Mayumi Takeuchi

Diffusion-Weighted Magnetic Resonance Imaging of Endometrial Cancer: Differentiation from Benign Endometrial Lesions and Preoperative Assessment of Myometrial Invasion

Background: Uterine endometrial cancer is the most common gynecologic malignancy, and benign endometrial hyperplasia or polyps should be differentiated from endometrial cancer. In evaluating endometrial cancer on magnetic resonance imaging (MRI), the assessment of the depth of myometrial invasion is important because it closely correlates with the patients prognosis. Purpose: To verify the feasibility of diffusion-weighted magnetic resonance imaging (DWI) to distinguish benign and malignant endometrial lesions, and to evaluate myometrial invasion of endometrial cancer. Material and Methods: Sixty-seven endometrial lesions including 45 cancers and 22 benign lesions (hyperplasia and polyps) were evaluated by DWI with apparent diffusion coefficient (ADC) measurement. The staging accuracies of DWI and gadolinium-enhanced T1-weighted images in the assessment of myometrial invasion were evaluated in 33 patients with endometrial cancer. Results: The ADC values (×10−3 mm2/s) in cancer and benign lesions were 0.84±0.19 and 1.58±0.36, respectively (P<0.01). The staging accuracy (superficial or deep myometrial invasion) was 94% for DWI and 88% for gadolinium-enhanced T1-weighted images. Coexisting adenomyosis and infiltrative myometrial invasion caused staging errors on gadolinium-enhanced T1-weighted images, whereas DWI could demonstrate the tumor extent correctly. Conclusion: DWI provides helpful information in evaluating benign and malignant endometrial lesions.

Diffusion-weighted magnetic resonance imaging of ovarian tumors: differentiation of benign and malignant solid components of ovarian masses.

Objective: We evaluated the feasibility of diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) measurement in differentiating benign and malignant ovarian tumors. Methods: Surgically proven 49 ovarian tumors (39 malignant/borderline malignant and 10 benign) were examined. Results: The solid portion of all 39 malignant tumors showed homogeneous or heterogeneous high intensity on DWI, whereas only 3 of the 10 benign tumors (3 thecomas) showed high intensity. The mean (SD) ADC value in the 39 malignant tumors (1.03 [0.19]) was significantly lower than that in 10 benign tumors (1.38 [0.30]). A relatively low ADC (1.08-1.20) in the 3 thecomas may reflect their abundant cellular nature, and the presence of low intensity on T2-weighted images was suggestive for benign fibrous tumor. Conclusions: Low intensity on DWI with high ADC may suggest benign lesions; however, it may be occasionally difficult to differentiate benign and malignant lesions only on the basis of DWI.

High-b-Value Diffusion-Weighted Magnetic Resonance Imaging of Pancreatic Cancer and Mass-Forming Chronic Pancreatitis: Preliminary Results

Background: Mass-forming chronic pancreatitis may mimic a pancreatic cancer on dynamic computed tomography (CT) and magnetic resonance (MR) imaging, and preoperative differential diagnosis is often difficult. Recently, the usefulness of diffusion-weighted MR imaging (DWI) in the diagnosis of pancreatic cancer has been reported in several studies. Purpose: To determine whether high-b-value DWI can distinguish pancreatic cancer from benign mass-forming chronic pancreatitis. Material and Methods: Twenty pancreatic cancers and four cases of mass-forming chronic pancreatitis were evaluated by high-b-value DWI (b=800 s/mm2). The signal intensity on DWI was visually evaluated, and the isotropic apparent diffusion coefficients (ADCs) were measured. Results: All twenty pancreatic cancers showed high signal intensity (18 showed very high, two showed slightly high) on DWI. None of the mass-forming chronic pancreatitis cases showed very high intensity (three showed iso to low, one showed slightly high) on DWI. The ADCs in the pancreatic cancer and mass-forming chronic pancreatitis were 1.38±0.32×10−3 mm2/s and 1.00±0.18×10−3 mm2/s, respectively (P<0.05). Conclusion: On high-b-value DWI, most pancreatic cancers showed very high signal intensity, and may hence be distinguished from benign mass-forming chronic pancreatitis based on our preliminary results.

Serial brain imaging analysis of stroke-like episodes in MELAS

We report 2 patients of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) and consider the pathophysiology of stroke-like lesions, using magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI) on MRI, perfusion imaging on MRI, and 1H magnetic resonance spectroscopy (1H-MRS). In Patient 1, T2-weighted imaging (T2-WI) on MRI at onset and even at 44 days after onset of the stroke-like episode showed high intensity in left parietal, temporal, and occipital lobe lesions. In the temporal lobe lesion, the apparent diffusion coefficient (ADC) at 44 days after onset was higher (average: 1.219x10(-3)mm2/s) than that in a normal region (average: 0.796x10(-3)mm2/s). (1)H-MRS of the left parietal lobe lesion at the same day showed a decrease in N-acetylaspartate/(creatine+phosphocreatine) (NAA/Cr) (0.43) and a peak in lactate. 1H-MRS of the contralateral side at the same day showed NAA/Cr (1.57) and no peak in lactate. Thereafter, ADC gradually decreased and NAA/Cr gradually increased, and the peak in lactate disappeared in the lesion. In Patient 2, T2-WI at onset showed high intensity in bilateral occipital lobe lesions. In the left occipital lobe lesion, ADC at the same day was higher (1.082x10(-3)mm2/s) than that in a normal region (average: 0.841x10(-3)mm2/s). (1)H-MRS of the left occipital lobe lesion at the same day showed a decrease of NAA (3.0mM) and a peak in lactate (13.1mM) (measured by LCModel). In 1H-MRS of the normal left parietooccipital lobe at 4 months before onset, NAA was 7.6mM and there was no peak in lactate (0mM). Perfusion imaging at onset showed high intensity in bilateral occipital lobes, which indicated hyperperfusion in stroke-like lesions. Thereafter, ADC gradually decreased and the peak in lactate partially decreased, and the low concentration of NAA persisted (regardless of the partial recovery) in the lesion. These results suggest that the stroke-like episodes is related to vasogenic edema, hyperperfusion, and neuronal damage. Acute oxidative phosphorylation defect may have a crucial role in the pathophysiology of stroke-like episodes.

Susceptibility-Weighted MRI of Endometrioma: Preliminary Results

OBJECTIVE Susceptibility-weighted MRI combines magnitude and phase information from fully velocity-compensated gradient-echo sequences and depicts as signal voids the susceptibility effects caused by local inhomogeneity of the magnetic field. Our objective, based on MRI of 60 pathologically proven ovarian cystic lesions, including 42 endometriomas and 18 nonendometrial cysts, was to evaluate hemosiderin deposition within the walls of endometriomas on susceptibility-weighted MR images. Two radiologists blinded to the final diagnosis retrospectively reviewed the images in consensus. CONCLUSION On susceptibility-weighted MR images, punctate or curved linear signal voids along the cyst wall were observed in 39 endometriomas (92.9%) and in no nonendometrial cysts. The signal voids were more prominent on 3-T than on 1.5-T images, reflecting the higher sensitivity of 3-T MRI to magnetic susceptibility effects. Thirty-two endometriomas (76.2%) met definitive MRI criteria, that is, hyperintensity on T1-weighted images and hypointensity on T2-weighted images, and 41 endometriomas (97.6%) were correctly diagnosed with susceptibility-weighted MRI.

Adenomyosis: Usual and Unusual Imaging Manifestations, Pitfalls, and Problem-solving MR Imaging Techniques

Adenomyosis is a common nonneoplastic gynecologic disease characterized by the presence of ectopic endometrium within the myometrium. On T2-weighted magnetic resonance (MR) images, typical adenomyosis appears as an ill-demarcated low-signal-intensity lesion with uterine enlargement. However, various physiologic or pathologic states such as amount of functional endometrial tissue, phase of the menstrual cycle, endogenous hormonal abnormality, and exogenous hormonal stimulation may affect the MR imaging appearance of adenomyosis and may result in a tumorlike appearance. Problem-solving MR imaging techniques used in diagnosis of adenomyosis include diffusion-weighted imaging, susceptibility-weighted imaging, hydrogen 1 MR spectroscopy, cine MR imaging, and high-resolution MR imaging at 3 T. Adenomyotic lesions that show high signal intensity relative to the outer myometrium on T2-weighted images mimic malignancies such as leiomyosarcoma and endometrial stromal sarcoma. In these cases, a relatively high apparent diffusion coefficient at diffusion-weighted imaging and a low choline peak at MR spectroscopy are suggestive of a benign lesion. Small hemorrhagic foci suggestive of an adenomyotic lesion are well demonstrated as signal voids at susceptibility-weighted imaging. Cine MR imaging is useful in differentiating transient myometrial contraction from focal adenomyosis. High-resolution MR imaging at 3 T demonstrates anatomically detailed structures and may improve diagnostic accuracy in differentiating adenomyosis from its mimics, such as low-grade endometrial stromal sarcoma.

Hyperintense uterine myometrial masses on T2-weighted magnetic resonance imaging: differentiation with diffusion-weighted magnetic resonance imaging.

Objective: The objective was to determine whether diffusion-weighted imaging (DWI) might be useful in differentiating uterine leiomyomas exhibiting hyperintensity on T2-weighted images from malignant lesions. Methods: Thirty-four uterine myometrial lesions including 7 malignant tumors and 27 leiomyomas (6 cellular leiomyomas [CLM] and 21 degenerated leiomyomas [DLM]) were evaluated. The apparent diffusion coefficients (ADC) in cellular portions of the lesions were measured (10−3 mm2/s). Results: All malignant tumors showed high signal intensity on DWI with low ADC (mean [SD], 0.79 [0.26]), which was significantly lower (P < 0.01) than that in benign leiomyomas (1.51 [0.33]). The ADC in CLM (1.18 [0.16]) was significantly lower (P < 0.01) than that in DLM (1.60 [0.30]) and higher (P < 0.05) than that in malignant tumors. Conclusions: It was difficult to differentiate malignant tumors from leiomyomas on the basis of signal intensity on DWI; however, the ADC measurement may be helpful to distinguish malignant tumors, CLM, and DLM.

Pathologies of the uterine endometrial cavity: usual and unusual manifestations and pitfalls on magnetic resonance imaging

The endometrial cavity may demonstrate various imaging manifestations such as normal, reactive, inflammatory, and benign and malignant neoplasms. We evaluated usual and unusual magnetic resonance imaging (MRI) findings of the uterine endometrial cavity, and described the diagnostic clues to differential diagnoses. Surgically proven pathologies of the uterine endometrial cavity were evaluated retrospectively with pathologic correlation. The pathologies included benign endometrial neoplasms such as endometrial hyperplasia and polyp, malignant endometrial neoplasms such as endometrial carcinoma and carcinosarcoma, endometrial–myometrial neoplasm such as endometrial stromal sarcoma, pregnancy-related lesions in the endometrial cavity such as gestational trophoblastic diseases (hydatidiform mole, invasive mole and choriocarcinoma) and placental polyp, myometrial lesions simulating endometrial lesions such as submucosal leiomyoma and some adenomyosis, endometrial neoplasms simulating myometrial lesions such as adenomyomatous polyp and endometrial lesions arising in the hemicavity of a septate/bicornate uterus, and fluid collections in the uterine cavity (hydro/hemato/pyometra). It is important to recognize various imaging findings in these diseases, in order to make a correct preoperative diagnosis.

Magnetic resonance manifestations of decidualized endometriomas during pregnancy.

Objective: Decidual changes of endometrial tissue in endometriomas during pregnancy may manifest as mural nodules and mimic malignant transformation. We evaluated magnetic resonance findings of decidualized ovarian endometriomas for the differentiation from malignant transformation. Methods: Magnetic resonance manifestations of 5 decidualized ovarian endometriomas were evaluated. High b-value diffusion-weighted images were performed in 3 cases. Results: The mural nodules were demonstrated as linear, small nodular, broad-based nodular, or polypoid structures, which showed prominent hyperintensity on T2-weighted images and on diffusion-weighted images similar to normal endometrium or placenta. The apparent diffusion coefficient of decidualized mural nodules was significantly higher than that of malignant mural nodules of 7 ovarian cancers. Conclusions: Endometrioma with prominent hyperintense mural nodules on T2-weighted images in a pregnant woman is highly suggestive for decidualized endometriomas. Diffusion-weighted images with the apparent diffusion coefficient measurement may help the diagnosis of this rare entity.

Diffusion-weighted magnetic resonance imaging of urinary epithelial cancer with upper urinary tract obstruction: preliminary results.

Background: Various malignant tumors of the body show high signal intensity on diffusion-weighted magnetic resonance imaging (DWI). In the genitourinary region, DWI is expected to have a role in detecting urinary epithelial cancer noninvasively. Purpose: To demonstrate the feasibility of DWI for the diagnosis of urinary epithelial cancer with upper urinary tract obstruction. Material and Methods: Twenty upper urinary tract cancers in 16 patients were evaluated by high-b-value DWI (b=800s/mm2). The signal intensity was visually evaluated, and the apparent diffusion coefficients (ADCs) were measured. Results: All urinary epithelial cancers showed high signal intensity on DWI. The ADC in cancerous lesions was 1.31±0.27×10−3 mm2/s, which was significantly lower than that of the lumens of the ureter or renal pelvis (3.32±0.44×10−3 mm2/s; P<0.001). Maximum intensity projection images of DWI in combination with static-fluid MR urography provided three-dimensional entire urinary tract imaging with the extension of tumors. Conclusion: DWI is useful in the tumor detection and in evaluating the tumor extension of urinary epithelial cancer in patients with upper urinary tract obstruction.