Quantitative susceptibility mapping and a nonlinearly transformed atlas for targeting the ventral intermediate nucleus of the thalamus in a patient with tremor and thalamic hypertrophy: illustrative case.

BACKGROUND: The ventral intermediate nucleus (Vim) of the thalamus is a surgical target for treating various types of tremor. Because it is difficult to visualize the Vim using standard magnetic resonance imaging, the structure is usually targeted based on the anterior and posterior commissures. This standard targeting method is practical in most patients but not in those with thalamic asymmetry. The authors examined the usefulness of quantitative susceptibility mapping (QSM) and transformed Vim atlas images to estimate the Vim localization in a patient with tremor and significant thalamic hypertrophy. OBSERVATIONS: A 51-year-old right-handed female had experienced a predominant left-hand action tremor for 6 years. Magnetic resonance imaging showed significant hypertrophy of the right thalamus and caudal shift of the thalamic ventral border. The authors referred to the QSM images to localize the decreased susceptibility area within the lateral ventral thalamic nuclei to target the Vim. In addition, the nonlinearly transformed Vim atlas images complemented the imaging-based targeting. The radiofrequency thalamotomy at the modified Vim target relieved the tremor completely. LESSONS: A combination of QSM and nonlinear transformation of the thalamic atlas can be helpful in the targeting method of the Vim for tremor patients with thalamic asymmetry.

Prognostic value of pretreatment FDG PET/CT in uterine cervical cancer according to two major histologic types: squamous cell carcinoma and adenocarcinoma.

Objectives: The aim of this study was to assess the prognostic value of pretreatment Positron emission tomography / computed tomography using 18F-fluorodeoxyglucose (FDG-PET/CT) in cervical cancer according to two major histologic types. Methods: Eighty-three squamous cell carcinoma (SCC) patients and 35 adenocarcinoma (AC) patients who underwent pretreatment FDG-PET/CT were retrospectively analyzed. Maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the primary tumor were calculated. Kaplan-Meier analyses were used to compare correlations between each PET parameter and overall survival (OS). The prognostic values of imaging and clinical parameters were assessed using uni- and multivariable Cox proportional hazard models. Results: SUVmax, SUVmean, and TLG were significantly higher in SCC than in AC (p<0.01 each). No significant difference in MTV was seen between the two groups (p=0.10). As for Kaplan-Meier analyses, in SCC, patients with SUVmax, SUVmean, MTV, and TLG exceeding cutoff values tended to show worse OS than patients with lower values (p=0.07, p=0.27, p<0.01, and p=0.01, respectively, for OS). On the other hand, in AC, patients with MTV and TLG exceeding cutoff values showed significantly worse PFS and OS (p<0.01 each for OS), while SUVmax and SUVmean were unrelated to OS (p=0.91 and p=0.83, respectively for OS). As for multivariable analyses, in SCC, TLG was identified as an independent prognostic factor for OS (p=0.01). In AC, MTV was identified as an independent prognostic factor for OS (p=0.02). Conclusion: Our preliminary data suggest that FDG-PET/CT would be useful for predicting prognosis in cervical cancer, although the clinical significance of quantitative values may differ according to histopathological type.

Performance of dedicated breast PET in breast cancer screening: comparison with digital mammography plus digital breast tomosynthesis and ultrasound.

OBJECTIVE: To compare the diagnostic performance of dedicated breast positron emission tomography (dbPET) in breast cancer screening with digital mammography plus digital breast tomosynthesis (DM-DBT) and breast ultrasound (US). METHODS: Women who participated in opportunistic whole-body PET/computed tomography cancer screening programs with breast examinations using dbPET, DM-DBT, and US between 2016-2020, whose results were determined pathologically or by follow-up for at least 1 year, were included. DbPET, DM-DBT, and US assessments were classified into four diagnostic categories: A (no abnormality), B (mild abnormality), C (need for follow-up), and D (recommend further examination). Category D was defined as screening positive. Each modality's recall rate, sensitivity, specificity, and positive predictive value (PPV) were calculated per examination to evaluate their diagnostic performance for breast cancer. RESULTS: Out of 2156 screenings, 18 breast cancer cases were diagnosed during the follow-up period (10 invasive cancers and eight ductal carcinomas in situ [DCIS]). The recall rates for dbPET, DM-DBT, and US were 17.8%, 19.2%, and 9.4%, respectively. The recall rate of dbPET was highest in the first year and subsequently decreased to 11.4%. dbPET, DM-DBT, and US had sensitivities of 72.2%, 88.9%, and 83.3%; specificities of 82.6%, 81.4%, and 91.2%; and PPVs of 3.4%, 3.9%, and 7.4%, respectively. The sensitivities of dbPET, DM-DBT, and US for invasive cancers were 90%, 100%, and 90%, respectively. There were no significant differences between the modalities. One case of dbPET-false-negative invasive cancer was identified in retrospect. DbPET had 50% sensitivity for DCIS, while that of both DM-DBT and US was 75%. Furthermore, the specificity of dbPET in the first year was the lowest among all periods, and modalities increased over the years to 88.7%. The specificity of dbPET was significantly higher than that of DM-DBT (p < 0.01) in the last 3 years. CONCLUSIONS: DbPET had a compatible sensitivity to DM-DBT and breast US for invasive breast cancer. The specificity of dbPET was improved and became higher than that of DM-DBT. DbPET may be a feasible screening modality.

Evaluation of isocitrate dehydrogenase mutation in 2021 world health organization classification grade 3 and 4 glioma adult-type diffuse gliomas with 18F-fluoromisonidazole PET.

PURPOSE: This study aimed to investigate the uptake characteristics of 18F-fluoromisonidazole (FMISO), in mutant-type isocitrate dehydrogenase (IDH-mutant, grade 3 and 4) and wild-type IDH (IDH-wildtype, grade 4) 2021 WHO classification adult-type diffuse gliomas. MATERIALS AND METHODS: Patients with grade 3 and 4 adult-type diffuse gliomas (n = 35) were included in this prospective study. After registering 18F-FMISO PET and MR images, standardized uptake value (SUV) and apparent diffusion coefficient (ADC) were evaluated in hyperintense areas on fluid-attenuated inversion recovery (FLAIR) imaging (HIA), and in contrast-enhanced tumors (CET) by manually placing 3D volumes of interest. Relative SUVmax (rSUVmax) and SUVmean (rSUVmean), 10th percentile of ADC (ADC10pct), mean ADC (ADCmean) were measured in HIA and CET, respectively. RESULTS: rSUVmean in HIA and rSUVmean in CET were significantly higher in IDH-wildtype than in IDH-mutant (P = 0.0496 and 0.03, respectively). The combination of FMISO rSUVmean in HIA and ADC10pct in CET, that of rSUVmax and ADC10pct in CET, that of rSUVmean in HIA and ADCmean in CET, were able to differentiate IDH-mutant from IDH-wildtype (AUC 0.80). When confined to astrocytic tumors except for oligodendroglioma, rSUVmax, rSUVmean in HIA and rSUVmean in CET were higher for IDH-wildtype than for IDH-mutant, but not significantly (P = 0.23, 0.13 and 0.14, respectively). The combination of FMISO rSUVmean in HIA and ADC10pct in CET was able to differentiate IDH-mutant (AUC 0.81). CONCLUSION: PET using 18F-FMISO and ADC might provide a valuable tool for differentiating between IDH mutation status of 2021 WHO classification grade 3 and 4 adult-type diffuse gliomas.

Diagnostic Utility of an Adjusted DWI Lexicon Using Multiple b-values to Evaluate Breast Lesions in Combination with BI-RADS.

PURPOSE: We aimed to investigate the diagnostic feasibility of an adjusted diffusion-weighted imaging (DWI) lexicon using multiple b values to assess breast lesions according to DWI-based breast imaging reporting and data system (BI-RADS). METHODS: This Institutional Review Board (IRB)-approved prospective study included 127 patients with suspected breast cancer. Breast MRI was performed using a 3T scanner. Breast DW images were acquired using five b-values of 0, 200, 800, 1000, and 1500 s/mm2 (5b-value DWI) on 3T MRI. Two readers independently assessed lesion characteristics and normal breast tissue using DWI alone (5b-value DWI and 2b-value DWI with b = 0 and 800 s/mm2) according to DWI-based BI-RADS and in combination with the standard dynamic contrast-enhanced images (combined MRI). Interobserver and intermethod agreements were assessed using kappa statistics. The specificity and sensitivity of lesion classification were evaluated. RESULTS: Ninety-five breast lesions (39 malignant and 56 benign) were evaluated. Interobserver agreement for lesion assessment on 5b-value DWI was very good (k ≥ 0.82) for DWI-based BI-RADS categories, lesion type, and mass characteristics; good (k = 0.75) in breast composition; and moderate (k ≥ 0.44) in background parenchymal signal (BPS) and non-mass distribution. Intermethod agreement between assessments performed using either 5b-value DWI or combined MRI was good-to-moderate (k = 0.52-0.67) for lesion type; moderate (k = 0.49-0.59) for DWI-based BI-RADS category and mass characteristics; and fair (k = 0.25-0.40) for mass shape, BPS, and breast composition. The sensitivity and positive predictive values (PPVs) for 5b-value DWI were 79.5%, 84.6% and 60.8%, 61.1% for each reader, respectively; 74.4%, 74.4% and 63.0%, 61.7% for 2b-value DWI; and 97.4%, 97.4% and 73.1%, 76.0% for combined MRI. The specificity and negative predictive values (NPVs) were 64.3%, 62.5% and 81.8%, 85.4% for 5b-value DWI; 69.6%, 67.9% and 79.6%, 79.2% for 2b-value DWI; and 75.0%, 78.6% and 97.7%, 97.8% for combined MRI. CONCLUSION: Good observer agreement was observed in the 5b-value DWI. The 5b-value DWI based on multiple b-values might have the potential to complement the 2b-value DWI; however, their diagnostic performance tended to be inferior to that of combined MRI for the characterization of breast tumors.

Brain imaging of sequential acquisition using a flexible PET scanner and 3-T MRI: quantitative and qualitative assessment.

OBJECTIVE: A mobile PET scanner termed flexible PET (fxPET) has been designed to fit existing MRI systems. The purpose of this study was to assess brain imaging with fxPET combined with 3-T MRI in comparison with conventional PET (cPET)/CT. METHODS: In this prospective study, 29 subjects with no visible lesions except for mild leukoaraiosis on whole brain imaging underwent 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) cPET/CT followed by fxPET and MRI. The registration differences between fxPET and MRI and between cPET and CT were compared by measuring spatial coordinates. Three-dimensional magnetization-prepared rapid acquisition gradient-echo T1-weighted imaging (T1WI) was acquired. We applied two methods of attenuation correction to the fxPET images: MR-based attenuation correction, which yielded fxPETMRAC; and CT-based attenuation correction, which yielded fxPETCTAC. The three PET datasets were co-registered to the T1WI. Following subcortical segmentation and cortical parcellation, volumes of interest were placed in each PET image to assess physiological accumulation in the brain. SUVmean was obtained and compared between the three datasets. We also visually evaluated image distortion and clarity of fxPETMRAC. RESULTS: Mean misregistration of fxPET/MRI was < 3 mm for each margin. Mean registration differences were significantly larger for fxPET/MRI than for cPET/CT except for the superior margin. There were high correlations between the three PET datasets regarding SUVmean. On visual evaluation of image quality, the grade of distortion was comparable between fxPETMRAC and cPET, and the grade of clarity was acceptable but inferior for fxPETMRAC compared with cPET. CONCLUSIONS: fxPET could successfully determine physiological [18F]FDG uptake; however, improved image clarity is desirable. In this study, fxPET/MRI at 3-T was feasible for brain imaging.

Reproducibility assessment of uptake on dedicated breast PET for noise discrimination.

OBJECTIVES: Dedicated breast PET (dbPET) systems have improved the detection of small breast cancers but have increased false-positive diagnoses due to an increased chance of noise detection. This study examined whether reproducibility assessment using paired images helped to improve noise discrimination and diagnostic performance in dbPET. METHODS: This study included 21 patients with newly diagnosed breast cancer who underwent [18F]FDG-dbPET and contrast-enhanced breast MRI. A 10-min dbPET data scan was acquired per breast, and two sets of reconstructed images were generated (named dbPET-1 and dbPET-2, respectively), each of which consisted of randomly allocated 5-min data from the 10-min data. Uptake spots higher than the background were indexed for the study with visual assessment. All indexed uptakes on dbPET-1 were evaluated using dbPET-2 for reproducibility. MRI findings based on the Breast Imaging-Reporting and Data System (BI-RADS) 2013 were used as the gold standard. Uptake spots that corresponded to BI-RADS 1 on MRI were considered noise, while those with BI-RADS 4b-6 were considered malignancies. The diagnostic performance of dbPET for malignancy was evaluated using four different criteria: any uptake on dbPET-1 regarded as positive (criterion A), a subjective visual assessment of dbPET-1 (criterion B), reproducibility assessment between dbPET-1 and dbPET-2 (criterion C), and a combination of B and C (criterion D). RESULTS: A total of 213 indexed uptake spots were identified on dbPET-1, including 152, 15, 6, 6, and 34 lesions classified as BI-RADS MRI categories 1, 2, 4b, 4c, and 5, respectively. Overall, 31.9% of the index uptake values were reproducible. All malignant lesions were reproducible, whereas 93.4% of noise was not reproducible. The sensitivities for malignancy for criteria A, B, C, and D were 100%, 91.3%, 100%, and 91.3%, respectively, with positive predictive values (PPVs) of 21.4%, 68.9%, 67.6%, and 82.4%, respectively. CONCLUSIONS: Our results demonstrated that reproducibility assessment helped reduce false-positive findings caused by noise on dbPET without lowering the sensitivity for malignancy. While subjective visual assessment was also efficient in increasing PPV, it occasionally missed malignant uptake.

Nonsuperiority of technetium-99m-galactosyl human serum albumin scintigraphy over conventional volumetry for assessing the future liver remnant in patients undergoing hepatectomy after portal vein embolization.

BACKGROUND: Technetium-99m-galactosyl human serum albumin scintigraphy is preferred for assessing the liver functional reserve in patients undergoing hepatectomy, but its superiority over computed tomography volumetry after portal vein embolization and subsequent hepatectomy remains elusive. We aimed to compare technetium-99m-galactosyl human serum albumin scintigraphy with conventional computed tomography volumetry for predicting posthepatectomy liver failure in patients after portal vein embolization. METHODS: This retrospective study analyzed 152 consecutive patients who underwent hepatobiliary cancer resection after portal vein embolization between 2006 and 2021. Posthepatectomy liver failure was graded according to the International Study Group of Liver Surgery criteria. The predictive abilities for posthepatectomy liver failure were compared between the future remnant uptake (%) by technetium-99m-galactosyl human serum albumin scintigraphy and the future remnant volume (%) by computed tomography volumetry. RESULTS: Future remnant uptake (%) was significantly greater than future remnant volume (%) after portal vein embolization (47.9% vs 40.8%; P < .001), while the values were comparable before portal vein embolization (32.7% vs 31.2%; P = .116). Receiver operating characteristic curve analysis revealed that post-portal vein embolization future remnant volume (%) had a significantly higher area under the curve than post-portal vein embolization future remnant uptake (%) (0.709 vs 0.630; P = .046) for predicting posthepatectomy liver failure. Multivariable analysis revealed that post-portal vein embolization future remnant volume (%) independently predicted posthepatectomy liver failure, but future remnant uptake (%) did not. Although the incidence of posthepatectomy liver failure grade ≥B was 17.8% when indocyanine green-clearance of the future liver remnant based on both future remnant volume (%) and future remnant uptake (%) was ≥0.05, it was higher in other combinations: 55.6% for indocyanine green clearance of the remnant volume ≥0.05/indocyanine green clearance of the remnant uptake ≤0.05; 50.0% for indocyanine green clearance of the remnant volume ≤0.05/indocyanine green clearance of the remnant uptake ≥0.05; and 50% for indocyanine green clearance of the remnant volume ≤0.05/indocyanine green clearance of the remnant uptake ≤0.05. CONCLUSIONS: Technetium-99m-galactosyl human serum albumin scintigraphy is not superior to computed tomography volumetry for assessing the future liver remnant in patients undergoing major hepatectomy after portal vein embolization.

Association between diffuse renal uptake of 18F-FDG and acute kidney injury.

OBJECTIVE: The aim of this study was to investigate the clinical characteristics of patients with diffuse renal uptake (DRU) of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG), with particular focus on renal function. METHODS: We retrospectively analyzed 40 patients who showed DRU on FDG PET/CT and the same number of matched controls. The clinical features, imaging parameters (the mean SUVmax of the kidneys and the kidney size), and laboratory data including renal function parameters (Cr, the serum creatinine level; estimated glomerular filtration ratio (eGFR); Cr-ratio, Cr divided by the baseline; max-Cr-ratio, the maximum serum creatinine level within 30 days divided by the baseline) and C-reactive protein (CRP) were compared between the two groups. In the DRU group, follow-up FDG PET/CT scans were additionally evaluated to determine the presence of DRU. RESULTS: No significant differences were observed in the clinical features except for antibiotic administration, Cr, and eGFR. Significantly more patients underwent antibiotic administration within 30 days in the DRU group (p = 0.002). The mean SUVmax of the kidneys was significantly higher (p < 0.001) and the kidney size was significantly larger in the DRU group (p = 0.003). Cr-ratio and max-Cr-ratio were significantly higher in the DRU group (p = 0.005 and p < 0.001, respectively). CRP was significantly higher in the DRU group (p < 0.001). Eighteen of the 40 patients in the DRU group underwent a second FDG PET/CT scan, and 16 of them did not show DRU. Six of the 18 patients showed acute kidney injury (AKI, i.e., Cr-ratio ≥ 1.5) at the time of the initial scan and recovered before the second scan. None of the six patients showed DRU on the second scan. CONCLUSION: DRU indicates the presence of AKI, could be a reversible finding, and may disappear as renal function improves.

Detection efficacy of PET/CT with 18F-FSU-880 in patients with suspected recurrent prostate cancer: a prospective single-center study.

PURPOSE: Our objective was to investigate the efficacy of PET/CT with a novel prostate-specific membrane antigen (PSMA)-targeted PET probe, 18F-FSU-880, for detection and localization of recurrent disease in prostate cancer patients in whom recurrence was suspected based on an increase in plasma prostate-specific antigen (PSA) levels after initial treatment. METHODS: This study was a prospective institutional review board-approved study of 72 patients (age 56-84 years, PSA level 0.22-40.00 ng/ml) with suspected relapse of prostate cancer after primary therapy, including radical prostatectomy (RP) (n = 35) or radiation therapy (RT) (n = 37). Patients underwent PET/CT approximately 1 h and 3 h after injection of 18F-FSU-880 (101.8-380 MBq). The correlation between patient-based detection rate and Gleason score (GS) of the primary tumor and plasma PSA levels at the time of PET/CT was evaluated. Maximum standardized uptake values (SUVmax) of the positive uptakes at 1 h post-injection were compared with those at 3 h post-injection. RESULTS: In total, 51 patients (71%) showed at least one positive PSMA PET result. The PSA-stratified detection rates were 22% (2/9), 36% (4/11), 89% (16/18) and 85% (29/34) for PSA levels of 0.2 to < 0.5, 0.5 to < 1.0, 1.0 to < 2.0 and ≥ 2.0 ng/ml, respectively. The GS-stratified detection rates were 33% (2/6), 67% (16/24), 70% (16/23) and 89% (17/19) for GS 6, 7, 8 and 9, respectively. In lesion-based analysis, 157 positive lesions were detected at 3 h post-injection, 18 in the prostate or prostate bed, 65 in lymph nodes, 71 in the bone and 3 in the lung. Two local recurrences, eight pelvic lymph nodes and one distant lymph node were depicted only at 3 h post-injection. SUV max at 3 h post-injection was significantly higher than SUVmax at 1 h post-injection (p < 0.001). CONCLUSION: Our preliminary data suggest that 18F-FSU-880 might be a promising new PSMA-targeting tracer for detecting recurrence after initial treatment in patients with prostate cancer.

Application of a Flexible PET Scanner Combined with 3 T MRI Using Non-local Means Reconstruction: Qualitative and Quantitative Comparison with Whole-Body PET/CT.

PURPOSE: Flexible positron emission tomography (fxPET) employing a non-local means reconstruction algorithm was designed to fit existing magnetic resonance imaging (MRI) systems. We aimed to compare the qualitative and quantitative performance of fxPET among fxPET with MR-based attenuation correction (MRAC), fxPET with CT-based attenuation correction (CTAC) using CT as a part of WB PET/CT, and whole-body (WB) PET/CT. PROCEDURES: Sixteen patients with suspected head and neck cancer underwent 2-deoxy-2-[18F]fluoro-D-glucose WB PET/CT scans, followed by fxPET and 3 T MRI scans. Phantom data were compared among the three datasets. For registration accuracy, we measured the distance between the center of the tumor determined by fxPET and that in MRI. We compared image quality, detection rates, and quantitative values including maximal standardized uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and tumor-to-muscle ratio (TMR) among the three datasets. RESULTS: The phantom data in fxPET, except the percent contrast recoveries of 17-mm and 22-mm hot spheres, were inferior to those in WB PET/CT. The mean registration accuracy was 4.4 mm between fxPET using MRAC and MRI. The image quality was comparable between two fxPET datasets, but significantly inferior to WB PET/CT (p < 0.0001). In contrast, detection rates were comparable among the three datasets. SUVmax was significantly higher, and MTV and TLG were significantly lower in the two fxPET datasets compared with the WB PET/CT dataset (p < 0.005). There were no significant differences in SUVmax, MTV, and TLG between the two fxPET datasets or in TMR among the three datasets. All quantitative values had significantly positive correlations. CONCLUSIONS: Compared with WB PET/CT, the phantom data and image quality were inferior in fxPET. However, the results of the detection rates and quantitative values suggested the clinical feasibility of fxPET.

First-in-Human Evaluation of Positron Emission Tomography/Computed Tomography With [18F]FB(ePEG12)12-Exendin-4: A Phase 1 Clinical Study Targeting GLP-1 Receptor Expression Cells in Pancreas.

Pancreatic ß-cell mass (BCM) has a central importance in the pathophysiology of diabetes mellitus. Recently, pancreatic ß-cell-specific imaging, especially positron emission tomography (PET) with exendin-based probes, has emerged for non-invasive evaluation of BCM. We developed a novel exendin-based probe labeled with fluorine-18, [18F]FB(ePEG12)12-exendin-4 (18F-Ex4) for PET imaging. We subsequently conducted a first-in-human phase 1 study of 18F-Ex4 PET/computed tomography (CT) and investigated the safety and utility for visualizing the pancreas. Six healthy male subjects were enrolled in this study. A low dose (37.0 MBq) of 18F-Ex4 PET/CT was administered (first cohort: n = 2), and subsequently a higher dose (74.0 MBq) was administered (second cohort: n = 4). In the first and second cohorts, 38.6 ± 4.8 and 71.1 ± 4.8 MBq of 18F-Ex4 were administered, respectively. No serious adverse events were observed in both groups. Only one participant in the first cohort showed transient hypoglycemia during the PET scans. 18F-Ex4 PET/CT successfully visualized the pancreas in all participants. The mean standardized uptake value of the pancreas was found to be higher than that in the surrounding organs, except for the bladder and kidney, during the observation. Dosimetry analyses revealed the effective systemic doses of 18F-Ex4 as 0.0164 ± 0.0019 mSv/MBq (first cohort) and 0.0173 ± 0.0020 mSv/MBq (second cohort). 18F-Ex4 PET/CT demonstrated the safety and utility for non-invasive visualization of the pancreas in healthy male subjects. 18F-Ex4 is promising for clinical PET imaging targeting pancreatic ß cells.

A Proposed Dedicated Breast PET Lexicon: Standardization of Description and Reporting of Radiotracer Uptake in the Breast.

Dedicated breast positron emission tomography (dbPET) is a new diagnostic imaging modality recently used in clinical practice for the detection of breast cancer and the assessment of tumor biology. dbPET has higher spatial resolution than that of conventional whole body PET systems, allowing recognition of detailed morphological attributes of radiotracer accumulation within the breast. 18F-fluorodeoxyglucose (18F-FDG) accumulation in the breast may be due to benign or malignant entities, and recent studies suggest that morphology characterization of 18F-FDG uptake could aid in estimating the probability of malignancy. However, across the world, there are many descriptors of breast 18F-FDG uptake, limiting comparisons between studies. In this article, we propose a lexicon for breast radiotracer uptake to standardize description and reporting of image findings on dbPET, consisting of terms for image quality, radiotracer fibroglandular uptake, breast lesion uptake.

Diagnostic performance of 68Ga-DOTATOC PET/CT in tumor-induced osteomalacia.

OBJECTIVE: Tumor-induced osteomalacia (TIO) is caused by typically small tumors that secrete fibroblast growth factor 23 (FGF23). As tumor resection is the only effective treatment for TIO, it is important to detect the culprit tumor. We aimed to assess the utility of 68Gallium-DOTA-D-Phe(1)-Tyr(3)-octreotide (68Ga-DOTATOC) PET/CT in TIO and the correlation between biochemical parameters and the PET/CT results. METHODS: Thirty-five patients with clinically suspected TIO who had undergone 68Ga-DOTATOC PET/CT were retrospectively analyzed. 68Ga-DOTATOC PET/CT results were compared with biochemical parameters and the final diagnosis, including histopathology. RESULTS: 68Ga-DOTATOC PET/CT detected focal uptake consistent with TIO in 21/35 patients, one of which was considered false positive. In 16 patients, the cause of osteomalacia was confirmed histologically as phosphaturic mesenchymal tumor (n = 15) or fibrous dysplasia (n = 1). The other four patients were judged clinically as true positive by subsequent MRI and the clinical course. Overall, the detection rate of 68Ga-DOTATOC PET/CT was 57% (20/35). Median tumor maximum standardized uptake value (SUVmax) was 6.9 (range 1.5-37.7). There was no significant difference in serum intact FGF23 level between DOTATOC-positive and DOTATOC-negative cases, and no significant correlation was observed between intact FGF23 level and tumor SUVmax. CONCLUSIONS: 68Ga-DOTATOC PET/CT was clinically useful in detecting culprit tumors and subsequent patient management in TIO.

Evaluation of Optimal Post-Injection Timing of Hypoxic Imaging with 18F-Fluoromisonidazole-PET/CT.

PURPOSE: Positron emission tomography (PET)/computed tomography (CT) using 18F-fluoromisonidazole (FMISO) has been used as an imaging tool for tumour hypoxia. However, it remains unclear whether they are useful when scanning is performed earlier, e.g. at 2-h post-injection with a high sensitivity PET scanner. This study aimed to investigate the relationship between quantitative values in 18F-fluoromisonidazole (18F-FMISO)-PET obtained at 2- and 4-h post-injection in patients with head and neck cancer. PROCEDURES: We enrolled 20 patients with untreated locally advanced head and neck cancer who underwent 18F-FMISO-PET/CT scan between August 2015 and March 2018 at our institute. Image acquisition was performed 2 h and 4 h after 18F-FMISO administration using a combined PET/CT scanner. The SUVmax, SUVmean, SUVpeak, tumour-to-blood ratio (TBR), tumour-to-muscle ratio (TMR), metabolic tumour volume (MTV), and total lesion hypoxia (TLH) were measured in the region of interest of the primary tumour. We evaluated the between-image Spearman's rank correlation coefficients and percentage differences in the quantitative values. The locations of the maximum uptake pixel were identified in both scans, and the distance between them was measured. RESULTS: The mean (SD) SUVmax at 2 h and 4 h was 2.2(0.7) and 2.4(0.8), respectively. The Spearman's rank correlation coefficients (ρ) and mean (SD) of the percentage differences of the measures were as follows: SUVmax (0.97; 7.0 [5.1]%), SUVmean (0.97; 5.2 [5.8]%), SUVpeak (0.94; 5.3 [4.7]%), TBR (0.96; 14.2 [9.8]%), TMR (0.96; 14.7 [8.4]%), MTV (0.98; 39.9 [41.3]%), and TLH (0.98; 40.1 [43.4]%). There were significant between-scan correlations in all quantitative values. The mean (SD) distance between the two maximum uptake pixels was 7.3 (5.3) mm. CONCLUSIONS: We observed a high correlation between the quantitative values at 2 h and 4 h. When using a combined high-quality PET/CT, the total examination time for FMISO-PET can be shortened by skipping the 4-h scan.

Physiological FDG uptake in growth plate on pediatric PET.

OBJECTIVES: 18F-Fluorodeoxyglucose (FDG) uptake in children is different from that in adults. Physiological accumulation is known to occur in growth plates, but the pattern of distribution has not been fully investigated. Our aim was to evaluate the metabolic activity of growth plates according to age and location. METHODS: We retrospectively evaluated 89 PET/CT scans in 63 pediatric patients (male : female=25 : 38, range, 0-18 years). Patients were classified into four age groups (Group A: 0-2 years, Group B: 3-9 years, Group C: 10-14 years and Group D: 15-18 years). The maximum standardized uptake value (SUVmax) of the proximal and distal growth plates of the humerus, the forearm bones and the femur were measured. The SUVmax of each site and each age group were compared and statistically analyzed. We also examined the correlations between age and SUVmax. RESULTS: As for the comparison of SUVmax in each location, the SUVmax was significantly higher in the distal femur than those in the other sites (p< 0.01). SUVmax in the distal humerus and the proximal forearm bones were significantly lower than those in the other sites (p< 0.01). In the distal femur, there was large variation in SUVmax, while in the distal humerus and the proximal forearm bones, there was small variation. As for the comparison of SUVmax in each age group, the SUVmax in group D tended to be lower than those in the other groups, but in the distal femur, there was no significant difference among each age group. CONCLUSION: Our data indicate that FDG uptake in growth plates varies depending on the site and age with remarkable uptake especially in the distal femur.

Qualitative and Quantitative Assessment of Nonlocal Means Reconstruction Algorithm in a Flexible PET Scanner.

OBJECTIVE. Flexible PET (fxPET) was designed to fit existing MRI systems. The newly modified nonlocal means (NLM) algorithm is combined with the 3D dynamic row-action maximum likelihood algorithm (DRAMA). We investigated qualitative and quantitative acceptability of fxPET images reconstructed by modified NLM compared with whole-body (WB) PET/CT images and conventional 3D DRAMA reconstruction alone. MATERIALS AND METHODS. Fifty-nine patients with known or suspected malignancies underwent WB PET/CT scanning approximately 1 hour after the injection of 18F-FDG, after which they underwent fxPET scanning. Two readers rated the quality of fxPET images by consensus. Detection rate (the proportion of lesions found on PET), maximal standardized uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG), tumor-to-normal liver ratio (TNR), and background liver signal-to-noise ratio (SNR) were compared among the three datasets. RESULTS. Higher image quality was obtained by modified NLM reconstruction than by conventional reconstruction without statistical significance. The detection rate was comparable among three datasets. SUVmax was significantly higher, and MTV and TLG were significantly lower in the modified NLM dataset (p < 0.002) than in the other two datasets, with significantly positive correlations (p < 0.001; Spearman rank correlation coefficient, 0.87-0.99). The TNRs in modified NLM images were significantly larger than in the other datasets (p < 0.05). The background SNRs in modified NLM images were comparable with those in WB PET/CT images, and significantly higher than in the conventional fxPET images (p < 0.005). CONCLUSION. The modified NLM algorithm was clinically acceptable, yielding higher TNR and background SNR compared with conventional reconstruction. Image quality and the lesion detection rate were comparable in this population.

[MRI Connecting Functions and Anatomy: A New Bridge for Radiotherapy].

Advances in medical devices have allowed the use of CT, MRI, and PET-CT for the diagnosis of tumors and the detailed evaluation of the extent of lesions. For several decades, CT has been established as the gold standard modality for the treatment planning of radiotherapy, while MRI has emerged as a tool to evaluate the functional characteristics of tumors without radiation exposure. To further optimize precision radiation therapy, we should consider how functional images can be used in the workflow for radiation therapy. In this regard, MRI, as a modality without the need for a contrast agent, may allow more frequent scans and more detailed dose painting, such as increasing the dose to viable lesion parts while reducing the dose to less aggressive parts. Thus, a more personalized treatment based on precision radiation medicine might be realized. In recent years, MR-Linac systems (MRI integrated linear accelerator radiation therapy systems) have been applied in clinical settings by fusing MRI with Linac planning, and further development of radiation therapy utilizing MRI-derived functional images is expected. The use of MR-Linac techniques allows the characteristics of the tumor to be evaluated in more detail before treatment, and the treatment planning can be modified according to the position and characteristics of the tumor (which may change daily during irradiation) to avoid harming normal tissue. Compared with conventional cone beam CT, MR-Linac can offer MR images with much better contrast of soft tissue for image-guided radiation therapy, even when acquired at 0.35 T. A multicenter study of liver tumors using MR-Linac was recently reported. In current tumor imaging, various MRI sequences can be used to evaluate tumor functional information such as tumor heterogeneity, cell density, microenvironment, angiogenesis, necrosis, hypoxic status, and microstructure. In this article, we introduce state-of-the-art acquisition methods for MRI imaging, and discuss how the functional information obtained from these imaging methods can be useful for radiation therapy.

Prognostic Value of Quantitative Parameters of 18F-FDG PET/CT for Patients With Angiosarcoma.

OBJECTIVE. The purpose of this study was to evaluate quantitative parameters in 18F-FDG PET/CT in terms of correlation with histologic grade and overall survival in patients with angiosarcoma. MATERIALS AND METHODS. The cases of 16 patients with histologically confirmed angiosarcoma who had undergone pretreatment FDG PET/CT were retrospectively analyzed. Maximum standardized uptake value for the primary tumor (pSUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) for the whole body, tumor-to-blood ratio (TBR) for the primary tumor, and summed ratios of tumor-to-blood glycolytic activity for all lesions (whole-body TLG ratio) were calculated. Tumors were divided into high grade and low grade, according to the pathologic results. Correlations between these metabolic parameters and tumor grade were investigated. The prognostic value of these parameters and various clinicopathologic factors with respect to overall survival was assessed with the Cox proportional hazards regression model. RESULTS. Histopathologic examination revealed 10 high-grade and six low-grade tumors. Among the quantitative parameters, pSUVmax (p < 0.0001) and primary TBR (p = 0.0003) were significantly higher for high-grade tumors than for low-grade tumors. Ten patients died during follow-up (median survival time, 19.6 months). Higher pSUVmax (p = 0.040), MTV (p = 0.016), whole-body TLG (p = 0.010), primary TBR (p = 0.019), and whole-body TLG ratio (p = 0.007) correlated significantly with poorer overall survival. Single lesion at initial diagnosis (p = 0.0008) and performance of curative surgery (p = 0.0008) were strong favorable prognostic factors for overall survival, but histologic grade was not identified as a significant predictor. CONCLUSION. In angiosarcoma, high-grade tumors had significantly higher pSUVmax and primary TBR at FDG PET/CT. All quantitative parameters evaluated in this study were found to be significant prognostic factors for overall survival.