrid SPECT/CT imaging modality two decades ago. The main advantage of SPECT/CT is the increased specificity achieved through a more precise localization and characterization of functional findings. The improved diagnostic accuracy is also associated with greater diagnostic confidence and better inter-specialty communication. METHODS: This review presents a critical assessment of the relevant literature published so far on the role of SPECT/CT in a variety of clinical conditions. It also includes an update on the established evidence demonstrating both the advantages and limitations of this modality. CONCLUSIONS: For the majority of applications, SPECT/CT should be a routine imaging technique, fully integrated into the clinical decision-making process, including oncology, endocrinology, orthopaedics, paediatrics, and cardiology. Large-scale prospective studies are lacking, however, on the use of SPECT/CT in certain clinical domains such as neurology and lung disorders. The review also presents data on the complementary role of SPECT/CT with other imaging modalities and a comparative analysis, where available.

Performance evaluation of quantitative SPECT/CT using NEMA NU 2 PET methodology.

Although PET is routinely evaluated using NEMA NU2 as standard in the clinic, standard methodology for evaluating the performance of quantitative SPECT systems has not been established. In this study, the quantitative performance of the Symbia Intevo SPECT/CT was evaluated for two common isotopes (99mTc, 177Lu) and benchmarked against the performance of a PET/CT. A further aim was to demonstrate the utility of adapting NEMA NU2 PET measurements to SPECT. In addition, dead-time and resolution recovery were evaluated to provide more complete system evaluations. Spatial resolution of the SPECT system at 1 cm from the center in the transverse direction was 13.1 mm and 22.4 mm for 99mTc and 177Lu respectively, compared with 4.3 mm (18F) and 5.8 mm (68Ga) for PET. Sensitivity at the center of the FoV was 119 cps MBq-1 and 48 cps MBq-1 (99mTc, 177Lu) for SPECT and 9632 cps MBq-1 and 8216 cps MBq-1 (18F, 68Ga) for PET. Scatter fraction was 0.25 and 0.36 (99mTc, 77Lu) for SPECT and 0.32 and 0.29 (18F, 68Ga) for PET. Contrast recovery coefficient in the largest spheres was 0.79 and 0.65 (99mTc, 177Lu) for SPECT, 1.00 and 0.97 (18F, 68Ga) for PET and the background variability was 2.7%, 6.5% (99mTc, 177Lu), 1.5% and 1.6% (18F, 68Ga), respectively. Partial volume effect was evaluated using the NEMA IQ phantom with six sphere inserts (diameter: 37 mm, 28 mm, 22 mm, 17 mm, 13 mm and 10 mm). Full contrast recovery was reached with the 17 mm for 18F, while SPECT did not reach full recovery for any sphere. Count rate losses were 2% for 99mTc at 1 GBq and 11% for 177Lu at 8.5 GBq which are well below the typical activities for clinical applications. We concluded NEMA NU2 methodology can be easily adapted to SPECT/CT as a routine quality assurance procedure in the clinic.

Spectral CT in patients with acute thoracoabdominal bleeding-a safe technique to improve diagnostic confidence and reduce dose?

Computed tomography (CT) protocols for the detection of bleeding sources often include unenhanced CT series to distinguish contrast agent extravasation from calcification. This study evaluates whether virtual non-contrast images (VNC) can safely replace real non-contrast images (RNC) in the search for acute thoracoabdominal bleeding and whether monoenergetic imaging can improve the detection of the bleeding source.The 32 patients with active bleeding in spectral CT angiography (SCT) were retrospectively analyzed. RNC and SCT series were acquired including VNC and monoenergetic images at 40, 70, and 140 keV. CT numbers were measured in regions of interest (ROIs) in different organs and in the bleeding jet for quantitative image analysis (contrast-to-noise ratios [CNR] and signal-to-noise ratio [SNR]). Additionally, 2 radiologists rated detectability of the bleeding source in the different CT series. Wilcoxon rank test for related samples was used.VNC series suppressed iodine sufficiently but not completely (CT number of aorta: RNC: 33.3±12.3, VNC: 44.8 ±â€Š9.5, P = .01; bleeding jet: RNC: 43.1 ±â€Š16.9, VNC: 56.3 ±â€Š16.7, P = .02). VNC showed significantly higher signal-to-noise ratios than RNC for all regions investigated. Contrast-to-noise ratios in the bleeding jet were significantly higher in 40 keV images than in standard 140 keV images. The 40 keV images were also assigned the best subjective ratings for bleeding source detection.VNC can safely replace RNC in a CT protocol used to search for bleeding sources, thereby reducing radiation exposure by 30%. Low-keV series may enhance diagnostic confidence in the detection of bleeding sources.

Impact of Mobile Phone Interference on Gamma Camera Performance.

INTRODUCTION: Electromagnetic interference (EMI) due to a mobile phone device has been reported to produce a detrimental effect on the function of a gamma camera system. This effect provides evidentiary support of potential bans or restrictions regarding mobile phone use within a nuclear medicine department. METHODOLOGY: A 3G Apple iPhone 6 was tested against a thyroid phantom in four operating modes, in three positions. Testing was carried out on a Siemens E-Cam gamma camera and a GE Discovery 670 SPECT/CT gamma camera. The protocols were standardized for operation on both systems with static images obtained for assessment. The static images were arithmetically assessed by means of subtraction from a baseline image, for results of potential EMI to be determined following comparison to the baseline image. RESULTS: Initial assessment of static images acquired provided no abnormality between modes and positions. Following the application of arithmetic processes, the inferior right lobe presented with an increased ring of activity on activation of mobile signals regardless of position when tested on the Siemens E-Cam gamma camera. When compared to the GE Discovery 670 SPECT/CT gamma camera, these results did not appear to be present. This was confirmed numerically as a statistical significant difference was noted in count differences between the Siemens E-Cam and GE Discovery (P = 0.0004). CONCLUSION: The function of a gamma camera has the potential to be influenced by EMI produced by mobile phone devices. Further investigation is warranted employing SPECT acquisition to assess the potential for amplification of errors.

Visual and Semiquantitative Accuracy in Clinical Baseline 123I-Ioflupane SPECT/CT Imaging.

PURPOSE: We aimed to (a) elucidate the concordance of visual assessment of an initial I-ioflupane scan by a human interpreter with comparison to results using a fully automatic semiquantitative method and (b) to assess the accuracy compared to follow-up (f/u) diagnosis established by movement disorder specialists. METHODS: An initial I-ioflupane scan was performed in 382 patients with clinically uncertain Parkinsonian syndrome. An experienced reader performed a visual evaluation of all scans independently. The findings of the visual read were compared with semiquantitative evaluation. In addition, available f/u clinical diagnosis (serving as a reference standard) was compared with results of the human read and the software. RESULTS: When comparing the semiquantitative method with the visual assessment, discordance could be found in 25 (6.5%) of 382 of the cases for the experienced reader (ĸ = 0.868). The human observer indicated region of interest misalignment as the main reason for discordance. With neurology f/u serving as reference, the results of the reader revealed a slightly higher accuracy rate (87.7%, ĸ = 0.75) compared to semiquantification (86.2%, ĸ = 0.719, P < 0.001, respectively). No significant difference in the diagnostic performance of the visual read versus software-based assessment was found. CONCLUSIONS: In comparison with a fully automatic semiquantitative method in I-ioflupane interpretation, human assessment obtained an almost perfect agreement rate. However, compared to clinical established diagnosis serving as a reference, visual read seemed to be slightly more accurate as a solely software-based quantitative assessment.