Purpose This phantom-based study aimed to identify acceptable velocity encoding (VENC) settings for flow measurements in straight-tube and aortic aneurysm phantoms using 4-D flow magnetic resonance (MR) imaging. Methods A pulse flow pump was connected to 2 types of plastic phantoms (straight-tube and aortic aneurysm) to create steady and pulsatile flow, respectively. The validity of flow measurements with 4-D flow MR imaging using 2 VENC settings (16 and 32 cm/s) was examined, using flow meter measurements as the gold standard. The optimal VENC setting was 16 cm/s. Equivalence tests were conducted to identify acceptable VENC settings using an equivalence margin of 25%. A P value of less than .05 was considered significant. Results Using either steady or pulsatile flow in the straight phantom, it was found that the 4-D flow MR imaging measurement results with a VENC of 32 cm/s (P < .008) and 16 cm/s (P < .049) were acceptable (ie, within the range of equivalence). 4-D flow MR imaging measurements with VENC of 32 cm/s showed equivalence with flow meters under all conditions except for the aneurysm form and pulsatile flow conditions (P < .008). None of the VENC settings were acceptable using pulsatile flow in the aneurysm phantom because of overestimation (VENC of 16 cm/s) or underestimation (VENC of 32 cm/s). Discussion In the case of straight-tube morphology, acceptable measurement results can be obtained even with VENC settings twice the actual flow velocity. However, in the context of aortic aneurysm morphology, the authors speculated that achieving precise measurements with a VENC setting tailored to a straight tube would be challenging. Conclusion Twice the optimal VENC is acceptable in straight vessels. However, an appropriate VENC setting would be difficult for measuring pulsatile flow in an aneurysm.

2021年に肝癌診療ガイドラインの改訂が行われた．肝細胞癌の診断にEOB-MRIが多く用いられるようになったため，サーベイランスアルゴリズムにおいて超音波で結節が検出された後にまずEOB-MRIを撮像するアルゴリズムが追加された．治療アルゴリズムにおいては，3 cm以内の単発肝細胞癌に対する治療推奨が切除と焼灼療法が同等に推奨されることになり，また，脈管侵襲陽性肝細胞癌に対しては，まず切除が推奨され，切除不能例に対して薬物療法，次いで肝動注化学療法ならびにTACEが推奨されることとなった．前回の改訂後に，肝細胞癌に対する薬物療法の選択肢が大幅に増えたため，従来の治療アルゴリズムを補完する形で，新たに薬物療法アルゴリズムが作成された．また，前版では弱く推奨されないとされていた薬物療法とTACEの併用療法が，今回の改訂で行うことを考慮しても良いとの弱い推奨に変更がなされた．

HomeRadiologyVol. 307, No. 3 PreviousNext Reviews and CommentaryEditorialHepatocellular Carcinoma: It Is Time to Focus on PrognosisKathryn J. Fowler , Victoria Chernyak, Maxime Ronot, Valerie Vilgrain, Azusa Kitao, Jeong Min Lee, Utaroh Motosugi, Bin Song, Hanyu Jiang, Claude B. Sirlin, Mustafa R. BashirKathryn J. Fowler , Victoria Chernyak, Maxime Ronot, Valerie Vilgrain, Azusa Kitao, Jeong Min Lee, Utaroh Motosugi, Bin Song, Hanyu Jiang, Claude B. Sirlin, Mustafa R. BashirAuthor AffiliationsFrom the Department of Radiology, University of California San Diego, 6206 Lakewood St, San Diego, CA 92122 (K.J.F., C.B.S.); Department of Radiology, Beth Israel Deaconess Medical Center, Boston, Mass (V.C.); Department of Radiology, Université Paris Cité, Paris, France (M.R., V.V.); Department of Radiology, Hôpital Beaujon, APHP.Nord, Clichy, France (M.R., V.V.); Department of Radiology, Kanazawa University Graduate School of Medicine, Kanazawa, Japan (A.K.); Department of Radiology, Seoul National University College of Medicine, Seoul, Korea (J.M.L.); Department of Radiology, Kofu Kyoritsu Hospital, Kofu, Japan (U.M.); Department of Radiology, West China Hospital, Chengdu, China (B.S., H.J.); and Department of Radiology, Duke University Medical Center, Durham, NC (M.R.B.).Address correspondence to K.J.F. (email: [email protected]).Kathryn J. Fowler Victoria ChernyakMaxime RonotValerie VilgrainAzusa KitaoJeong Min LeeUtaroh MotosugiBin SongHanyu JiangClaude B. SirlinMustafa R. BashirPublished Online:Apr 4 2023https://doi.org/10.1148/radiol.220884MoreSectionsFull textPDF ToolsAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookXLinked In References1. European Association For The Study Of The Liver; European Organization For Research And Treatment Of Cancer. EASL-EORTC clinical practice guidelines: management of hepatocellular carcinoma. J Hepatol 2012;56(4):908–943. [Published correction appears in J Hepatol 2012;56(6):1430.] Crossref, Medline, Google Scholar2. Yoon JH, Park JW, Lee JM. Noninvasive Diagnosis of Hepatocellular Carcinoma: Elaboration on Korean Liver Cancer Study Group-National Cancer Center Korea Practice Guidelines Compared with Other Guidelines and Remaining Issues. Korean J Radiol 2016;17(1):7–24. [Published correction appears in Korean J Radiol 2016;17(2):306.] Crossref, Medline, Google Scholar3. Heimbach JK, Kulik LM, Finn RS, et al. AASLD guidelines for the treatment of hepatocellular carcinoma. Hepatology 2018;67(1):358–380. Crossref, Medline, Google Scholar4. Bolondi L, Burroughs A, Dufour JF, et al. Heterogeneity of patients with intermediate (BCLC B) Hepatocellular Carcinoma: proposal for a subclassification to facilitate treatment decisions. Semin Liver Dis 2012;32(4):348–359. Medline, Google Scholar5. Lauwers GY, Terris B, Balis UJ, et al. Prognostic histologic indicators of curatively resected hepatocellular carcinomas: a multi-institutional analysis of 425 patients with definition of a histologic prognostic index. Am J Surg Pathol 2002;26(1):25–34. Crossref, Medline, Google Scholar6. Torbenson MS. Morphologic Subtypes of Hepatocellular Carcinoma. Gastroenterol Clin North Am 2017;46(2):365–391. Crossref, Medline, Google Scholar7. Vij M, Calderaro J. Pathologic and molecular features of hepatocellular carcinoma: An update. World J Hepatol 2021;13(4):393–410. Crossref, Medline, Google Scholar8. Fowler KJ, Burgoyne A, Fraum TJ, et al. Pathologic, molecular, and prognostic radiologic features of hepatocellular carcinoma. RadioGraphics 2021;41(6):1611–1631. Link, Google Scholar9. Ronot M, Chernyak V, Burgoyne Aet al. Imaging to Predict Prognosis in Hepatocellular Carcinoma: Current and Future Perspectives. Radiology 2023. https://doi.org/10.1148/radiol.221429. Published online April 4, 2023. Link, Google Scholar10. Chernyak V, Tang A, Do RKG, et al. Liver imaging: it is time to adopt standardized terminology. Eur Radiol 2022. https://doi.org/10.1007/s00330-022-08769-5. Published online April 7, 2022. Crossref, Google ScholarArticle HistoryReceived: Apr 25 2022Revision requested: May 13 2022Revision received: July 5 2022Accepted: July 12 2022Published online: Apr 04 2023 FiguresReferencesRelatedDetailsCited ByReliability of LI-RADS for MRI and CT: Is Excellence Achievable?Sarah A. Johnson, 27 June 2023 | Radiology, Vol. 307, No. 5Recommended Articles Proliferative versus Nonproliferative Hepatocellular Carcinoma: Clinical and Imaging ImplicationsRadiology2021Volume: 300Issue: 3pp. 583-585Imaging to Predict Prognosis in Hepatocellular Carcinoma: Current and Future PerspectivesRadiology2023Volume: 307Issue: 3Using MRI to Assess Microvascular Invasion in Hepatocellular CarcinomaRadiology2020Volume: 297Issue: 3pp. 582-583Development of a Model including MRI Features for Predicting Advanced-stage Recurrence of Hepatocellular Carcinoma after Liver ResectionRadiology2023Volume: 309Issue: 2Dynamic CT and Gadoxetic Acid-enhanced MRI Characteristics of P53-mutated Hepatocellular CarcinomaRadiology2022Volume: 306Issue: 2See More RSNA Education Exhibits Imaging and Radiomics in Hepatocellular Carcinoma (HCC): Current Update and Future PerspectivesDigital Posters2021Imaging Diagnosis of Hepatocellular Carcinoma in the Era of Molecular Targeted Therapy and ImmunotherapyDigital Posters2022Choices, Choices, Choices: What Your Multidisciplinary HCC Treatment Team Wants to Know?Digital Posters2022 RSNA Case Collection LI-RADS 5RSNA Case Collection2022Gallbladder CarcinomaRSNA Case Collection2021HepatoblastomaRSNA Case Collection2021 Vol. 307, No. 3 Metrics Altmetric Score PDF download

Stereotactic body radiotherapy (SBRT) is a local treatment option for hepatocellular carcinoma (HCC). SBRT-induced focal reactions on the liver parenchyma have not been thoroughly evaluated using quantitative magnetic resonance imaging (MRI). To quantitatively evaluate liver parenchymal changes caused by SBRT for HCC using magnetic resonance elastography (MRE) and diffusion-weighted imaging (DWI). We retrospectively evaluated 22 adult patients who received SBRT for HCC and 27 who received locoregional therapy other than SBRT (controls). Liver stiffness by MRE and apparent diffusion coefficient (ADC) values by DWI of the liver parenchyma were measured before and after SBRT. Regions of interest (ROIs) were drawn on the two areas of radiation dose distribution levels, > 30 Gy and ≤ 30 Gy; a ROI was drawn in the control group. The two indices were compared before and after SBRT using a Wilcoxon matched-pairs signed-rank test. Liver stiffness and ADC values were significantly increased after SBRT in the dose areas of > 30 Gy compared with those before SBRT (4.05 vs 4.85 kPa; p < 0.05 in liver stiffness, and 1.10 vs 1.40 ×10−3 s/mm2; p < 0.05 in ADC values). In the dose area of ≦ 30 Gy, liver stiffness showed a significant increase in one reader (p = 0.033) but not in another reader (p = 0.085); ADC value showed no significant difference before and after SBRT as per both readers (p > 0.05). The control group demonstrated no significant differences before and after treatment (p > 0.05). MRE and DWI can be used to detect SBRT-induced liver parenchymal changes.

AIM:To determine risk factors associated with hepatocellular carcinoma (HCC) development following direct-acting antiviral (DAA) therapy.METHODS:We enrolled patients with chronic hepatitis C who underwent direct-acting antiviral therapy and achieved sustained virologic response at 12 weeks between 2012 and 2018. Subsequently, patients were followed up. The primary endpoint was the development of HCC or the date of the last follow up when the absence of HCC was confirmed. Uni- and multivariate Cox proportional hazards models were used to identify factors contributing to HCC development, including gadoxetic acid-enhanced magnetic resonance imaging findings. The cumulative incidence rates of HCC development were calculated using the Kaplan-Meier method, and differences between groups were assessed using the log-rank test.RESULTS:The final study cohort comprised 482 patients (median age 70.5 years; 242 men). The median follow-up period was 36.8 months. Among 482 patients, 96 developed HCC (19.9%). The 1-, 3-, and 5-year cumulative rates of HCC development were 4.9%, 18.6%, and 30.5%, respectively. Multivariate analysis revealed that age, male sex, history of HCC, and hepatobiliary phase hypointense nodules without arterial phase hyperenhancement were independent risk factors significantly associated with HCC development (p < 0.001-0.04). The highest risk group included patients with both a history of HCC and the presence of hepatobiliary phase hypointense nodules without arterial phase hyperenhancement (the 1- and 3-year cumulative HCC development rates were 14.2% and 62.2%, respectively).CONCLUSION:History of HCC and presence of hepatobiliary phase hypointense nodules without arterial phase hyperenhancement were strong risk factors for HCC development following direct-acting antiviral therapy.

PURPOSE:To compare the quality of dynamic imaging between stack-of-stars acquisition without breath-holding (DISCO-Star) and the breath-holding method (Cartesian LAVA and DISCO).METHODS:This retrospective study was conducted between October 2019 and February 2020. Two radiologists performed visual assessments of respiratory motion or pulsation artifacts, streak artifacts, liver edge sharpness, and overall image quality using a 5-point scale for two datasets: Dataset 1 (n = 107), patients with Cartesian LAVA and DISCO-Star; Dataset 2 (n = 41), patients with DISCO and DISCO-Star at different time points. Diagnosable image quality was defined as ≥ 3 points in overall image quality. Whether the scan timing of the arterial phase (AP) was appropriate was evaluated, and results between the pulse sequences were compared. In cases of inappropriate scan timing in the DISCO-Star group, retrospective reconstruction with a high frame rate (80 phases, 3 s/phase) was added.RESULTS:The overall image quality of Cartesian LAVA was better than that of DISCO-Star in AP. However, noninferiority was shown in the ratio of diagnosable images between Cartesian LAVA and DISCO-Star in AP. There was no significant difference in the ratio of appropriate scan timing between DISCO-Star and Cartesian LAVA; however, the ratio of appropriate scan timing in DISCO-Star with high frame rate reconstruction was significantly higher than that in Cartesian LAVA in both readers. Overall image quality scores between DISCO and DISCO-Star were not significantly different in AP. There was no significant difference in the ratio of appropriate scan timing between DISCO-Star with high frame rate reconstruction and DISCO in both readers.CONCLUSION:The use of DISCO-Star with high frame rate reconstruction is a good solution to obtain appropriate AP scan timing compared with Cartesian LAVA. DISCO-Star showed equivalent image quality in all phases and in the ratio of appropriate AP scan timing compared with DISCO.

The fifth version of the Clinical Practice Guidelines for Hepatocellular Carcinoma was revised by the Japan Society of Hepatology, according to the methodology of evidence-based medicine and partly to the Grading of Recommendations Assessment, Development and Evaluation system, which was published in October 2021 in Japanese. In addition to surveillance-diagnostic and treatment algorithms, a new algorithm for systemic therapy has been created, as multiple drugs for hepatocellular carcinoma can be currently selected. Here, new or revised algorithms and evidence on which the recommendations are based are described.

Recent high-performance gradient coils are fabricated mainly at the expense of spatial linearity. In this study, we measured the spatial nonlinearity of the magnetic field generated by the gradient coils of two MRI systems with high-performance gradient coils. The nonlinearity of the gradient fields was measured using 3D gradient echo sequences and a spherical phantom with a built-in lattice structure. The spatial variation of the gradient field was approximated to the 3rd order polynomials. The coefficients of the polynomials were calculated using the steepest descent method. The geometric distortion of the acquired 3D MR images was corrected using the polynomials and compared with the 3D images corrected using the harmonic functions provided by the MRI venders. As a result, it was found that the nonlinearity correction formulae provided by the vendors were insufficient and needed to be verified or corrected using a geometric phantom such as used in this study.

Background The role of hepatic iron overload (HIO) in nonalcoholic fatty liver disease (NAFLD) pathogenesis has not been fully elucidated. Purpose This study aimed to investigate the effect of HIO and examine the diagnostic usefulness of magnetic resonance imaging (MRI)‐based R2 * quantification in evaluating hepatic iron content (HIC) and pathological findings in NAFLD. Study Type Prospective and retrospective. Population A prospective study of 168 patients (age, 57.2 ± 15.0; male/female, 80/88) and a retrospective validation study of 202 patients (age, 57.0 ± 14.4; male/female, 113/89) with liver‐biopsy‐confirmed NAFLD were performed. Field Strength/Sequence 3 T; chemical‐shift encoded multi‐echo gradient echo. Assessment Using liver tissues obtained by liver biopsy, HIC was prospectively evaluated in 168 patients by atomic absorption spectrometry. Diagnostic accuracies of HIC and R2 * for grading hepatic inflammation plus ballooning (HIB) as an indicator of NAFLD activity were assessed. Statistical Tests Student's t ‐test and analysis of variance (ANOVA) with Scheffe's multiple testing correction for univariate comparisons; multivariate logistic analysis. P ‐value less than 0.05 is statistically significant. Results HIC was significantly correlated with HIB grades ( r = 0.407). R2 * was significantly correlated with HIC ( r = 0.557) and HIB grades ( r = 0.569). R2 * mapped an area under the receiver operating characteristic (AUROC; 0.774) for HIC ≥808 ng/mL (median value) with cutoff value of 62.5 s −1 . In addition, R2 * mapped AUROC of HIB for grades ≥3 was 0.799 with cutoff value of 58.5 s −1 . When R2 * was <62.5 s −1 , R2 * correlated weakly with HIC ( r = 0.372) as it was affected by fat deposition and did not correlate with HIB grades ( P = 0.052). Conversely, when R2 * was ≥62.5 s −1 , a significant correlation of R2 * with HIC ( r = 0.556) and with HIB grades was observed ( P < 0.0001) with being less affected by fat deposition. Data Conclusion R2 * ≥ 62.5 s −1 is a promising modality for non‐invasive diagnosis of clinically important high grades (≥3) of HIB associated with increased HIC. Level of Evidence 1 Technical Efficacy Stage 2

Purpose: To evaluate the feasibility of folded image training strategy (FITS) and the quality of images reconstructed using the improved model-based deep learning (iMoDL) network trained with FITS (FITS-iMoDL) for abdominal MR imaging. Methods: This retrospective study included abdominal 3D T1-weighted images of 122 patients. In the experimental analyses, peak SNR (PSNR) and structure similarity index (SSIM) of images reconstructed with FITS-iMoDL were compared with those with the following reconstruction methods: conventional model-based deep learning (conv-MoDL), MoDL trained with FITS (FITS-MoDL), total variation regularized compressed sensing (CS), and parallel imaging (CG-SENSE). In the clinical analysis, SNR and image contrast were measured on the reference, FITS-iMoDL, and CS images. Three radiologists evaluated the image quality using a 5-point scale to determine the mean opinion score (MOS). Results: The PSNR of FITS-iMoDL was significantly higher than that of FITS-MoDL, conv-MoDL, CS, and CG-SENSE (P < 0.001). The SSIM of FITS-iMoDL was significantly higher than those of the others (P < 0.001), except for FITS-MoDL (P = 0.056). In the clinical analysis, the SNR of FITS-iMoDL was significantly higher than that of the reference and CS (P < 0.0001). Image contrast was equivalent within an equivalence margin of 10% among these three image sets (P < 0.0001). MOS was significantly improved in FITS-iMoDL (P < 0.001) compared with CS images in terms of liver edge and vessels conspicuity, lesion depiction, artifacts, blurring, and overall image quality. Conclusion: The proposed method, FITS-iMoDL, allowed a deeper MoDL reconstruction network without increasing memory consumption and improved image quality on abdominal 3D T1-weighted imaging compared with CS images.

BACKGROUND:The damping ratio (DR) and the loss modulus (G″) obtained by 3D MR elastography complex modulus analysis has been reported recently to reflect early intrahepatic inflammation, and is expected to be a noninvasive biomarker of inflammation in nonalcoholic fatty liver disease (NAFLD). However, the role of the DR and the G″ in Japanese NAFLD patients remains unclear.METHODS:We enrolled 39 Japanese patients with NAFLD who underwent liver biopsy and 3D MR elastography within 1 month and analyzed the association between DR, G″, and histological activity.RESULTS:Regarding DR, no evident correlation was observed between the DR and histological activity (p = 0.14) when patients with all fibrosis stages were included. However, when patients were restricted up to stage F2 fibrosis, the association of the DR and inflammation became significant, the DR increasing with the degree of activity (p = 0.02). Among the constituents of fibrosis activity, ballooning correlated with the DR (p < 0.01) while lobular inflammation did not. Regarding G″, it was correlated with histological activity (p < 0.01), ballooning (p < 0.01), and lobular inflammation (p < 0.01) in patients with all fibrosis stages and in patients up to F2 fibrosis (p = 0.03 for activity and p = 0.04 for ballooning). The best cutoff value of DR for hepatitis activity in patients within the F2 stage was 0.094 (area under the receiver operating characteristic curve 0.775, 95% CI: 0.529-1.000) and G″ was 0.402 (area under the receiver operating characteristic curve 0.825, 95% CI: 0.628-1.000).CONCLUSIONS:The DR and G″ reflected the histological activity in Japanese patients with NAFLD during the early stage, indicating these values for noninvasive diagnosis of inflammation in Japanese patients with NAFLD.

PURPOSE:To determine the optimal combination of gadoxetate disodium-enhanced magnetic resonance imaging (MRI) findings for the diagnosis of hepatocellular carcinoma (HCC) and to compare its diagnostic ability to that of dynamic computed tomography (CT) in patients with chronic liver disease.METHODS:This multi-institutional study consisted of two parts: Study 1, a retrospective study to determine the optimal combination of gadoxetate disodium-enhanced MRI findings (decision tree and logistic model) to distinguish HCC (n = 199) from benign (n = 81) or other malignant lesions (n = 95) (375 nodules in 269 patients) and Study 2, a prospective study to compare the diagnostic ability of gadoxetate disodium-enhanced MRI to distinguish HCC (n = 73) from benign (n = 15) or other malignant lesions (n = 12) with that of dynamic CT (100 nodules in 83 patients). Two radiologists independently evaluated the imaging findings (Study 1 and 2) and made a practical diagnosis (Study 2).RESULTS:In Study 1, rim or whole enhancement on arterial phase images, signal intensities on T2-weighted/diffusion-weighted/portal venous/transitional/hepatobiliary phase images, and signal drop on opposed-phase images were independently useful for differential diagnosis. In Study 2, the accuracy, sensitivity, negative predictive value, and negative likelihood ratio of the CT decision tree (reader 2) were higher than those of MRI Model 2 (P = 0.015-0.033). There were no other significant differences in diagnostic ability (P = 0.059-1.000) and radiologist-made practical diagnosis (P = 0.059-1.000) between gadoxetate disodium-enhanced MRI and CT.CONCLUSION:We identified the optimal combination of gadoxetate disodium-enhanced MRI findings for HCC diagnosis. However, its diagnostic ability was not superior to that of dynamic CT.

OBJECTIVE:To evaluate the diagnostic performance and image quality of the low-tube voltage and low-contrast medium dose protocol for hepatic dynamic CT.METHODS:This retrospective study was conducted between January and May 2018. All patients underwent hepatic dynamic CT using one of the two protocols: tube voltage, 80 kVp and contrast dose, 370   mgI/kg with hybrid iterative reconstruction or tube voltage, 120 kVp and contrast dose, 600  mgI/kg with filtered back projection. Two radiologists independently scored lesion conspicuity and image quality. Another radiologist measured the CT numbers of abdominal organs, muscles, and hepatocellular carcinoma (HCC) in each phase. Lesion detectability, HCC diagnostic ability, and image quality of the arterial phase were compared between the two protocols using the non-inferiority test. CT numbers and HCC-to-liver contrast were compared between the protocols using the Mann-Whitney U test.RESULTS:424 patients (70.5 ± 10.1 years) were evaluated. The 80-kVp protocol showed non-inferiority in lesion detectability and diagnostic ability for HCC (sensitivity, 85.7-89.3%; specificity, 96.3-98.6%) compared with the 120-kVp protocol (sensitivity, 91.0-93.3%; specificity, 93.6-97.3%) (p < 0.001-0.038). The ratio of fair image quality in the 80-kVp protocol also showed non-inferiority compared with that in the 120-kVp protocol in assessments by both readers (p < 0.001). HCC-to-liver contrast showed no significant differences for all phases (p = 0.309-0.705) between the two protocols.CONCLUSION:The 80-kVp protocol with hybrid iterative reconstruction for hepatic dynamic CT can decrease iodine doses while maintaining diagnostic performance and image quality compared with the 120-kVp protocol.ADVANCES IN KNOWLEDGE:The 80- and 120-kVp protocols showed equivalent hepatic lesion detectability, diagnostic ability for HCC, image quality, and HCC-to-liver contrast.The 80-kVp protocol showed a 38.3% reduction in iodine dose compared with the 120-kVp protocol.

Background Using phantoms and clinical studies in prone hanging breast imaging, we assessed the image quality of a commercially available dedicated breast PET (dbPET) at the detector’s edge, where mammary glands near the chest wall are located. These are compared to supine PET/CT breast images of the same clinical subjects. Methods A breast phantom with four spheres (16-, 10-, 7.5-, and 5-mm diameter) was filled with 18 F-fluorodeoxyglucose solution (sphere-to-background activity concentration ratio, 8:1). The spheres occupied five different positions from the top edge to the centre of the detector and were scanned for 5 min in each position. Reconstructed images were visually evaluated, and the contrast-to-noise ratio (CNR), contrast recovery coefficient (CRC) for all spheres, and coefficient of variation of the background (CV B ) were calculated. Subsequently, clinical images obtained with standard supine PET/CT and prone dbPET were retrospectively analysed. Tumour-to-background ratios (TBRs) between breast cancer near the chest wall (close to the detector’s edge; peripheral group) and at other locations (non-peripheral group) were compared. The TBR of each lesion was compared between dbPET and PET/CT. Results Closer to the detector’s edge, the CNR and CRC of all spheres decreased while the CV B increased in the phantom study. The disadvantages of this placement were visually confirmed. Regarding clinical images, TBR of dbPET was significantly higher than that of PET/CT in both the peripheral (12.38 ± 6.41 vs 6.73 ± 3.5, p = 0.0006) and non-peripheral (12.44 ± 5.94 vs 7.71 ± 7.1, p = 0.0183) groups. There was no significant difference in TBR of dbPET between the peripheral and non-peripheral groups. Conclusion The phantom study revealed poorer image quality at < 2-cm distance from the detector’s edge than at other more central parts. In clinical studies, however, the visibility of breast lesions with dbPET was the same regardless of the lesion position, and it was higher than that in PET/CT. dbPET has a great potential for detecting breast lesions near the chest wall if they are at least 2 cm from the edge of the FOV, even in young women with small breasts.

direct-reversing flow was observed from the dilated left PA to the right PA (Supplementary Movie, Figure F), which can cause an imbalance between the left and right pulmonary blood flows. This is the first report of 4D flow MRI showing that a dilated PA in TOF with APV may act as a reservoir and contribute to direct-reversing flow between the right and left PAs even after pulmonary valve replacement.

AIMS:To evaluate the association between contrast patterns on gadoxetic acid-enhanced hepatobiliary phase (HBP) MR images and transporter expression in surgically resected hypovascular hepatocellular nodules including early hepatocellular carcinomas (HCCs).METHODS:Forty-two hypovascular hepatic nodules and 43 hypervascular HCCs as a control were included in this retrospective study. Contrast of the nodules on HBP images was graded as hypo-, iso-, or hyperintense. Histopathological assessment was performed in the context of multistep hepatocarcinogenesis. Immunohistochemical staining of organic anion transporter 1B3 (OATP1B3) and multidrug resistance protein 2 (MRP2) was performed. Cramer's coefficient was used to determine the linear relationship between contrast grades and transporter expression, and the Cochran-Armitage trend test was used to determine the relationship between transporter expression and progression of multistep hepatocarcinogenesis.RESULTS:Moderate linear relationships between contrast grades and OATP1B3 expression were observed for both hypo- and hypervascular nodules. OATP1B3 expression was negatively correlated with the progression of multistep hepatocarcinogenesis. MRP2 expression was not associated with the contrast grades or histopathological results.CONCLUSION:OATP1B3 expression was associated with contrast grades of hepatocellular nodules observed in HBP image of gadoxetic acid-enhanced MRI in the hypovascular hepatocellular nodules and was negatively correlated with hepatocarcinogenesis.

To accelerate high-resolution diffusion-weighted imaging with a multi-shot echo-planar sequence, we propose an approach based on reduced averaging and deep learning. Denoising convolutional neural networks can reduce amplified noise without requiring extensive averaging, enabling shorter scan times and high image quality. The preliminary experimental results demonstrate the superior performance of the proposed denoising method over state-of-the-art methods such as the widely used block-matching and 3D filtering.

PURPOSE:To investigate whether shortened acquisition or multiple arterial phase acquisition improves image quality of the arterial phase compared with conventional protocol.METHODS:This retrospective study was approved by the relevant Institutional Review Board. A total of 615 consecutive patients who underwent gadoxetate disodium-enhanced MRI including one of the following three sequences in three different periods were included: (i) conventional liver acquisition with volume acceleration (LAVA) (between October 2014 and January 2015, n = 149), (ii) Turbo-LAVA (between March and August 2016, n = 216), and (iii) differential sub-sampling with Cartesian ordering (DISCO) (between January and September 2015, n = 250). We monitored the respiratory bellows waveform during breath holding for each patient and recorded breath-hold fidelity of the patients. Two radiologists independently evaluated the degree of respiratory artifact and scan timing on the arterial phase and compared them between the three protocols (i.e., conventional LAVA, Turbo-LAVA, and DISCO), with conventional LAVA as control.RESULTS:The ratio of patients with breath-hold failure was not significantly different among the three protocols (P = 0.6340 and 0.1085). Respiratory artifact was significantly lower in DISCO than in conventional LAVA (P = 0.0424), while there was no significant difference between Turbo-LAVA and conventional LAVA (P = 0.2593). The ratio of adequate scan timing and diagnosable image defined as no or mild artifact and adequate scan timing were higher in DISCO than in conventional LAVA (P = 0.0025 and 0.0019), while there was no significant difference between Turbo-LAVA and conventional LAVA (P = 0.0780 and 0.0657).CONCLUSION:Compared with conventional protocol, multiple arterial phase acquisition (DISCO) obtained a higher number of diagnosable images by reducing respiratory motion artifact and optimizing the scan timing of arterial phase.

BACKGROUND AND PURPOSE:When managing meningiomas, intraoperative tumor consistency and histologic subtype are indispensable factors influencing operative strategy. The purposes of this study were the following: 1) to investigate the correlation between stiffness assessed with MR elastography and perfusion metrics from perfusion CT, 2) to evaluate whether MR elastography and perfusion CT could predict intraoperative tumor consistency, and 3) to explore the predictive value of stiffness and perfusion metrics in distinguishing among histologic subtypes of meningioma.MATERIALS AND METHODS:Mean tumor stiffness and relative perfusion metrics (blood flow, blood volume, and MTT) were calculated (relative to normal brain tissue) for 14 patients with meningiomas who underwent MR elastography and perfusion CT before surgery (cohort 1). Intraoperative tumor consistency was graded by a neurosurgeon in 18 patients (cohort 2, comprising the 14 patients from cohort 1 plus 4 additional patients). The correlation between tumor stiffness and perfusion metrics was evaluated in cohort 1, as was the ability of perfusion metrics to predict intraoperative tumor consistency and discriminate histologic subtypes. Cohort 2 was analyzed for the ability of stiffness to determine intraoperative tumor consistency and histologic subtypes.RESULTS:The relative MTT was inversely correlated with stiffness (P = .006). Tumor stiffness was positively correlated with intraoperative tumor consistency (P = .01), while perfusion metrics were not. Relative MTT significantly discriminated transitional meningioma from meningothelial meningioma (P = .04), while stiffness did not significantly differentiate any histologic subtypes.CONCLUSIONS:In meningioma, tumor stiffness may be useful to predict intraoperative tumor consistency, while relative MTT may potentially correlate with tumor stiffness and differentiate transitional meningioma from meningothelial meningioma.