Published papers

本稿では,TransformerベースのBERTモデルを用いた肺領域における所見文の疾患分類を行う方法を提案する.これは疾患名が付与された画像データセット構築の初期検討である.画像処理において,一般的には機械学習モデルの性能向上のため多くの学習データが必要である.しかし,医用画像のアノテーションには膨大な手間がかかる問題がある.そこで,放射線科医がCT画像の診断結果から作成し,患者の状態を詳細に記載している所見文を利用する.本研究では疾患名が付与された画像データセット構築の初期検討として,TransformerベースのモデルでFine-tuningを行い,肺領域において4クラス分類を行った.肺領域における400例の疾患分類実験によりMacro-F1で79.4%となった.(著者抄録)

The objectives of this study were to visualize the surgical anatomical structures in the female pelvis by computed tomography and to investigate the components of the parametrium for anatomical education, radiological diagnosis, and surgical simulation. We surgically dissected fresh female cadavers maintained in precise surgical anatomic positions and examined the anatomical structures using experimental fine cell detector multislice computed tomography (FDCT) with a slice thickness of 0.3125 mm. In addition, we established a three-dimensional (3D) reconstruction model for precise observation of the surgical anatomy using Materialise's Interactive Medical Image Control System (Mimics). We evaluated two-dimensional (2D) images of the surgical anatomical structures in combination with the 3D reconstruction model. The 3D model was reconstructed from 430 serial axial pelvic CT images of a cadaver. The cardinal ligament, uterosacral ligament, paravesical space, and pararectal space were visualized on the CT images obtained from the surgically dissected part. The parametrium components were clearly distinguished on the surgically dissected side. Based on the information from the dissected side, these components on the undissected side could be distinguished as well. We recognized the parametrium components in the area extirpated during radical hysterectomy. The approach using cadavers, experimental FDCT, and 3D software provided excellent visualization of pelvic structures. High-quality images of surgical anatomical structures provide new insight regarding precise surgical anatomy in the female pelvis. The radiological information has practical usefulness for radiotherapeutic planning and surgical simulation. Copyright © 2013 Wiley Periodicals, Inc.

An 84-year-old man with symptomatic severe aortic stenosis received transcatheter aortic valve implantation (TAVI). Dual-antiplatelet therapy was continued for 6 months post TAVI, and aspirin alone was used thereafter. Four-dimensional multidetector computed tomography revealed a new hypoattenuated leaflet thickening (HALT) with reduced leaflet motion at 1 year, considered to indicate leaflet thrombosis. At the 2-year follow-up, leaflet mobility had improved, with spontaneous regression of HALT. This is the first report of confirmed spontaneous regression of possible transcatheter heart valve thrombosis and recovery of leaflet mobility without the need for additional anticoagulant.

PURPOSE: To evaluate the effectiveness of the single-energy metal artifact reduction (SEMAR) technique for improving the accuracy of I-125 seed identification in postimplant computed tomography (CT) after prostate brachytherapy. METHODS AND MATERIALS: Postimplant CT images of 40 patients treated with I-125 prostate brachytherapy were acquired. For all patients, 2 data sets were reconstructed, 1 with SEMAR algorithms (SEMAR image), and the other without SEMAR algorithms (non-SEMAR image). Seed locations are automatically detected by the automatic seed finder tool, and their locations were compared between the SEMAR and non-SEMAR images. Dosimetric parameters using seed locations as detected were compared. RESULTS: The true-positive fraction of properly detected seeds on the SEMAR image as determined from a reference seed distribution defined by one investigator was significantly higher than the true-positive fraction on the non-SEMAR image (p = 0.011). The variabilities in D90 (p = 0.001), V100 (p = 0.007), and V150 (p = 0.007) were significantly reduced for seed location on the SEMAR image as compared with non-SEMAR image. CONCLUSIONS: Prostate postimplant CT with SEMAR improved the accuracy of seed localization and postimplant dosimetric parameters. Copyright © 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Intravenous urography has been widely used for the evaluation of upper tract urothelial carcinoma. However, computed tomography urography presently has a higher diagnostic accuracy for upper tract urothelial carcinoma (94.2-99.6%) than intravenous urography (80.8-84.9%), and has replaced intravenous urography as the first-line imaging test for investigating patients with a high risk of upper tract urothelial carcinoma. Although the detection rate for bladder tumors using standard computed tomography urography is not yet high enough to replace cystoscopy, the addition of a 60- to 80-s delayed scan after the administration of contrast material for the whole pelvis improves the detection rate. A drawback to computed tomography urography is the higher radiation dose of 15-35 mSv, compared with a mean effective dose of 5-10 mSv for intravenous urography. Among several approaches to reducing the radiation dose, the use of an iterative reconstruction algorithm is most likely to become an effective solution because of its simplicity. One advantage of computed tomography urography over intravenous urography is its ability to reliably differentiate between upper tract urothelial carcinoma and calculi or blood clots. Computed tomography urography also shows characteristic findings of other benign conditions. These findings, in combination with negative cytology, are very important diagnostic clues for avoiding an unnecessary nephroureterectomy. For the clinical staging, a recent study has reported the high diagnostic accuracy of computed tomography urography with respect to ≥pT3 tumors. The present review shows the current status of computed tomography urography for the evaluation of upper tract urothelial carcinoma.

OBJECTIVE: In patients with hypertrophic obstructive cardiomyopathy (HOCM), left atrial (LA) volume measurement is very important to provide prognostic information. Recent studies demonstrated that multidetector CT (MDCT) is useful to assess the changes in LA volume. Our aim was to examine the utility of a follow-up cardiac MDCT for long-term evaluation of the effect of percutaneous transluminal septal myocardial ablation (PTSMA) on LA volume. METHODS: We studied a consecutive cohort of 20 patients with drug-refractory symptomatic HOCM after PTSMA. We evaluated LA volume analyses with cardiac MDCT on patients who underwent PTSMA as compared to echocardiography. RESULTS: Before PTSMA, 75% of all patients had heart failure-associated symptoms in the New York Heart Association functional class III/IV. All patients experienced relief from heart failure-associated symptoms after PTSMA. Cardiac MDCT showed significant reduction in the index of maximum LA volume during follow-up compared to before PTSMA in the same way as in echocardiography (93.6±34.1 mL/m(2) vs 82.6±35.3 mL/m(2), p=0.035). A Bland-Altman plot showed small mean differences and limits of agreement in the measurements of the index of maximum LA volume before and after PTSMA between echocardiography and MDCT. CONCLUSIONS: The follow-up cardiac MDCT was a useful tool to evaluate the effectiveness of PTSMA on reduction of LA volume. Cardiac MDCT might provide comparable measurements of the LA volume in patients with drug-refractory symptomatic HOCM before and after PTSMA compared to echocardiography.

© 2020, Springer-Verlag GmbH Germany, part of Springer Nature. Purpose: MR angiography using the silent MR angiography algorithm (silent MRA), which combines arterial spin labeling and an ultrashort time echo, has not been used for the evaluation of cerebral arteriovenous malformations (CAVMs). We aimed to determine the usefulness of silent MRA for the evaluation of CAVMs. Methods: Twenty-nine CAVMs of 28 consecutive patients diagnosed by 4D CT angiography or digital subtraction angiography, who underwent both time-of-flight (TOF) MRA and silent MRA, were enrolled. Two observers independently assessed the TOF-MRA and silent MRA images of CAVMs. Micro AVM was defined as AVM with a nidus diameter less than 10 mm. The detection rate, visualization of the components, and accuracy of Spetzler–Martin grade were evaluated with statistical software R. Results: For all 29 CAVMs, 23 (79%) lesions were detected for TOF-MRA and all for silent MRA. Of 10 micro AVMs, only 4 (40%) lesions were detectable on TOF-MRA and all (100%) on silent MRA. The visibility of the nidus and drainer was significantly better for silent MRA than TOF-MRA (p < 0.001), while there was no significant difference in the feeder between the two sequences. The accuracy rates of the Spetzler–Martin grade for the TOF and silent MRA were 38% (11/29) and 79.3% (23/29), respectively (p < 0.001). Conclusions: Silent MRA is useful for evaluating CAVM components and detecting micro AVM.

© 2017 International Society for Magnetic Resonance in Medicine Purpose: To develop and demonstrate the feasibility of a silent respiratory navigator technique for prospective triggering, which was incorporated into a three-dimensional radial zero-echo-time sequence for respiratory navigated silent abdominal imaging. Methods: A nonselective hard excitation radiofrequency pulse was used for the navigator sequence with a derated readout gradient, to avoid generation of high levels of acoustic noise. The acquired navigator signals were processed in real time and used for prospective triggering of the zero-echo-time sequence. Ten healthy volunteers were scanned using the proposed and conventional techniques at 1.5 T. An acoustic noise measurement with A-weighted continuous equivalent sound pressure level was also performed. Results: The sound pressure–level values of the background noise, zero-echo-time imaging, conventional, and silent navigators were 68.3, 68.4, 102.5, and 69.4 dBA, respectively. Excellent correlation with correlation coefficients greater than 0.9 was observed between the bellows signals and displacement values calculated from the navigators. Sharpness of the portal vein of both conventional and silent navigator–triggered images was significantly higher than those of nontriggered images. Conclusions: The silent navigator–triggered zero-echo-time technique is feasible and might improve image quality and workflow of abdominal MRI of patients who are prone to acoustic noise. Magn Reson Med 79:2170–2175, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

© 2020, Springer-Verlag GmbH Austria, part of Springer Nature. Sinking skin flap syndrome is a craniectomy complication characterized by new neurological dysfunction that typically worsens in the upright position and improves after cranioplasty. We present a 33-year-old man who experienced hemiparesis in the upright position after craniectomy. Upright computed tomography (CT) before cranioplasty showed a remarkable shift of the brain compared to supine CT. After cranioplasty, both symptoms and brain shift on CT resolved. Upright CT enables detection and objective evaluation of paradoxical herniation and midline shift that is not obvious on supine imaging modalities. Clinicians need to be aware of positional brain shift in postcraniectomy patients.

© 2019 The Author(s). Background: Gastrointestinal stromal tumors (GISTs) in transplant recipients are very rare and only a handful of cases have been reported to date. Here we present the first known case of a huge GIST in a kidney transplant recipient with perforation of small intestine. Case presentation: A 64-year-old male presented at our hospital with right colic pain; he had received an ABO incompatible kidney transplant 6 years earlier and was treated with cyclosporine, mycophenolate mofetil, and methylprednisolone. Radiological evaluation revealed a huge (11 cm in diameter) solitary tumor at the small intestine without distant metastasis. The small intestinal wall at the tumor location was perforated one week after diagnosis and the patient underwent emergency surgery. The pathological findings were compatible with GIST and the tumor consisted of spindle cells with positive staining for KIT, CD34, and DOG1 and negative or weak staining for desmin and S-100 protein. A mutation in exon 11 of the c-kit gene was also detected. Cyclosporine was withdrawn and imatinib mesylate (400 mg daily) was introduced. However, thereafter, we needed to decrease the dose at 300 mg daily due to severe hyponatremia. Reduced imatinib treatment was well tolerated and recurrence was not observed for 18 months after surgery. Conclusions: The occurrence of GISTs in transplant patients is rare, and huge GISTs should be resected immediately after diagnosis because gastrointestinal tract at the tumor site could be perforated. Imatinib treatment is feasible in transplant recipients under immunosuppression, although immunosuppressive drugs metabolized by CYP3A4 should be used at a reduced dosage or withdrawn.

© 2020 Associazione Italiana di Fisica Medica Purpose: Hybrid iterative reconstruction (IR) is useful to reduce noise in computed tomography (CT) images. However, it often decreases the spatial resolution. The ability of high spatial resolution kernels (harder kernels) to compensate for the decrease in the spatial resolution of hybrid IRs was investigated. Methods: An elliptic cylindrical phantom simulating an adult abdomen was used. Two types of rod-shaped objects with ~330 and ~130 HU were inserted to simulate contrasts of arteries in CT angiography. Two multi-slice CT systems were used to scan the phantoms with 120 kVp and scan doses of 20 and 10 mGy. The task transfer functions (TTFs) were measured from the circular edges of the rod images. The noise power spectrum (NPS) was measured from the images of the water-only section. The CT images were reconstructed using a filtered back projection (FBP) with baseline kernels and two levels of hybrid IRs with harder kernels. The profiles of the clinical images across the aortic dissection flaps were measured to evaluate actual spatial resolutions. Results: The TTF degradation of each hybrid IR was recovered by the harder kernels, whereas the noise reduction effect was retained, for both the 20 and 10 mGy. The profiles of the dissection flaps for the FBP were maintained by using the harder kernels. Even with the best combination of hybrid IR and harder kernel, the noise level at 10 mGy was not reduced to the level of FBP at 20 mGy, suggesting no capability of a 50% dose reduction while maintaining noise.

© RSNA, 2020. Background: Detailed visualization of the lymphatic vessels would greatly assist in the diagnosis and monitoring of lymphatic diseases and aid in preoperative planning of lymphedema surgery and postoperative evaluation. Purpose: To evaluate the usefulness of photoacoustic imaging (PAI) for obtaining three-dimensional images of both lymphatic vessels and surrounding venules. Materials and Methods: In this prospective study, the authors recruited healthy participants from March 2018 to January 2019 and imaged lymphatic vessels in the lower limbs. Indocyanine green (5.0 mg/mL) was injected into the subcutaneous tissue of the first and fourth web spaces of the toes and below the lateral malleolus. After confirmation of the lymphatic flow with near-infrared fluorescence (NIRF) imaging as the reference standard, PAI was performed over a field of view of 270 3 180 mm. Subsequently, the number of enhancing lymphatic vessels was counted in both proximal and distal areas of the calf and compared between PAI and NIRF. Results: Images of the lower limbs were obtained with PAI and NIRF in 15 participants (three men, 12 women; average age, 42 years 6 12 [standard deviation]). All participants exhibited a linear pattern on NIRF images, which is generally considered a reflection of good lymphatic function. A greater number of lymphatic vessels were observed with PAI than with NIRF in both the distal (mean: 3.6 vessels 6 1.2 vs 2.0 vessels 6 1.1, respectively; P , .05) and proximal (mean: 6.5 vessels 6 2.6 vs 2.6 vessels 6 1.6; P , .05) regions of the calf. Conclusion: Compared with near-infrared fluorescence imaging, photoacoustic imaging provided a detailed, three-dimensional representation of the lymphatic vessels and facilitated an increased understanding of their relationship with the surrounding venules.

© The Author(s) 2020. A 49-year-old man with CTEPH (pre-procedural mean pulmonary artery pressure: 36 mmHg) underwent balloon pulmonary angioplasty. Chronic total occlusion of the left inferior pulmonary artery trunk was observed. To evaluate the collateral vessels of the chronic total occlusion, 4D-CTA was performed. The examination was performed using a 256-row detector CT system using the test bolus tracking method. 4D-CTA showed the bronchial artery-to-left inferior pulmonary artery collateral supply, which was confirmed by a selective bronchial artery angiography. The patient’s symptoms improved with balloon pulmonary angioplasty of the other stenotic lesions. 4D-CTA can noninvasively evaluate the anatomy and hemodynamics of multiple systemic collaterals simultaneously. This technique can support interventions in systemic artery-to-pulmonary artery collaterals, such as embolization, and could be helpful in challenging balloon pulmonary angioplasty interventions for chronic total occlusion to identify vessel structures distal to the chronic total occlusion and collateral channels for a retrograde approach.

© 2019, American Society of Nuclear Cardiology. Background: Fluoride-18 sodium fluoride (18F-NaF) localizes in microcalcifications in atheroma. The microcalcifications may aggregate, passing the resolution threshold to visualize on computed tomography (CT). We evaluated serial NaF positron emission tomography (PET)-CT scans to determine the temporal relationship between vascular NaF uptake and CT evident calcification in the abdominal aorta. Methods: Prostate cancer patients who had at least 3 NaF PET-CT scans over at least 1.5 years were retrospectively enrolled. Regions of interest were traced in the abdominal aorta on both PET and CT images, excluding skeletal NaF activity. The maximum standardized uptake value (SUVmax) of NaF and the density and volume of calcium (exceeding 130 HU) were summed and divided by the number of slices to produce the SUVmax/slice and the mm3·slice−1 of calcium. Results: Of 437 patients, 45 patients met criteria. NaF uptake waxed and waned between scans, while the calcium volume plateaued or increased over time. NaF uptake correlated with calcium volume on the baseline scan (P =.60, <.0001†) and calcium volume increment, especially from 1.0 to 1.5 years (r =.79, P <.0001†). Patients with persistently high NaF uptake showed a higher calcium volume increment (0-1.5 years) than patients with low or transiently high NaF uptake. Conclusions: Abdominal aortic NaF uptake varied over time. NaF uptake on the baseline scans and high NaF uptake on the serial scans preceded an increase in calcium volume, especially by 1.0-1.5 years. Persistently high NaF uptake was associated with a greater increment in calcium volume than patients with transiently elevated or persistently low fluoride uptake.

© 2018 The Authors. Objective: The diagnostic performance of endoscopic retrograde cholangiography (ERC) with radiography is imperfect. We assessed the value of adding tomosynthesis to ERC with radiography for the detection of choledocholithiasis. Methods: This study included 102 consecutive patients (choledocholithiasis/non-choledocholithiasis, n = 57/45), who underwent both radiography and tomosynthesis for ERC in the same examination and were not diagnosed with malignancy. The reference standard for the existence of choledocholithiasis was confirmed by endoscopic stone extraction during ERC, intraoperative cholangiography, or follow up with magnetic resonance cholangiopancreatography (n = 78, 11, and 13, respectively). A gastroenterologist and a radiologist independently evaluated the radiographs and the combination of tomosynthesis and radiographic images in a blinded and randomised manner. Receiver operating characteristic analysis was used for statistical analysis. Results: The areas under the receiver operating characteristic curve for combined tomosynthesis and radiography were significantly higher than those for radiography alone for both readers: Reader 1/ Reader 2, 0.929/0.956 [95% confidence interval (CI), 0.861-0.965/0.890-0.983) vs 0.803/0.769 (95% confidence interval, 0.707-0.873/0.668-0.846), respectively (p = 0.0047/> 0.0001). Conclusion: Adding tomosynthesis to radiography improved the diagnostic performance of ERC for detection of choledocholithiasis. Advances in knowledge: Adding tomosynthesis to radiography improves detection of choledocholithiasis and tomosynthesis images can be obtained easily after radiographs and repeated immediately.