Reproducibility of the principal component analysis (PCA)-based data-driven respiratory gating on texture features in non-small cell lung cancer patients with 18 F-FDG PET/CT.

OBJECTIVE: Texture analysis is one of the lung cancer countermeasures in the field of radiomics. Even though image quality affects texture features, the reproducibility of principal component analysis (PCA)-based data-driven respiratory gating (DDG) on texture features remains poorly understood. Hence, this study aimed to clarify the reproducibility of PCA-based DDG on texture features in non-small cell lung cancer (NSCLC) patients with 18 F-Fluorodeoxyglucose (18 F-FDG) Positron emission tomography/computed tomography (PET/CT). METHODS: Twenty patients with NSCLC who underwent 18 F-FDG PET/CT in routine clinical practice were retrospectively analyzed. Each patient's PET data were reconstructed in two PET groups of no gating (NG-PET) and PCA-based DDG gating (DDG-PET). Forty-six image features were analyzed using LIFEx software. Reproducibility was evaluated using Lin's concordance correlation coefficient ( ρ c ${\rho _c}$ ) and percentage difference (%Diff). Non-reproducibility was defined as having unacceptable strength ( ρ c $({\rho _c}$  < 0.8) and a %Diff of >10%. NG-PET and DDG-PET were compared using the Wilcoxon signed-rank test. RESULTS: A total of 3/46 (6.5%) image features had unacceptable strength, and 9/46 (19.6%) image features had a %Diff of >10%. Significant differences between the NG-PET and DDG-PET groups were confirmed in only 4/46 (8.7%) of the high %Diff image features. CONCLUSION: Although the DDG application affected several texture features, most image features had adequate reproducibility. PCA-based DDG-PET can be routinely used as interchangeable images for texture feature extraction from NSCLC patients.

Harmonized pretreatment quantitative volume-based 18F-FDG PET/CT parameters for stage IV breast cancer prognosis. Multicenter study in Japan.

OBJECTIVE: The prognostic value of harmonized pretreatment volume-based quantitative fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) parameters in metastatic breast cancer patients was investigated. SUBJECTS AND METHODS: Records of 65 stage IV breast cancer patients, including 29 estrogen receptor (ER)-positive/human epidermal growth factor receptor 2 (HER2)-negative, 23 HER2-positive, and 13 triple-negative cases, from four different institutions were retrospectively reviewed. Harmonized standardized uptake value (SUVmax) of the primary tumor (pSUVmax), highest SUVmax of all malignant lesions (wSUVmax), whole-body metabolic tumor volume (WB MTV), and whole-body total lesion glycolysis (WB TLG) shown by pretreatment 18F-FDG PET/CT imaging were calculated. Cox proportional hazards model and log-rank test results were used to evaluate relationships among clinicopathological factors, volume-based quantitative 18F-FDG PET/CT parameters, progression-free survival, and overall survival (OS). RESULTS: Disease progression occurred in 54 patients and 28 died during a median follow-up period of 52.5 months (range 2.6-133.6 months). Univariate analysis of all cases showed associations of negative ER and progesterone receptor (PR) status (P=0.0025), and high T/N stage (P=0.037/P=0.019), pSUVmax (P=0.049), WB MTV (P=0.021), and WB TLG (P=0.0010) with significantly shorter OS. Multivariate analysis confirmed negative ER and PR status (hazard ratio [HR]: 6.42, 95% confidence interval [CI]: 2.27-19.38; P=0.0054), high T stage (HR: 5.10, 95% CI:1.96-18.61, P=0.0064) and WB TLG (HR: 4.69, 95% CI:1.67-12.79, P=0.049) as independent negative OS predictors. In two groups of ER-positive/HER2-negative and triple-negative, WB TLG had a significant association with death (P=0.021 and P=0.037, respectively) on univariate analysis. In a HER2-positive group, no independent negative OS predictors were observed. CONCLUSION: In metastatic breast cancer patients, harmonized pretreatment quantitative volume-based 18F-FDG PET/CT parameters, especially whole-body TLG, are potential surrogate markers for prognosis.

Evaluation of two-dimensional total bone uptake (2D-TBU) and bone scan index (BSI) extracted from active bone metastatic burden on the bone scintigraphy in patients with radium-223 treatment.

OBJECTIVE: Radium-223 is a first alpha-emitting radionuclide treatment for metastatic castration-resistant prostate cancer (mCRPC) patients with bone metastases. Although the spread-based bone scan index (BSI) and novel index of the intensity-based two-dimensional total bone uptake (2D-TBU) from bone scintigraphy may provide useful input in radium-223 treatment, they have not been evaluated in detail yet. This study aimed to fill this gap by evaluating BSI and 2D-TBU in patients treated with radium-223. METHODS: Twenty-seven Japanese patients with mCRPC treated with radium-223 were retrospectively analyzed. The patients were evaluated via blood tests and bone scans at baseline and 3 cycles intervals of treatment. BSI and 2D-TBU were analyzed via VSBONE BSI in terms of correlations, response to radium-223 treatment, association with treatment completion, and the Kaplan-Meier survival analysis was performed. RESULTS: Nineteen patients (70.4%) completed six cycles of radium-223 treatment, whereas eight patients (29.6%) did not complete the treatment regimen. A significant difference in baseline BSI and 2D-TBU was observed between these groups of patients. Both BSI and 2D-TBU were highly correlated (r = 0.96, p < 0.001). Univariate analysis showed an association between radium-223 completion in median BSI and 2D-TBU values (p = 0.015) and completion percentage differences (91.7% vs. 45.5%; p = 0.027). The Kaplan-Meier product limit estimator showed that the median overall survival was 25.2 months (95% CI 14.0-33.6 months) in the completion group and 7.5 months (95% CI 3.3-14.2 months) in the without completion group (p < 0.001). The overall survival based on median cutoff levels showed a significant difference in 2D-TBU (p = 0.007), but not in BSI (p = 0.15). CONCLUSIONS: The 2D-TBU may offer advantages over BSI in classifying patients towards radium-223 treatment based on the degree of progression of bone metastases. This study supports the importance of preliminary assessment of bone metastasis status using BSI and 2D-TBU extracted from VSBONE BSI for radium-223 treatment decisions.

Correction: Investigation of the new non-invasive semi-quantitative method of 123I-IMP pediatric cerebral perfusion SPECT.

[This corrects the article DOI: 10.1371/journal.pone.0241987.].

[Validation of Quantitative Accuracy and Variability in 177Lu Imaging Using Monte Carlo Simulation].

PURPOSE: To predict side effects and optimize injection doses in the dosimetry of 177Lu imaging, highly accurate quantitative SPECT images are required. Monte Carlo simulations were performed to verify the accuracy and variability of quantitative values for 177Lu imaging under various imaging conditions. METHODS: SPECT data of NEMA body phantom were assumed to simulate intrahepatic tumors 6 h after administration of 7.4 GBq of 177Lu-Dotatate. SPECT data were acquired using the SIMIND program with different combinations of collimators and energy windows. For variability evaluation, 30 SPECT images with Poisson noise were generated for each acquisition time. The relative error was evaluated for accuracy evaluation, and the coefficient of variation was estimated for variability evaluation. RESULTS: The accuracy of BG quantification was less than 10% relative error. The accuracy of hot sphere quantification was highest with the combination of MEGP and an energy window of 208 keV±10%. However, the accuracy of hot sphere quantification decreased significantly with decreasing hot sphere diameter. Variability varied with imaging conditions and improved with longer acquisition time. CONCLUSION: Monte Carlo simulations revealed the accuracy and variability of quantitative values for each SPECT imaging condition for 177Lu imaging.

[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 SUVmax (MaxSUVmax) and (2) average SUVmax (AveSUVmax) 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 MaxSUVmax and AveSUVmax 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.

A review of harmonization strategies for quantitative PET.

PET can reveal in vivo biological processes at the molecular level. PET-derived quantitative values have been used as a surrogate marker for clinical decision-making in numerous clinical studies and trials. However, quantitative values in PET are variable depending on technical, biological, and physical factors. The variability may have a significant impact on a study outcome. Appropriate scanner calibration and quality control, standardization of imaging protocols, and any necessary harmonization strategies are essential to make use of PET as a biomarker with low bias and variability. This review summarizes benefits, limitations, and remaining challenges for harmonization of quantitative PET, including whole-body PET in oncology, brain PET in neurology, PET/MR, and non-18F PET imaging. This review is expected to facilitate harmonization of quantitative PET and to promote the contribution of PET-derived biomarkers to research and development in medicine.

Prognostic significance of the harmonized maximum standardized uptake value of 18F-FDG-PET/CT in patients with resectable oral tongue squamous cell carcinoma: a multicenter study.

OBJECTIVES: To investigate the usefulness of harmonized 18F-FDG-PET/CT parameters for predicting the postoperative recurrence and prognosis of oral tongue squamous cell carcinoma (OTSCC). METHODS: We retrospectively analyzed the cases of 107 OTSCC patients who underwent surgical resection at four institutions in Japan in 2010-2016 and evaluated the harmonized PET parameters of the maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) for the primary tumor as the pSUVmax, pMTV, and pTLG. For lymph node metastasis, we used harmonized PET parameters of nodal-SUVmax, nodal-total MTV (tMTV), and nodal-total TLG (tTLG). The associations between the harmonized PET parameters and the patients' relapse-free survival (RFS) and overall survival (OS) were evaluated by the Kaplan-Meier method and Cox proportional hazard regression analysis for model 1 (preoperative stage) and model 2 (preoperative + postoperative stages). RESULTS: The harmonized SUVmax values were significantly lower than those before harmonization (p=0.012). The pSUVmax was revealed as a significant preoperative risk factor for RFS and OS. Nodal-SUVmax, nodal-tMTV, and nodal-tTLG were significant preoperative risk factors for OS. The combination of pSUVmax + nodal-SUVmax significantly stratified the patients into a low-risk group (pSUVmax <3.97 + nodal-SUVmax <2.85 or ≥2.85) and a high-risk group (pSUVmax ≥3.97 + nodal-SUVmax <2.85 or pSUVmax ≥3.97 + nodal-SUVmax ≥2.85) for recurrence and prognosis (RFS: p=0.001; OS: p<0.001). CONCLUSIONS: The harmonized pSUVmax is a significant prognostic factor for the survival of OTSCC patients. The combination of pSUVmax and nodal-SUVmax identified OTSCC patients at high risk for recurrence and poor prognosis at the preoperative stage.

Prognostic role of preoperative fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography with an image-based harmonization technique: A multicenter retrospective study.

Objectives: Despite the prognostic impacts of preoperative fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography examination, fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography-based prognosis prediction has not been used clinically because of the disparity in data between institutions. By applying an image-based harmonized approach, we evaluated the prognostic roles of fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography parameters in clinical stage I non-small cell lung cancer. Methods: We retrospectively examined 495 patients with clinical stage I non-small cell lung cancer who underwent fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography examinations before pulmonary resection between 2013 and 2014 at 4 institutions. Three different harmonization techniques were applied, and an image-based harmonization, which showed the best-fit results, was used in the further analyses to evaluate the prognostic roles of fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography parameters. Results: Cutoff values of image-based harmonized fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography parameters, maximum standardized uptake, metabolic tumor volume, and total lesion glycolysis were determined using receiver operating characteristic curves that distinguish pathologic high invasiveness of tumors. Among these parameters, only the maximum standardized uptake was an independent prognostic factor in recurrence-free and overall survivals in univariate and multivariate analyses. High image-based maximum standardized uptake value was associated with squamous histology or lung adenocarcinomas with higher pathologic grades. In subgroup analyses defined by ground-glass opacity status and histology or by clinical stages, the prognostic impact of image-based maximum standardized uptake value was always the highest compared with other fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography parameters. Conclusions: The image-based fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography harmonization was the best fit, and the image-based maximum standardized uptake was the most important prognostic marker in all patients and in subgroups defined by ground-glass opacity status and histology in surgically resected clinical stage I non-small cell lung cancers.

Comparative study of the value of dual tracer PET/CT in evaluating breast cancer.

The present study was conducted to assess the relationship between tumor uptake and pathologic findings using dual-tracer PET/computed tomography (CT) in patients with breast cancer. Seventy-four patients with breast cancer (mean age 54 years) who underwent (11)C-choline and 2-[(18)F]fluoro-2-deoxy-d-glucose ((18)F-FDG) PET/CT prior to surgery on the same day were enrolled in the present study. Images were reviewed by a board-certified radiologist and two nuclear medicine specialists who were unaware of any clinical information and a consensus was reached. Uptake patterns and measurements of dual tracers were compared with the pathologic findings of resected specimens as the reference standard. Mean (±SD) tumor size was 5.9 ± 3.2 cm. All primary tumors were identified on (18)F-FDG PET/CT and (11)C-choline PET/CT. However, (18)F-FDG PET/CT demonstrated focal uptake of the primary tumor with (n = 38; 51%) or without (n = 36; 49%) diffuse background breast uptake. Of the pathologic findings, multiple logistic regression analysis revealed an independent association between fibrocystic change and diffuse background breast uptake (odds ratio [OR] 8.57; 95% confidence interval [CI] 2.86-25.66; P < 0.0001). Tumors with higher histologic grade, nuclear grade, structural grade, nuclear atypia, and mitosis had significantly higher maximum standardized uptake values (SUV(max)) and tumor-to-background ratios (TBR) for both tracers. Multiple logistic regression analysis revealed that only the degree of mitosis was independently associated with a high SUV(max) (OR 7.45; 95%CI 2.21-25.11; P = 0.001) and a high TBR (OR 5.41; 95%CI 1.13-25.96; P = 0.035) of (11)C-choline PET/CT. In conclusion, (11)C-choline may improve tumor delineation and reflect tumor aggressiveness on PET/CT in patients with breast cancer.

Neoadjuvant chemotherapy in breast cancer: prediction of pathologic response with PET/CT and dynamic contrast-enhanced MR imaging--prospective assessment.

PURPOSE: To clarify whether fluorine 18 ((18)F) fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) and dynamic contrast-enhanced (DCE) magnetic resonance (MR) imaging performed after two cycles of neoadjuvant chemotherapy (NAC) can be used to predict pathologic response in breast cancer. MATERIALS AND METHODS: Institutional human research committee approval and written informed consent were obtained. Accuracy after two cycles of NAC for predicting pathologic complete response (pCR) was examined in 142 women (mean age, 57 years: range, 43-72 years) with histologically proved breast cancer between December 2005 and February 2009. Quantitative PET/CT and DCE MR imaging were performed at baseline and after two cycles of NAC. Parameters of PET/CT and of blood flow and microvascular permeability at DCE MR were compared with pathologic response. Patients were also evaluated after NAC by using Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 based on DCE MR measurements and European Organization for Research and Treatment of Cancer (EORTC) criteria and PET Response Criteria in Solid Tumors (PERCIST) 1.0 based on PET/CT measurements. Multiple logistic regression analyses were performed to examine continuous variables at PET/CT and DCE MR to predict pCR, and diagnostic accuracies were compared with the McNemar test. RESULTS: Significant decrease from baseline of all parameters at PET/CT and DCE MR was observed after NAC. Therapeutic response was obtained in 24 patients (17%) with pCR and 118 (83%) without pCR. Sensitivity, specificity, and accuracy to predict pCR were 45.5%, 85.5%, and 82.4%, respectively, with RECIST and 70.4%, 95.7%, and 90.8%, respectively, with EORTC and PERCIST. Multiple logistic regression revealed three significant independent predictors of pCR: percentage maximum standardized uptake value (%SUV(max)) (odds ratio [OR], 1.22; 95% confidence interval [CI]: 1.11, 1.34; P < .0001), percentage rate constant (%k(ep)) (OR, 1.07; CI: 1.03, 1.12; P = .002), and percentage area under the time-intensity curve over 90 seconds (%AUC(90)) (OR, 1.04; CI: 1.01, 1.07; P = .048). When diagnostic accuracies are compared, PET/CT is superior to DCE MR for the prediction of pCR (%SUV(max) [90.1%] vs %κ(ep) [83.8%] or %AUC(90) [76.8%]; P < .05). CONCLUSION: The sensitivities of %SUV(max) (66.7%), %k(ep) (51.7%), and %AUC(90) (50.0%) at (18)F-FDG PET/CT and DCE MR after two cycles of NAC are not acceptable, but the specificities (96.4%, 92.0%, and 95.2%, respectively) are high for stratification of pCR cases in breast cancer.

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 (QH, 17 mm), background noise (NB, 17 mm), contrast-to-noise ratio (CNR), maximum standardized uptake value (SUVmax, 17 mm), and visual assessment for a 17 mm hot sphere. RESULTS: Image quality in the 300 s acquisition showed that values of QH, 17 mm, CNR, and SUVmax, 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 NB, 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.

Tumor response evaluation in patients with malignant melanoma undergoing immune checkpoint inhibitor therapy and prognosis prediction using 18F-FDG PET/CT: multicenter study for comparison of EORTC, PERCIST, and imPERCIST.

OBJECTIVE: In malignant melanoma patients treated with immune checkpoint inhibitor (ICI) therapy, three different FDG-PET criteria, European Organization for Research and Treatment of Cancer (EORTC), PET Response Criteria in Solid Tumors (PERCIST), immunotherapy-modified PERCIST (imPERCIST), were compared regarding response evaluation and prognosis prediction using standardized uptake value (SUV) harmonization of results obtained with various PET/CT scanners installed at different centers. MATERIALS AND METHODS: Malignant melanoma patients (n = 27) underwent FDG-PET/CT examinations before and again 3 to 9 months after therapy initiation (nivolumab, n = 21; pembrolizumab, n = 6) with different PET scanners at five hospitals. EORTC, PERCIST, and imPERCIST criteria were used to evaluate therapeutic response, then concordance of the results was assessed using Cohen's κ coefficient. Log-rank and Cox methods were employed to determine progression-free (PFS) and overall (OS) survival. RESULTS: Complete metabolic response (CMR)/partial metabolic response (PMR)/stable metabolic disease (SMD)/progressive metabolic disease (PMD) with harmonized EORTC, PERCIST, and imPERCIST was seen in 3/5/4/15, 4/5/3/15, and 4/5/5/13 patients, respectively. Nearly perfect concordance between each pair of criteria was noted (κ = 0.939-0.972). Twenty patients showed progression and 14 died from malignant melanoma after a median 19.2 months. Responders (CMR/PMR) showed significantly longer PFS and OS than non-responders (SMD/PMD) (harmonized EORTC: p < 0.0001 and p = 0.011; harmonized PERCIST: p < 0.0001 and p = 0.0012; harmonized imPERCIST: p < 0.0001 and p = 0.0012, respectively). CONCLUSIONS: All harmonized FDG-PET criteria (EORTC, PERCIST, imPERCIST) showed accuracy for response evaluation of ICI therapy and prediction of malignant melanoma patient prognosis. Additional studies to determine their value in larger study populations will be necessary.

New standards for phantom image quality and SUV harmonization range for multicenter oncology PET studies.

Not only visual interpretation for lesion detection, staging, and characterization, but also quantitative treatment response assessment are key roles for 18F-FDG PET in oncology. In multicenter oncology PET studies, image quality standardization and SUV harmonization are essential to obtain reliable study outcomes. Standards for image quality and SUV harmonization range should be regularly updated according to progress in scanner performance. Accordingly, the first aim of this study was to propose new image quality reference levels to ensure small lesion detectability. The second aim was to propose a new SUV harmonization range and an image noise criterion to minimize the inter-scanner and intra-scanner SUV variabilities. We collected a total of 37 patterns of images from 23 recent PET/CT scanner models using the NEMA NU2 image quality phantom. PET images with various acquisition durations of 30-300 s and 1800 s were analyzed visually and quantitatively to derive visual detectability scores of the 10-mm-diameter hot sphere, noise-equivalent count (NECphantom), 10-mm sphere contrast (QH,10 mm), background variability (N10 mm), contrast-to-noise ratio (QH,10 mm/N10 mm), image noise level (CVBG), and SUVmax and SUVpeak for hot spheres (10-37 mm diameters). We calculated a reference level for each image quality metric, so that the 10-mm sphere can be visually detected. The SUV harmonization range and the image noise criterion were proposed with consideration of overshoot due to point-spread function (PSF) reconstruction. We proposed image quality reference levels as follows: QH,10 mm/N10 mm ≥ 2.5 and CVBG ≤ 14.1%. The 10th-90th percentiles in the SUV distributions were defined as the new SUV harmonization range. CVBG ≤ 10% was proposed as the image noise criterion, because the intra-scanner SUV variability significantly depended on CVBG. We proposed new image quality reference levels to ensure small lesion detectability. A new SUV harmonization range (in which PSF reconstruction is applicable) and the image noise criterion were also proposed for minimizing the SUV variabilities. Our proposed new standards will facilitate image quality standardization and SUV harmonization of multicenter oncology PET studies. The reliability of multicenter oncology PET studies will be improved by satisfying the new standards.

Dopamine dysfunction in depression: application of texture analysis to dopamine transporter single-photon emission computed tomography imaging.

Dopamine dysfunction has been associated with depression. However, results of recent neuroimaging studies on dopamine transporter (DAT), which reflect the function of the dopaminergic system, are inconclusive. The aim of this study was to apply texture analysis, a novel method to extract information about the textural properties of images (e.g., coarseness), to single-photon emission computed tomography (SPECT) imaging in depression. We performed SPECT using 123I-ioflupane to measure DAT binding in 150 patients with major depressive disorder (N = 112) and bipolar disorder (N = 38). The texture features of DAT binding in subregions of the striatum were calculated. We evaluated the relationship between the texture feature values (coarseness, contrast, and busyness) and severity of depression, and then examined the effects of medication and diagnosis on such relationship. Furthermore, using the data from 40 healthy subjects, we examined the effects of age and sex on the texture feature values. The degree of busyness of the limbic region in the left striatum linked to the severity of depression (p = 0.0025). The post-hoc analysis revealed that this texture feature value was significantly higher in both the severe and non-severe depression groups than in the remission group (p = 0.001 and p = 0.028, respectively). This finding remained consistent after considering the effect of medication. The effects of age and sex in healthy individuals were not evident in this texture feature value. Our findings imply that the application of texture analysis to DAT-SPECT may provide a state-marker of depression.

Evaluation of data-driven respiratory gating for subcentimeter lesions using digital PET/CT system and three-axis motion phantom.

Introduction.The application of data-driven respiratory gating (DDG) for subcentimeter lesions with respiratory movement remains poorly understood. Hence, this study aimed to clarify DDG application for subcentimeter lesions and the ability of digital Positron emission tomography/computed tomography (PET/CT) system combined with DDG to detect these lesions under three-axis respiration.Methods.Discovery MI PET/CT system and National Electrical Manufacturers Association (NEMA) body phantom with Micro Hollow Sphere (4, 5, 6, 8, 10, and 13 mm) were used. The NEMA phantom was filled with18F-FDG solutions of 42.4 and 5.3 kBq/ml for each hot sphere and background region. The 3.6 s cycles of three-axis respiratory motion were reproduced using the motion platform UniTraQ. The PET data acquisition was performed in stationary and respiratory-moving states. The data were reconstructed in three PET groups: stationary (NM-PET), no gating with respiratory movement (NG-PET), and DDG gating with respiratory movement (DDG-PET) groups. For image quality, percent contrast (QH); maximum, peak, and mean standardized uptake value (SUV); background region; and detectability index (DI) were evaluated in each PET group. Visual assessment was also conducted.Results.The groups with respiratory movement had deteriorated QHand SUVs compared with NM-PET. Compared with NG-PET, DDG-PET has significantly improved QHand SUVs in spheres above 6 mm. The background region showed no significant difference between groups. The SUVmax, SUVpeak, and QHvalues of 8 mm sphere were highest in NM-PET, followed by DDG-PET and NG-PET. In visual assessment, the spheres above 6 mm were detected in all PET groups. DDG application did not detect new lesions, but it increased DI and visual score.Conclusions. The application of principal component analysis (PCA)-based DDG algorithm improves both image quality and quantitative SUVs in subcentimeter lesions measuring above 6 mm. Although DDG application cannot detect new subcentimeter lesions, it increases the visual indices.

Effect of position and volume of spaceoccupying liver lesions on liver function index in 99mTc-GSA scintigraphy.

BACKGROUND: The authors aimed to elucidate the effect of liver space-occupying lesions (SOL) on the quantitative index of the hepatic reserve, calculated using the dynamic planar image (LHLplanar), and a three-dimensional quantitative index (LHLSPECT) calculated using quantitative combined modality single-photon emission computed tomography (SPECT/CT). MATERIAL AND METHODS: Water balloons of different volumes that simulated liver SOL were placed in various positions in the combined cardiac-liver phantom to examine the effects of liver SOL on visualization and quantitative indicators (LHLplanar and LHLSPECT). A 200 mL water balloon was placed in the anterior right, posterior right, left medial and left lateral lobes in the liver phantom to compare LHLplanar and LHLSPECT values with and without liver SOL at each position. Subsequently, volumes of those in the front of the right lobe were changed to 50 mL, 100 mL, 200 mL, and 400 mL, followed by statistically comparing LHLplanar and LHLSPECT values in the presence and absence of liver SOL. RESULTS: Despite the variation in the degree of defect accumulation with the location of the balloon when using frontal planar imaging, quantitative SPECT/CT imaging identified all defects. Multiple comparison analysis revealed that unlike LHLSPECT, the LHLplanar values changed according to liver SOL position and volume. CONCLUSIONS: Liver SOL position and volume may affect the hepatic reserve assessments performed using LHLplanar values. In contrast, LHLSPECT is calculated using quantitative SPECT/CT and considers the effects of scattering and attenuation corrections. Therefore, LHLSPECT is a more accurate quantitative indicator of hepatic reserve than LHLplanar and is expected to facilitate future clinical research.

Image quality and quantification accuracy dependence on patient body mass in 89Zr PET/CT imaging.

BACKGROUND: This study was conducted to clarify how patient body mass affects the image quality and quantification accuracy of images obtained using 89Zr PET/CT. 89Zr PET/CT images from time-of-flight (TOF) PET/CT and semiconductor (SC) PET/CT were obtained using three types (M, L, LL; corresponding to increasing patient body weight) of custom-made body phantoms designed similarly to the National Electrical Manufacturers Association (NEMA) IEC body phantom. The phantom data were analyzed visually and quantitatively to derive image quality metrics, namely detectability of the 10-mm-diameter hot sphere, percent contrast for the 10-mm-diameter hot sphere (QH,10 mm), percent background variability (N10mm), contrast-to-noise ratio (QH,10 mm/N10mm), and coefficient of variation of the background area (CVBG). RESULTS: Visual assessment revealed that all the 10-mm-diameter hot spheres of the three types of phantoms were identifiable on both SC and TOF PET/CT images. The N10mm and CVBG values were within the proposed reference levels, and decreased with acquisition duration for both PET/CT types. At 10-min acquisition, the QH,10 mm/N10mm of SC PET/CT was greater than the proposed reference level in all phantoms. However, the QH,10 mm/N10mm of TOF PET/CT was greater than the proposed reference level in M-type phantom alone. All the SUVBG values were within 1.00 ± 0.05 for both PET/CT types. CONCLUSIONS: This study showed that the image quality and quantification accuracy depend on the patient's body mass, suggesting that acquisition time on 89Zr PET/CT should be changed according to the patient's body mass.

[Report in 2018 April ～ 2020 March].

To establish a feasible and practical methodology for harmonization of FDG-PET, we have investigated quantitative physical performance of recent clinical PET scanners (23 scanners) using the NEMA image quality phantom. Compared with the previous phantom data (13 scanners) acquired in the early 2000s, the current phantom data showed better contrasts of small spheres even with a smaller number of coincidence counts. This result suggests that clinical PET image quality and small lesion detectability might have been significantly improved in the past 10 years. Based on the data acquired in this working group, we are planning to update the standard phantom test methodology and harmonizing criteria for FDG-PET.