Use of a digital phantom developed by QIBA for harmonizing SUVs obtained from the state-of-the-art SPECT/CT systems: a multicenter study

Prognostic value of left ventricular mechanical dyssynchrony indices derived from gated myocardial perfusion SPECT in coronary artery disease: a systematic review and meta-analysis

PURPOSE

Left ventricular mechanical dyssynchrony (LVMD) is an important prognostic factor in coronary artery disease. A growing body of evidence indicates that LVMD parameters derived from phase analysis of gated myocardial SPECT may allow risk stratification for future cardiac events. We performed a systematic review and meta-analysis on the prognostic value of LVMD on gated SPECT in patients with coronary artery disease.

METHODS

PubMed, Embase, and the Cochrane library were searched until August 25, 2022, for studies reporting the prognostic value of LVMD on gated SPECT for outcomes of all-cause death, cardiac death, or major adverse cardiovascular event (MACE) in patients with coronary artery disease. Hazard ratios (HRs) and their 95% confidence intervals (CIs) were meta-analytically pooled using a random-effects model.

RESULTS

Nine studies (26,750 patients) were included in a qualitative synthesis. Among the SPECT LVMD parameters used in various studies, high phase standard deviation, phase bandwidth, and phase entropy were widely evaluated and reported to be associated with high rates of all-cause death, cardiac death, or MACE. For five studies (23,973 patients) in the quantitative synthesis, the pooled HR of LVMD for predicting MACE was 2.81 (95% CI 2.03-3.88). Studies using combined phase parameters to define LVMD showed higher HRs than a study using phase entropy (p = 0.0180).

CONCLUSION

LVMD from gated myocardial SPECT is a significant prognostic factor for coronary artery disease. Phase analysis of gated SPECT may be useful for accurate risk stratification and could be applied for clinical decision-making in such patients.

A single centre intercomparison between commercial treatment planning systems for 90Y radioembolization using virtual and experimental phantoms

INTRODUCTION

Dedicated Treatment Planning Systems (TPSs) were developed to personalize 90Y-transarterial radioembolization. This study evaluated the agreement among four commercial TPSs assessing volumes of interest (VOIs) volumes and dose metrics.

METHODS

A homogeneous (EH) and an anthropomorphic phantom with hot and cold inserts (EA) filled with 99mTc-pertechnetate were acquired with a SPECT/CT scanner. Their virtual versions (VH and VA, respectively) and a phantom with activity inside a single voxel (VK) were generated by an in-house MATLAB script. Images and delineated VOIs were imported into the TPSs to compute voxel-based absorbed dose distributions with various dose deposition approaches: local deposition method (LDM) and dose kernel convolution (DKC) with/without local density correction (LDC). VOI volumes and mean absorbed doses were assessed against their median value across TPSs. Dose-volume histograms (DVHs) and VK-derived dose profiles were evaluated.

RESULTS

Small (<2.1 %) and large (up to 42.4 %) relative volume differences were observed on large (>500 ml) and small VOIs, respectively. Mean absorbed doses relative differences were < 3 % except for small VOIs with steep dose gradients (up to 89.1 % in the VA Cold Sphere VOI). Within the same TPS, LDC negligibly affected the mean absorbed dose, while DKC and LDM showed differences up to 63 %. DHVs were mostly overlapped in experimental phantoms, with some differences in the virtual versions. Dose profiles agreed within 1 %.

CONCLUSION

TPSs showed an overall good agreement except for small VOI volumes and mean absorbed doses of VOIs with steep dose gradients. These discrepancies should be considered in the dosimetry uncertainty assessment, thus requiring an appropriate harmonization.

Comparison of the detectability of hot lesions on bone SPECT using six state-of-the-art SPECT/CT systems: a multicenter phantom study to optimize reconstruction parameters

Single-photon emission computed tomography with X-ray computed tomography (SPECT/CT) systems have diversified due to the remarkable developments made by each manufacturer. This study aimed to optimize the reconstruction parameters of six state-of-the-art SPECT/CT systems and compare their image quality of bone SPECT. SPECT images were acquired on SPECT/CT systems, including Symbia Intevo, Discovery NM/CT 670, Discovery NM/CT 870 CZT, Brightview XCT, and VERITON-CT. SIM² bone phantom with tough lung phantoms on both sides of the spinal inserts that simulate the thorax was used for image quality assessment. SPECT images were obtained at individual workstations using an ordered subset expectation maximization method with three-dimensional resolution recovery, as well as CT attenuation and scatter correction, subset 2, iteration 12-84, and a full width at half maximum 10-mm Gaussian smooth filter. An automatic image analysis software dedicated to SIM² bone phantom was used to assess the contrast-to-noise ratio (CNR), relative recovery coefficient, percentage of coefficient of variance, contrast, and detectability. The optimal parameters for each system were defined with superior detectability of spherical lesions and noise characteristics, as well as the highest CNR. All systems exhibited better image quality indexes using the optimal parameters than using the manufacturer's recommended parameters. The detectability of all systems was in agreement while using the optimal parameters. Detectability agreement can be achieved by optimizing the reconstruction parameters for different reconstruction algorithms, which can further improve the image quality. Therefore, future research should focus on optimal reconstruction parameters for SPECT alone.

Impact of bone-equivalent solution density in a thoracic spine phantom on bone single-photon emission computed tomography image quality and quantification

This study aimed to evaluate the effects of dipotassium hydrogen phosphate (K₂HPO₄) solution density on single-photon emission computed tomography (SPECT) image quality and quantification. We used a JSP phantom containing six cylinders filled with K₂HPO₄ solutions of varying densities. Computed tomography (CT) was performed, and CT values and linear attenuation coefficients were measured. Subsequently, SPECT images of an SIM² bone phantom filled with ^99mTc with/without K₂HPO₄ solution were acquired using a SPECT/CT camera. The full width at half maximum (FWHM), percentage coefficient of variation (%CV), recovery coefficient, and standardized uptake value (SUV) were evaluated to investigate the impact of the K₂HPO₄ solution density. The CT values and linear attenuation coefficients increased with the K₂HPO₄ solution density. The CT values for cancellous and cortical bones were reflected by K₂HPO₄ solution densities of 0.15-0.20 and 1.50-1.70 g/cm³, respectively. FWHM values were significantly lower with the K₂HPO₄ solution than those with water alone (18.0 ± 0.9 mm with water alone, 15.6 ± 0.2 mm with 0.15 g/cm³ K₂HPO₄, and 16.1 ± 0.3 mm with 1.49 g/cm³ K₂HPO₄). Although the %CVs showed no significant differences, the recovery coefficients obtained with water alone tended to be slightly lower than those obtained with the K₂HPO₄ solution. The SUV obtained using the standard density of the K₂HPO₄ solution differed from that obtained using the optimized density. In conclusion, SPECT image quality and quantification depends on the presence and concentration of the bone-equivalent solution. The optimal bone-equivalent solution density should be used to evaluate the bone image phantoms.

Hybrid imaging of neuroendocrine tumors in the heart: Union is strength

Cardiac neuroendocrine tumors (NETs) are particularly rare tumors that can lead to a very poor clinical outcome, partly because of metastases but mainly because of manifestations of the hormonal activity they exhibit. Prompt diagnosis is important in order to start the most effective treatment for their removal or management, with the fewest complications. They are often difficult to diagnose, especially in their early stages. One of the reasons for this is that the heart is an organ with a high rate of metabolism and is located in close proximity to other high-metabolism organs. In addition, the anatomic location and their small size render their diagnosis extremely challenging. In recent years, hybrid imaging methods have revolutionized the diagnostic approach to oncology patients and have established a place in the diagnosis of cardiac NETs, because they provide both anatomical and functional information at the same time. Positron emission tomography/computed tomography (PET/CT), PET/magnetic resonance imaging (PET/MRI) and single-photon emission computed tomography/CT (SPECT/CT) are widely used in clinical practice because of the very important metabolic information, the high sensitivity and specificity. However, prospective studies are needed to confirm the true clinical and prognostic value of various hybrid imaging diagnostic techniques in cardiac NETs.

AAPM task group report 273: Recommendations on best practices for AI and machine learning for computer-aided diagnosis in medical imaging

Rapid advances in artificial intelligence (AI) and machine learning, and specifically in deep learning (DL) techniques, have enabled broad application of these methods in health care. The promise of the DL approach has spurred further interest in computer-aided diagnosis (CAD) development and applications using both "traditional" machine learning methods and newer DL-based methods. We use the term CAD-AI to refer to this expanded clinical decision support environment that uses traditional and DL-based AI methods. Numerous studies have been published to date on the development of machine learning tools for computer-aided, or AI-assisted, clinical tasks. However, most of these machine learning models are not ready for clinical deployment. It is of paramount importance to ensure that a clinical decision support tool undergoes proper training and rigorous validation of its generalizability and robustness before adoption for patient care in the clinic. To address these important issues, the American Association of Physicists in Medicine (AAPM) Computer-Aided Image Analysis Subcommittee (CADSC) is charged, in part, to develop recommendations on practices and standards for the development and performance assessment of computer-aided decision support systems. The committee has previously published two opinion papers on the evaluation of CAD systems and issues associated with user training and quality assurance of these systems in the clinic. With machine learning techniques continuing to evolve and CAD applications expanding to new stages of the patient care process, the current task group report considers the broader issues common to the development of most, if not all, CAD-AI applications and their translation from the bench to the clinic. The goal is to bring attention to the proper training and validation of machine learning algorithms that may improve their generalizability and reliability and accelerate the adoption of CAD-AI systems for clinical decision support.

[Three-dimensional Quantitative Evaluation Method in 123I-MIBG Myocardial SPECT-CT]

PURPOSE

To distinguish neurodegenerative diseases using ¹²³I-metaiodobenzylguanidine (MIBG). This study proposes a method to evaluate myocardial standardized uptake value (SUV) and assess its accuracy.

METHODS

We created a 17-segment polar map of the myocardial region from single-photon emission computed tomography-computed tomography (SPECT-CT) images using a cardioliver phantom simulating the standard uptake of MIBG. We clarified the optimal reconstruction conditions with good repeatability and accuracy of quantitative values and compared them with the H/M ratio. Myocardial SUVs were evaluated from eight normal cases using our method established from the phantom experiment and compared with the H/M ratio.

RESULTS

The optimal numbers of iterations and subsets in OSEM reconstruction were both 10. The optimal full width at half maximum (FWHM) value of the Gaussian filter was 4 pixels. The RCs and %CV of (1) maximum SUV_max (MaxSUV_max) and (2) average SUV_max (AveSUV_max) were (1) 36.5% and 4.99%, and (2) 33.6% and 4.84%, respectively. The RC and %CV of the H/M ratio was 15.0% and 1.50%, respectively. In clinical cases, average MaxSUV_max and AveSUV_max were 8.27 and 7.58, respectively.

CONCLUSION

Myocardial SUV can provide quantitative values slightly closer to theoretical values than the H/M ratios. Besides, using the optimal reconstruction parameters makes it feasible to quantitatively assess myocardial uptake with good repeatability.

EANM practice guideline for quantitative SPECT-CT

PURPOSE

Quantitative SPECT-CT is a modality of growing importance with initial developments in post radionuclide therapy dosimetry, and more recent expansion into bone, cardiac and brain imaging together with the concept of theranostics more generally. The aim of this document is to provide guidelines for nuclear medicine departments setting up and developing their quantitative SPECT-CT service with guidance on protocols, harmonisation and clinical use cases.

METHODS

These practice guidelines were written by members of the European Association of Nuclear Medicine Physics, Dosimetry, Oncology and Bone committees representing the current major stakeholders in Quantitative SPECT-CT. The guidelines have also been reviewed and approved by all EANM committees and have been endorsed by the European Association of Nuclear Medicine.

CONCLUSION

The present practice guidelines will help practitioners, scientists and researchers perform high-quality quantitative SPECT-CT and will provide a framework for the continuing development of quantitative SPECT-CT as an established modality.

Harmonization based on quantitative analysis of standardized uptake value variations across PET/CT scanners: a multicenter phantom study

OBJECTIVES

This study aimed to measure standardized uptake value (SUV) variations across different PET/computed tomography (CT) scanners to harmonize quantification across systems.

METHODS

We acquired images using the National Electrical Manufacturers Association International Electrotechnical Commission phantom from three PET/CT scanners operated using routine imaging protocols at each site. The SUVs of lesions were assessed in the presence of reference values by a digital reference object (DRO) and recommendations by the European Association of Nuclear Medicine (EANM/EARL) to measure inter-site variations. For harmonization, Gaussian filters with tuned full width at half maximum (FWHM) values were applied to images to minimize differences in SUVs between reference and images. Inter-site variation of SUVs was evaluated in both pre- and postharmonization situations. Test-retest analysis was also carried out to evaluate repeatability.

RESULTS

SUVs from different scanners became significantly more consistent, and inter-site differences decreased for SUVmean, SUVmax and SUVpeak from 17.3, 20.7, and 15.5% to 4.8, 4.7, and 2.7%, respectively, by harmonization (P values <0.05 for all). The values for contrast-to-noise ratio in the smallest lesion of the phantom verified preservation of image quality following harmonization (>2.8%).

CONCLUSIONS

Harmonization significantly lowered variations in SUV measurements across different PET/CT scanners, improving reproducibility while preserving image quality.

Impact of patient body habitus on image quality and quantitative value in bone SPECT/CT

OBJECTIVE

The first edition of guidelines for standardization of bone single photon emission computed tomography (SPECT) imaging was published in 2017, and the optimization and standardization are widely promoted. To the purpose, clarification of the factors related to image quality and quantitative values and their influence are required. The present study aimed to clarify and optimize the influence of patient body habitus on image quality and quantitative values in bone SPECT/CT.

METHODS

National Electrical Manufacturers Association body phantom (S-size) and custom-made large body phantoms (M-size and L-size) that simulate the abdomens of Japanese patients weighing 60, 80, and 100 kg, were used. Each phantom was filled with ^99mTc-solutions of 108  and 18 kBq/mL for the hot spheres and background, respectively. Dynamic SPECT acquisition was performed for 6000 s (150 s /rotation × 40 rotation). The data were divided into six projection data and reconstructed each acquisition time (150, 300, 450, 600, 750, 900 s, and single projection 6000 s). Image quality was evaluated for contrast (Q_{H, 17 mm}), background noise (N_{B, 17 mm}), contrast-to-noise ratio (CNR), maximum standardized uptake value (SUV_{max, 17 mm}), and visual assessment for a 17 mm hot sphere.

RESULTS

Image quality in the 300 s acquisition showed that values of Q_{H, 17 mm}, CNR, and SUV_{max, 17 mm} decreased (-16.7%, -11.8%, and -11.3%) for M-size and (-28.2%, -30.1%, and -21.7%) for L-size compared with S-size, respectively. No significant difference was observed in N_{B, 17 mm} values. M-size and L-size required 1.2 and 2.3 times longer acquisition, to achieve same CNR as S-size. In visual assessment, 17 mm hot sphere could not be detected only in the L-size. When the Japanese bone SPECT guidelines criteria were applied in 600 s, the sphere could be detected between all phantoms.

CONCLUSIONS

Patient body habitus significantly affects image quality and decreases the quantitative value in bone SPECT/CT. For the optimization, extend acquisition time according to the patient body habitus is effective for image quality. And for the standardization, it is important to achieve imaging conditions that meet the Japanese bone SPECT guidelines criteria to ensure adequate detectability.

Optimization of pediatric FDG-PET/CT examinations based on physical indicators using the SiPM-PET/CT system

OBJECTIVE

This study aimed to investigate the appropriate Silicon photomultiplier -PET/CT acquisition and image reconstruction conditions for each age group.

METHODS

The original phantom was developed to reflect the thickness and width of the torso in each age group (neonates, 1-year-olds, 5-year-olds, 10-year-olds, 15-year-olds, and adults). The ratio of hot spheres to background radioactivity was 4:1, and the radioactivity concentration was adjusted according to the Japanese consensus guidelines for appropriate implementation of pediatric nuclear medicine examinations. We evaluated the root mean square error (RMSE) as an assessment/function of the standardized uptake value of each hot sphere, the background variability (N10 mm), the % contrast of the hot sphere (QH, 10 mm/N10 mm), and the noise equivalent counts to determine the optimal reconstruction parameters and the appropriate acquisition time.

RESULTS

The minimum RMSE was obtained by setting the half-width of the Gaussian filter to 0-2 mm for iteration 1 or 2 and to 2-4 mm for iteration 3 or more. The acquisition times that satisfied the image quality equivalent to 120 s acquisitions in the adult phantoms were 30 s in the neonatal and 1-year-old phantoms, 60 s in the 5- and 10-year-old phantoms, and 75 s in the 15-year-old phantoms.

CONCLUSION

This study demonstrated that good PET images could be obtained with short acquisition times when the examination is performed under appropriate reconstruction conditions.

Maximum standardized uptake value of normal structures in the head and neck with bone SPECT/CT

INTRODUCTION

The quantitative parameter was successfully derived from the quantitative bone SPECT/CT images. The aim of this study was to evaluate maximum standardized uptake value (SUV) of normal structures in the head and neck with bone SPECT/CT.

METHODS

Fifty-three patients with jaw lesions (11 chronic osteomyelitis, eight osteoradionecrosis and 34 medication-related osteonecrosis of the jaw) who had bone SPECT/CT were prospectively included. The maximum SUV of normal structures including vertebrae, sternal body, parietal bone and hyoid bone were analysed. Statistical analyses for the maximum SUV were performed by Pearson's rank correlation test. A P value lower than 0.05 was considered statistically significant.

RESULTS

The maximum SUVs of vertebrae, sternal body, parietal bone and hyoid bone of all patients were 8.10 ± 3.72, 5.16 ± 2.05, 3.67 ± 1.55 and 1.44 ± 0.56, respectively. Furthermore, the maximum SUV of vertebrae was significantly correlated with that of sternal body (Y = 0.527X + 5.388 (R²  = 0.084, P = 0.035)).

CONCLUSIONS

Maximum SUV with bone SPECT/CT should be useful for characterization of normal structures in the head and neck. Furthermore, the data reported herein can be used for reference in future studies and in clinical settings for head and neck lesions.

Development of a new quantification method using partial volume effect correction for individual energy peaks in 111In-pentetreotide SPECT/CT

Objectives

Somatostatin receptor scintigraphy (SRS) using ¹¹¹In-pentetreotide has no established quantification method. The purpose of this study was to develop a new quantitative method to correct the partial volume effect (PVE) for individual energy peaks in ¹¹¹In-pentetreotide single-photon emission computed tomography (SPECT).

Methods

Phantom experiments were performed to construct a new quantitative method. In the phantom experiments, a NEMA IEC body phantom was used. Acquisition was performed using two energy peaks (171 keV and 245 keV) on the SPECT/CT system. The volume of interest was set at each hot sphere and lung insert in the SPECT images of each energy peak, and the recovery coefficient (RC) was calculated to understand the PVE. A new quantitative index, the indium uptake index (IUI), was calculated using the RC to correct the PVE. The quantitative accuracy of the IUI in the hot sphere was confirmed. Case studies were performed to clarify the quantitative accuracy. In a case study, the relationship between the IUI and the Krenning score, which is used as a visual assessment, was evaluated for each lesion.

Results

The obtained RCs showed that the energy peak at 171 keV was faster in recovering the effect of PVE than that at 245 keV. The IUI in the 17-mm-diameter hot sphere was overestimated by 4.8% and 8.3% at 171 keV and 245 keV, respectively, compared to the actual IUIs. The relationship between IUI and Krenning score was rs=0.773 (p<0.005) at sum, rs=0.739 (p<0.005) at 171 keV, and rs=0.773 (p<0.005) at 245 keV.

Conclusion

We have developed a new quantification method for ¹¹¹In-pentetreotide SPECT/CT using RC-based PVE correction for an individual energy peak of 171 keV. The quantitative accuracy of this method was high even for accumulations of less than 20 mm, and it showed a good relationship with the Krenning score; therefore, the clinical usefulness of IUI was demonstrated.

Quantitative SPECT/CT for dosimetry of peptide receptor radionuclide therapy

Neuroendocrine tumors (NETs) are uncommon malignancies of increasing incidence and prevalence. As these slow growing tumors usually overexpress somatostatin receptors (SSTRs), the use of ⁶⁸Ga-DOTA-peptides (gallium-68 chelated with dodecane tetra-acetic acid to somatostatin), which bind to the SSTRs, allows for PET based imaging and selection of patients for peptide receptor radionuclide therapy (PRRT). PRRT with radiolabeled somatostatin analogues such as ¹⁷⁷Lu-DOTATATE (lutetium-177-[DOTA,Tyr³]-octreotate), is mainly used for the treatment of metastatic or inoperable NETs. However, PRRT is generally administered at a fixed injected activity in order not to exceed dose limits in critical organs, which is suboptimal given the variability in radiopharmaceutical uptake among patients. Advances in SPECT (single photon emission computed tomography) imaging enable the absolute quantitative measure of the true radiopharmaceutical distribution providing for PRRT dosimetry in each patient. Personalized PRRT based on patient-specific dosimetry could improve therapeutic efficacy by optimizing effective tumor absorbed dose while limiting treatment related radiotoxicity.

Optimization of cross-calibration factor for quantitative bone SPECT without attenuation and scatter correction in the lumbar spine: head-to-head comparison with attenuation and scatter correction

OBJECTIVES

Quantitative single-photon emission computed tomography (SPECT) with computed tomography (SPECT/CT) is known to improve diagnostic performance. Although SPECT-alone systems are used widely, accurate quantitative SPECT using these systems is challenging. This study aimed to improve the accuracy of quantitative bone SPECT of the lumbar spine with the SPECT-alone system.

METHODS

The cross-calibration factor (CCF) was measured using three kinds of phantoms and the optimal values were determined. The recovery coefficient with and without attenuation and scatter correction (ACSC) were compared. Bone SPECT/CT was performed on 93 consecutive patients with prostate cancer, and the standardized uptake values (SUVs) were compared using the respective CCFs. The first 60 patients were classified according to body weight, and the correlation coefficient between SUVs with and without ACSC were calculated; the slopes were defined as body weight-based coefficients (BWCs). In the remaining 33 patients, the SUV was adjusted according to BWC, and the accuracy of the adjustment was verified.

RESULTS

The quantitative SPECT values obtained from the CCF using SIM2 bone phantom showed nearly accurate radioactivity concentrations, even without ACSC. The recovery coefficients with and without ACSC were similar. Unadjusted SUVs with and without ACSC were strongly correlated; however, SUVs without ACSC were significantly higher than those with ACSC (P < 0.0001). The mean difference between the SUVs with and without ACSC disappeared when the SUVs without ACSC were adjusted by BWC (P = 0.9814).

CONCLUSIONS

Our cross-calibration method for quantitative bone SPECT enables interpretation with a harmonized SUV even in SPECT-alone systems.

Feasibility of ultra-high-speed acquisition in xSPECT bone algorithm: a phantom study with advanced bone SPECT-specific phantom

OBJECTIVE

Although xSPECT Bone (xB) provides quantitative single-photon emission computed tomography (SPECT) high-resolution images, patients' burden remains high due to long acquisition time; therefore, this study aimed to investigate the feasibility of shortening the xB acquisition time using a custom-designed phantom.

METHODS

A custom-designed xSPECT bone-specific (xSB) phantom with simulated cortical and spongious bones was developed based on the thoracic bone phantom. Both standard- and ultra-high-speed (UHS) xB acquisitions were performed in a male patient with lung cancer. In this phantom study, SPECT was acquired for 3, 6, 9, 12, and 30 min. The clinical SPECT acquisition time per rotation was 9 and 3 min for standard and UHS, respectively. SPECT images were reconstructed using ordered subset expectation maximization with three-dimensional resolution recovery (Flash3D; F3D) and xB algorithms. Quantitative SPECT value (QSV) and coefficient of variation (CV) were measured using the volume of interests (VOIs) placed at the center of the vertebral body and hot sphere. A linear profile was plotted on the spinous process at the center of the xSB phantom; then, the full width at half maximum (FWHM) was measured. The standardized uptake value (SUV) and standard deviation from the first thoracic to the fifth lumbar vertebrae in clinical standard- and UHS-xB images were measured using a 1-cm³ VOI.

RESULTS

The QSV of F3D images was underestimated even in large regions, whereas those of xB images were close to actual radioactivity concentration. The CV was similar or lower for xB images than that for F3D images but was not decreased with increasing acquisition time for both reconstruction images. The FWHM of xB images was lower than those of F3D images at all acquisition times. The mean SUV values from the first thoracic to fifth lumbar vertebrae for standard- and UHS-xB images were 6.73 ± 0.64 and 6.19 ± 0.87, respectively, showing a strong positive correlation.

CONCLUSIONS

Results of this phantom study suggest that xB imaging can be obtained in only one-third of the acquisition time without compromising the image quality. The SUV of UHS-xB images can be similar to that of standard-xB images in terms of clinical interpretation.

Normal Skeletal Standardized Uptake Values Obtained from Quantitative Single-Photon Emission Computed Tomography/Computed Tomography: Time-Dependent Study on Breast Cancer Patients

Aim:

To estimate the standard uptake values (SUVs) of Tc-99m methylene-diphosphonate (Tc-99m MDP) from normal skeletal sites in breast cancer patients using quantitative single-photon emission computed tomography (SPECT).

Materials and Methods:

A total of 60 breast cancer patients who underwent Tc-99m MDP SPECT/CT study at different postinjection acquisition times were included in this study. Based on postinjection acquisition time, patients were divided into four study groups (n_15 each), i.e. I^st (2 h), II^nd (3 h), III^rd (4 h), and IV^th (5 h). Image quantification (SUVmax and SUVmean) was performed using Q.Metrix software. Delineation of volume of interest was shaped around different bones of the skeletal system.

Results:

The highest normal SUVmax and SUVmean values were observed in lumber and thoracic vertebra (8.89 ± 2.26 and 2.89 ± 0.58) for Group I and in pelvis and thoracic (9.6 ± 1.32 and 3.04 ± 0.64), (10.93 ± 3.91 and 3.65 ± 0.97), (11.33 ± 2.67 and 3.65 ± 0.22) for Group II, III and IV, respectively. Lowest normal SUVmax and SUVmean values were observed in humerus and ribs (3.22 ± 0.67 and 0.97 ± 0.18), (5.16 ± 1.82 and 1.18 ± 0.16) for Group I, IV, and in humerus (3.17 ± 0.58 and 0.85 ± 0.26), (3.98 ± 1.12 and 1.04 ± 0.28) for Group II and III, respectively. Significant difference (P < 0.05) noted in SUVmax for sternum, cervical, humerus, ribs, and pelvis with respect to time. However, significant difference (P < 0.05) noted in SUVmean for all skeletal sites with respect to time.

Conclusions:

Our study shows variability in normal SUV values for different skeletal sites in breast cancer patients. Vertebral bodies and pelvis contribute highest SUV values. Time dependency of SUVs emphasizes the usefulness of routinely acquired images at the same time after Tc-99m MDP injection, especially in follow-up studies.

Impacts of acquisition and reconstruction parameters on the absolute technetium quantification of the cadmium-zinc-telluride-based SPECT/CT system: a phantom study

Background

The digital cadmium–zinc–telluride (CZT)-based SPECT system has many advantages, including better spatial and energy resolution. However, the impacts of different acquisition and reconstruction parameters on CZT SPECT quantification might still need to be validated. This study aimed to evaluate the impacts of acquisition parameters (the main energy window and acquisition time per frame) and reconstruction parameters (the number of iterations, subsets in iterative reconstruction, post-filter, and image correction methods) on the technetium quantification of CZT SPECT/CT.

Methods

A phantom (PET NEMA/IEC image quality, USA) was filled with four target-to-background (T/B) ratios (32:1, 16:1, 8:1, and 4:1) of technetium. Mean uptake values (the calculated mean concentrations for spheres) were measured to evaluate the recovery coefficient (RC) changes under different acquisition and reconstruction parameters. The corresponding standard deviations of mean uptake values were also measured to evaluate the quantification error. Image quality was evaluated using the National Electrical Manufacturers Association (NEMA) NU 2–2012 standard.

Results

For all T/B ratios, significant correlations were found between iterations and RCs (r = 0.62–0.96 for 1–35 iterations, r = 0.94–0.99 for 35–90 iterations) as well as between the full width at half maximum (FWHM) of the Gaussian filter and RCs (r = − 0.86 to − 1.00, all P values < 0.05). The regression coefficients of 1–35 iterations were higher than those of 35–90 iterations (0.51–1.60 vs. 0.02–0.19). RCs calculated with AC (attenuation correction) + SC (scatter correction) + RR (resolution recovery correction) combination were more accurate (53.82–106.70%) than those calculated with other combinations (all P values < 0.05). No significant statistical differences (all P values > 0.05) were found between the 15% and 20% energy windows except for the 32:1 T/B ratio (P value = 0.023) or between the 10 s/frame and 120 s/frame acquisition times except for the 4:1 T/B ratio (P value = 0.015) in terms of RCs.

Conclusions

CZT-SPECT/CT of technetium resulted in good quantification accuracy. The favourable acquisition parameters might be a 15% energy window and 40 s/frame of acquisition time. The favourable reconstruction parameters might be 35 iterations, 20 subsets, the AC + SC + RR correction combination, and no filter.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-021-00412-4.

[Improvement of Standardized Uptake Value Accuracy in the 99mTc Body SPECT and SPECT/CT: Optimization of the Phantom for Calculating Becquerel Calibration Factor and Correction Method]

PURPOSE

The purpose of this study was to evaluate the best phantom for calculating the becquerel calibration factor (BCF) and correction method to obtain the improvement of standardized uptake value (SUV) accuracy in both single photon emission computed tomography (SPECT) and SPECT/CT.

METHOD

A SPECT/CT scanner was used in this study. BCFs were calculated using four phantoms with different cross sections including National Electrical Manufacturers Association International Electrotechnical Commission body phantom (NEMA IEC body phantom) filled with ^99mTcO₄^-, and five correction methods were used for reconstruction. SUVs were calculated by the NEMA IEC body phantom and pediatric phantom in house with these BCFs. We then measured SUV_mean in the background region of the NEMA IEC body phantom, SUV_max and SUV_peak of the 37-mm-diameter sphere.

RESULTS

In the SPECT scanner, SUV_mean and SUV_max measured 1.04 and 4.02, respectively, in the case of BCF calculation and SUV measurement using NEMA IEC body phantoms without corrections. In the SPECT/CT scanner, SUV_mean with CT attenuation correction (AC) was in agreement with the theoretical values using each phantom. SUV_max showed the same trend.

CONCLUSION

In the SPECT scanner, it is possible to obtain a highly accurate SUV by using a phantom that matches the size of the subject for BCF calculation and without correction. In the SPECT/CT scanner, highly accurate SUVs can be obtained by using CT-based attenuation correction, and these values do not depend on the size of the BCF calculation phantom.

[Determination of Bone SPECT Image Reconstruction Conditions in the Head and Neck Region]

PURPOSE

Quantitative analysis using a standardized uptake value (SUV) has become possible for single-photon emission computed tomography-computed tomography (SPECT-CT) of bone. However, previous research was targeted to the trunk area, and there are few studies for the head and neck region. Therefore, the purpose of this study was to determine the optimal image reconstruction conditions for bone SPECT of the head and neck using a phantom study.

METHOD

The radioactivity concentration of the ^99mTc solution enclosed in the cylindrical phantom was set to the same count rate as in clinical cases, and six hot spheres (10, 13, 17, 22, 28, 37 mm) with four times the concentration were placed within it. The image reconstruction was 3D-OSEM, and the reconstruction conditions were varied by the number of iterative updates and the width of the Gaussian filter. Quantitative evaluations of the image quality were performed using the % contrast, background variability, and SUV for the hot spheres and background. A visual evaluation was performed by four observers to determine the optimal image reconstruction conditions for bone SPECT of the head and neck region.

RESULT

The concentration of the ^99mTc solution enclosed in the phantom was 6.95 (kBq/ml). Based on the results of the quantitative and visual evaluations, the optimal image reconstruction conditions were iterative updates=60 (subset: 10, iteration: 6) and a Gaussian filter of 7.8 mm.

CONCLUSION

The optimal image reconstruction conditions were subset=10, iterations=6, and a Gaussian filter of 7.8 mm.

An alternative method for radioactivity measurement in quantitative bone SPECT/CT imaging

Bone scintigraphy with combined single-photon emission computed tomography (SPECT) and computed tomography (CT) has become widely used for the detection of bone metastases. However, calculation of the semi-quantitative standardized uptake value (SUV) requires measurement of the pre- and post-injection radioactivity of the radiopharmaceutical. This study aimed to compare measured and fixed input radioactivity values for quantitative SPECT/CT bone imaging to examine whether the fixed measurement method of radiopharmaceutical radioactivity could be used as an alternative method. Four different methods were used to quantify the Tc-99m hydroxymethylene diphosphonate input radioactivity: (A) measured pre- and post-injection radioactivity values; (B) measured pre-injection and fixed post-injection radioactivity values; (C) fixed pre-injection and measured post-injection radioactivity values; (D) fixed pre- and post-injection radioactivity values. All SPECT/CT acquisitions were analyzed using bone SPECT analysis software, and the semi-quantitative parameters (SUVpeak and SUVmean) were recorded and compared for each analytical method. Two semi-quantitative parameters showed significant differences between analytical methods A and B, A and D, and C and D. However, an additional subgroup analysis performed on patients whose median post-injection measured radioactivity value was <1.5 MBq showed no significant differences in parameters between all analytical methods. Measurement of the radiopharmaceutical radioactivity can be an alternative method because it reduces the volume of radioactivity post-injection. The simplified fixed measurement method of radiopharmaceutical radioactivity can be used as an alternative method in cases when measuring the radioactivity in quantitative bone SPECT/CT imaging is missed.

Analysis of medication-related osteonecrosis of the jaw with bone SPECT/CT: relationship between patient characteristics and maximum standardized uptake value

Objective:

To analyze medication-related osteonecrosis of the jaw (MRONJ) with bone single photon emission computed tomography (SPECT)/CT, especially relationship between patient characteristics and maximum standardized uptake value (SUV).

Methods:

48 patients with MRONJ who underwent bone SPECT/CT were prospectively included. MRONJ patients were included 34 osteoporosis and 14 bone metastases from 6 lung cancer, 6 breast cancer and 2 rectal cancer. The maximum SUV of the MRONJ patient characteristics were analyzed such as gender, location, underlying disease, medication and staging of MRONJ by Mann–Whitney U test. P-values lower than 0.05 indicate significant differences.

Results:

Regarding underlying disease, maximum SUV of patients with osteoporosis (18.69 ± 8.57) were significantly higher than those with bone metastases (12.28 ± 4.32, p = 0.005). Furthermore, maximum SUV of MRONJ was a significant difference for medication (denosumab: 13.62 ± 5.70 and minodronate: 22.98 ± 11.73, p = 0.009) and staging of MRONJ (Stage 2: 15.59 ± 8.06 and Stage 3: 21.51 ± 7.15, p = 0.014).

Conclusion:

Maximum SUV assessed by SPECT/CT was significantly increased in MRONJ patients with osteoporosis and Stage 3. Bone SPECT/CT could be an effective tool for the analysis of MRONJ.

Two-versus three-dimensional regions of interest for quantifying SPECT-CT images

The aim of this study was to investigate the relationship of quantitative parameters between the two-dimensional region of interest (ROI) and the three-dimensional volume of interest (VOI) for accumulation of radiopharmaceutical. Single-photon emission computed tomography combined with computed tomography (SPECT/CT) images of the NEMA/IEC phantom were acquired. The ROIs and VOIs were automatically set to the sphere and background in the phantom. We defined as two-dimensional analysis (2D analysis) that which used ROIs set on the center section of the sphere, and as three-dimensional analysis (3D analysis) that which used VOIs set on the center of gravity of the sphere. Dose linearity (DL), the recovery coefficient (RC), the contrast-to-noise ratio (CNR), and standardized uptake value (SUV) were evaluated. Each index value was compared between both analyses. DL was almost 1 under both conditions. RC showed a similar tendency with 2D and 3D analyses. The CNR for 3D analysis was smaller than for 2D analysis. The maximum SUV was almost equal with both analyses. The mean SUV with 3D analysis was underestimated by 4.83% on average compared with 2D analysis. For the same accumulation, a difference may occur in the quantitative index between 2 and 3D analyses. In particular, the quantitative parameters based on the average value tends to be smaller with 3D analysis than 2D analysis. The quantitative parameters in 2D analysis showed dependence upon the cross section used for setting the ROI, whereas 3D analysis showed less dependence on the position of the VOI.

Quantitative bone single-photon emission computed tomography imaging for uninfected nonunion: comparison of hypertrophic nonunion and non-hypertrophic nonunion

BACKGROUND

Recently, a standardized uptake value (SUV) has been used to evaluate bone single-photon emission computed tomography (SPECT). The aim of this study was to investigate quantitative SPECT imaging of uninfected nonunion to compare hypertrophic nonunion and non-hypertrophic nonunion using volume-based parameters.

METHODS

We evaluated 23 patients with uninfected nonunion who underwent SPECT acquisition 3 h after an injection of ^99mTc-hydroxymethylene diphosphonate or ^99mTc-methylene diphosphonate from April 2014 to November 2019. We reconstructed the acquired data and performed voxel-based quantitative analysis using the GI-BONE software. Quantitative parameters, maximum SUV (SUV_max), peak SUV (SUV_peak), and mean SUV (SUV_mean) in the high and low uptake areas of nonunion were compared between hypertrophic nonunion and non-hypertrophic nonunion. The contralateral limb was used as a control, and the ratios of the quantitative parameters were calculated.

RESULTS

The values for the quantitative parameters (high uptake area/low uptake area, respectively), SUV_max control ratio (12.13 ± 4.95/6.44 ± 4.71), SUV_peak control ratio (11.65 ± 4.58/6.45 ± 4.64), and SUV_mean control ratio (11.94 ± 5.03/6.28 ± 4.95) for hypertrophic nonunion were higher than those for non-hypertrophic nonunion (7.82 ± 4.76/3.41 ± 2.09 (p = 0.065/0.12), 7.56 ± 4.51/3.61 ± 2.23 (p = 0.065/0.22), and 7.59 ± 5.18/3.05 ± 1.91 (p = 0.076/0.23)).

CONCLUSIONS

SUV_max, SUV_peak, and SUV_mean control ratios obtained from bone SPECT images can quantitatively evaluate the biological activity of nonunions and may be an effective evaluation method for treatment decisions, especially the necessity of autologous bone grafting.

[Validation of Simulation Codes for Nuclear Imaging Using Digital Phantoms]

Validation study of simulation codes was performed based on the measurement of a sphere phantom and the National Electrical Manufacturers Association (NEMA) body phantoms. SIMIND and Prominence Processor were used for the simulation. Both source and density maps were generated using the characteristics of ^99mTc energy. A full width at half maximum (FWHM) of the sphere phantom was measured and simulated. Simulated recovery coefficient and the background count coefficient of variation were also compared with the measured values in the body phantom study. When the two simulation codes were compared with actual measurements, maximum relative errors of FWHM values were 3.6% for Prominence Processor and -10.0% for SIMIND. The maximum relative errors of relative recovery coefficients exhibited 11.8% for Prominence Processor and -2.0% for SIMIND in the body phantom study. The coefficients of variation of the SPECT count in the background were significantly different among the measurement and two simulation codes. The simulated FWHM values and recovery coefficients paralleled measured results. However, the noise characteristic differed among actual measurements and two simulation codes in the background count statistics.

Optimization of Number of Iterations as a Reconstruction Parameter in Bone SPECT Imaging Using a Novel Thoracic Spine Phantom

The aim of this study was to optimize the number of iterations in bone SPECT imaging using a novel thoracic spine phantom (ISMM phantom). Methods: The quality and quantitative accuracy of bone SPECT images were evaluated by changing the number of iterations and the size of the hot spot in the phantom. True SUVs in the vertebra, tumor, and background parts were 9.8, 52.2, and 1.0, respectively. The phantom image was reconstructed using the ordered-subset expectation-maximization algorithm with CT-based attenuation correction, scatter correction, and resolution recovery; the number of ordered-subset expectation-maximization subsets was fixed at 10, with iterations ranging from 1 to 40. Full width at half maximum, percentage coefficient of variation, contrast ratio for the sphere and background (contrast), and recovery coefficient were evaluated as a function of the number of iterations for a given number of subsets (10) using the reconstructed images. In addition, SUV_max, SUV_peak, and SUV_mean were calculated with various numbers of iterations for each sphere (13, 17, 22, and 28 mm) simulating a tumor. Results: Full width at half maximum decreased as the number of iterations was increased, and full width at half maximum converged uniformly when the number of iterations exceeded 10. The percentage coefficient of variation increased as the number of iterations was increased. Recovery coefficient decreased with decreasing sphere size. Contrast and all SUVs increased as the number of iterations was increased, and contrast and all SUVs converged uniformly when the number of iterations exceeded 5 and 10, respectively, for all sphere sizes. When the SUV was defined as the converged value for 10 iterations in the 28-mm sphere, the converged values of SUV_max, SUV_peak, and SUV_mean were 75.1, 66.5, and 55.6, respectively. The relative error in the converged values for SUV_max, SUV_peak, and SUV_mean were 43.8%, 27.3%, and 7.2% of the true value (52.2); all SUVs were overestimated. Conclusion: Using a thoracic spine phantom to evaluate the optimal reconstruction parameters in bone SPECT imaging, we determined the optimal number of iterations for 10 subsets to be 10.

Patient arm position during quantitative bone single-photon emission computed tomography/computed tomography acquisition can affect image quality and quantitative accuracy: a phantom study

PURPOSE

The present study used a phantom to determine the effects of various arm positions on bone SPECT/computed tomography (CT) images and the optimal arm position to acquire good-quality and quantitatively accurate images.

MATERIALS AND METHODS

We designed a phantom study of five simulated arm positions that are assumed during SPECT image acquisition. All SPECT data were acquired during a total of 120 projections of 10 and 100 s/view over 360° in a non-circular mode and reconstructed using Flash 3D (Siemens Healthineers). We evaluated contrast (QH,17 mm), image noise (NB,17 mm), contrast-to-noise ratios (QNRs), and visual scores according to the guidelines for bone SPECT acquisition protocols published by the Japanese Society of Nuclear Medicine Technology. The SUVmean, SUVmax, and SUVpeak were calculated and quantitative errors were evaluated using the recovery coefficient (RC) and the root means square error (RMSE).

RESULTS

The spatial resolution of SPECT images was better when the arms were down than raised with simulated shoulder disorders. Raised arms with shoulder disorders significantly increased the NB,17 mm and decreased the QH,17 mm, and the QNR in each image differed over a range from 2.2 to 5.2. The visual score was >1.5 with the arms down, raised normally, and raised with moderate shoulder disorders. The SUVmax and SUVpeak were overestimated compared with 100-min data for all images, whereas SUVmean was underestimated. Raised arms with a shoulder disorder decreased RCmax, and RCmean and RCpeak suppressed differences among arm positions. In addition, RMSE with the arms down and raised normally were close to that for 100-min data.

CONCLUSION

Bone SPECT images with good quality and quantitative accuracy can be acquired with patients holding their arms down by their sides. This will help patients with shoulder pain who have difficulties raising their arms.

Bone single-photon emission computed tomography-CT peak standardized uptake value for chronic osteomyelitis, osteoradionecrosis and medication-related osteonecrosis of the jaw

INTRODUCTION

Recently, standardized uptake value (SUV) has been applied for the evaluation of SPECT-CT. This study was performed to investigate the bone SPECT-CT peak SUV for chronic osteomyelitis, osteoradionecrosis and medication-related osteonecrosis of the jaw (MRONJ).

METHODS

Sixty-five patients with jaw lesions (12 chronic osteomyelitis, 12 osteoradionecrosis and 41 MRONJ) underwent SPECT-CT after injection of technetium-99m hydroxymethylene diphosphonate. The peak SUV was compared for the chronic osteomyelitis with osteoradionecrosis and MRONJ using GI-BONE software. Statistical analyses for the peak SUV were performed by one-way repeated measures analysis of variance with Tukey's HSD test. A P-value lower than 0.05 was considered as statistically significant.

RESULTS

Peak SUV for chronic osteomyelitis (15.6 ± 4.4) was significantly higher than those for osteoradionecrosis (6.7 ± 2.1, P = 0.000) and MRONJ (10.7 ± 6.1, P = 0.019).

CONCLUSION

The SPECT-CT peak SUV using GI-BONE software can be useful for the evaluation of jaw lesions, such as chronic osteomyelitis, osteoradionecrosis and MRONJ.

Assessment of SPECT-CT fusion images and semi-quantitative evaluation using SUV in 123I-IMP SPECT in patients with choroidal melanoma

OBJECTIVES

The aim of this study was to assess the diagnostic ability of N-isopropyl-p-[I-123] iodoamphetamine (IMP) SPECT semi-quantitative evaluation based on the standardized uptake value (SUV) in patients with choroidal melanoma. The secondary aim was to investigate the 6-h IMP SPECT imaging in comparison with 24-h imaging.

METHODS

Twenty-five patients (14 males and 11 females, mean age of 59.2-year-old) were analyzed in this retrospective study. Patients underwent 24-h IMP SPECT imaging with a gamma camera after intravenous injection of IMP. Twelve of 25 patients underwent 6-h SPECT imaging in addition to the 24-h imaging. All acquired SPECT images were fused with CT images using an image-analysis software. To assess the utility of semi-quantitative evaluation method, we introduced an image evaluation method using SUVmax comparing with conventional count-based uptake index (UI) evaluation of the lesion. Volumes-of-interest (VOIs) for SUVmax and regions-of-interest (ROIs) for UI were drawn referring to the SPECT-CT fusion image. Then the relationship between the 6- and 24-h images was examined both in SUV and UI evaluation. Furthermore, the relationship between the size category classification (SCC) by UICC/AJCC: 1-4 scales and each semi-quantitative value using SUVmax and UI was also assessed.

RESULTS

SUVmax of the tumor was significantly higher than that of the normal side; 2.37 ± 0.88 and 1.77 ± 0.39 (P < 0.05) on 6-h image, 4.17 ± 1.73 and 2.04 ± 0.45 (P < 0.001) on 24-h image, respectively. UI of the tumor was also significantly higher than that of the normal side; 2.24 ± 0.67 and 1.53 ± 0.35 (P < 0.01) on 6-h image, 3.79 ± 1.24 and 1.67 ± 0.44 (P < 0.001) on 24-h image, respectively. There was a strong significant linear relationship in the evaluation with SUVmax between 6- and 24-h on the tumor side (R² = 0.88, P < 0.0001), compared to that with Tumor-UI (R² = 0.35, P < 0.05). In addition, SUVmax of the tumor clearly differentiated the SCC of the tumor category 4 from that of category 1, where SUVmax of the tumor for categories 1‒4 were 2.56 ± 0.59, 4.33 ± 1.92, 4.63 ± 1.45, and 5.73 ± 1.69, respectively (P < 0.05, for categories 1 and 4).

CONCLUSIONS

The semi-quantitative evaluation by SUV of ¹²³I-IMP SPECT images fused with CT images is useful for detecting choroidal melanoma. Moreover, 6-h imaging with SUV-based evaluation of ¹²³I-IMP SPECT is promising compared to the conventional count-based UI evaluation method. Trial registration This study is registered in UMIN Clinical Trials Registry (UMIN-CTR) as UMIN study ID: UMIN000038174.

Phantom and clinical evaluation of bone SPECT/CT image reconstruction with xSPECT algorithm

BACKGROUND

Two novel methods of image reconstruction, xSPECT Quant (xQ) and xSPECT Bone (xB), that use an ordered subset conjugate gradient minimizer (OSCGM) for SPECT/CT reconstruction have been proposed. The present study compares the performance characteristics of xQ, xB, and conventional Flash3D (F3D) reconstruction using images derived from phantoms and patients.

METHODS

A custom-designed body phantom for bone SPECT was scanned using a Symbia Intevo (Siemens Healthineers), and reconstructed xSPECT images were evaluated. The phantom experiments proceeded twice with different activity concentrations and sphere sizes. A phantom with 28-mm spheres containing a 99mTc-background and tumor-to-normal bone ratios (TBR) of 1, 2, 4, and 10 were generated, and convergence property against various TBR was evaluated across 96 iterations. A phantom with four spheres (13-, 17-, 22-, and 28-mm diameters), containing a 99mTc-background at TBR4, was also generated. The full width at half maximum of an imaged spinous process (10 mm), coefficients of variance (CV), contrast-to-noise ratio (CNR), and recovery coefficients (RC) were evaluated after reconstructing images of a spine using Flash 3D (F3D), xQ, and xB. We retrospectively analyzed images from 20 patients with suspected bone metastases (male, n = 13) which were acquired using [99mTc]Tc-(H)MDP SPECT/CT, then CV and standardized uptake values (SUV) at the 4th vertebral body (L4) were compared after xQ and xB reconstruction in a clinical setup.

RESULTS

Mean activity concentrations with various TBR converged according to increasing numbers of iterations. The spatial resolution of xB was considerably superior to xQ and F3D, and it approached almost the actual size regardless of the iteration numbers during reconstruction. The CV and RC were better for xQ and xB than for F3D. The CNR peaked at 24 iterations for xQ and 48 iterations for F3D and xB, respectively. The RC between xQ and xB significantly differed at lower numbers of iterations but were almost equivalent at higher numbers of iterations. The reconstructed xQ and xB images of the clinical patients showed a significant difference in the SUVmax and SUVpeak.

CONCLUSIONS

The reconstructed xQ and xB images were more accurate than those reconstructed conventionally using F3D. The xB for bone SPECT imaging offered essentially unchanged spatial resolution even when the numbers of iterations did not converge. The xB reconstruction further enhanced SPECT image quality using CT data. Our findings provide important information for understanding the performance characteristics of the novel xQ and xB algorithms.

Assessment of inflammatory jaw pathologies using bone SPECT/CT maximum standardized uptake value

OBJECTIVES

To investigate the assessment of inflammatory jaw pathologies using bone single-photon emission CT-CT (SPECT/CT) maximum standardized uptake value (SUV_max).

METHODS

44 patients with inflammatory jaw pathologies (7 chronic osteomyelitis, 8 osteoradionecrosis and 29 medication-related osteonecrosis of the jaw (MRONJ)) underwent SPECT/CT at 4 h after injection of ^99mTc hydroxymethylene diphosphonate. The SPECT/CT parameters SUV_max of the inflammatory jaw pathologies were analyzed. Statistical analyses for the SUV_max were performed by one-way repeated measures analysis of variance with Tukey's honestly significant difference test. A p-value lower than 0.05 was considered statistically significant.

RESULTS

The mean and standard deviation of SUV_max for 7 chronic osteomyelitis, 8 osteoradionecrosis and 29 MRONJ were 24.94 ± 3.65, 12.27 ± 5.47 and 16.55 ± 9.12, respectively. The SUV_max for chronic osteomyelitis were significantly higher than those for osteoradionecrosis (p = 0.011) and MRONJ (p = 0.043).

CONCLUSIONS

Bone SPECT/CT SUV_max in the uptake of ^99mTc hydroxymethylene diphosphonate reflecting bone physiological changes for chronic osteomyelitis were significantly higher than those of osteonecrosis, such as osteoradionecrosis and MRONJ. Bone SPECT/CT SUV_max should be useful for the assessment of inflammatory jaw pathologies, such as chronic osteomyelitis, osteoradionecrosis and MRONJ.

Towards standardization of absolute SPECT/CT quantification: a multi-center and multi-vendor phantom study

Abstract

Absolute quantification of radiotracer distribution using SPECT/CT imaging is of great importance for dosimetry aimed at personalized radionuclide precision treatment. However, its accuracy depends on many factors. Using phantom measurements, this multi-vendor and multi-center study evaluates the quantitative accuracy and inter-system variability of various SPECT/CT systems as well as the effect of patient size, processing software and reconstruction algorithms on recovery coefficients (RC).

Methods

Five SPECT/CT systems were included: Discovery™ NM/CT 670 Pro (GE Healthcare), Precedence™ 6 (Philips Healthcare), Symbia Intevo™, and Symbia™ T16 (twice) (Siemens Healthineers). Three phantoms were used based on the NEMA IEC body phantom without lung insert simulating body mass indexes (BMI) of 25, 28, and 47 kg/m². Six spheres (0.5–26.5 mL) and background were filled with 0.1 and 0.01 MBq/mL ^99mTc-pertechnetate, respectively. Volumes of interest (VOI) of spheres were obtained by a region growing technique using a 50% threshold of the maximum voxel value corrected for background activity. RC, defined as imaged activity concentration divided by actual activity concentration, were determined for maximum (RC_max) and mean voxel value (RC_mean) in the VOI for each sphere diameter. Inter-system variability was expressed as median absolute deviation (MAD) of RC. Acquisition settings were standardized. Images were reconstructed using vendor-specific 3D iterative reconstruction algorithms with institute-specific settings used in clinical practice and processed using a standardized, in-house developed processing tool based on the SimpleITK framework. Additionally, all data were reconstructed with a vendor-neutral reconstruction algorithm (Hybrid Recon™; Hermes Medical Solutions).

Results

RC decreased with decreasing sphere diameter for each system. Inter-system variability (MAD) was 16 and 17% for RC_mean and RC_max, respectively. Standardized reconstruction decreased this variability to 4 and 5%. High BMI hampers quantification of small lesions (< 10 ml).

Conclusion

Absolute SPECT quantification in a multi-center and multi-vendor setting is feasible, especially when reconstruction protocols are standardized, paving the way for a standard for absolute quantitative SPECT.

Evaluation of edge-preserving and noise-reducing effects using the nonlinear diffusion method in bone single-photon emission computed tomography

OBJECTIVES

This study aims to evaluate nonlinear diffusion (NLD) processing to smoothen images while suppressing resolution degradation in single-photon emission computed tomography (SPECT) images. Phantom data were used for NLD method optimization. The resultant optimal settings were used for NLD processing of clinical images.

MATERIALS AND METHODS

Tc was used to simulate tumors and normal soft tissues. Using the data collected, images were reconstructed. Images were processed using various k values and iteration. The background region's coefficient of variation (CV) was determined, and the effects of parameters on image properties were examined. NLD-processed images with optimal parameters were compared with Butterworth (BW)-filtered and nine-point smoothing (SM)-processed images to evaluate smoothing filter properties in real and frequency space. Receiver operating characteristic curve analysis was carried out on NLD-processed and BW048-processed bone SPECT images.

RESULTS

From CVs in background, with NLD, increased k value and iteration led to a low CV, indicating enhanced smoothing effect. At k=0.9, a strong noise-reducing effect with less iteration was achieved. Contrasts and recovery coefficients of NLD were the highest. The visual score for SPECT image quality was significantly higher with NLD than with BW048, BW090, and SM. In the low-frequency and high-frequency ranges, BW048, BW090, and NLD showed similar signal strengths and NLD and BW090 showed high signal strength, respectively. SM processing reduced the signal strength at all frequency ranges. On receiver operating characteristic analysis, noise reduction using NLD processing enhanced diagnostic performance than with the use of BW processing.

CONCLUSION

NLD processing of bone SPECT images using optimized parameters enabled smoothing with less resolution degradation.

Does quantification have a role to play in the future of bone SPECT?

Routinely, there is a visual basis to nuclear medicine reporting: a reporter subjectively places a patient's condition into one of multiple discrete classes based on what they see. The addition of a quantitative result, such as a standardised uptake value (SUV), would provide a numerical insight into the nature of uptake, delivering greater objectivity, and perhaps improved patient management.For bone scintigraphy in particular quantification could increase the accuracy of diagnosis by helping to differentiate normal from abnormal uptake. Access to quantitative data might also enhance our ability to characterise lesions, stratify and monitor patients' conditions, and perform reliable dosimetry for radionuclide therapies. But is there enough evidence to suggest that we, as a community, should be making more effort to implement quantitative bone SPECT in routine clinical practice?We carried out multiple queries through the PubMed search engine to facilitate a cross-sectional review of the current status of bone SPECT quantification. Highly cited papers were assessed in more focus to scrutinise their conclusions.An increasing number of authors are reporting findings in terms of metrics such as SUVmax. Although interest in the field in general remains high, the rate of clinical implementation of quantitative bone SPECT remains slow and there is a significant amount of validation required before we get carried away.

Bone SPECT-based segmented attenuation correction for quantitative analysis of bone metastasis (B-SAC): comparison with CT-based attenuation correction

Background

Evidence has shown the clinical usefulness of measuring the metastatic tumor burden of bone for prognostic assessment especially in prostate cancer; quantitative evaluation by dedicated SPECT is difficult due to the lack of attenuation correction (AC) method.

We developed a novel method for attenuation correction using bone SPECT emission data (bone SPECT-based segmented attenuation correction; B-SAC) where emission data were virtually segmented into three tissues (i.e., bone, soft tissue, and air). Then, the pixel values in SPECT were replaced by 50 for the virtual soft tissue, and − 1000 for the virtual air. The replaced pixel values for the virtual bone were based on the averaged CT values of the normal vertebrae (B-SAC_N) or the metastatic bones (B-SAC_M). Subsequently, the processed SPECT data (i.e., SPECT value) were supposed to realize CT data (i.e., CT value) that were used for B-SAC. The standardized uptake values (SUVs) of 112 metastatic bone tumors in 15 patients with prostate cancer were compared between CTAC with scatter correction (SC) and resolution recovery (RR) and the following reconstruction conditions: B-SAC_N (+)SC(+)RR(+), B-SAC_M (+)SC(+)RR(+), uniform AC(UAC)(+)SC(+)RR(+), AC(−)SC(+)RR(+), and no correction (NC).

Results

The SUVs in the five reconstruction conditions were all correlated with those in CTAC(+)SC(+)RR(+) (p < 0.01), and the correlations between B-SAC_N or B-SAC_M and CTAC images were excellent (r > 0.94). Bland-Altman analysis showed that the mean SUV differences between CTAC (+)SC(+)RR(+) and the other five reconstructions were 0.85 ± 2.25 for B-SAC_N (+)SC(+)RR(+), 1.61 ± 2.36 for B-SAC_M (+)SC(+)RR(+), 1.54 ± 3.84 for UAC(+)SC(+)RR(+), − 3.12 ± 4.97 for AC(−)SC(+)RR(+), and − 5.96 ± 4.59 for NC. Compared to CTAC(+)SC(+)RR(+), B-SAC_N (+)SC(+)RR(+) showed a slight but constant overestimation (approximately 17%) of the metastatic tumor burden of bone when the same threshold of metabolic tumor volume was used.

Conclusions

The results of this preliminary study suggest the potential for B-SAC to improve the quantitation of bone metastases in bone SPECT when X-ray CT or transmission CT data are not available. Considering the small but unignorable differences of lesional SUVs between CTAC and B-SAC, SUVs obtained with the current version of B-SAC seem difficult to be directly compared with those obtained with CTAC.

Applying standardized uptake values in gallium-67-citrate single-photon emission computed tomography/computed tomography studies and their correlation with blood test results in representative organs

OBJECTIVES

Recently, semiquantitative analysis using standardized uptake value (SUV) has been introduced in bone single-photon emission computed tomography/computed tomography (SPECT/CT). Our purposes were to apply SUV-based semiquantitative analytic method for gallium-67 (Ga)-citrate SPECT/CT and to evaluate correlation between SUV of physiological uptake and blood test results in representative organs.

METHODS

The accuracy of semiquantitative method was validated using an National Electrical Manufacturers Association body phantom study (radioactivity ratio of sphere : background=4 : 1). Thereafter, 59 patients (34 male and 25 female; mean age, 66.9 years) who had undergone Ga-citrate SPECT/CT were retrospectively enrolled in the study. A mean SUV of physiological uptake was calculated for the following organs: the lungs, right atrium, liver, kidneys, spleen, gluteal muscles, and bone marrow. The correlation between physiological uptakes and blood test results was evaluated using Pearson's correlation coefficient.

RESULTS

The phantom study revealed only 1% error between theoretical and actual SUVs in the background, suggesting the sufficient accuracy of scatter and attenuation corrections. However, a partial volume effect could not be overlooked, particularly in small spheres with a diameter of less than 28 mm. The highest mean SUV was observed in the liver (range: 0.44-4.64), followed by bone marrow (range: 0.33-3.60), spleen (range: 0.52-2.12), and kidneys (range: 0.42-1.45). There was no significant correlation between hepatic uptake and liver function, renal uptake and renal function, or bone marrow uptake and blood cell count (P>0.05).

CONCLUSION

The physiological uptake in Ga-citrate SPECT/CT can be represented as SUVs, which are not significantly correlated with corresponding blood test results.

Multicentre analysis of PET SUV using vendor-neutral software: the Japanese Harmonization Technology (J-Hart) study

Background

Recent developments in hardware and software for PET technologies have resulted in wide variations in basic performance. Multicentre studies require a standard imaging protocol and SUV harmonization to reduce inter- and intra-scanner variability in the SUV. The Japanese standardised uptake value (SUV) Harmonization Technology (J-Hart) study aimed to determine the applicability of vendor-neutral software on the SUV derived from positron emission tomography (PET) images. The effects of SUV harmonization were evaluated based on the reproducibility of several scanners and the repeatability of an individual scanner.

Images were acquired from 12 PET scanners at nine institutions. PET images were acquired over a period of 30 min from a National Electrical Manufacturers Association (NEMA) International Electrotechnical Commission (IEC) body phantom containing six spheres of different diameters and an ¹⁸F solution with a background activity of 2.65 kBq/mL and a sphere-to-background ratio of 4. The images were reconstructed to determine parameters for harmonization and to evaluate reproducibility. PET images with 2-min acquisition × 15 contiguous frames were reconstructed to evaluate repeatability. Various Gaussian filters (GFs) with full-width at half maximum (FWHM) values ranging from 1 to 15 mm in 1-mm increments were also applied using vendor-neutral software. The SUV_max of spheres was compared with the reference range proposed by the Japanese Society of Nuclear Medicine (JSNM) and the digital reference object (DRO) of the NEMA phantom. The coefficient of variation (CV) of the SUV_max determined using 12 PET scanners (CV_repro) was measured to evaluate reproducibility. The CV of the SUV_max determined from 15 frames (CV_repeat) per PET scanner was measured to determine repeatability.

Results

Three PET scanners did not require an additional GF for harmonization, whereas the other nine required additional FWHM values of GF ranging from 5 to 9 mm. The pre- and post-harmonization CV_repro of six spheres were (means ± SD) 9.45% ± 4.69% (range, 3.83–15.3%) and 6.05% ± 3.61% (range, 2.30–10.7%), respectively. Harmonization significantly improved reproducibility of PET SUV_max (P = 0.0055). The pre- and post-harmonization CV_repeat of nine scanners were (means ± SD) 6.59% ± 1.29% (range, 5.00–8.98%) and 4.88% ± 1.64% (range, 2.65–6.72%), respectively. Harmonization also significantly improved the repeatability of PET SUV_max (P < 0.0001).

Conclusions

Harmonizing SUV using vendor-neutral software produced SUV_max for 12 scanners that fell within the JSNM reference range of a NEMA body phantom and improved SUV_max reproducibility and repeatability.

Semiquantitative analysis using standardized uptake value in 123I-FP-CIT SPECT/CT

PURPOSE

To evaluate potential of a semiquantitative method using standardized uptake value (SUV) in ¹²³I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (¹²³I-FP-CIT) single photon emission computed tomography/computed tomography (SPECT/CT) compared with specific binding ratio (SBR).

MATERIALS AND METHODS

First, we performed a phantom study to validate the accuracy of measuring SUV. 52 patients (25 male, 27 female; mean age of 75.1-year-old; 40 and 12 patients with neurodegenerative diseases with or without presynaptic dopaminergic deficits, respectively) were enrolled in a retrospective study. We measured SBR, maximum SUV, peak SUV, mean SUV, and striatum-to-background ratio of SUV (SUV_ratio) for striatum with lower ¹²³I-FP-CIT uptake using commercial software. We calculated Pearson's correlation coefficient between SBR and SUV. We also calculated the sensitivity, specificity, and accuracy of each parameter for differential diagnosis.

RESULTS

The phantom study revealed errors of <10% between theoretical and actual SUVs. Although there were significant correlations between SBR and all SUV-based parameters, SUV_ratio showed the most strong correlation with SBR (r = 0.877, p < 0.001). However, diagnostic capability of SUV_ratio (cutoff = 2.35) yielded to that of SBR (cutoff = 3.90) for diagnosing neurodegenerative diseases with presynaptic dopaminergic deficits (sensitivity of 85.0% vs 92.5%, specificity of 100% vs 91.7%, and accuracy of 88.5% vs 92.3%, respectively).

CONCLUSION

SBR is a promising parameter to aid differential diagnosis of neurodegenerative diseases with or without presynaptic dopaminergic deficit. Although technically acceptable, SUV may not be superior to SBR when clinically applied in ¹²³I-FP-CIT SPECT/CT.

A retrospective study of SPECT/CT scans using SUV measurement of the normal pelvis with Tc-99m methylene diphosphonate

OBJECTIVE

To perform quantitative measurement based on the standardized uptake value (SUV) of Tc-99m methylene diphosphonate (MDP) in the normal pelvis using a single-photon emission tomography (SPECT)/computed tomography (CT) scanner.

MATERIAL AND METHODS

This retrospective study was performed on 31 patients with cancer undergoing bone SPECT/CT scans with 99mTc-MDP. SUVmax and SUVmean of the normal pelvis were calculated based on the body weight. SUVmax and SUVmean of the bilateral anterior superior iliac spine, posterior superior iliac spine, facies auricularis ossis ilii, ischial tuberosity, and sacrum were also calculated. Furthermore, the correlation of SUVmax and SUVmean of all parts of pelvis with weight, height, and CT was assessed.

RESULTS

The data for 31 patients (20 women and 11 men; mean age 58.97±9.12 years; age range 37-87 years) were collected. SUVmax and SUVmean changed from 1.65±0.40 to 3.8±1.0 and from 1.15±0.25 to 2.07±0.58, respectively. The coefficient of variation of SUVmax and SUVmean ranged from 0.22 to 0.31. SUVmax and SUVmean had no statistically significant difference between men and women. SUVmax and SUVmean also showed no significant correlation with weight and height. However, part of SUVmax and SUVmean showed a significant correlation with CT. In addition, SUVmax and SUVmean of the bilateral ischial tuberosity showed a significant correlation with CT values.

CONCLUSIONS

Determination of the SUV value of the normal pelvis with 99m Tc-MDP SPECT/CT is feasible and highly reproducible. SUVs of the normal pelvis showed a relatively large variability. As a quantitative imaging biomarker, SUVs might require standardization with adequate reference data for the participant to minimize variability.