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Purpose To evaluate the utility of deep learning-based image reconstruction (DLIR) algorithm in unenhanced abdominal low-dose CT (LDCT). Materials and methods Two patient groups were included in this prospective study: 58 consecutive patients who underwent unenhanced abdominal standard-dose CT reconstructed with hybrid iterative reconstruction (SDCT group) and 48 consecutive patients who underwent unenhanced abdominal LDCT reconstructed with high strength level of DLIR (LDCT group). The background noise and signal-to-noise ratio (SNR) of the liver, pancreas, spleen, kidney, abdominal aorta, inferior vena cava, and portal vein were calculated. Two radiologists qualitatively assessed the overall image noise, overall image quality, and abdominal anatomical structures depiction. Quantitative and qualitative parameters and size-specific dose estimates (SSDE) were compared between SDCT and LDCT groups. Results The background noise was lower in LDCT group than in SDCT group (P = 0.02). SNRs were higher in LDCT group than in SDCT group (P P P = 0.25–0.26). Depiction of almost all abdominal anatomical structures was equal to or better in LDCT group than in SDCT group (P P Conclusions DLIR facilitates substantial radiation dose reduction of > 75% and significantly reduces background noise. DLIR can maintain image quality and anatomical structure depiction in unenhanced abdominal LDCT.

Purpose This study aimed to describe the MRI findings of epithelial-myoepithelial carcinoma (EMC) of the parotid gland. Materials and methods Seven patients (four males and three females) aged 40–86 years (mean age, 64 years) with histologically proven EMC of the parotid gland who underwent surgical resection after preoperative MRI were enrolled. MRI images were retrospectively reviewed and contrasted with pathological findings. Results Five patients (71%) had predominantly solid lesions, and two (29%) had predominantly cystic lesions. All seven lesions had well-demarcated margins and capsules without the invasion of adjacent structures. The capsules were incomplete in five lesions (71%) and complete in two (29%). Four lesions (57%) exhibited a multinodular structure with internal septa. Cystic components were observed in three lesions (43%). On T1-weighted images, the solid components were frequently homogeneous (5/7, 71%), and demonstrated isointensity in five lesions (71%) and hypointensity in two (29%) relative to the spinal cord. On T2-weighted images, the solid components were usually heterogeneous (6/7, 86%), and demonstrated hyperintensity in five lesions (71%) and isointensity in two (29%) relative to the spinal cord. The mean apparent diffusion coefficient value of the solid components was 0.967 × 10−3 mm2/s. Conclusion Parotid gland EMCs usually appeared as predominantly solid lesions with well-demarcated margins and capsules. A multinodular structure with internal septa was characteristics of EMCs.

To evaluate the differences in MR findings between nonhemophilic hemosiderotic synovitis (HS) and diffuse-type tenosynovial giant cell tumor (D-TGCT) of the knee. This study included 13 patients with histopathologically confirmed intra-articular hemosiderin deposition of the knee (eight with nonhemophilic HS and five with D-TGCT) who underwent preoperative MR imaging including T2*-weighted images (T2*WI). We retrospectively reviewed the MR images and compared MR findings between the two pathologies. Lateral meniscus tear and lateral articular cartilage injury (88% vs. 20%, p

To assess MR imaging findings of low-grade serous carcinoma (LGSC) of the ovary compared with those of serous borderline tumor (SBT). Twenty-four patients with histopathologically proven 7 LGSCs and 25 SBTs who underwent preoperative MR imaging were included. We retrospectively reviewed MR images and compared MR findings between the two pathologies. The predominantly solid lesions were marginally more frequent in LGSCs than in SBTs (43% vs. 8%, p = 0.057). All predominantly cystic LGSCs were multilocular cystic lesions with mural nodules. Predominantly solid LGSCs exhibited pure solid masses in 2 of 3 and solid masses with intratumoral cysts in 1 of 3. Papillary growth pattern with internal branching was observed only in 18 of 25 SBTs. Signal intensity ratio on T2-weighted images (4.48 ± 1.55 vs. 8.40 ± 3.53, p

This study aimed to assess the imaging features and natural course of hilar and mediastinal sarcoid-like reaction on 18F-fluorodeoxyglucose (FDG) PET/CT after the treatment of malignancies. Sixteen patients with the appearance of sarcoid-like reaction seen on 18F-FDG-PET/CT after treatment were included. Hilar and mediastinal lymph node metastases were pathologically or clinically ruled out. Posttreatment 18F-FDG-PET/CT imaging features were assessed. The maximum standardized uptake values of sarcoid-like reaction were 3.8–13.6 (mean 6.8). FDG uptake of hilar nodes was symmetrical in 12 (75%) patients and asymmetrical in 4 (25%). The time interval between the initiation of therapy and appearance of sarcoid-like reaction was 9–86 months (median 27.1 months). Among 14 patients who underwent further follow-up using 18F-FDG-PET/CT, sarcoid-like reaction regressed in 11 (79%) patients and did not regress in 3 (21%) patients. The time interval between the appearance of sarcoid-like reaction and its regression was 3–80 months (median, 8.5 months). After the treatment of malignancies, benign sarcoid-like reaction was rarely observed during follow-up. Although sarcoid-like reaction appeared a long time after the treatment of malignancies, it frequently and spontaneously regressed in a relatively short period of time.

Pleomorphic adenoma (PA) is the most common salivary gland tumor and is characterized by cytomorphological and architectural diversity. On CT and MR images, PAs are shown as well-defined lesions occasionally accompanied by characteristic lobulated contours. On T2-weighted images, typical PAs show marked hyperintensity, which reflects the abundant myxochondroid stroma, with a hypointense rim indicating the fibrous capsule. However, intratumoral signal intensity varies according to the cellular density, proportion of epithelial and stromal components, and type of stromal components. In addition, a variety of secondary histological changes, including fibrosis, lipometaplasia, ossification, cystic degeneration, and infarction, occur rarely in PAs; therefore, they are associated with difficulty in differential diagnosis from other salivary gland tumors. This review article describes the common and uncommon CT and MR imaging features of PA of the salivary glands.

To assess the MR imaging findings of vertebral involvement in Gorham–Stout disease (GSD), generalized lymphatic anomaly (GLA), and kaposiform lymphangiomatosis (KLA). Nine patients (three patients with GSD, three with GLA, and three with KLA) who underwent whole-spine MR examinations were included. MR findings of fatty marrow replacement and prolonged T1 and T2 lesions of the vertebrae were retrospectively assessed. Prolonged T1 and T2 lesions were defined as well-defined and round-, oval-, or geographic-shaped areas. Six patients [one (33%) patient with GSD, two (67%) with GLA, and three (100%) with KLA] showed both fatty marrow replacement and prolonged T1 and T2 lesions. Fatty marrow replacement was seen in the cervical spine of two (33%) patients, thoracic spine of six (100%), lumbar spine of six (100%), and sacral spine of two (33%). Prolonged T1 and T2 lesions were seen in the cervical spine of three (50%) patients, thoracic spine of three (50%), lumbar spine of six (100%), and sacral spine of three (50%). Both fatty marrow replacement and prolonged T1 and T2 lesions of the vertebrae could be observed in GSD, GLA, and KLA. The most commonly affected site was the lumbar spine, followed by the thoracic spine.

To assess the efficacy of diffusion-weighted (DW) MR imaging for differentiating between Warthin’s tumor and oncocytoma of the parotid gland. Forty-five histopathologically confirmed parotid gland tumors (41 Warthin’s tumors and 4 oncocytomas) were examined by MR imaging including DW imaging. 18F-fluorodeoxyglucose PET/CT was also performed in 9 Warthin’s tumors and 3 oncocytomas. We retrospectively reviewed the images and compared the MR signal intensities, apparent diffusion coefficients (ADCs), and maximum standardized uptake values (SUVmax) of the solid components between the two pathologies. The signal intensity ratios (SIRs) on both T2-weighted images (0.92 ± 0.18 vs 0.65 ± 0.13, p

A variety of neoplastic and non-neoplastic lesions of the parotid gland can present with a predominantly cystic architecture, and although radiologists frequently encounter cystic parotid tumors, other non-neoplastic lesions should also be included in the differential diagnoses of cystic parotid lesions. Non-neoplastic cystic lesions are usually classified as either congenital/acquired cystic lesions or inflammatory/infectious lesions. Adequate knowledge about these rare conditions is essential for appropriate diagnosis and optimal treatment strategy. This review article describes CT and MR imaging features of non-neoplastic cystic lesions of the parotid gland and provides helpful suggestions on the differential diagnoses for cystic parotid lesions.

To assess the correlation between T2*-weighted MR imaging and pathological findings of giant cell tumors (GCT) of bone. Of the 33 patients with histopathologically proven GCT of bone, 12 were examined using 1.5-T MR imaging, including T2*-weighted imaging, and were included in this study. The imaging and pathological findings of GCTs were compared between GCTs with and without hypointensity on T2*-weighted images (T2* hypointensity). T2* hypointensity was observed in 6 out of 12 (50%) GCTs. Septal formation (83% vs. 17%; p

To assess MR imaging findings of rebound adenoid hyperplasia after chemotherapy in pediatric patients with head and neck lymphoma. Eight pediatric patients with head and neck lymphoma treated with chemotherapy alone or concurrent chemoradiotherapy were included. All patients underwent pre-therapeutic assessment and post-therapeutic follow-up by MR imaging. The maximum thickness of the adenoid was assessed on transverse T2-weighted images. Rebound adenoid hyperplasia was defined as more than half of the pre-therapeutic thickness after severe atrophy. The pre-therapeutic maximum thickness of the adenoid ranged from 10 to 18 mm (mean, 15 mm). In all patients, the thickness of the adenoid dramatically decreased (mean 1 mm) within 1 year after the cessation of chemotherapy. On follow-up MR imaging, rebound adenoid hyperplasia was observed in five patients (63 %). Re-atrophy following rebound adenoid hyperplasia was observed in two patients (25 %), and no re-atrophy was observed in three patients (37 %). Rebound adenoid hyperplasia was not observed in three patients (37 %) who were in their late teens, and who had been treated with concurrent chemoradiotherapy. Rebound adenoid hyperplasia was often observed after chemotherapy in pediatric patients with lymphoma. MR imaging was useful for the assessment of rebound adenoid hyperplasia.

This study aimed to assess the imaging features and natural course of hilar and mediastinal sarcoid-like reaction onSixteen patients with the appearance of sarcoid-like reaction seen onThe maximum standardized uptake values of sarcoid-like reaction were 3.8-13.6 (mean 6.8). FDG uptake of hilar nodes was symmetrical in 12 (75%) patients and asymmetrical in 4 (25%). The time interval between the initiation of therapy and appearance of sarcoid-like reaction was 9-86 months (median 27.1 months). Among 14 patients who underwent further follow-up usingAfter the treatment of malignancies, benign sarcoid-like reaction was rarely observed during follow-up. Although sarcoid-like reaction appeared a long time after the treatment of malignancies, it frequently and spontaneously regressed in a relatively short period of time.

The purpose of this study was to determine whether adenoid cystic carcinomas (ACCs) of the maxillary sinus have features on CT and MR imaging. Nine patients with histopathologically proved maxillary sinus ACCs were included. The growth pattern was classified as expansile or destructive types on the basis of CT images. CT images were also reviewed for adjacent bony defects and MR images were reviewed for tumor extension. Fluid accumulation in the ipsilateral maxillary sinus was also assessed. The tumors had caused adjacent bony expansion with minimal bony defects in 4 patients whereas those in the remaining 5 patients had caused extensive destruction of adjacent bones comprising the maxillary sinus walls. Nasal cavity invasion was observed in 7 patients, retroantral fat pad invasion in 5, pterygopalatine fossa invasion in 4, and orbital invasion in 3. All 4 expansile ACCs were accompanied by accumulation of a small amount of fluid in the surroundings of the tumors, which was revealed as hyperintensity on T1-weighted images. The growth pattern of maxillary sinus ACCs can be classified into an expansile type with minimal bony defects and a destructive type with extensive bony defects.

To determine if a 20 % reduction in the contrast material dose is acceptable in the CT evaluation of patients with head and neck malignancy. Sixty consecutive patients (mean age 67 years) with head and neck malignancy underwent contrast-enhanced CT according to two different protocols: protocol A (80 mL of contrast material administered at an injection rate of 1.5 mL/s) and protocol B (100 mL at 1.9 mL/s). The enhancement of anatomical structures and detectability of metastatic nodes were compared between the two protocols. Pathologic analysis of the surgical resection served as the reference standard. CT numbers of the anatomical structures were not significantly different between the two protocols. Mean sensitivity (64 and 77 % for protocols A and B, respectively), specificity (78 and 84 %), and accuracy (74 and 83 %) tended to be higher for protocol B than for A, but no significant difference was found. Reducing the contrast material dose by 20 % did not significantly impair the enhancement of anatomical structures or the detection of metastatic cervical lymph nodes. Radiologists should therefore consider reducing the contrast material dose used in head and neck CT.

We describe the magnetic resonance (MR) imaging findings in a 20-year-old woman with a fibroepithelial polyp of the vulva. Within the lesion, abundant fibrous tissue was visualized as stratiform hypointense areas on T2-weighted magnetic resonance imaging (MRI) scans. At the center of the attachment site, clustered fatty tissue was revealed as linear hyperintense areas on T1-weighted MRI. A mild degree of edematous stroma including less fibrosis and cellularity was demonstrated as hyperintense areas on T2-weighted MRI and hypointense areas on T1-weighted MRI. Although the MRI findings of fibroepithelial polyps of the vulva are often similar to those of aggressive angiomyxoma, angiomyofibroblastoma, and cellular angiofibroma, a fibroepithelial polyp should be considered when radiological images demonstrate the following features: stratiform hypointense areas surrounded by patchy hyperintense areas on T2-weighted MRI and hyperintense areas on T1-weighted MRI.

The purpose of this study was to assess imaging findings of parapharyngeal space (PPS) pleomorphic adenoma (PA) in comparison with parotid gland (PG) PA retrospectively. Ten patients with PPS PAs and 66 with PG PAs were included. CT and MR images were reviewed for the size, presence of calcification or cystic degeneration, and MR signal intensity of solid components. The maximum diameter was greater in PPS PA (57.3 ± 11.4 mm) than in PG PA (28.7 ± 20.8 mm) (p

The authors present a rare case of spontaneous infarcted Warthin’s tumor of the parotid gland mimicking malignancies. CT and MR images demonstrated the presence of extensive necrosis and rim enhancement with ill-demarcated margins. Although the differentiation of infarcted Warthin’s tumors and primary salivary gland malignancies is challenging, radiologists should recognize this uncommon pathological condition.

We describe a case of the appearance of iodinated contrast agents in the same locations of twins' neonatal gastrointestinal tracts 1 day after maternal contrast-enhanced computed tomography (CT). The CT examination had been performed on the expectant mother for suspected deep venous thrombosis on the day previous to the twin delivery. At 23 h after the CT examination and after cesarean section, iodinated contrast agents appeared in the same place in the twins' neonatal gastrointestinal tracts, mainly in the ascending colon, on plain abdominal radiographs. Radiologists, obstetricians, and pediatricians should understand the mechanism of appearance of iodinated contrast agents in fetal gastrointestinal tracts when the expectant mother had been given iodinated contrast agents intravenously shortly before delivery.

We compared the diagnostic accuracy of fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) and PET/magnetic resonance imaging (MRI) fusion images for gynecological malignancies.A total of 31 patients with gynecological malignancies were enrolled. FDG-PET images were fused to CT, T1- and T2-weighted images (T1WI, T2WI). PET-MRI fusion was performed semiautomatically. We performed three types of evaluation to demonstrate the usefulness of PET/MRI fusion images in comparison with that of inline PET/CT as follows: depiction of the uterus and the ovarian lesions on CT or MRI mapping images (first evaluation); additional information for lesion localization with PET and mapping images (second evaluation); and the image quality of fusion on interpretation (third evaluation).For the first evaluation, the score for T2WI (4.68 +/- 0.65) was significantly higher than that for CT (3.54 +/- 1.02) or T1WI (3.71 +/- 0.97) (P0.01). For the second evaluation, the scores for the localization of FDG accumulation showing that T2WI (2.74 +/- 0.57) provided significantly more additional information for the identification of anatomical sites of FDG accumulation than did CT (2.06 +/- 0.68) or T1WI (2.23 +/- 0.61) (P0.01). For the third evaluation, the three-point rating scale for the patient group as a whole demonstrated that PET/T2WI (2.72 +/- 0.54) localized the lesion significantly more convincingly than PET/CT (2.23 +/- 0.50) or PET/T1WI (2.29 +/- 0.53) (P0.01).PET/T2WI fusion images are superior for the detection and localization of gynecological malignancies.