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Y O Tanaka

Publications and source records attributed to Y O Tanaka.

At least 19 recordsLinked to original sources
PubMed2004

Pelvic imaging: multicystic uterine cervical lesions. Can magnetic resonance imaging differentiate benignancy from malignancy?

PURPOSE: To evaluate whether magnetic resonance imaging (MRI) can be used to differentiate between malignant and benign multicystic uterine cervical lesions. MATERIAL AND METHODS: Twenty-two patients with cervical adenocarcinomas, including minimal deviation adenocarcinoma, and five patients with benign multicystic lesions were classified as a percentage of solid components on MRI. Cystic components were further classified by average cyst diameter and signal intensity of the cyst fluid on T1WI. RESULTS: All nine of the entirely solid lesions were malignant. In contrast, two of the entirely cystic lesions were benign. Ten of the ordinary adenocarcinomas had both solid and cystic components. However, three of the 16 solid and cystic lesions were benign. Lesions composed of cysts smaller than 5mm tended to be malignant; however, some lesions composed of larger cysts were also malignant. Three of 5 lesions with low-signal and 7 of 10 with intermediate-signal fluid were malignant. CONCLUSION: The malignancy potential was higher in the lesions with a higher percentage of solid components. However, determining whether multicystic lesions were benign or malignant based on the existence of solid components, the average cyst size, and the signal intensity of cyst fluid was impossible. Although a multicystic lesion with solid components in the deep cervical stroma had been reported as a MR finding of a minimal deviation adenocarcinoma, this does not appear to be pathognomonic.

Adenocarcinoma↗
PubMed2002

A decidualized endometrial cyst in a pregnant woman: a case observed with a steady-state free precession imaging sequence.

Decidual changes of the ectopic endometrial stroma during pregnancy are well known among pathologists and obstetricians. However, they appear very similar to endometrial cysts with malignant transformation when imaged. Balanced fast field echo (BFFE) is a steady-state free precession imaging sequence and its contrast is decided by the T1/T2 ratio. The authors report a case of a decidualized endometrial cyst in which mural nodules were isointense with the nomotopic decidualized endometrium on T1- and T2-weighted images and BFFE. Isointensity with the nomotopic endometrium is an MR characteristic that can differentiate a decidualized endometrial cyst from malignant transformation. BFFE is a good alternative sequence during pregnancy because of its shorter acquisition time and lower radiofrequency absorption.

Adult↗
PubMed2001

High temporal resolution dynamic contrast MRI in a high risk group for placenta accreta.

Antenatal diagnosis of placenta accreta with MR is not easy even now because T2-weighted images (T2WI) cannot differentiate chorionic villi from decidua basalis. We performed dynamic contrast MRI to study whether trophoblastic villi could be separately demonstrated from the decidua basalis, and whether the contrast resolution between the placenta and myometrium could improve compared to T2WI. Six pregnant women with prior cesarean section were examined at 34-38 gestational weeks. Sagittal T2-weighted images with fast spin echo sequences and dynamic contrast studies with fast field echo sequence every 10-14 s after contrast injection were performed. We analyzed the enhancing pattern of the placenta and compared the contrast between placenta and myometrium. We reviewed medical records to identify complications during the placental delivery and the complications of their newborns. In the early phase after contrast enhancement, multiple foci of the strong lobular enhancement were observed in all cases. Other parts of placenta were slowly but strongly enhanced following them. We speculated that the former corresponded to intervillous space and the latter decidua basalis. The contrast between placenta and myometrium tended to be distinct near the inner cervical os on both T2WI and dynamic contrast study. On the other hand, it was indistinct in the upper part of the uterine body on T2WI despite it was clearly demonstrated on dynamic contrast study. The placentae were delivered without any complication in all cases. Although two neonates showed fetal distress, none of the infant remained any sequelae at the time of the discharge. The other four were well although one of them complicated with meconium staining. As dynamic contrast MRI can differentiate chorionic villi and decidua basalis, and can provide excellent contrast between placenta and myometrium at anywhere within the uterus, it may be a promising technique for antepartum diagnosis of the placenta accreta.

Chorionic Villi↗
PubMed2000

MRI of gynaecological solid masses.

Differential diagnosis of gynaecological masses is sometimes difficult, as there are so many histological types. However, magnetic resonance characteristics of some gynaecological tumours have been reported past several years. On the basis of the recent literature, we have made a decision tree for differential diagnosis of solid gynaecological tumours, in which there are some important divergences. Bilateral disease and invasive growth are malignant signs in most cases. Specific findings for different tumour types include: fibrovascular septa in dysgerminomas; preserving ovarian follicles in round cell tumours; pseudolobular patterns in young patients in sclerosing stromal tumours; and extremely hypointense masses on T2WI in Brenner tumours. Distinguishing between sex-cord stromal tumours, Brenner tumours and metastatic tumours may be hard, however, especially in middle age, because they all tend to show well-demarcated, hypointense masses on T2WI. Disproportionately clear zonal anatomy of the uterus, enlarged uterus and thickened endometrium, which are indirect findings of oestrogen-producing tumours, are useful diagnostic findings in children and postmenopausals.

Adult↗
PubMed2000

Ovarian carcinoma in patients with endometriosis: MR imaging findings.

OBJECTIVE: Various types of malignancy can develop in patients with endometriosis. Enhancing mural nodules have been reported as an imaging characteristic of malignant transformations. We evaluated contrast-enhanced MR imaging to determine the optimum sequence to reveal mural nodules and other characteristics of malignant transformations. MATERIALS AND METHODS: We examined 10 patients with pathologically proven ovarian adenocarcinoma in endometriosis and 10 patients (the control group) with ovarian endometrioma suggestive of malignant transformation on the basis of sonographic findings. We analyzed the size and nature of the endometriomas in each patient. We compared four types of contrast-enhanced MR imaging to determine which sequence best revealed mural nodules. RESULTS: In the malignant and control groups, 80% of the cysts with findings suggestive of malignant transformation showed unilateral disease or larger endometrial cysts on the suggestive side than on the contralateral side. High signal intensity on T1-weighted images and low signal intensity on T2-weighted images relative to the myometrium were observed only in two of 10 malignant endometrial cysts and in all control cysts. All malignant endometriomas had small mural nodules with low signal intensity on T1-weighted contrast-enhanced images. Only three benign endometriomas had mural nodules and none of them enhanced. The enhancement of mural nodules was easily seen on dynamic subtraction imaging. CONCLUSION: On the basis of our findings, endometrial cysts with malignant transformation rarely show low signal intensity on T2-weighted images and usually have enhancing mural nodules. Because the enhancement of mural nodules is often difficult to evaluate on conventional T1-weighted images, dynamic subtraction imaging can be valuable.

Adenocarcinoma↗
PubMed2000

[Pitfalls in diagnosing female genital tract: ovarian disease].

Because the ovaries are composed of surface epithelial cells, germ cells, sex-cord stromal cells and stroma, tumors of various histopathologies arise from this organ. In addition, a number of non-tumorous diseases form adnexal masses such as endometriosis and tubo-ovarian abscess. Furthermore, tumors arising from other pelvic organs are sometimes mis-diagnosed as ovarian tumors. Therefore, it is difficult to predict the histological type of an adnexal mass prior to surgery even though the MR characteristics of various ovarian tumors have been reported. Because of the large number of patients, there are two 'common sense' considerations in diagnosing female intrapelvic masses in daily practice: 1) solid adnexal masses are malignant ovarian tumors, 2) predominantly cystic intrapelvic masses originate from the ovaries. However, certain tumors do not conform to common sense. For example, fibrothecomas and benign teratomas are exceptions to 1), and subserosal pedunculated leiomyomas and cystic adenomyosis are exceptions to 2). The MR characteristics, pitfalls to diagnosis, and clues to correct imaging diagnosis are discussed in this review.

Diagnosis, Differential↗
PubMed1999

Differential diagnosis of gynaecological "stained glass" tumours on MRI.

Although multilocular cystic gynaecological masses in which the loculi show variable signal intensity on both T1 and T2 weighted images have been considered to be mucinous cystadenoma or adenocarcinoma, other gynaecological tumours can demonstrate this "stained glass" appearance. These include mature cystic teratoma, fibrothecoma, endometrioma, Brenner's tumour of the ovary and degenerated leiomyoma of the uterus, all of which may mimic mucinous tumours of the ovaries.

Diagnosis, Differential↗
PubMed1998

Mature teratoma of the posterior mediastinum.

The vast majority of germ cell tumors in the thorax arise at or near the thymus. We report a case of a 41-year-old man with mature teratoma of the posterior mediastinum. He was asymptomatic and was incidentally found to have a posterior mediastinal mass. Computed tomography was helpful in suggesting a diagnosis of mature teratoma by demonstrating the presence of fat and calcification. The differential diagnosis included neurogenic tumors, liposarcoma, and extramedullary hematopoiesis.

Adult↗
PubMed1998

Well-differentiated liposarcoma of the retroperitoneum with a fat-fluid level: US, CT, and MR appearance.

We report a case of retroperitoneal liposarcoma with a fat-fluid level that has not been previously described. A 36-year-old man presented with abdominal distension. Ultrasonography, CT, and MR imaging showed a tumor with a fat-fluid level; nondependent fluid was characteristic of fat. Liposarcoma should be included in the differential diagnosis of tumors exhibiting a fat-fluid level.

Adipose Tissue↗
PubMed1997

Multishot echoplanar MR imaging of the female pelvis: comparison with fast spin-echo MR imaging in an initial clinical trial.

OBJECTIVE: The purpose of this study was to apply multishot echoplanar MR imaging (EPI) to the female pelvis and compare image quality with that of fast spin-echo MR imaging. SUBJECTS AND METHODS: Twenty-one patients with suspected pelvic disease and five healthy female volunteers were prospectively examined. MR imaging was obtained using an EPI-capable 1.0-T imager and a pelvic phased-array coil. Axial EPI and fast Spin-echo sequences were obtained at identical image locations in each patient and volunteer. Spin-echo EPI images were obtained using a multishot number of 16. Acquisition time for each EPI sequence was 2 min 10 sec. Fat-suppressed T2-weighted fast spin-echo images were obtained in 2 min 12 sec. Paired EPI and fast spin-echo MR images were independently evaluated by three reviewers. RESULTS: Delineation of the perivaginal and parametrial venous plexus on EPI was rated superior to the fast spin-echo images in 62 (77%) of 81 cases. On EPI, uterine zone anatomy and ovary visualization were judged to be inferior in 44 (56%) of 78 cases and in 18 (33%) of 54 cases, respectively. For delineation of uterine abnormalities, including leiomyoma and adenomyosis, both sequences performed almost equally well. However, ovarian cystic lesions were revealed more precisely by the fast spin-echo sequence. An overall fat-suppression effect was seen on EPI images in 62 (77%) of 81 cases. CONCLUSION: Multishot EPI cannot replace fast spin-echo sequences for imaging the female pelvis; however, because EPI has a potent fat-suppression effect and heavily T2-weighted contrast, EPI sequences can be a valuable adjunct to routine examination.

Echo-Planar Imaging↗
PubMedDate not supplied

Uterus didelphys associated with obstructed hemivagina and ipsilateral renal agenesis: MR findings in seven cases.

BACKGROUND: Although a specific syndrome of the uterus didelphys, obstructive hemivagina, and ipsilateral renal agenesis had been reported in gynecologic literatures, it is not familiar to radiologists. We introduce this syndrome with radiological, especially MR findings. METHODS: Imaging findings and medical records of seven patients with this syndrome were retrospectively reviewed. RESULTS: MR clearly demonstrated uterus didelphys with obstructed hemivagina in six of the seven patients. A remaining one showed uterus didelphys with left-sided hematometra and hematosalpinx who had undergone vaginal septum incision prior to the MR. We could also recognize ipsilateral renal agenesis in all five patients, in whom renal areas were examined on MR. After vaginal septum resection, symptoms disappeared in six patients. We could observe the disappearance of the obstructive complications with MR in three patients. CONCLUSIONS: MR can do much for the early diagnosis and the prevention against further complications of this condition because it can demonstrate the müllerian duct anomaly complicated with obstructed hemivagina in detail and even ipsilateral renal agenesis.

Adolescent↗
PubMedDate not supplied

Angiomyolipoma of the liver: significance of CT and MR dynamic study.

Angiomyolipoma is a benign mesenchymal tumor that has been reported frequently in the kidney but rarely in the liver. In the present study, we present four cases of hepatic angiomyolipoma with different radiologic appearances, discuss differential diagnosis, and review previously reported cases. One of our cases was followed for 8 years. Computed tomography (plain, enhanced, and dynamic study), magnetic resonance imaging (T1-weighted spin echo, T2-weighted spin echo, and dynamic study), ultrasonography, and angiography were performed in all cases. Although different radiologic appearances were observed in the tumors, based on different proportions of fat, blood vessels, and muscle, three cases were diagnosed as angiomyolipoma. In one case, it was quite difficult to make radiologic diagnosis; hepatocellular carcinoma with fatty metamorphosis in part was most likely suspected, but histopathological examination revealed angiomyolipoma with few fat elements. In the present study, early and prolonged enhancement of the lesion with the special pattern of time density/intensity curve was significant for angiomyolipoma, and we suggest that preoperative radiologic diagnosis of the lesion is possible in most of the cases. However, it can be quite difficult to distinguish angiomyolipoma from some hepatocellular carcinomas with fatty metamorphosis.

Adipose Tissue↗