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To determine whether temporal subtraction (TS) CT obtained with non-rigid image registration improves detection of various bone metastases during serial clinical follow-up examinations by numerous radiologists. Six board-certified radiologists retrospectively scrutinized CT images for patients with history of malignancy sequentially. These radiologists selected 50 positive and 50 negative subjects with and without bone metastases, respectively. Furthermore, for each subject, they selected a pair of previous and current CT images satisfying predefined criteria by consensus. Previous images were non-rigidly transformed to match current images and subtracted from current images to automatically generate TS images. Subsequently, 18 radiologists independently interpreted the 100 CT image pairs to identify bone metastases, both without and with TS images, with each interpretation separated from the other by an interval of at least 30 days. Jackknife free-response receiver operating characteristics (JAFROC) analysis was conducted to assess observer performance. Compared with interpretation without TS images, interpretation with TS images was associated with a significantly higher mean figure of merit (0.710 vs. 0.658; JAFROC analysis, P = 0.0027). Mean sensitivity at lesion-based was significantly higher for interpretation with TS compared with that without TS (46.1% vs. 33.9%; P = 0.003). Mean false positive count per subject was also significantly higher for interpretation with TS than for that without TS (0.28 vs. 0.15; P < 0.001). At the subject-based, mean sensitivity was significantly higher for interpretation with TS images than that without TS images (73.2% vs. 65.4%; P = 0.003). There was no significant difference in mean specificity (0.93 vs. 0.95; P = 0.083). TS significantly improved overall performance in the detection of various bone metastases. [ABSTRACT FROM AUTHOR]

Granulocyte colony-stimulating factor (G-CSF)-producing tumors have an aggressive clinical course. Here, we report five cases of G-CSF-producing tumors and review the literature, focusing on imaging findings related to tumor-produced G-CSF. In addition to our cases, we identified 30 previous reports of G-CSF-producing tumors on which 18F-fluorodeoxyglucose positron emission tomography (FDG-PET)/CT, bone scintigraphy, or evaluation of bone marrow MR findings was performed. White blood cell count, serum C-reactive protein, and serum interleukin-6 were elevated in all cases for which these parameters were measured. G-CSF-producing tumors presented large necrotic masses (mean diameter 83.2 mm, range 17–195 mm) with marked FDG uptake (mean maximum standardized uptake value: 20.09). Diffuse FDG uptake into the bone marrow was shown in 28 of the 31 cases in which FDG-PET/CT was performed. The signal intensity of bone marrow suggested marrow reconversion in all seven MRI-assessable cases. Bone scintigraphy demonstrated no significant uptake, except in two cases with bone metastases. Splenic FDG uptake was increased in 8 of 10 cases in which it was evaluated. These imaging findings may reflect the effects of tumor-produced G-CSF. The presence of G-CSF-producing tumors should be considered in patients with cancer who show these imaging findings and marked inflammatory features of unknown origin. [ABSTRACT FROM AUTHOR]

Pancreatic β-cell mass (BCM) has a central importance in the pathophysiology of diabetes mellitus. Recently, pancreatic β-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 β cells. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the clinical feasibility of a newly developed mobile PET system with MR-compatibility (flexible PET; fxPET), compared with conventional PET (cPET)/CT for brain imaging. Methods: Twenty-one patients underwent cPET/CT with subsequent fxPET/MRI using 18F-FDG. As qualitative evaluation, we visually rated image quality of MR and PET images using a four-point scoring system. We evaluated overall image quality for MR, while we evaluated overall image quality, sharpness and lesion contrast. As quantitative evaluation, we compared registration accuracy between two modalities [(fxPET and MRI) and (cPET and CT)] measuring spatial coordinates. We also examined the accuracy of regional 18F-FDG uptake. Results: All acquired images were of diagnostic quality and the number of detected lesions did not differ significantly between fxPET/MR and cPET/CT. Mean misregistration was significantly larger with fxPET/MRI than with cPET/CT. SUVmax and SUVmean for fxPET and cPET showed high correlations in the lesions (R = 0.84, 0.79; P < 0.001, P = 0.002, respectively). In normal structures, we also showed high correlations of SUVmax (R = 0.85, 0.87; P < 0.001, P < 0.001, respectively) and SUVmean (R = 0.83, 0.87; P < 0.001, P < 0.001, respectively) in bilateral caudate nuclei and a moderate correlation of SUVmax (R = 0.65) and SUVmean (R = 0.63) in vermis. Conclusions: The fxPET/MRI system showed image quality within the diagnostic range, registration accuracy below 3 mm and regional 18F-FDG uptake highly correlated with that of cPET/CT. [ABSTRACT FROM AUTHOR]

Several studies have evaluated the usefulness of deep learning for lung segmentation using chest X‐ray (CXR) images with small‐ or medium‐sized abnormal findings. Here, we built a database including both CXR images with severe abnormalities and experts' lung segmentation results, and aimed to evaluate our network's efficacy in lung segmentation from these images. For lung segmentation, CXR images from the Japanese Society of Radiological Technology (JSRT, N = 247) and Montgomery databases (N = 138) were included, and 65 additional images depicting severe abnormalities from a public database were evaluated and annotated by a radiologist, thereby adding lung segmentation results to these images. U‐net was used to segment the lungs in images from the three databases. Subsequently, the U‐net network architecture was automatically optimized for lung segmentation from CXR images using Bayesian optimization. Dice similarity coefficient (DSC) was calculated to confirm segmentation. Our results demonstrated that using baseline U‐net yielded poorer lung segmentation results in our database than those in the JSRT and Montgomery databases, implying that robust segmentation of lungs may be difficult because of severe abnormalities. The DSC values with baseline U‐net for the JSRT, Montgomery and our databases were 0.979, 0.941, and 0.889, respectively, and with optimized U‐net, 0.976, 0.973, and 0.932, respectively. For robust lung segmentation, the U‐net architecture was optimized via Bayesian optimization, and our results demonstrate that the optimized U‐net was more robust than baseline U‐net in lung segmentation from CXR images with large‐sized abnormalities. [ABSTRACT FROM AUTHOR]

Background: Ultrasonography (US) is useful when implanting fiducial markers in the liver. However, the implant position is sometimes lost. Recently, real-time image fusion technology (Volume Navigation [V-navi]; GE Healthcare, Milwaukee, WI, USA) has been introduced as a technique for using images from different modalities, and its utility for fiducial marker implantation has been hypothesized.Purpose: To evaluate the utility of US-guided fiducial marker implantation in the liver using V-navi compared to conventional US.Material and Methods: We retrospectively reviewed 35 patients who underwent fiducial marker implantation for stereotactic body radiation therapy of liver tumors in 2013-2018. To avoid artifacts obscuring the tumor, the target point of implantation was set 10 mm cranial or caudal to the tumor. Marker implantation was then performed using US alone (US group, n = 24) or V-navi with computed tomography (CT) or magnetic resonance imaging (V-navi group, n = 11). Postprocedural CT was evaluated to determine technical success, distances between marker and either tumor surface or target point, and whether marker-induced artifacts obscured the tumor. Complications were also evaluated. Results were compared between groups.Results: Technical success was obtained in 33 patients. Distance between the tumor and marker showed no significant difference between groups. Distance between target point and marker was shorter in the V-navi group (P = 0.0093). Tumor-obscuring artifacts were seen in 12 patients (V-navi group, n = 1; US group, n = 11; P = 0.055). The only complication was minor bleeding in the US group (n = 1).Conclusion: V-navi appears useful for US-guided fiducial marker implantation in the liver compared with conventional US. [ABSTRACT FROM AUTHOR]

Background: Hypothalamic–pituitary–thyroid (HPT) maturation has not been extensively evaluated using neonatal MRI, even though both structures are visualized on MRI. Hypothesis: That signal intensity and volume of pituitary and thyroid (T) glands on MRI in neonates may be interrelated. Study Type: Retrospective. Subjects: In all, 102 participants. Field Strength/Sequence: 3.0T, T1‐weighted pointwise encoding time reduction with radial acquisition (PETRA). Assessment: The volume of interest of the anterior pituitary (AP), posterior pituitary (PP), and T on MRI were defined on T1‐PETRA by two radiologists, and volumes of AP (AP_vol) and thyroid (T_vol) were calculated. Gestational age (GA), chronological age (CA), GA+CA, birth weight (BW), and thyroid function were recorded. Mean and maximum signal intensities of AP, PP, and T were normalized using signals from the pons and spinal cord as follows: signal ratio of anterior pituitary/pons (AP/pons), signal ratio of posterior pituitary/pons (PP/pons), and signal ratio of thyroid/cord (T/cord) T/cord, respectively. Statistical Tests: Correlations between signal intensity and volume measures and GA, CA, GA+CA, and BW were assessed using Pearson's correlation coefficient or Spearman's rank correlation coefficient. Thyroid function analysis and Tmean/cord, Tmax/cord, and T_vol were evaluated using the Steel–Dwass test. Results: APmean/pons correlated positively with GA (ρ = 0.62, P < 0.001) and BW (ρ = 0.74, P < 0.001), and negatively with CA (ρ = −0.86, P < 0.001) and GA+CA (ρ = −0.46, P < 0.001). PPmean/pons correlated positively with GA (ρ = 0.49, P < 0.001) and BW (ρ = 0.63, P < 0.001), and negatively with CA (ρ = −0.70, P < 0.001) and GA+CA (r = −0.38, P < 0.001). Tmean/cord correlated positively with GA (ρ = 0.48, P < 0.001) and BW (ρ = 0.55, P < 0.001), and negatively with CA (ρ = −0.59, P < 0.001) and GA+CA (ρ = −0.22, P = 0.03). AP_vol correlated positively with GA (ρ = 0.68, P < 0.001) and BW (ρ = 0.73, P < 0.001), and negatively with CA (ρ = −0.72, P < 0.001). T_vol correlated positively with GA (ρ = 0.50, P < 0.001) and BW (ρ = 0.61, P < 0.001), and negatively with CA (ρ = −0.54, P < 0.001). APmean/pons correlated positively with Tmean/cord (ρ = 0.61, P < 0.001). Data Conclusion: Signal and volume of pituitary and thyroid glands correlated positively with GA and BW, and negatively with CA in neonates. Level of Evidence: 4 Technical Efficacy Stage: 5 [ABSTRACT FROM AUTHOR]

Aim: To elucidate correlation between signal intensity on diffusion‐weighted images (SI‐DWI) and clinical backgrounds for uterine adenomyosis and to compare SI‐DWI of adenomyosis and malignant uterine tumors. Methods: This study examined 46 adenomyosis patients diagnosed using magnetic resonance imaging and 25 patients with surgically confirmed malignant uterine myometrial tumor. First, adenomyosis cases were classified visually into high‐intensity and low‐intensity groups based on the SI‐DWI compared with that of normal uterine myometrium. Secondly, correlation was assessed between SI‐DWI of adenomyosis and patient clinical background information such as age, menopausal status, menstrual cycle and dysmenorrhea severity. Third, quantitative comparison was made of low‐intensity adenomyosis (LIA), high‐intensity adenomyosis (HIA) and malignant tumor groups for the signal intensity ratio (SIR) on DWI and the apparent diffusion coefficient (ADC). Their diagnostic performance was evaluated using logistic regression analysis and receiver operating characteristic (ROC) analysis. Results: The 46 adenomyosis cases were classified as 26 low‐intensity and 20 high‐intensity cases. Significant correlation was found only for menstrual cycle phases. HIA had significantly lower SIR and higher ADC than malignant tumor. The ADC of HIA was significantly higher than that of LIA. The combination of SIR and ADC showed excellent diagnostic performance (area under ROC curve, 0.99). Conclusion: There is a variation in signal intensity on DWI of uterine adenomyosis and it is associated with menstrual cycle phase. Adenomyosis with high signal intensity on DWI can be differentiated from malignant lesions by its lower signal intensity on DWI and higher ADC than that found for malignant uterine tumors, however overlaps exist. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Purpose: We aimed to evaluate mid- to long-term results of endovascular treatment for portal vein thrombosis (PVT) after living-donor liver transplantation (LDLT).Methods: Thirty cases (14 males, 16 females; age range, 0.67-65 years) who underwent endovascular treatment including thrombolysis, angioplasty, stent placement, and/or collateral embolization for PVT after LDLT from 2001 to 2017 were retrospectively reviewed. Clinical and procedural data were collected and analyzed regarding the patency of the PVT site at the last follow-up date (PVT-free persistency) using Log-rank test. Results were considered statistically significant at P < 0.05.Results: Median follow-up was 120 months. The technical success rate was 80% (n=24). Patency rates at 1 week and 1, 3, 6, 12, 36, and 60 months were 73%, 59%, 55%, 51%, 51%, 51%, and 51% for primary patency and 80%, 70%, 66%, 66%, 66%, 61%, and 61% for assisted patency after secondary endovascular treatment. PVT-free persistency rates regarding the subgroups were as follows: children under 12 years vs. adults, 50% vs. 68% (P = 0.42); acute vs. nonacute, 76% vs. 46% (P = 0.10); localized vs. extensive, 90% vs. 50% (P = 0.035); transileocolic approach vs. percutaneous-transhepatic approach, 71% vs. 54% (P = 0.39); and thrombolysis-based treatment vs. non-thrombolysis-based treatment, 71% vs. 44% (P = 0.12), respectively. Among technically successful cases, PVT-free persistency rate was 94% for those with hepatopetal flow in the peripheral portal vein vs. 17% for those without hepatopetal flow (P < 0.001). The only major complication occurring was pleural hemorrhage (n=1). Minor complications (i.e., fever) occurred in 18 patients (60%).Conclusion: In conclusion, mid- to long-term portal patency following endovascular treatment was approximately 50%-60% in PVT patients after LDLT. PVT site patency over three months after the first endovascular treatment, localized PVT, and hepatopetal flow in the peripheral portal vein were identified as key prognostic factors for mid- to long-term portal patency. [ABSTRACT FROM AUTHOR]

Objective: To compare the absolute values and repeatability of magnetic resonance fingerprinting (MRF) with 3000 and 1500 echoes/slice acquired in 41 s and 20 s (MRF3k and MRF1.5k, respectively). Materials and methods: MRF3k and MRF1.5k scans based on fast imaging with steady precession (FISP) were conducted using a 3 T scanner. Inter-scan agreement and intra-scan repeatability were investigated in 41 and 28 subjects, respectively. Region-of-interest (ROI) analysis was conducted on T1 values of MRF3k by two raters, and their agreement was evaluated using intraclass correlation coefficients (ICCs). Between MRF3k and MRF1.5k, differences in T1 and T2 values and inter-measurement correlation coefficients (CCs) were investigated. Intra-measurement repeatability was evaluated using coefficients of variation (CVs). A p value < 0.05 was considered statistically significant. Results: The ICCs of ROI measurements were 0.77–0.96. Differences were observed between the two MRF scans, but the CCs of the overall ROIs were 0.99 and 0.97 for the T1 and T2 values, respectively. The mean and median CVs of repeatability were equal to or less than 1.58% and 3.13% in each of the ROIs for T1 and T2, respectively; there were some significant differences between MRF3k and MRF1.5k, but they were small, measuring less than 1%. Discussion: Both MRF3k and MRF1.5k had high repeatability, and a strong to very strong correlation was observed, with a trend toward slightly higher values in MRF1.5k. [ABSTRACT FROM AUTHOR]

Temporal subtraction (TS) technique calculates a subtraction image between a pair of registered images acquired from the same patient at different times. Previous studies have shown that TS is effective for visualizing pathological changes over time; therefore, TS should be a useful tool for radiologists. However, artifacts caused by partial volume effects degrade the quality of thick-slice subtraction images, even with accurate image registration. Here, we propose a subtraction method for reducing artifacts in thick-slice images and discuss its implementation in high-speed processing. The proposed method is based on voxel matching, which reduces artifacts by considering gaps in discretized positions of two images in subtraction calculations. There are two different features between the proposed method and conventional voxel matching: (1) the size of a searching region to reduce artifacts is determined based on discretized position gaps between images and (2) the searching region is set on both images for symmetrical subtraction. The proposed method is implemented by adopting an accelerated subtraction calculation method that exploit the nature of liner interpolation for calculating the signal value at a point among discretized positions. We quantitatively evaluated the proposed method using synthetic data and qualitatively using clinical data interpreted by radiologists. The evaluation showed that the proposed method was superior to conventional methods. Moreover, the processing speed using the proposed method was almost unchanged from that of the conventional methods. The results indicate that the proposed method can improve the quality of subtraction images acquired from thick-slice images. [ABSTRACT FROM AUTHOR]

Objectives: To determine imaging hallmarks for distinguishing intrahepatic mass-forming biliary carcinomas (IMBCs) from hepatocellular carcinoma (HCC) and to validate their diagnostic ability using Bayesian statistics. Methods: Study 1 retrospectively identified clinical and imaging hallmarks that distinguish IMBCs (n = 41) from HCC (n = 247) using computed tomography (CT) and magnetic resonance imaging (MRI). Study 2 retrospectively assessed the diagnostic ability of these hallmarks to distinguish IMBCs (n = 37) from HCC (n = 111) using Bayesian statistics with images obtained from a different institution. We also assessed the diagnostic ability of the hallmarks in the patient subgroup with high diagnostic confidence (≥ 80% of post-test probability). Two radiologists independently evaluated the imaging findings in studies 1 and 2. Results: In study 1, arterial phase peritumoral parenchymal enhancement on CT/MRI, delayed enhancement on CT/MRI, diffusion-weighted imaging peripheral hyperintensity, and bile duct dilatation were hallmarks indicating IMBCs, whereas chronic liver disease, non-rim arterial phase hyperenhancement on CT/MRI, enhancing capsule on CT/MRI, and opposed-phase signal drop were hallmarks indicating HCC (p = 0.001–0.04). In study 2, Bayesian statistics-based post-test probability combining all hallmark features had a diagnostic accuracy of 89.2% (132/148) in distinguishing IMBCs from HCC for both readers. In the high diagnostic confidence subgroup (n = 120 and n = 124 for readers 1 and 2, respectively), the accuracy improved (95.0% (114/120) and 93.5% (116/124) for readers 1 and 2, respectively). Conclusions: Combined interpretation of CT and MRI to identify hallmark features is useful in discriminating IMBCs from HCCs. High post-test probability by Bayesian statistics allows for a more reliable non-invasive diagnosis. Key Points: • Combined interpretation of CT and MRI to identify hallmark features was useful in discriminating intrahepatic mass-forming biliary carcinomas from hepatocellular carcinoma. • Bayesian method-based post-test probability combining all hallmark features determined in study 1 showed high (> 90%) sensitivity and specificity for distinguishing intrahepatic mass-forming biliary carcinomas from hepatocellular carcinoma. • If the post-test probability or the confidence was ≥ 80% when combining the imaging features of CT and MRI, the high specificity of > 95% was achieved without any loss of sensitivity to distinguish hepatocellular carcinoma from intrahepatic mass-forming biliary carcinomas. [ABSTRACT FROM AUTHOR]

Diffusion-weighted imaging (DWI) is increasingly being incorporated into routine breast MRI protocols in many institutions worldwide, and there are abundant breast DWI indications ranging from lesion detection and distinguishing malignant from benign tumors to assessing prognostic biomarkers of breast cancer and predicting treatment response. DWI has the potential to serve as a noncontrast MR screening method. Beyond apparent diffusion coefficient (ADC) mapping, which is a commonly used quantitative DWI measure, advanced DWI models such as intravoxel incoherent motion (IVIM), non-Gaussian diffusion MRI, and diffusion tensor imaging (DTI) are extensively exploited in this field, allowing the characterization of tissue perfusion and architecture and improving diagnostic accuracy without the use of contrast agents. This review will give a summary of the clinical literature along with future directions. Level of Evidence: 5 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;52:70-90. [ABSTRACT FROM AUTHOR]

Background: Time-resolved angiography with interleaved stochastic trajectories (TWIST) is a keyhole imaging with frequent sampling of central k-space data and view-sharing for the peripheral k-space of dynamic phases. IT-TWIST is a technique to reconstruct images with a smaller temporal footprint using the same raw data obtained with TWIST by iterative reconstruction.Purpose: To compare image quality between TWIST and IT-TWIST in 3D pituitary DCE-MRI.Study Type: Retrospective observation study.Population: Fifty-one patients (23 men, 28 women) who underwent 3D pituitary DCE-MRI using TWIST between July 2016 and April 2017.Field Strength/sequence: 3T/TWIST and IT-TWIST.Assessment: Visual evaluation was conducted for image quality of delineation of the pituitary stalk and posterior lobe during the early arterial phase, cerebral white matter near the sella turcica, and the mass lesion. Bolus sharpness of the pituitary stalk, posterior lobe, and bilateral cavernous sinus was evaluated on the enhancement slope map calculated from TWIST and IT-TWIST. Temporal stability of intensity of the nonenhanced area was evaluated on temporal standard deviation (SD) maps calculated from TWIST and IT-TWIST.Statistical Tests: Paired t-test or Wilcoxon rank-sum test was used to test the differences between TWIST and IT-TWIST in both visual evaluation and region of interest evaluation.Results: Scores of visual evaluations for IT-TWIST were significantly better than those for TWIST (P < 0.001) in all items. Enhancement slope for IT-TWIST was significantly higher than that for TWIST in posterior lobe, and right and left cavernous sinus (P < 0.001). Temporal SD for IT-TWIST was significantly lower than that for TWIST in all items, with statistical significance (P < 0.001).Data Conclusion: IT-TWIST yielded better visualization, and better enhancement slope, and less temporal SD compared with TWIST in 3D pituitary DCE-MRI. Evidence Level: 4 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:1497-1506. [ABSTRACT FROM AUTHOR]

Purpose: A mobile positron emission tomography (PET) scanner called flexible PET (fxPET), designed to fit existing magnetic resonance imaging (MRI) or computed tomography (CT) system, has been developed. The purpose of this study was to evaluate the image quality, lesion detection rate, and quantitative values of fxPET compared with conventional bismuth germanium oxide (BGO)-based PET/CT without time-of-flight capability.Procedures: Fifty-nine patients underwent whole-body (WB) PET/CT scans approximately 1 h after injection of 2-deoxy-2-[18F]fluoro-D-glucose, followed by the fxPET scans with detectors located above and below the patients (layout A) and with detectors closer to the patients (layout B). Two readers assessed the image quality using a 4-point grade for each layout and reached a consensus. We evaluated the differences and/or correlations between fxPET and WB PET/CT, including the lesion detection rates, the standardized uptake value (SUV), the metabolic tumor volume (MTV), the total lesion glycolysis (TLG), the tumor-to-normal liver ratio (TLR), and the background liver signal-to-noise ratio (SNR).Results: The image quality of layout B was better than layout A (p < 0.0001). Of 184 lesions, the detection rate of layout B was significantly higher than WB PET/CT (p = 0.041), while the detection rate of layout A was comparable to WB PET/CT. The SUVmax/mean/peak were larger, and the MTVs were smaller in fxPET than WB PET/CT, especially in the lesions smaller than 2 cm (p < 0.01). The SUVmax/mean/peak, the MTVs and the TLGs of fxPET had significant positive correlations with WB PET/CT (p < 0.0001). The TLRs were significantly larger (p < 0.0001), but the background SNRs were significantly lower in fxPET than WB PET/CT (p < 0.05).Conclusions: The fxPET system yielded reasonable image quality and quantitative accuracy. Bringing the detectors closer to the patient yielded improved results. [ABSTRACT FROM AUTHOR]

Objectives: In patients with advanced ovarian, fallopian and primary peritoneal carcinoma, complete interval debulking surgery (IDS) is often performed after neoadjuvant chemotherapy (NAC) to achieve long progression-free survival (PFS) and overall survival (OS). We aimed to investigate the utility of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) PET/CT in patients with these malignancies who underwent complete IDS.Methods: Between 2009 and 2017, twenty-two patients underwent FDG PET/CT scans before and after NAC. The highest SUVmax/peak (standardized uptake value), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) for whole lesions were defined as target SUVmax/peak, tMTV and tTLG, respectively. We also calculated these reduction rates during NAC. These parameters were compared between the groups with platinum-free interval (PFI) > 12 months (n = 10) and those with PFI ≤ 12 months (n = 12). The PFS and OS were evaluated using these quantitative parameters, and in terms of the presence of visually detectable residual lesions after NAC.Results: The target SUVmax/peak before NAC, the reduction rates in the target SUVmax, tMTV and tTLG were significantly higher in the group with PFI > 12 months than the shorter PFI group (p < 0.05). Especially in PFS, the higher reduction rates in the target SUVmax/peak, tMTV, and tTLG had an excellent prognostic stratification (p < 0.05) and the FDG visually negative group after NAC had a significantly better prognosis than the other group (p < 0.01).Conclusions: The reduction rate of FDG PET-based quantitative values and visual analysis after NAC demonstrated prognostic potential, especially in PFS. [ABSTRACT FROM AUTHOR]

Background: Ultrafast dynamic contrast-enhanced (UF-DCE) breast MRI is considered a promising method of accelerated breast MRI. However, the value of new kinetic parameters derived from UF-DCE need clinical evaluation.Purpose: To evaluate the diagnostic performance of the maximum slope (MS), time to enhancement (TTE), and time interval between arterial and venous visualization (AVI) derived from UF-DCE MRI using compressed sensing (CS).Study Type: Retrospective.Population: Seventy-five patients with histologically proven breast lesions. The total number of analyzed lesions was 90 (61 malignant and 29 benign).Field Strength/sequence: 3T MRI with UF-DCE MRI based on the 3D gradient-echo volumetric interpolated breath-hold examination (VIBE) sequence using incoherent k-space sampling combined with a CS reconstruction followed by conventional DCE MRI.Assessment: The diagnostic performance of the MS, TTE, AVI, and conventional kinetic analysis was analyzed and compared with histology.Statistical Tests: Wilcoxon rank sum test, receiver operating characteristic analysis.Results: The MS was larger and the TTE and AVI were smaller for malignant lesions compared with benign lesions: MS: 29.3%/s and 18.4%/s (P < 0.001), TTE: 7.0 and 12.0 seconds (P < 0.001), AVI: 2.7 and 4.4 frames (P = 0.006) for malignant and benign lesions. The discriminating power of the MS (area under the curve [AUC], 0.76) was slightly better than that of conventional kinetic analysis (AUC, 0.69) and comparable to that of the TTE and AVI (AUC, 0.78 and 0.76 for TTE and AVI, respectively). Invasive lobular carcinoma had smaller MS (21.8%/s) among malignant lesions (29.3%/s).Data Conclusion: The MS, TTE, and AVI can be used to evaluate breast lesions with clinical performance equivalent to that of conventional kinetic analysis. These parameters vary among histologies.Level Of Evidence: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:164-174. [ABSTRACT FROM AUTHOR]

Objective: To develop and evaluate a radiomics approach for classifying histological subtypes and epidermal growth factor receptor (EGFR) mutation status in lung cancer on PET/CT images.Methods: PET/CT images of lung cancer patients were obtained from public databases and used to establish two datasets, respectively to classify histological subtypes (156 adenocarcinomas and 32 squamous cell carcinomas) and EGFR mutation status (38 mutant and 100 wild-type samples). Seven types of imaging features were obtained from PET/CT images of lung cancer. Two types of machine learning algorithms were used to predict histological subtypes and EGFR mutation status: random forest (RF) and gradient tree boosting (XGB). The classifiers used either a single type or multiple types of imaging features. In the latter case, the optimal combination of the seven types of imaging features was selected by Bayesian optimization. Receiver operating characteristic analysis, area under the curve (AUC), and tenfold cross validation were used to assess the performance of the approach.Results: In the classification of histological subtypes, the AUC values of the various classifiers were as follows: RF, single type: 0.759; XGB, single type: 0.760; RF, multiple types: 0.720; XGB, multiple types: 0.843. In the classification of EGFR mutation status, the AUC values were: RF, single type: 0.625; XGB, single type: 0.617; RF, multiple types: 0.577; XGB, multiple types: 0.659.Conclusions: The radiomics approach to PET/CT images, together with XGB and Bayesian optimization, is useful for classifying histological subtypes and EGFR mutation status in lung cancer. [ABSTRACT FROM AUTHOR]

Objective: Temporal subtraction of CT (TS) images improves detection of newly developed bone metastases (BM). We sought to determine whether TS improves detection of BM by radiology residents as well.Methods: We performed an observer study using a previously reported dataset, consisting of 60 oncology patients, each with previous and current CT images. TS images were calculated using in-house software. Four residents independently interpreted twice the 60 sets of CT images, without and with TS. They identified BM by marking suspicious lesions likely to be BM. Lesion-based sensitivity and number of false positives per patient were calculated. Figure-of-merit (FOM) was calculated. Detectability of BM, with and without TS, was compared between radiology residents and board-certified radiologists, as published previously.Results: FOM of residents significantly improved by implementing TS (p value < 0.0001). Lesion-based sensitivity, false positives per patients, and FOM were 40.8%, 0.121, and 0.657, respectively, without TS, and 58.1%, 0.0958, and 0.796, respectively, with TS. These findings were comparable with the previously published values for board-certified radiologists without TS (58.0%, 0.19, and 0.758, respectively).Conclusion: The detectability of BM by residents improved markedly by implementing TS and reached that of board-certified radiologists without TS.Key Points: • Detectability of bone metastases on CT by residents improved significantly when using temporal subtraction of CT (TS). • Detections by residents with TS and board-certified radiologists without TS were comparable. • TS is useful for residents as it is for board-certified radiologists. [ABSTRACT FROM AUTHOR]

Purpose: Recently, the potential value of isocitrate dehydrogenase (IDH) mutation as a prognostic marker in glioblastomas has been established. Glioblastomas are classified by their IDH mutation status under the 2016 WHO classification system. However, noninvasive diagnostic methods for the mutation status in glioblastoma patients have not been established so far. The purpose of this study was to evaluate the difference of acetate metabolism between in glioblastomas with wild-type IDH and in those with IDH mutation by comparing the uptake of 14C-acetate using genetically engineered glioblastoma cell lines in vitro and in vivo. Methods: We established glioblastoma cells (U251) expressing IDH1 R132H and examined the cell uptake of [1-14C]acetate. Biodistribution studies and an autoradiographic study for U251 cell tumor-bearing mice (BALB/c-nu/nu) with or without the IDH1 mutation were performed 1 h after [1-14C]acetate administration. Results: Significantly higher uptake of [1-14C]acetate was observed in U251/IDH1 R132H cells than in U251/IDH1 wild-type cells both in vitro (10.11 ± 0.94 vs. 4.26 ± 0.95%dose/mg, p = 0.0047) and in vivo (0.97 ± 0.14 vs. 0.66 ± 0.05%ID/g; p = 0.0037). Tumor-to-muscle ratios were also significantly higher in U251/IDH1 R132H tumors (3.36 ± 0.41 vs. 1.88 ± 0.59, p = 0.0030). The autoradiographic study shows the entirely higher radioactivity of the U251/IDH1 R132H tumor tissue section than that of the U251/IDH1 Wild-type tumor. Conclusions: In vitro and in vivo studies demonstrated that the uptake of radiolabeled acetate was significantly higher in IDH-mutated cells than in IDH-wild-type cells. [ABSTRACT FROM AUTHOR]

On the posterior aspect of the anterior abdominal wall, there are four kinds of "fine" ligaments. They are: the round ligament of the liver, median umbilical ligament (UL), a pair of medial ULs, and a pair of lateral ULs. Four of them (the round ligament, median UL, and paired medial ULs) meet at the umbilicus because they originate from the contents of the umbilical cord. The round ligament of the liver originates from the umbilical vein, the medial ULs from the umbilical arteries, and the median UL from the urachus. These structures help radiologists identify right-sided round ligament (RSRL) (a rare, but surgically important normal variant), as well as to differentiate groin hernias. The ligaments can be involved in inflammation; moreover, tumors can arise from them. Unique symptoms such as umbilical discharge and/or location of pathologies relating to their embryology are important in diagnosing their pathologies. In this article, we comprehensively review the anatomy, embryology, and pathology of the "fine" abdominal ligaments and highlight representative cases with emphasis on clinical significance. [ABSTRACT FROM AUTHOR]

Background: Visualizing non-dilated biliary system is important for preoperative mapping of living donor liver transplantation (LDLT) donors. Purpose: To evaluate diagnostic accuracy of three-dimensional (3D) magnetic resonance cholangiography (MRC) within a breath-hold (BH) using compressed sensing (CS) acceleration in visualizing non-dilated biliary system in LDLT donors. Material and Methods: For this prospective study, 43 donors who underwent LDLT were enrolled. Preoperative MRC sequence included BH CS-MRC (17-s BH) and conventional respiratory-triggered (RT) MRC. Two radiologists evaluated biliary configurations of the hepatic hilum, left lobe, and cystic duct. Diagnostic accuracy was assessed using intraoperative cholangiography and surgical records as a reference standard. The association between severity of artifact in RT MRC and better accuracy of BH CS-MRC in visualizing hilar biliary configuration was also evaluated. Results: Diagnostic accuracy of BH CS-MRC was not significantly different from that of RT MRC for biliary configurations of the hepatic hilum (69.8% vs. 76.7%, P = 0.579 and 72.1% vs. 74.4%, P > 0.999), left lobe (48.8% vs. 60.5%, P = 0.332 and 48.8% vs. 67.4%, P = 0.080), and cystic duct (90.7% vs. 93.0%, P > 0.999 and 95.3% vs. 95.3%, P > 0.999), though it showed a slight tendency to be lower. Severe artifacts seen in RT MRC were significantly associated with better accuracy of BH CS-MRC (both P < 0.001). Conclusions: BH CS-MRC can be seen as complementary to RT MRC in visualizing non-dilated biliary anatomy in LDLT donors and be useful especially for individuals whose RT MRC images show severe artifacts. [ABSTRACT FROM AUTHOR]

Objectives: To compare observer performance of detecting bone metastases between bone scintigraphy, including planar scan and single-photon emission computed tomography, and computed tomography (CT) temporal subtraction (TS).Methods: Data on 60 patients with cancer who had undergone CT (previous and current) and bone scintigraphy were collected. Previous CT images were registered to the current ones by large deformation diffeomorphic metric mapping; the registered previous images were subtracted from the current ones to produce TS. Definitive diagnosis of bone metastases was determined by consensus between two radiologists. Twelve readers independently interpreted the following pairs of examinations: NM-pair, previous and current CTs and bone scintigraphy, and TS-pair, previous and current CTs and TS. The readers assigned likelihood levels to suspected bone metastases for diagnosis. Sensitivity, number of false positives per patient (FPP), and reading time for each pair of examinations were analysed for evaluating observer performance by performing the Wilcoxon signed-rank test. Figure-of-merit (FOM) was calculated using jackknife alternative free-response receiver operating characteristic analysis.Results: The sensitivity of TS was significantly higher than that of bone scintigraphy (54.3% vs. 41.3%, p = 0.006). FPP with TS was significantly higher than that with bone scintigraphy (0.189 vs. 0.0722, p = 0.003). FOM of TS tended to be better than that of bone scintigraphy (0.742 vs. 0.691, p = 0.070).Conclusion: Sensitivity of TS in detecting bone metastasis was significantly higher than that of bone scintigraphy, but still limited to 54%. TS might be superior to bone scintigraphy for early detection of bone metastasis.Key Points: • Computed tomography temporal subtraction was helpful in early detection of bone metastases. • Sensitivity for bone metastasis was higher for computed tomography temporal subtraction than for bone scintigraphy. • Figure-of-merit of computed tomography temporal subtraction was better than that of bone scintigraphy. [ABSTRACT FROM AUTHOR]

Objectives: To compare visualization of carotid plaques and vessel walls between 3D T1-fast spin echo imaging with conventional SPACE (T1-SPACE) and with a prototype compressed sensing T1-SPACE (CS-T1-SPACE) METHODS: This retrospective study was approved by the institutional review board. Participants comprised 43 patients (36 males, 7 females; mean age, 71 years) who underwent carotid MRI including T1-SPACE and CS-T1-SPACE. The quality of visualization for carotid plaques and vessel walls was evaluated using a 5-point scale, and signal intensity ratios (SRs) of the carotid plaques were measured and normalized to the adjacent sternomastoid muscle. Scores for the quality of visualization were compared between T1-SPACE and CS-T1-SPACE using the Wilcoxon signed-rank test. Statistical differences between SRs of plaques with T1-SPACE and CS-T1-SPACE were also evaluated using the Wilcoxon signed-rank test, and Spearman's correlation coefficient was calculated to investigate correlations.Results: Visualization scores were significantly higher for CS-T1-SPACE than for T1-SPACE when evaluating carotid plaques (p = 0.0212) and vessel walls (p < 0.001). The SR of plaques did not differ significantly between T1-SPACE and CS-T1-SPACE (p = 0.5971). Spearman's correlation coefficient was significant (0.884; p < 0.0001).Conclusions: CS-T1-SPACE allowed better visualization scores and sharpness compared with T1-SPACE in evaluating carotid plaques and vessel walls, with a 2.5-fold accelerated scan time with comparable image quality. CS-T1-SPACE appears promising as a method for investigating carotid vessel walls, offering better image quality with a shorter acquisition time.Key Points: • CS-T1-SPACE allowed better visualization compared with T1-SPACE in evaluating carotid plaques and vessel walls, with a 2.5-fold accelerated scan time with comparable image quality. • CS-T1-SPACE offers a promising method for investigating carotid vessel walls due to the better image quality with shorter acquisition time. • Physiological movements such as swallowing, arterial pulsations, and breathing induce motion artifacts in vessel wall imaging, and a shorter acquisition time can reduce artifacts from physiological movements. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to investigate the incidence of rim uptake (RU) or multifocal uptake (MU) by invasive breast cancers on a ring-type dedicated breast positron emission tomography (dbPET) scanner compared with whole-body PET (wbPET) scanner imaging and to correlate uptake patterns with pathological features and prognosis.Methods: Between 2009 and 2011, 76 lesions in 74 patients with primary invasive breast cancers were included. Each patient underwent dbPET and wbPET scanning on the same day after administration of 18F-fluorodeoxyglucose (FDG). The images were evaluated to identify specific uptake patterns (RU and MU). Their association with pathological characteristics and prognosis was analyzed.Results: On dbPET, RU and MU patterns were observed in 18 lesions (24%) and 28 lesions (37%), respectively. On wbPET, RU and MU patterns were observed in six lesions (8%) and 17 lesions (22%), respectively. Lesions with RU on dbPET were of higher grade than lesions without RU (P = 0.024) and a higher Ki-67 index (mean; 31% vs. 18%, P = 0.015). They tended to be triple-negative (33% vs. 12%, P = 0.046) and less likely to be luminal A subtype (17% vs. 47%, P = 0.020). On wbPET, however, no significant differences in these markers were seen between RU and non-RU. The MU pattern did not correlate with pathological characteristics in either scanner. Lesions with RU or MU were not significantly associated with disease-free survival.Conclusions: DbPET can identify detailed FDG distribution patterns of breast cancer better than wbPET. Breast cancer with RU on dbPET was associated with higher grade and triple-negative subtype. [ABSTRACT FROM AUTHOR]

Background: There is growing interest in the effect of diffusion time on apparent diffusion coefficient (ADC) values in cancers; however, little evidence exists regarding its utility to differentiate malignant from benign head and neck tumors.Purpose: To investigate the utility of ADC value changes in distinguishing between malignant and benign head and neck tumors using the different diffusion times obtained from oscillating gradient spin-echo (OGSE) and pulsed gradient spin-echo (PGSE) MRI sequences.Study Type: Prospective.Subjects: Thirty-one consecutive patients with suspected head and neck tumors and a phantom.Field Strength/sequence: 3T MRI with diffusion-weighted imaging (DWI) using OGSE (effective diffusion time: 4.3 msec) and PGSE (effective diffusion time: 82.6 msec) sequences and b-values of 0 and 700 s/mm2 .Assessment: ADC values using OGSE (ADCOGSE ) and PGSE (ADCPGSE ) and relative ADC value changes between ADCOGSE and ADCPGSE .Statistical Tests: Wilcoxon test, Mann-Whitney test, and McNemar test.Results: Relative ADC changes for each polyvinylpyrrolidone (PVP) and water in the phantom between OGSE and PGSE sequences were small (relative ADC change within 0.6%). Malignant tumors had significantly smaller ADCOGSE and ADCPGSE values than benign tumors (P < 0.001 and < 0.0001, respectively). Significantly larger relative ADC changes were observed in malignant compared with benign head and neck tumors (P < 0.0001). ADCPGSE values were significantly lower than ADCOGSE values in both malignant and benign head and neck tumors (0.97 vs. 1.28 × 10-3 mm2 /s: P < 0.0001 and 1.93 vs. 1.99 × 10-3 mm2 /s: P = 0.0056, respectively). Relative ADC change and ADCPGSE tended to have higher diagnostic performance than ADCOGSE , with area under the curve (AUC) values of 0.97, 0.96, and 0.89, respectively.Data Conclusion: ADC values obtained using the PGSE sequence were lower than those obtained with OGSE. This difference was larger for malignant than benign tumors, suggesting differences in tissue structure (diffusion hindrance) or cell permeability, revealed by changes in diffusion time. The results underline the potential importance of reporting diffusion time for interpretation of head and neck diffusion MRI.Level Of Evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:88-95. [ABSTRACT FROM AUTHOR]

Purpose: Positron emission tomography (PET)/computed tomography (CT) with 68Ga-labelled 1,4,7,10-tetraazacyclododecane-N,N′,N″,N″'-tetraacetic acid-d-Phe1-Tyr3-octreotide (DOTATOC) has been accepted as a diagnostic imaging tool especially for patients with neuroendocrine tumours. However, its clinical usefulness for restaging of renal cell carcinoma (RCC) has not been fully investigated. This retrospective study was performed to elucidate the clinical value of PET/CT using 68Ga-DOTATOC in patients with known or suspected recurrent RCC. Methods: We analysed 25 consecutive patients who underwent DOTATOC-PET/CT scans after surgery for RCC (23 clear cell, 1 papillary, 1 unclassified). PET/CT findings were reviewed and the detection rate was calculated on a patient and lesion basis. The detectability was compared in patients who also underwent PET/CT scans with 18F-fluorodeoxyglucose (FDG). Histopathological findings or clinical follow-up were used as the reference standard. Results: Based on the final diagnosis, 76 recurrent or metastatic lesions were confirmed in this population. Of these lesions, 66 lesions in 22 patients were positive by DOTATOC-PET/CT. The patient-based and lesion-based sensitivity was 88% (22/25) and 87% (66/76), respectively. Twelve patients underwent both DOTATOC-PET/CT and FDG-PET/CT. The lesion-based sensitivity of DOTATOC was 74% (20/27), while that of FDG was 59% (16/27). Eight lesions were identified only by DOTATOC, but four lesions from papillary RCC were detected only by FDG. Conclusion: Our data indicate that DOTATOC-PET/CT would be useful for detecting recurrent foci in patients with clear cell RCC. DOTATOC-PET/CT and FDG-PET/CT are considered to have complementary roles. [ABSTRACT FROM AUTHOR]

Background: While periventricular anastomosis, a unique abnormal vasculature in moyamoya disease, has been studied in relation to intracranial hemorrhage, no study has addressed its change after bypass surgery. The authors sought to test whether direct bypass surgery could restore normal periventricular vasculature. Methods: Patients who had undergone direct bypass surgery for moyamoya disease at a single institution were eligible for the study. Baseline, postoperative, and follow-up magnetic resonance angiography (MRA) scans were scheduled before surgery, after the first surgery, and 3 to 6 months after contralateral second surgery, respectively. Sliding-thin-slab maximum-intensity-projection coronal MRA images of periventricular anastomoses were scored according to the three subtypes (lenticulostriate, thalamic, and choroidal anastomosis). Baseline and postoperative MRA images were compared to obtain a matched comparison of score changes in the surgical and nonsurgical hemispheres within individuals (intra-individual comparison). Results: Of 110 patients, 42 were identified for intra-individual comparisons. The periventricular anastomosis score decreased significantly in the surgical hemispheres (median, 2 versus 1; p < 0.001), whereas the score remained unchanged in the nonsurgical hemispheres (median, 2 versus 2; p = 0.57); the score change varied significantly between the surgical and nonsurgical hemispheres (p < 0.001). Of the 104 periventricular-anastomosis-positive hemispheres undergoing surgery, 47 (45.2%) were assessed as negative in the follow-up MRA. Among the subtypes, choroidal anastomosis was most likely to be assessed as negative (79.7% of positive hemispheres). Conclusions: Periventricular vasculature can be restored after direct bypass. The likelihood of correction of choroidal anastomosis is a subject requiring further studies. [ABSTRACT FROM AUTHOR]

Tuberous sclerosis complex (TSC), a rare autosomal dominant neurocutaneous disorder, is characterized by the presence of benign congenital tumors in multiple organs. Neoplasms with perivascular epithelioid cell differentiation (PEComas), including angiomyolipoma (AML) and lymphangioleiomyomatosis (LAM), can occur in association with TSC. This report describes two cases of uterine PEComas presenting characteristic MR imaging features reflecting pathological findings. From MR images, both cases showed single or multiple large, irregularly shaped or lobulated hemorrhagic lesions within the myometrium. They differed from typical adenomyotic cysts in their large size and irregular margins. Histopathologic analysis revealed that the hemorrhage was caused by adenomyosis and tumor cells that proliferated in surrounding stroma of the hemorrhagic lesions, compatible with PEComas. Microscopic observation revealed an infiltrative growth pattern of PEComas, with small nodules formed. The tumor lesions, however, were difficult to detect on MR images. The myometrium showed normal appearance on both T1-weighted and T2-weighted images in both cases. We speculate that PEComas may infiltrate extensively into the myometrium even when the myometrium shows almost normal radiologic appearance. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to evaluate the clinical and radiological findings of hemorrhagic hepatic cysts with enhancing mural nodules. Methods: The radiology databases of five facilities were retrospectively searched for reports indicating hemorrhagic hepatic cysts or hepatic cystic tumors. Cases of hemorrhagic hepatic cysts with enhancing mural nodules based on pathological or radiological findings were identified and reviewed. Results: We included 14 cases (11 female and 3 male) with a mean patient age of 72.6 years. Up until the enhancing mural nodules were detected, the cysts had decreased in size in all ten cases for which radiological imaging was available for a period of > 3 years previous to detection. Dynamic contrast-enhanced CT or MRI showed focal enhancement in the early phase and progressive centrifugal enhancement in the delayed phase in all 16 mural nodules ≥ 10 mm in diameter. Thirteen of 14 MRI assessable enhancing mural nodules ≥ 10 mm in diameter showed a hypointense rim with central hyperintensity on T2-weighted imaging. All cases showed calcification of the cyst wall. In the three referred cases, 18F-fluorodeoxyglucose (FDG) positron emission tomography/CT demonstrated no intense FDG uptake in the enhancing mural nodules. In the four resected cases, histopathology of the enhancing mural nodules revealed neovascularization within an organized hematoma, including extensive dilated vessels and hemangioma-like lesions. Conclusions: Features including a decrease in cyst size, a progressive centrifugal enhancing pattern on dynamic contrast-enhanced CT or MRI, a hypointense rim with central hyperintensity on T2-weighted MRI, and cyst wall calcification may indicate a hemorrhagic hepatic cyst. [ABSTRACT FROM AUTHOR]

Bladder cancer usually forms a papillary structure. Progression along the cavity or membranous structures surrounding the bladder, rectum, or retroperitoneum without formation of a discrete mass is rare. We here present two patients with duodenal obstruction caused by retroperitoneal progression of bladder cancer, in both of whom computed tomography revealed bladder and rectal wall thickening with a malignant target sign, thickened mesorectal fascia with abnormal tissue stranding, and increased perirectal fat density. Both cancers progressed despite treatment, as indicated by faint abnormal tissue stranding and increased retroperitoneal fat density along the retromesenteric plane from the pelvis to the duodenum. Subsequently, both patients developed obstruction in the horizontal portion of the duodenum, still without formation of a mass lesion. These two patients highlight the challenges associated with retroperitoneal invasion by bladder cancer in the absence of a mass lesion and underscore the importance of considering cancer progression in patients with bowel obstruction, even when there is no obvious mass lesion and/or only minor retroperitoneal findings. Progression along the retromesenteric plane may be the key pathway via which progressive bladder cancer results in duodenal obstruction without or with a minor mass lesion. [ABSTRACT FROM AUTHOR]

Gallium‐68 (68Ga, t1/2 = 68 min) can be easily obtained from a 68Ge/68Ga generator, and several such systems are commercially available. The use of positron emission tomography (PET) imaging using 68Ga‐labeled radiopharmaceuticals is expected to increase in both preclinical and clinical settings. However, the chelation between a 68Ga cation and the bifunctional macrocyclic chelates that are used for labeling bioactive substances, such as 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA), requires a relatively long reaction time and high temperature to achieve a high radiochemical yield. Previously, we reported on a novel resonant‐type microwave reactor that can be used for radiosynthesis and the usefulness of this reactor in the PET radiosynthesis of 18F. In the present study, the usefulness of this resonant‐type microwave reactor was evaluated for the radiolabeling of model macrocyclic chelates with 68Ga. As a result, microwave heating of resonant‐type microwave reactor notably improved the rate of the 68Ga labeling chelate reaction in a short time period of 2 minutes, compared with the use of a conventional heating method. Additionally, it was found that the use of this reactor made it possible to decrease the amount of precursors required in the reaction and to improve the molar activity of the labeled compounds. In the synthetic study of [68Ga]p‐Bn–NCS–DOTA and [68Ga]DOTA–TOC, we found that microwave heating using the resonant‐type microwave reactor notably improved the rate of the 68Ga labeling chelate reaction for 2 minutes, compared with the use of a conventional heating method. Additionally, it was found that the use of this reactor made it possible to decrease the amount of precursors required in the reaction and to improve the specific activity of the labeled compounds. [ABSTRACT FROM AUTHOR]

Objective: To assess whether temporal subtraction (TS) images of brain CT improve the detection of suspected brain infarctions.Methods: Study protocols were approved by our institutional review board, and informed consent was waived because of the retrospective nature of this study. Forty-two sets of brain CT images of 41 patients, each consisting of a pair of brain CT images scanned at two time points (previous and current) between January 2011 and November 2016, were collected for an observer performance study. The 42 sets consisted of 23 cases with a total of 77 newly developed brain infarcts or hyperdense artery signs confirmed by two radiologists who referred to additional clinical information and 19 negative control cases. To create TS images, the previous images were registered to the current images by partly using a non-rigid registration algorithm and then subtracted. Fourteen radiologists independently interpreted the images to identify the lesions with and without TS images with an interval of over 4 weeks. A figure of merit (FOM) was calculated along with the jackknife alternative free-response receiver-operating characteristic analysis. Sensitivity, number of false positives per case (FPC) and reading time were analyzed by the Wilcoxon signed-rank test.Results: The mean FOM increased from 0.528 to 0.737 with TS images (p < 0.0001). The mean sensitivity and FPC improved from 26.5% and 0.243 to 56.0% and 0.153 (p < 0.0001 and p = 0.239), respectively. The mean reading time was 173 s without TS and 170 s with TS (p = 0.925).Conclusion: The detectability of suspected brain infarctions was significantly improved with TS CT images.Key Points: • Although it is established that MRI is superior to CT in the detection of strokes, the first choice of modality for suspected stroke patients is often CT. • An observer performance study with 14 radiologists was performed to evaluate whether temporal subtraction images derived from a non-rigid transformation algorithm can significantly improve the detectability of newly developed brain infarcts on CT. • Temporal subtraction images were shown to significantly improve the detectability of newly developed brain infarcts on CT. [ABSTRACT FROM AUTHOR]

This first‐in‐man study was carried out to evaluate the safety, whole‐body distribution, dose estimation, and lesion accumulation of 18F‐FSU‐880, a newly developed probe targeting prostate‐specific membrane antigen. Six prostate cancer patients with known metastatic lesions underwent serial whole‐body PET/computed tomography (CT) with 18F‐FSU‐880. Blood and urine were analyzed before and after PET/CT. Accumulation of 18F‐FSU‐880 in organs and metastatic lesions in serial PET images were evaluated by measuring the standardized uptake values. From the biodistribution data, the organ doses and whole‐body effective dose were calculated using OLINDA/EXM software was developed by Dr. Michael Stabin of Vanderbilt University, Nashville, Tennessee, USA. 18F‐FSU‐880 PET/CT could be carried out without significant adverse effects. High physiological uptake was observed in the salivary/lachrymal glands and kidneys. The effective dose was calculated to be 0.921 × 10−2mSv/MBq. Known metastatic lesions were clearly visualized with high image contrast that increased with time, except in 1 patient, whose bone metastases were well‐controlled and inactive. The PET/CT with 18F‐FSU‐880 could be carried out safely and could clearly visualize active metastatic lesions. The present results warrant further clinical studies with a larger number of cases to verify the clinical utility of 18F‐FSU‐880 PET/CT in the management of prostate cancer patients. The first‐in‐man study of PET/computed tomography (CT) with 18F‐FSU‐880 targeting prostate‐specific membrane antigen was carried out in 6 prostate cancer patients. PET/CT with 18F‐FSU‐880 could be carried out safely and could clearly visualize active metastatic lesions, suggesting that PET/CT with 18F‐FSU‐880 can afford important information on the management of patients with prostate cancer. [ABSTRACT FROM AUTHOR]

Purpose: To examine the feasibility and potential difficulties of automatically generating radiologic reports (RRs) to articulate the clinically important features of brain magnetic resonance (MR) images. Materials and Methods: We focused on examining brain atrophy by using magnetization-prepared rapid gradient-echo (MPRAGE) images. The technology was based on multi-atlas whole-brain segmentation that identified 283 structures, from which larger superstructures were created to represent the anatomic units most frequently used in RRs. Through two layers of data-reduction filters, based on anatomic and clinical knowledge, raw images (~10 MB) were converted to a few kilobytes of human-readable sentences. The tool was applied to images from 92 patients with memory problems, and the results were compared to RRs independently produced by three experienced radiologists. The mechanisms of disagreement were investigated to understand where machine–human interface succeeded or failed. Results: The automatically generated sentences had low sensitivity (mean: 24.5%) and precision (mean: 24.9%) values; these were significantly lower than the inter-rater sensitivity (mean: 32.7%) and precision (mean: 32.2%) of the radiologists. The causes of disagreement were divided into six error categories: mismatch of anatomic definitions (7.2 ± 9.3%), data-reduction errors (11.4 ± 3.9%), translator errors (3.1 ± 3.1%), difference in the spatial extent of used anatomic terms (8.3 ± 6.7%), segmentation quality (9.8 ± 2.0%), and threshold for sentence-triggering (60.2 ± 16.3%). Conclusion: These error mechanisms raise interesting questions about the potential of automated report generation and the quality of image reading by humans. The most significant discrepancy between the human and automatically generated RRs was caused by the sentence-triggering threshold (the degree of abnormality), which was fixed to z-score >2.0 for the automated generation, while the thresholds by radiologists varied among different anatomical structures. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess whether homology-based emphysema quantification (HEQ) is significantly associated with lung cancer risk. This retrospective study was approved by our institutional review board. We included 576 patients with lung nodules (317 men and 259 women; age, 66.8 ± 12.3 years), who were selected from a database previously generated for computer-aided diagnosis. Of these, 283 were diagnosed with lung cancer, whereas the remaining 293 showed benign lung nodules. HEQ was performed and percentage of low-attenuation lung area (LAA%) was calculated on the basis of computed tomography scans. Statistical models were constructed to estimate lung cancer risk using logistic regression; sex, age, smoking history (Brinkman index), LAA%, and HEQ were considered independent variables. The following three models were evaluated: the base model (sex, age, and smoking history); the LAA% model (the base model + LAA%); and the HEQ model (the base model + HEQ). Model performance was assessed using receiver operating characteristic analysis and the associated area under the curve (AUC). Differences in AUCs among the models were evaluated using Delong’s test. AUCs of the base, LAA%, and HEQ models were 0.585, 0.593, and 0.622, respectively. HEQ coefficient was statistically significant in the HEQ model (P = 0.00487), but LAA% coefficient was not significant in the LAA% model (P = 0.199). Delong’s test revealed significant difference in AUCs between the LAA% and HEQ models (P = 0.0455). In conclusion, after adjusting for age, sex, and smoking history (Brinkman index), HEQ was significantly associated with lung cancer risk. [ABSTRACT FROM AUTHOR]

Left atrial contrast computed tomography (LA-CT) as well as transesophageal echocardiography (TEE) can exclude left atrial appendage (LAA) thrombus, but is sometimes unable to evaluate LAA due to incomplete LAA filling. The aim of the current study was to validate the utility of real-time approach of LA-CT with real-time surveillance of LAA-filling defect (FD). We enrolled consecutive 894 patients with LA-CT studies acquired for catheter ablation and compared the diagnostic accuracy in demonstrating LAA-FD between conventional protocol (N = 474) and novel protocol with real-time surveillance of LAA-FD immediately after the initial scanning and, when necessary, adding delayed scanning in the supine or prone position (N = 420). Primary endpoint was severity of LAA-FD classified into the 3 groups: "Grade-0" for complete filling of contrast, "Grade-1" for incomplete filling of contrast, and "Grade-2" for complete FD of contrast. The prevalence of Grade-1 and Grade-2 FD was 17.3% and 11.2% in conventional protocol, whereas there was no patient with Grade-2 FD, and only 1 patient with Grade-1 FD after the additional scanning in novel protocol. In 5 patients with suspected LAA thrombus both by TEE and Grade-2 FD in LA-CT by the conventional protocol, ablation procedure was canceled due to diagnosis of LAA thrombus. Conversely, 4 patients with suspected LAA thrombus by TEE in novel protocol group was proved to have intact LAA by LA-CT with and without additional scanning. This novel approach with real-time surveillance improved the diagnostic accuracy of LA-CT in detecting LAA-FD, suggesting potential superiority of LA-CT over TEE in excluding LAA thrombus. [ABSTRACT FROM AUTHOR]

Objective: Positron emission tomography (PET)/computed tomography (CT) using 68Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid-D-Phe1-Tyr3-octreotide (DOTATOC) is usually performed about 1-h post-injection; however, because of rapid blood clearance, the waiting time for scanning could possibly be shortened without affecting diagnostic performance. The purpose of this study was to investigate the feasibility of early scanning at 30 min post-injection.Methods: Thirty-eight patients who underwent DOTATOC-PET/CT were analyzed. After administration of 68Ga-DOTATOC, data acquisition was performed twice, at 30-min and 60-min post-injection. The number of known or suspected pathological lesions, and quantitative values of those lesions and physiological uptake were compared. SUVmax, SUVpeak, metabolic tumor volume (MTV), and total lesion uptake (TLU) were calculated as quantitative values of the pathological lesions.Results: A total of 125 known or suspected pathological lesions were found at both timepoints, with no differences between the two datasets. The SUVmax, SUVpeak, MTV, and TLU were highly reproducible, with Spearman's ρ of 0.983, 0.986, 0.918, and 0.981, respectively. The average percent differences (%DIFFave) defined as the differences of the values divided by the value at 1-h post-injection were 11.1% for SUVmax, 8.5% for SUVpeak, 15.1% for MTV, and 20.6% for TLU. Physiological uptake in the two datasets was closely comparable in the pituitary gland (Spearman's ρ = 0.954, %DIFFave = 11.0%), liver (0.989, 3.9%), spleen (0.970, 6.3%), adrenal glands (0.879, 13.0%), and pancreatic uncus (0.946, 12.7%).Conclusion: The diagnostic performance of visual interpretation should be comparable between DOTATOC-PET/CT images obtained at 30-min and 60-min post-injection. Some differences between quantitative values may exist; however, they appear to be minimal. [ABSTRACT FROM AUTHOR]

We aimed to describe the development of an inference model for computer-aided diagnosis of lung nodules that could provide valid reasoning for any inferences, thereby improving the interpretability and performance of the system. An automatic construction method was used that considered explanation adequacy and inference accuracy. In addition, we evaluated the usefulness of prior experts’ (radiologists’) knowledge while constructing the models. In total, 179 patients with lung nodules were included and divided into 79 and 100 cases for training and test data, respectively. F-measure and accuracy were used to assess explanation adequacy and inference accuracy, respectively. For F-measure, reasons were defined as proper subsets of Evidence that had a strong influence on the inference result. The inference models were automatically constructed using the Bayesian network and Markov chain Monte Carlo methods, selecting only those models that met the predefined criteria. During model constructions, we examined the effect of including radiologist’s knowledge in the initial Bayesian network models. Performance of the best models in terms of F-measure, accuracy, and evaluation metric were as follows: 0.411, 72.0%, and 0.566, respectively, with prior knowledge, and 0.274, 65.0%, and 0.462, respectively, without prior knowledge. The best models with prior knowledge were then subjectively and independently evaluated by two radiologists using a 5-point scale, with 5, 3, and 1 representing beneficial, appropriate, and detrimental, respectively. The average scores by the two radiologists were 3.97 and 3.76 for the test data, indicating that the proposed computer-aided diagnosis system was acceptable to them. In conclusion, the proposed method incorporating radiologists’ knowledge could help in eliminating radiologists’ distrust of computer-aided diagnosis and improving its performance. [ABSTRACT FROM AUTHOR]

Background Interim PET/CT is widely performed in lymphoma patients in clinical practice and clinical trials. Visual assessment using a 5-point scale is proposed for PET/CT interpretation, but intra- and inter-observer variation is not fully investigated. Purpose To investigate intra- and inter-observer variations in the reporting of interim positron emission tomography/computed tomography (PET/CT) in lymphoma patients, and the influence of clinical information on the interpretation. Material and Methods Three expert readers from different institutions interpreted interim PET/CT images of 42 consecutive patients with malignant lymphoma twice, with and without clinical information. The intra- and inter-observer agreements were calculated using the kappa statistic on a patient and a region basis. Results On a patient basis, intra-observer agreement, inter-observer agreement without information, and inter-observer agreement with information were within the ranges 0.48-0.62, 0.51-0.62, and 0.42-0.76, respectively. In the evaluation of lymph nodes, intra-observer agreement, inter-observer agreement without information, and inter-observer agreement with information were within the ranges 0.78-0.92, 0.80-0.82, and 0.77-0.83, respectively. Observer agreements were in almost perfect to substantial agreement categories for most lymphatic organs, but were generally low for the other organs. Conclusion The intra- and inter-observer agreements in evaluating interim PET/CT were relatively low for extranodal lesions, but they were substantial to almost perfect when interpreting nodal regions in malignant lymphoma, irrespective of the provision of clinical information, although memory at the first interpretation might have affected the intra-observer results. [ABSTRACT FROM AUTHOR]

Background: The heterogeneous distribution of emphysema is a key feature of chronic obstructive pulmonary disease (COPD) patients that typically is evaluated using high-resolution chest computed tomography (HRCT). Oxygen-enhanced pulmonary magnetic resonance imaging (OEMRI) is a new method to obtain information regarding regional ventilation, diffusion, and perfusion in the lung without radiation exposure. We aimed to compare OEMRI with HRCT for the assessment of heterogeneity in COPD patients. Methods: Forty patients with stable COPD underwent quantitative HRCT, OEMRI, and pulmonary function tests, including arterial blood gas analysis. OEMRI was also performed on nine healthy control subjects. We measured the severity of emphysema (percent low attenuation volume; LAV%) in whole lungs and the standard deviations (SDs) of the LAV% values of 10 isovolumetric partitions (SD-LAV) as an index of cranial-caudal heterogeneity. Similarly, relative enhancement ratios of oxygen (RERs) in whole lungs from OEMRI and SD-RER were analyzed. Results: COPD patients showed a lower mean RER than control subjects (12.6% vs 22.0%, p<0.01). The regional heterogeneity of the RERs was not always consistent with the LAV distribution. Both the HRCT (LAV% and SD-LAV) and the OEMRI (RER and SD-RER) indices were significantly associated with the diffusion capacity (DLCO) and partial pressure of oxygen in arterial blood (PaO2). The PaO2 was associated only with the heterogeneity index of HRCT (SD-LAV) (R2 = 0.39); however, the PaO2 was associated with both the mean RER and heterogeneity (SD-RER) in the multivariate analysis (R2 = 0.38). Conclusions: OEMRI-derived parameters were directly associated with oxygen uptake in COPD patients. Although the OEMRI-derived parameters were not identical to the HRCT-derived parameters, the cranial-caudal heterogeneity in HRCT or OEMRI was complementary to that in evaluations of oxygen uptake in the lungs. Functional imaging seems to provide new insights into COPD pathophysiology without radiation exposure. [ABSTRACT FROM AUTHOR]

Objectives: To compare breast density measured on digital breast tomosynthesis (DBT) (BI-RADS-based breast composition and fully-automatic estimation) and magnetic resonance imaging (MRI) (BI-RADS amount of fibroglandular tissue), and to evaluate the diagnostic performance in terms of sensitivity and specificity of DBT and MRI in a predominantly dense breast population.Methods: Between 2015 and 2016, 152 women with 103 breast malignancies, who underwent 3-T breast MRI and DBT within 2 months' time, were enrolled in this study. Breast composition/fibroglandular tissue and findings on DBT (two readers) and MRI were reported using BI-RADS 5th edition. Digital mammography images were analysed for breast percent density (PD) using the Libra software tool.Results: A majority of women had dense breasts as categorised by breast composition c (heterogeneously dense) (68%) and d (extremely dense) (15%). The mean PD was 44% (range, 18-89%) and the correlation between breast composition and PD was r = 0.6. The diagnostic performance of MRI was significantly higher compared to DBT for one reader as described by the area under the receiver operating characteristic (ROC) curve (p = 0.004) and of borderline significance for the other reader (p = 0.052).Conclusions: MRI had higher diagnostic performance than DBT in a dense breast population in the tertiary setting.Key Points: • MRI had higher diagnostic performance than DBT in a dense breast population • Diagnostic performance of DBT was comparable to MRI in women with fatty breasts • MRI was superior to DBT in preoperative breast cancer size assessment. [ABSTRACT FROM AUTHOR]

Abstract: Convolutional neural network (CNN), a class of artificial neural networks that has become dominant in various computer vision tasks, is attracting interest across a variety of domains, including radiology. CNN is designed to automatically and adaptively learn spatial hierarchies of features through backpropagation by using multiple building blocks, such as convolution layers, pooling layers, and fully connected layers. This review article offers a perspective on the basic concepts of CNN and its application to various radiological tasks, and discusses its challenges and future directions in the field of radiology. Two challenges in applying CNN to radiological tasks, small dataset and overfitting, will also be covered in this article, as well as techniques to minimize them. Being familiar with the concepts and advantages, as well as limitations, of CNN is essential to leverage its potential in diagnostic radiology, with the goal of augmenting the performance of radiologists and improving patient care.Key Points: • Convolutional neural network is a class of deep learning methods which has become dominant in various computer vision tasks and is attracting interest across a variety of domains, including radiology.• Convolutional neural network is composed of multiple building blocks, such as convolution layers, pooling layers, and fully connected layers, and is designed to automatically and adaptively learn spatial hierarchies of features through a backpropagation algorithm.• Familiarity with the concepts and advantages, as well as limitations, of convolutional neural network is essential to leverage its potential to improve radiologist performance and, eventually, patient care. [ABSTRACT FROM AUTHOR]

We developed a computer-aided diagnosis (CADx) method for classification between benign nodule, primary lung cancer, and metastatic lung cancer and evaluated the following: (i) the usefulness of the deep convolutional neural network (DCNN) for CADx of the ternary classification, compared with a conventional method (hand-crafted imaging feature plus machine learning), (ii) the effectiveness of transfer learning, and (iii) the effect of image size as the DCNN input. Among 1240 patients of previously-built database, computed tomography images and clinical information of 1236 patients were included. For the conventional method, CADx was performed by using rotation-invariant uniform-pattern local binary pattern on three orthogonal planes with a support vector machine. For the DCNN method, CADx was evaluated using the VGG-16 convolutional neural network with and without transfer learning, and hyperparameter optimization of the DCNN method was performed by random search. The best averaged validation accuracies of CADx were 55.9%, 68.0%, and 62.4% for the conventional method, the DCNN method with transfer learning, and the DCNN method without transfer learning, respectively. For image size of 56, 112, and 224, the best averaged validation accuracy for the DCNN with transfer learning were 60.7%, 64.7%, and 68.0%, respectively. DCNN was better than the conventional method for CADx, and the accuracy of DCNN improved when using transfer learning. Also, we found that larger image sizes as inputs to DCNN improved the accuracy of lung nodule classification. [ABSTRACT FROM AUTHOR]