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

Quantitative bone single photon emission computed tomography/computed tomography in symptomatic and asymptomatic foot and ankle osteoarthritis

PURPOSE

The purpose of this study was to evaluate and quantify the prevalence of increased uptake in SPECT/CT in symptomatic and asymptomatic foot and ankle joints in patients with osteoarthritis.

METHODS

In 63 patients with osteoarthritis (OA), the painful symptomatic foot (SF) and asymptomatic contralateral foot (AF) were imaged with bone SPECT/CT. Presence, localization, and maximum standardized uptake value (SUVmax) of the active joints were assessed for SF and AF. CT OA grade (grade 1: mild, grade 2: moderate, grade 3: severe) and presence of five morphological features of OA (joint space narrowing, subchondral sclerosis, subchondral cysts, irregular joint margins, and osteophytes) were evaluated.

RESULTS

In total 32 (51%) patients showed additional uptake in the AF, whereas 31 (49%) patients showed it only in the SF. SF showed more active joints than AF (106 vs. 43). CT OA grades positively correlated with SUVmax (Kendall's tau b = 0.62, P < 0.001). SUVmax values (per foot) in SF were higher in patients with uptake in bilateral feet (SF+, AF+) [median (IQR): 17.9 (10.7-23.3)] as compared with patients with active sites only in the SF (SF+, AF-) [10.4 (6.4-19.1); P < 0.001]. Number of active OA joints in SF was higher in patients with bilateral uptake (P = 0.017).

CONCLUSION

In conclusion, half of the patients exhibited increased uptake in the contralateral asymptomatic foot. SUVmax showed a significant correlation to CT osteoarthritis grade, in the symptomatic and asymptomatic foot. Future follow-up studies will provide further insights into the prognostic and therapeutic value of these findings.

Detectability of cold tumors by xSPECT bone technology compared with hot tumors: a supine phantom study

Detecting cold as well as hot tumors is vital for interpreting bone tumors on single-photon emission computed tomography (SPECT) images. This study aimed to visually and quantitatively demonstrate the detectability of cold tumors using xSPECT technology compared with that of hot tumors in the phantom study. Five tumors of different sizes and normal bone contained a mixture of 99mTc and K2HPO4 in a spine phantom. We acquired SPECT data using an xSPECT protocol and transverse images were reconstructed using xSPECT Bone (xB) and xSPECT Quant (xQ). Mean standardized uptake values (SUVmean) in volumes of interest (VOI) were calculated. Recovery coefficients (RCs) for each tumor site were calculated with reference to radioactive concentrations. The SUVmeans of the whole vertebral body for hot tumor bone image in cortical bone phantom reconstructed by with xB and xQ were 5.77 and 4.86 respectively. The SUVmean of xB was similar to the true value. The SUVmeans for xB and xQ reconstructed images of cold tumors were both approximately 0.16. The RC of the cold tumor on xQ images increased as the tumor diameter decreased, whereas that of xB remained almost constant regardless of the tumor diameter. In conclusion, the quantitative accuracy of detecting hot and cold tumors was higher in the xB image than in the xQ image. Moreover, the visual detectability of cold tumors was also excellent in xB images.

Implementation of xSPECT, xSPECT bone and Broadquant from literature, clinical survey and innovative phantom study with task-based image quality assessment

OBJECTIVE

From patient and phantom studies, we aimed to highlight an original implementation process and share a two-years experience clinical feedback on xSPECT (xS), xSPECT Bone (xB) and Broadquant quantification (Siemens) for 99mTc-bone and 177Lu-NET (neuroendocrine tumors) imaging.

METHODS

Firstly, we checked the relevance of implemented protocols and Broadquant module on the basis of literature and with a homogeneous phantom study respectively. Then, we described xS and xB behaviours with reconstruction parameters (10i-0mm to 40i-20mm) and optimized the protocols through a blinded survey (7 physicians). Finally, the preferred 99mTc-bone reconstruction was assessed through an IEC NEMA phantom including liquid bone spheres. Conventional SNR, CNR, spatial resolution, Q.%error, and recovery curves; and innovative NPS, TTF and detectability score d' were performed (ImQuest software). We also sought to review the adoption of these tools in clinical routine and showed the potential of quantitative xB in the context of theranostics (Xofigo®).

RESULTS

We showed the need of optimization of implemented reconstruction algorithms and pointed out a decay correction particularity with Broadquant. Preferred parameters were 1s-25i-8mm and 1s-25i-5mm for xS/xB-bone and xS-NET imaging respectively. The phantom study highlighted the different image quality especially for the enhanced spatial resolution xB algorithm (1/TTF10%=2.1 mm) and showed F3D and xB shared the best performances in terms of image quality and quantification. xS was generally less efficient.

CONCLUSIONS

Qualitative F3D still remains the clinical standard, xB and Broadquant offer challenging perspectives in theranostics. We introduced the potential of innovative metrics for image quality analysis and showed how CT tools should be adapted to fit nuclear medicine imaging.

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.

Hot spot imaging in cardiovascular diseases: an information statement from SNMMI, ASNC, and EANM

This information statement from the Society of Nuclear Medicine and Molecular Imaging, American Society of Nuclear Cardiology, and European Association of Nuclear Medicine describes the performance, interpretation, and reporting of hot spot imaging in nuclear cardiology. The field of nuclear cardiology has historically focused on cold spot imaging for the interpretation of myocardial ischemia and infarction. Hot spot imaging has been an important part of nuclear medicine, particularly for oncology or infection indications, and the use of hot spot imaging in nuclear cardiology continues to expand. This document focuses on image acquisition and processing, methods of quantification, indications, protocols, and reporting of hot spot imaging. Indications discussed include myocardial viability, myocardial inflammation, device or valve infection, large vessel vasculitis, valve calcification and vulnerable plaques, and cardiac amyloidosis. This document contextualizes the foundations of image quantification and highlights reporting in each indication for the cardiac nuclear imager.

Evaluation of standardized uptake value on 131I-6β-iodomethyl-19-norcholesterol scintigraphy for diagnosis of primary aldosteronism and correspondence with adrenal venous sampling

PURPOSE

Adrenal venous sampling (AVS) is a reliable method for lateralization of adrenal hormone secretion, which is important for discriminating between aldosterone-producing adenoma and bilateral adrenal hyperplasia, both of which cause primary aldosteronism (PA). The aim of this study was to evaluate the diagnostic accuracy of the maximum and mean standardized uptake values (SUV_max and SUV_mean, respectively) of ¹³¹I-6β-iodomethyl-19-norcholesterol (NP-59) single-photon emission computed tomography (SPECT) for PA and its correspondence with AVS.

METHODS

Adrenal NP-59 scintigraphy was performed in 14 patients with suspected PA, and AVS was also performed in 7 of them. SUV_max and SUV_mean of the adrenal lesions on the dominant side and their ratios to the values on the non-dominant side (SUVR_max and SUVR_mean, respectively) were calculated on SPECT images using ordered-subset conjugate gradient minimization (OSCGM) and three-dimensional ordered-subset expectation maximization (3D-OSEM) reconstruction algorithms.

RESULTS

SUV_max and SUV_mean on NP-59 SPECT images were significantly higher for aldosterone-producing adenoma than for bilateral adrenal hyperplasia or non-functioning adenoma and slightly superior to SUVR_max and SUVR_mean (P = 0.0475 and P = 0.0447 vs. P = 0.124 and P = 0.132, respectively, with OSCGM). The respective areas under the receiver-operating characteristic curve for SUV and SUVR were 0.933 and 0.725 with OSCGM and 0.844 and 0.750 with 3D-OSEM, while SUV_max and SUVR_max had exactly the same diagnostic accuracy as SUV_mean and SUVR_mean. SUV and SUVR were associated with the diagnostic features on AVS and consistent with lateralization by AVS in most patients.

CONCLUSION

In this study, SUV on NP-59 SPECT helped in the diagnosis of PA and was consistent with the results of AVS in nearly all cases.

Quantification of bone metabolic activity in the natural course of fractural lesions measured by quantitative SPECT/CT

Objectives

While increased uptake at the bone fractural site gradually decreases over time on bone scans, the rate of change has not been quantitatively evaluated. The purpose of this study was to quantify the extent of bone metabolic changes in fractural lesions on bone SPECT/CT.

Methods

We reviewed bone scans acquired by dedicated SPECT/CT and chose those scans in which quantitative SPECT/CT of the same range was acquired twice or more. We set the region of interest on lesions of bone fracture and degeneration, and measured the maximum standardized uptake value (SUV_max). From the SUV_max of lesions and the interval between scans, a value for 30-day change in SUV_max was calculated as ∆SUV_max30d. The relationship between preSUV_max, SUV_max for the first scan of the comparison, and ∆SUV_max30d was evaluated utilizing a linear least-squares method. Furthermore, we assessed the ability to differentiate between fracture and degeneration using receiver operating characteristics (ROC) analysis and the Mann-Whitney U test. All cases were then categorized into five groups according to preSUV_max. Values of p <0.05 were considered statistically significant.

Results

We investigated 175 scans from 60 patients and analyzed scan combinations for 157 fractural lesions and 266 degenerative lesions. The relationship between preSUV_max of fractural lesions and ∆SUV_max30d was approximated as ∆SUV_max30d =-0.15×preSUV_max +1.35 (R ²=0.60, p<0.0001). Area under the curves for all cases, 30≤ preSUV_max, 20≤ preSUV_max <30, 15≤ preSUV_max <20, 10≤ preSUV_max <15, and preSUV_max <10 were 0.73, 0.89, 0.86, 0.80, 0.91, and 0.59, respectively. Median ∆SUV_max30d was significantly lower at fractural lesions than at degenerative lesions (-0.62 vs -0.04; p <0.0001). As for analyses of groups divided by preSUV_max, all median ∆SUV_max30d for fractural lesions were significantly lower than those of degenerative lesions except for the group with preSUV_max <10.

Conclusion

The increased uptake at the fractural bone lesion observed in the quantitative bone SPECT/CT gradually decreased at the rate of SUV 0.15 per month, which showed a different trend with degenerative change.

Quantify total activity by volume-of-interest expansion with clinical SPECT/CT systems, a phantom study

PURPOSE

Quantitative measurements of activity in SPECT are important for radioisotope therapy planning and disease diagnosis. The aim of this manuscript is to develop a robust method to quantify the total activity in a volume-of-interest (VOI) of different quantitative SPECT reconstructions and validate the estimation accuracy.

METHODS

We customized an IEC body phantom using 3D printing technology and made six sphere inserts of 1-6 cm in diameter with at least 3 cm separation. The activity concentration within the spheres was in the range of patient lesion/organ activity. The background activity was then increased from zero to a sphere/background activity concentration of 8:1, 4:1, and 2:1. SPECT data were acquired with Philips Brightview and GE Discovery 670 SPECT/computed tomography (CT) systems under clinical acquisition protocols. Quantitative SPECT images were reconstructed with Hermes SUV-SPECT (both Philips and GE data) and GE Q.Metrix (GE data only). The quantitative SPECT reconstructions are iterative with scatter, CT attenuation correction, and resolution recovery. We quantified the total activity by expanding the sphere VOI to include a spill-out region. Background correction was applied by sampling a region outside the spill-out region. The true fractions (TFs) (total activity/true activity) were measured for all six spheres for all SPECT acquisitions.

RESULTS

The TF is close to 100% for 2-6 cm spheres for zero background, 8:1 and 4:1 sphere/background activity ratios. The TF was found to be unreliable for the 1-cm sphere because of the limit of phantom design. TF accuracy for 2:1 sphere/background ratio was degraded due to significantly large background, inadequate scatter correction and detector count loss.

CONCLUSIONS

The results demonstrated that the proposed quantification method is accurate for objects of different sizes in currently clinical quantitative reconstruction and has the potential for improving the accuracy for therapeutic treatment planning or radiation dosimetry calculations.

Verification of the effect of acquisition time for SwiftScan on quantitative bone single-photon emission computed tomography using an anthropomorphic phantom

Background

SwiftScan single-photon emission computed tomography (SPECT) is a recently released scanning technique with data acquired when the detector is stationary and when it moves from one view to the next. The influence of scan time for using SwiftScan on quantitative bone SPECT remains unclear. This study aimed to clarify the effect of the scan time for SwiftScan SPECT on the image quality and quantification of bone SPECT compared to step and shoot mode (SSM) using ^99mTc-filled anthropomorphic phantom (SIM² bone phantom).

Materials and methods

Phantom SPECT/computed tomography (CT) images were acquired using Discovery NM/CT 860 (GE Healthcare) with a low-energy high-resolution sensitivity collimator. We used the fixed parameters (subsets 10 and iterations 5) for reconstruction. The coefficient of variation (CV), contrast-to-noise ratio (CNR), full width at half maximum (FWHM), and quantitative value of SwiftScan SPECT and SSM were compared at various acquisition times (5, 7, 17, and 32 min).

Results

In the short-time scan (< 7 min), the CV and CNR of SwiftScan SPECT were better than those of SSM, whereas in the longtime scan (> 17 min), the CV and CNR of SwiftScan SPECT were similar to those of SSM. The FWHMs for SwiftScan SPECT (13.6–14.8 mm) and SSM (13.5–14.4 mm) were similar. The mean absolute errors of quantitative values at 5, 7, 17, and 32 min were 38.8, 38.4, 48.8, and 48.1, respectively, for SwiftScan SPECT and 41.8, 40.8%, 47.2, and 49.8, respectively, for SSM.

Conclusions

SwiftScan on quantitative bone SPECT provides improved image quality in the short-time scan with quantification similar to or better than SSM. Therefore, in clinical settings, using SwiftScan SPECT instead of the SSM scan protocol in the short-time scan might provide higher-quality diagnostic images than SSM. Our results could provide vital information on the use of SwiftScan SPECT.

Evaluation of quantitative accuracy among different scatter corrections for quantitative bone SPECT/CT imaging

Although scatter correction improves SPECT image contrast and thus image quality, the effects of quantitation accuracy under various conditions remain unclear. The present study aimed to empirically define the conditions for the optimal scatter correction of quantitative bone SPECT/CT images. Scatter correction was performed by applying dual and triple energy windows (DEW and TEW) with different sub-energy window widths, and effective scatter source estimation (ESSE) to CT-based scatter correction. Scattered radiation was corrected on images acquired using a triple line source (TLSP) phantom and an uniform cylinder phantom. The TLSP consisted of a line source containing 74.0 MBq of 99mTc in the middle, and a background component containing air, water or a K2HPO4 solution with a density equivalent to that of bone. The sum of all pixels in air, water and the K2HPO4 solution was measured on SPECT images. Scatter fraction (SF) and normalized mean square error (NMSE) based on counts from the air background as a reference were then calculated to assess quantitative errors due to scatter correction. The uniform cylinder phantom contained the same K2HPO4 solution and 222.0 MBq of 99mTc. The coefficient of variation (CV) was calculated from the count profile of this phantom to assess the uniformity of SPECT images across scatter correction under various conditions. Both SF and NMSE in SPECT images of phantoms containing water in the background were lower at a TEW sub-window of 3% (TEW3%), than in other scatter corrections, whereas those in K2HPO4 were lower at a DEW sub-window of 20% (DEW20%). Larger DEW and smaller TEW sub-energy windows allowed more effective correction. The CV of the uniform cylinder phantom, DEW20%, was inferior to all other tested scatter corrections. The quantitative accuracy of bone SPECT images substantially differed according to the method of scatter correction. The optimal scatter correction for quantitative bone SPECT was DEW20% (k = 1), but at the cost of slightly decreased image uniformity.

Clinical significance of quantitative bone SPECT/CT in the evaluation of hand and wrist pain in patients with rheumatic disease

We investigated the diagnostic value of the maximum standardized uptake value (SUV) at hand and wrist joints for differentiating rheumatic diseases via bone single-photon emission computed tomography (SPECT)/computed tomography (CT). A total of 84 patients manifesting hand and wrist pain (58 women; age, 49.8 ± 15.4 years) were finally diagnosed with rheumatoid arthritis (RA, n = 42), osteoarthritis (OA, n = 16), fibromyalgia (FM, n = 2), and other rheumatic diseases (n = 24). The SUV of each patient was measured in 32 joints including the distal interphalangeal (DIP), proximal interphalangeal (PIP), metacarpophalangeal (MCP), and wrist joints bilaterally. Differences in pain and SUVs between specific rheumatic diseases were assessed using the chi-squared test or one-way analysis of variance. Using the highest SUV (hSUV) in each patient, the diagnostic performance in differentiating specific diseases was evaluated by receiver operating characteristic (ROC) curve analysis. Pain symptoms were present in 886 (33.0%) sites in a total of 2688 joints. In four joint groups (DIP, PIP, MCP, and wrist), the SUVs of joints with pain were significantly higher than those of pain-free joints (all P < 0.001). Active joint sites with higher SUVs than the median value of each joint group were the most common in RA (55.1%). RA showed the greatest hSUV in the PIP (3.0 ± 2.4), MCP (3.5 ± 3.4), and wrist (3.3 ± 1.9) joint groups. FM was characterized by the lowest hSUV of all joint groups. In ROC curve analysis, the cumulative hSUV of the PIP, MCP, and wrist joint groups showed good performance for evaluating RA (area under the curve (AUC), 0.668; P = 0.005). The summation of the hSUVs at all joint groups had an excellent predictive performance for FM (AUC, 0.878; P < 0.001). Consequently, the arthritic activity of the hand and wrist joints based on SUV differed according to specific rheumatic diseases. Quantitative SPECT/CT may provide objective information related to arthritic activity for differentiating specific rheumatic diseases.

Quantitative analysis in parathyroid adenoma scintigraphy

OBJECTIVE

Surgery is the only curative treatment for primary hyperparathyroidism. Parathyroid scintigraphy is one method used to preoperatively localize the lesion. We examined time-related changes in radiopharmaceutical uptake in parathyroid adenomas (PTAs) and thyroid gland by quantitative single-photon-emission computed tomography (SPECT) imaging to assess differences between rapid and delayed washout patterns.

PATIENTS AND METHODS

The study group consisted of 35 histologically verified PTAs after radio-guided surgery extirpation in 33 patients with primary hyperparathyroidism. Patients underwent a three-phase SPECT/CT study of the neck and upper thorax post 99mTc-methoxyisobutylisonitrile (MIBI) injection. Images were reconstructed using a proprietary ordered-subset-conjugate-gradient-maximization algorithm (Siemens xSPECT Quant). PTAs were divided into those with a rapid (group A) and those with a slow (group B) washout pattern. SUVmax values of PTAs and thyroid gland tissue at 10, 90 and 180 min post 99mTc-MIBI injection were recorded and statistically assessed. Retention indexes related to the early examination were calculated for PTA and thyroid gland (RI-PTA and RI-TG).

RESULTS

There were 11 PTAs in group A and 24 in group B. Significant between-group differences in PTA SUVmax and PTA/thyroid gland ratios were observed only at 180 min postinjection (P = 0.0297, P = 0.0222, respectively). RI-PTAs differed significantly at 90 and 180 min postinjection (P = 0.0298, P = 0.0431). No differences in PTA volumes, thyroid gland SUVmax values or RI-TG were observed between the groups.

CONCLUSION

PTAs with rapid and slow washout patterns have different characteristics on quantitative analysis in later phases. No significant differences in directly measurable quantitative values (SUVmax, PTA/thyroid gland ratio) at the early stages of multi-phase examination were observed.

Satisfied quantitative value can be acquired by short-time bone SPECT/CT using a whole-body cadmium-zinc-telluride gamma camera

The aim of this study was to evaluate the quantitative values of short-time scan (STS) of metastatic lesions compared with a standard scan (SS) when acquired by whole-body bone SPECT/CT with cadmium-zinc-telluride (CZT) detectors. We retrospectively reviewed 13 patients with bone metastases from prostate cancer, who underwent SPECT/CT performed on whole-body CZT gamma cameras. STSs were obtained using 75, 50, 25, 10, and 5% of the list-mode data for SS, respectively. Regions of interest (ROIs) were set on the increased uptake areas diagnosed as metastases. Intraclass correlation coefficients (ICCs) of standardized uptake values (SUVs) for the ROIs were calculated between the SS and each STS, and ICC ≥ 0.8 was set as a perfect correlation. Moreover, the repeatability coefficient (RC) was calculated, and RC ≤ 20% was defined as acceptable. A total of 152 metastatic lesions were included in the analysis. The ICCs between the SS vs. 75%-STS, 50%-STS, 25%-STS, 10%-STS, and 5%-STS were 0.999, 0.997, 0.994, 0.983, and 0.955, respectively. The RCs of the SS vs. 75%-STS, 50%-STS, 25%-STS, 10%-STS, and 5%-STS were 7.9, 12.4, 19.8, 30.8, and 41.3%, respectively. When evaluating the quality of CZT bone SPECT/CT acquired by a standard protocol, 25%-STS may provide adequate quantitative values.

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.

Automatic quantification package (Hone Graph) for phantom-based image quality assessment in bone SPECT: computerized automatic classification of detectability

OBJECTIVE

We previously developed a custom-design thoracic bone scintigraphy-specific phantom ("SIM2 bone phantom") to assess image quality in bone single-photon emission computed tomography (SPECT). We aimed to develop an automatic assessment system for imaging technology in bone SPECT and demonstrate the validity of this system.

METHODS

Four spherical lesions of 13-, 17-, 22-, and 28-mm diameters in the vertebrae of SIM2 bone phantom simulating the thorax were filled with radioactivity (target-to-background ratio: 4). Dynamic SPECT acquisitions were performed for 15 min; reconstructions were performed using ordered subset expectation maximization at 3-15-min timepoints. Consequently, 216 lesions (54 SPECT images) were obtained: 120 and 96 lesions were used for software development and validation, respectively. The developed software used statistical parametric mapping to rigidly register and automatically calculate quantitative indexes (contrast-to-noise ratio, % coefficient of variance, % detectability equivalence volume, recovery coefficient, target-to-normal bone ratio, and full width at half maximum). A detectability score (DS) was used to define the four observation types (4, excellent; 3, adequate; 2, average; 1, poor) to score hot spherical lesions. The gold standard for DSs was independently classified by three experienced board-certified nuclear medicine technologists using the four observation types; thereafter, a consensus regarding the gold standard for DSs was reached. Using 120 lesions for development, decision tree analysis was performed to determine DS based on the quantitative indexes. We verified the validation of the quantitative indexes and their threshold values for automatic classification using 96 lesions for validation.

RESULTS

The trends in the automatically calculated quantitative indices were consistent. Decision tree analysis produced four terminal groups; two quantitative indexes (% detectability equivalence volume and contrast-to-noise ratio) were used to classify DS. The automatically classified DSs exhibited an almost perfect agreement with the gold standard. The percentage agreement and kappa coefficient were 91.7% and 0.93, respectively, in 96 lesions for validation.

CONCLUSIONS

The developed software automatically classified the detectability of hot lesions in the SIM2 bone phantom using the automatically calculated quantitative indexes, suggesting that this software could provide a means to automatically perform detectability analysis after data input that is excellent in reproducibility and accuracy.

Test-retest repeatability of quantitative bone SPECT/CT

OBJECTIVE

Technological innovations in single-photon emission computed tomography (SPECT) have enabled a more accurate quantitative evaluation of the uptake, and the standardized uptake value (SUV) can be measured as a semi-quantitative value, as in positron emission tomography. Nevertheless, the reliability of the SUV of bone SPECT has not been well established. The purpose of this study is to evaluate the test-retest repeatability of the SUV of bone SPECT/CT in clinical settings.

METHODS

This prospective study recruited patients with prostate cancer planning to receive bone SPECT/CT for the evaluation of bone abnormality between August 2017 and September 2019. Bone images were acquired twice by an integrated SPECT/CT scanner (Symbia Intevo, Siemens) within a 4- to 10-day interval. The maximum SUV (SUVmax) and peak SUV (SUVpeak) were calculated for the volumes of interests on the normal bone areas, degeneration/fracture lesions, and metastatic lesions. To determine repeatability, we calculated statistical indicators, including intraclass correlation coefficient (ICC), repeatability coefficient (RC), and mean absolute percentage difference (MAPD). For the ICC, the 95% confidential interval (CI) was also calculated, and an ICC of ≥ 0.8 was defined as an almost perfect correlation.

RESULTS

Twelve male patients were enrolled in the study (58-86 years; median, 71 years), and a total of 229 volumes of the interest were included in the analyses. The ICCs were 0.968 [95% CI (0.959, 0.975)] for SUVmax and 0.976 [95% CI (0.969, 0.981)] for SUVpeak. The RCs of the relative difference were 30.7% for SUVmax and 27.6% for SUVpeak, and the MAPDs (± standardized deviation) of all lesions were 12.3 ± 9.9% for SUVmax and 11.5 ± 8.3% for SUVpeak. The RCs and the MAPDs showed comparable value with the previous report regarding repeatability studies on PET.

CONCLUSION

An almost perfect correlation was demonstrated by repeated SUVmax and SUVpeak measured by quantitative integrated SPECT/CT. The quantitative values could be reliable indicators in patient management.

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.

Multicenter Study of Quantitative SPECT: Reproducibility of 99mTc Quantitation Using a Conjugated-Gradient Minimization Reconstruction Algorithm

This multicenter study aimed to determine the reproducibility of quantitative SPECT images reconstructed using a commercially available method of ordered-subset conjugate-gradient minimization. Methods: A common cylindric phantom containing a 100 kBq/mL concentration of ^99mTc-pertechnetate solution in a volume of 7 L was scanned under standard imaging conditions at 6 institutions using the local clinical protocol of each. Interinstitutional variation among the quantitative SPECT images was evaluated using the coefficient of variation. Dose calibrator accuracy was also investigated by measuring the same lot of commercially available ^99mTc vials at each institution. Results: The respective radioactivity concentrations under standard and clinical conditions ranged from 95.71 ± 0.60 (mean ± SD) to 108.35 ± 0.36 kBq/mL and from 96.78 ± 0.64 to 108.49 ± 0.11 kBq/mL, respectively. Interinstitutional variation in radioactivity concentration was 4.20%. The bias in the radioactivity concentrations in SPECT images was associated with the accuracy of the dose calibrator at each institution. Conclusion: The reproducibility of the commercially available quantitative SPECT reconstruction method is high and comparable to that of PET, for comparatively large (∼7 L), homogeneous objects.

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.