Published papers

We present a 50–year-old female with IgG4-related disease (IgG4-RD) of the urethra. She had been diagnosed with IgG4-RD involving the pancreas, lacrimal glands, salivary glands, kidneys, and right breast 5 years earlier, which had remitted after steroid treatment. In recent months, she had experienced urinary incontinence. Her local physician noted a urethral stricture. Magnetic resonance imaging (MRI) showed a lesion surrounding the urethra, with a slightly high signal intensity on T2-weighted and short-term inversion recovery images, and a mildly high signal intensity on diffusion-weighted images. Accordingly, IgG4-RD involving the urethra was suggested. Her serum IgG4 level was slightly elevated at 127 mg/dL, which is below the normal upper limit of 135 mg/dL. A transurethral biopsy revealed significant lymphocytic and IgG4-positive plasma cell infiltrates (50–80/high-power field), fibrosis, and obstructive phlebitis. Thus, IgG4-RD of the urethra was confirmed. A systematic search including CT and MRI did not reveal any new gross lesions. Steroid therapy improved her symptoms within a few days. Follow-up MRI revealed shrinking of the urethral lesion and lower signal intensity on T2-weighted images. IgG4-RD with urethral lesions is extremely rare. No cases of diagnosis of IgG4-RD urethral lesions based on MRI findings before biopsy have been reported to date. When a middle-aged woman presents with uniform circumferential urethral lesions, IgG4-RD should be considered in the differential diagnosis. Here, we report detailed imaging findings and radiological differential diagnoses, and discuss relevant literature.

Plasmacytoid urothelial carcinoma (PUC) is a rare and an aggressive subtype of invasive urothelial carcinoma, often diagnosed at advanced stages with poor prognosis. We report a case of PUC with characteristic radiological findings. A male patient in his 70s presented with nocturnal urinary incontinence; cystoscopy findings suggested cancer. Magnetic resonance imaging (MRI) revealed a 6-mm-sized protruding lesion of the bladder with early contrast enhancement and diffusion restriction, indicative of bladder cancer. Additionally, a diffuse bladder wall thickening, abnormal signal intensity, and contrast enhancement were observed around the bladder. Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography showed no significant FDG uptake in the lesion. The possibility of peritoneal dissemination of gastrointestinal malignancy was considered; however, no obvious primary lesions were identified. PUC was suggested as a differential diagnosis, prompting random bladder biopsies during resection of a protruding lesion in the bladder. Immunohistochemical staining confirmed PUC, with positivity for CD138, CK7, and GATA3 and negativity for CDX-2 and E-cadherin. Following treatment with gemcitabine and cisplatin, the lesion size decreased. Diagnosis of PUC can be difficult because the lesion is not easily detected by cystoscopy, misdiagnosed as peritoneal dissemination of gastrointestinal cancer on CT or MRI, or histopathologically similar to plasmacytoma or malignant lymphoma. PUC may present with pelvic peritoneal spread of the tumor as thick sheets extending along the fascial planes, which may be a characteristic imaging finding. Radiologists must be aware of these typical imaging findings to ensure accurate diagnosis of PUC.

The effect of gravity on the lungs has been evaluated using computed tomography (CT) in the supine and prone positions but not the standing position. However, as humans spend most of the daytime in the standing position, we aimed to compare lung attenuation gradients between the supine and standing positions, and to assess the correlations between the lung attenuation gradients and participant characteristics, including pulmonary function test results. Overall, 100 healthy participants underwent conventional/supine and upright CT, and lung attenuation gradients were measured. Lung attenuation gradients in anteroposterior direction were greater in the supine position than in standing position (all p values < 0.0001) in both upper lobes at the level of the aortic arch (right: standing/supine, -0.02 ± 0.19/0.53 ± 0.21; left: standing/supine, -0.06 ± 0.20/0.51 ± 0.21); in the right middle (standing/supine, -0.26 ± 0.41/0.53 ± 0.39), left upper (standing/supine, -0.35 ± 0.50/0.66 ± 0.54), and lower lobes at the level of the inferior pulmonary vein (right: standing/supine, -0.22 ± 0.30/0.65 ± 0.41; left: standing/supine, -0.16 ± 0.25/0.73 ± 0.54); and in both lower lobes just above the diaphragm (right: standing/supine, -0.13 ± 0.22/0.52 ± 0.32; left: standing/supine, -0.30 ± 0.57/0.55 ± 0.37). Craniocaudal gradients were greater in the standing position (right: standing/supine, 0.41 ± 0.30/0.00 ± 0.16; left: standing/supine, 0.35 ± 0.30/-0.02 ± 0.16, all p values < 0.0001). No moderate to very high correlations were observed between age, sex, height, weight, body index mass, or pulmonary function test results and each lung attenuation gradient. Lung attenuation gradients in anteroposterior direction, which was observed in the supine position, disappeared in the standing position. However, the craniocaudal lung attenuation gradient, which was not present in the supine position, appeared in the standing position.

Scrotal masses, whether cystic or solid lesions, are routinely evaluated using ultrasonography. Magnetic resonance imaging (MRI) may be used for further investigation in cases with atypical findings, difficult diagnoses, large masses, and/or unclear relationships with the surrounding tissues. Scrotal solid masses are divided into intra- and extra-testicular masses. A staggering 90% of the intratesticular masses are malignant, whereas 75% of extratesticular masses are benign. Extratesticular masses are less common than intratesticular masses; however, some extratesticular masses present characteristic MRI findings. Familiarity with these specific MRI features of extratesticular masses is beneficial to radiologists, as appropriate diagnoses can help avoid unnecessary invasive treatments such as orchiectomy. In this review, we describe fibrous pseudotumors, polyorchidism, adenomatoid tumors, and scrotal leiomyoma as benign paratesticular masses, focusing on their characteristic imaging features on MRI. Although these tumors are extremely rare, their MRI findings are distinctive, and accurate diagnoses can prevent unnecessary orchiectomy. In addition, to demonstrate the pitfalls of diagnosing extratesticular masses, we present a case of seminoma misidentified as extratesticular masses due to large extensions outside the testis. Spermatic cord sarcoma, including rhabdomyosarcoma, leiomyosarcoma, and liposarcoma, and metastasis to the spermatic cord are described as malignant extratesticular masses. This review focused on extratesticular masses and elaborates the imaging findings that can aid in the accurate diagnosis using MRI.

Diabetes mellitus is a systemic metabolic disease that causes a wide spectrum of complications affecting multiple organs. Advances in imaging modalities have substantially improved the detection, characterization, and clinical management of these conditions. However, the imaging manifestations of diabetic complications are highly diverse, often mimicking other diseases and posing diagnostic challenges for radiologists. This review aimed to provide an organ-based overview of the characteristic imaging features of diabetic complications from head to toe, integrating pathophysiological mechanisms relevant to image interpretation. Representative cases are illustrated using multimodal imaging—computed tomography (CT), magnetic resonance imaging, ultrasound, radiography, and 18F-fluorodeoxyglucose positron emission tomography/CT—to highlight key findings, differential diagnoses, and potential pitfalls. Specifically, this review focuses on conditions and diseases that are amenable to evaluation by radiological imaging. Understanding these imaging patterns is essential for early diagnosis, risk stratification, and optimal patient management. Through an educational, pictorial approach, this review aims to enhance radiologists’ recognition of diabetic complications across organ systems.

Introduction: Testicular malakoplakia is a very rare, chronic granulomatous inflammatory condition that frequently resembles testicular malignancy on imaging studies. Here, we report a case of testicular malakoplakia with characteristic magnetic resonance imaging (MRI) findings and present a brief review of the literature. Case Presentation: A man in his 70s presented with left-sided scrotal pain. Ultrasonography revealed a well-defined hypoechoic intratesticular mass without internal vascularity, whereas computed tomography revealed enlargement of the left testis with a relative hyperattenuation area. MRI demonstrated low signal intensity on T2-weighted images, diffusion restriction, and a markedly high signal intensity on fat-suppressed T1-weighted images with contrast enhancement. Based on these findings, a malignant testicular tumor was suspected, and radical orchidectomy was conducted. Histopathological examination confirmed testicular malakoplakia with characteristic Michaelis–Gutmann bodies. Conclusion: This case highlights the importance of recognizing T1 shortening on fat-suppressed T1-weighted MRI as a potential imaging modality for malakoplakia.

Upright multidetector CT (MDCT) enables whole-body, high-resolution, three-dimensional cross-sectional imaging in standing or sitting positions, providing detailed visualization of anatomy and biomechanics in physiologically relevant, load-bearing postures. This system maintains high spatial resolution and quantitative performance, including stable noise characteristics and consistent CT attenuation values, while improving workflow efficiency compared with conventional supine MDCT. In the shoulder and upper extremity, upright MDCT has clarified gravity-dependent alignment changes and enabled dynamic four-dimensional assessment of sternoclavicular and acromioclavicular joint motion. In the spine, it provides reproducible spinopelvic measurements, reveals posture-dependent narrowing of intervertebral foramina, and characterizes age- and sex-related differences in segmental spinal mobility. Upright MDCT of the knee allows precise evaluation of joint-line orientation, mechanical-axis migration, and rotational kinematics under weight-bearing conditions, enhancing diagnostic accuracy and preoperative planning in osteoarthritis. In the lower extremities, it captures kinetic-chain mechanics from the foot to the hip, integrating ground-reaction-force data to analyze load distribution and compensatory motion across adjacent joints. Upright MDCT also visualizes thoracic cage deformation and vertebral displacement in conditions such as pectus excavatum, demonstrating load-related changes that supine imaging may overlook. This review provides a state-of-the-art overview of upright MDCT applications in orthopedic imaging and highlights its potential to transform diagnostic strategies and deepen understanding of musculoskeletal pathophysiology under physiologically relevant weight-bearing conditions. Collectively, these studies demonstrate that upright MDCT is a quantitatively robust modality that offers new insights into functional anatomy, disease mechanisms, and biomechanical adaptation. By bridging diagnostic imaging with functional assessment, upright MDCT has the potential to refine understanding of musculoskeletal pathophysiology and to guide more personalized therapeutic strategies in orthopedic and related fields.

The original version of this article unfortunately contained a mistake. The “Abstract” and “Keywords” sections were missing in the published version. However, now it is corrected. We present a 50-year-old female with IgG4-related disease (IgG4-RD) of the urethra. She had been diagnosed with IgG4-RD involving the pancreas, lacrimal glands, salivary glands, kidneys, and right breast 5 years earlier, which had remitted after steroid treatment. In recent months, she had experienced urinary incontinence. Her local physician noted a urethral stricture. Magnetic resonance imaging (MRI) showed a lesion surrounding the urethra, with a slightly high signal intensity on T2-weighted and short-term inversion recovery images, and a mildly high signal intensity on diffusion-weighted images. Accordingly, IgG4-RD involving the urethra was suggested. Her serum IgG4 level was slightly elevated at 127 mg/dL, which is below the normal upper limit of 135 mg/dL. A transurethral biopsy revealed significant lymphocytic and IgG4-positive plasma cell infiltrates (50–80/high-power field), fibrosis, and obstructive phlebitis. Thus, IgG4-RD of the urethra was confirmed. A systematic search including CT and MRI did not reveal any new gross lesions. Steroid therapy improved her symptoms within a few days. Follow-up MRI revealed shrinking of the urethral lesion and lower signal intensity on T2-weighted images. IgG4-RD with urethral lesions is extremely rare. No cases of diagnosis of IgG4-RD urethral lesions based on MRI findings before biopsy have been reported to date. When a middle-aged woman presents with uniform circumferential urethral lesions, IgG4-RD should be considered in the differential diagnosis. Here, we report detailed imaging findings and radiological differential diagnoses, and discuss relevant literature. Keywords Urinary incontinence, Circumferential lesion, Dysuria, IgG4-related disease, Periurethral lesion, Urethra The original article has been corrected.

A dual imaging pattern of hyperattenuation on non-enhanced computed tomography and hypointensity on T2-weighted imaging is frequently encountered in various lesions. In the present review, we aimed to explore this imaging combination across a spectrum of abdominal and pelvic lesions to clarify its clinical implications.This pattern is commonly observed in lesions rich in fibrous or smooth muscle components, making it more frequently encountered in benign entities, including fat-poor angiomyolipomas, uterine leiomyomas, and tumors with predominant fibrous stroma. However, similar imaging findings may also be encountered in rare high-cellularity malignancies, selected systemic diseases, and lesions containing melanin, metal deposition, or thyroid tissue. Although not specific to a single disease, this imaging pattern offers valuable diagnostic clues for lesion characterization. When contrast-enhanced imaging is unavailable or contraindicated, combining non-enhanced computed tomography and T2-weighted imaging findings may help narrow the differential diagnosis. Despite its general association with benign lesions, this imaging phenotype requires careful exclusion of important pathologic mimics. Overall, integration with clinical information and other imaging findings remains essential for accurate interpretation.

Serous cystic neoplasms are relatively uncommon and rarely possess malignant potential. We report a rare case of pancreatic serous cystadenoma with splenic invasion in a female in her 60s. Dynamic contrast-enhanced CT revealed a 3 cm mass in the tail of the pancreas. The lesion showed marked enhancement in the arterial phase on dynamic CT, which extended into the spleen. No cystic components were detected in the pancreatic mass on either magnetic resonance cholangiopancreatography or T 2 weighted imaging. No metastasis or lymph node swelling was detected. Based on the hypervascularity of the tumour, the pre-operative diagnosis was pancreatic neuroendocrine tumour with splenic invasion. The patient underwent laparoscopic distal pancreatectomy with splenectomy. The pathological diagnosis was microcystic serous cystadenoma with locally aggressive features (infiltration into spleen, lymph nodes, and splenic vein). A few cases of pancreatic serous cystadenomas with splenic invasion have been reported; all were symptomatic, with diameters greater than approximately 9 cm. This is the first known case of incidentally detected serous cystadenoma with splenic invasion, reported with detailed imaging findings of dynamic CT and MRI.