Yasutaka Kawamura

Tissue characterization of glioma by proton magnetic resonance spectroscopy and perfusion-weighted magnetic resonance imaging : glioma grading and histological correlation

BACKGROUND AND PURPOSEnOur intent was to clarify the usefulness of proton magnetic resonance spectroscopy (MRS) and perfusion-weighted magnetic resonance imaging (PW-MRI) in the grading of glioma.nnnMETHODSnTwenty-three consecutive patients with gliomas were investigated by both proton MRS and PW-MRI. For quantitative analysis, the metabolite data of the gliomas were estimated using the LCModel software. Receiver operating characteristic (ROC) curve analyses were also performed to assess which metabolite parameter was optimal for discrimination of glioma grade. From the PW-MRI data, the value of blood volume was measured on the parametric map corresponding to the location of MRS analysis. We then compared tumor blood volume with the amount of choline (Cho).nnnRESULTSnThe mean Cho/creatine (Cre) ratio was useful to discriminate between Grades II and III, and the mean lactate (Lac)/Cre ratio was found to be significantly different between Grades III and IV. ROC curve analysis showed that measurements involving Cho were superior indices for grading glioma compared with blood volume information. Furthermore, the correlation between tumor blood volume and the amount of choline was statistically significant.nnnCONCLUSIONnMRS may provide valuable information for glioma grading.

Differentiation of prostate cancer from benign prostate hypertrophy using dual-echo dynamic contrast MR imaging

OBJECTIVEnTo investigate the usefulness of dynamic contrast magnetic resonance (MR) imaging in the differentiation of prostate cancer (PC) from benign prostate hypertrophy (BPH).nnnMATERIALS AND METHODSnEleven PC patients and 13 BPH patients were entered into the analysis. The mean gradient (MG) was calculated from the T2* term-eliminated time-signal intensity curve obtained from dynamic contrast MR data, and the MG of PC and that of BPH were compared.nnnRESULTSnThe MG of PC was significantly higher than that of BPH. When the threshold value was set to 1.88% per s for discriminating PC from BPH, the sensitivity, specificity, and accuracy were 100, 85, and 92%, respectively.nnnCONCLUSIONnThe MG, which is derived from the T2* term-eliminated time-signal intensity curve, may be a useful index for differentiating PC from BPH.

Time course of arterial hyperintensity with fast fluid-attenuated inversion-recovery imaging in acute and subacute middle cerebral arterial infarction.

The purpose of this study was to evaluate the time course of arterial hyperintensity (AH) in acute and subacute cerebral infarctions of the middle cerebral artery (MCA) distribution by using fast fluid‐attenuated inversion‐recovery (FLAIR) imaging. A total of 40 FLAIR MR examinations were performed in 27 patients with MCA infarction within 13 days after ictus. Thirteen patients underwent two MR examinations during this period. Thrombotic or embolic infarctions were included in this study, but lacunar infarctions were excluded. The presence or absence of AH and the location of AH were analyzed. Overall, AH was found in 24 (60%) of 40 FLAIR examinations within 13 days after onset. AH was seen in 17 (100%) examinations less than 24 hours old, four (40%) of 10 examinations 1–4 days old, two (18%) of 11 examinations 5–9 days old, and one (50%) of two examinations 10–13 days old. AH was most frequently found at the sylvian fissure (87%), followed by the sulci (54%), and the horizontal segment of MCA (29%) in the affected MCA distribution. Although AH could be seen even at 13 days after ictus, the presence of AH declined over time. AH represented an early sign of acute embolic or thrombotic infarction. J. Magn. Reson. Imaging 2001;13:987–990.

Muscle MRI findings of X-linked spinal and bulbar muscular atrophy.

We report here muscle MRI findings of the lower limb in X-linked spinal and bulbar muscular atrophy (SBMA). T1-weighted imaging of muscle MRI disclosed that the thigh muscles, including the semimembranosus, biceps femoris longus and the vastus lateralis muscles, showed high intensity signals with atrophy. Contrarily, the sartorius, gracilis and rectus femoris muscles were comparably preserved. Not only the thigh muscles, but also the calf muscles including the gastrocnemius medialis and lateralis, and soleus muscles showed high intensity signals. In amyotrophic lateral sclerosis (ALS), the leg muscles are generally atrophic, but the selective pattern of fatty degeneration, seen in SBMA was not observed. Muscle MRI is a useful method of estimating the distribution and severity of SBMA in affected muscles.

Muscle MRI in Myotonic Dystrophy Type 1 with Foot Drop

The purpose of this study was to investigate the relationship of muscle MRI findings and gait disturbance in myotonic dystrophy type 1 (DM1) patients. Thirteen patients with DM1 were evaluated by manual muscle strength test and muscle MRI of the lower limb. All DM1 patients presenting with foot drop showed high intensity signals in the tibialis anterior muscles on T1-weighted imaging (p < 0.001). The patients presenting with gait disturbance showed high intensity signals in the semimembranosus, vastus intermedius and gastrocnemius medialis muscles, too. Disturbance of the gastrocnemius lateralis muscles was mild in all DM1 patients. The patients without gait disturbance showed no abnormalities, especially in tibialis anterior muscles on muscle MRI. Muscle MRI is useful for the detection of pathological muscles in DM1 patients with gait disturbance.

Usefulness of fat-suppression magnetic resonance imaging for oral and maxillofacial lesions

In magnetic resonance imaging (MRI) of the oral and maxillofacial region, where large amounts of fat are normally present, the high signal intensity of fat on T1-weighted images (T1WI) and the chemical-shift artifact have limited the utility of paramagnetic contrast agents. Eliminating fat signal by fat-suppression techniques can increase the value of contrast-enhanced MRI. The present study was designed to evaluate the utility and role of chemical-shift imaging for fat suppression in the detection of oral and maxillofacial lesions in 22 patients (17 with malignant tumors, two with benign tumors, and three with inflammation). The depiction of lesions on the postcontrast fat-suppression T1WI was compared with that of conventional pre- and postcontrast T1 and T2WI on a four-grade scale (grades 0-3). The postcontrast fat-suppression T1WI (average grade, 2.86) were significantly superior to the precontrast T1WI (0.82) and postcontrast T1WI (1.86) and T2WI (1.68). Postcontrast fat-suppression T1WI were particularly beneficial in the detection of central necrosis or extracapsular invasion of metastatic neck lymph nodes as well as in defining the lesion extent at fat-containing areas such as the bone marrow or cheek. These findings demonstrated that the fat-suppression technique is extremely useful in the delineation of oral and maxillofacial lesions without increase of the scan time or image postprocessing procedures.

Diagnostic Performance and Patient Acceptance of Reduced-Laxative CT Colonography for the Detection of Polypoid and Non-Polypoid Neoplasms: A Multicenter Prospective Trial

Purpose To evaluate the diagnostic accuracy and patient acceptance of reduced-laxative computed tomographic (CT) colonography without computer-aided detection (CAD) for the detection of colorectal polypoid and non-polypoid neoplasms in a population with a positive recent fecal immunochemical test (FIT). Materials and Methods Institutional review board approval and written informed consent were obtained. This multicenter prospective trial enrolled patients who had positive FIT results. Reduced-laxative CT colonography and colonoscopy were performed on the same day. Patients received 380 mL polyethylene glycol solution, 20 mL iodinated oral contrast agent, and two doses of 20 mg mosapride the day before CT colonography. The main outcome measures were the accuracy of CT colonography for the detection of neoplasms 6 mm or larger in per-patient and per-lesion analyses and a survey of patient perceptions regarding the preparation and examination. The Clopper-Pearson method was used for assessing the 95% confidence intervals of per-patient and per-lesion accuracy. Survey scores were analyzed by using the Wilcoxon and χ2 tests. Results Three hundred four patients underwent both CT colonography and colonoscopy. Per-patient sensitivity, specificity, positive predictive value, and negative predictive value of CT colonography for detecting neoplasms 10 mm or larger were 0.91 (40 of 44), 0.99 (255 of 258), 0.93 (40 of 43), and 0.98 (255 of 259), respectively; these values for neoplasms 6 mm or larger were 0.90 (71 of 79), 0.93 (207 of 223), 0.82 (71 of 87), and 0.96 (207 of 215), respectively. Per-lesion sensitivities for detection of polypoid and non-polypoid neoplasms 10 mm or larger were 0.95 (40 of 42) and 0.67 (six of nine), respectively; those for neoplasms 6 mm or larger were 0.90 (104 of 115) and 0.38 (eight of 21), respectively (P < .05 for both). Patient acceptance of preparation and examination with CT colonography was significantly higher than that with colonoscopy, and 62% (176 of 282) of patients would choose CT colonography as the first examination if they have a positive FIT result in the future. Conclusion Reduced-laxative CT colonography without CAD is accurate in the detection of polypoid neoplasms 6 mm or larger but is less accurate in the detection of non-polypoid neoplasms. Reduced-laxative CT colonography has high patient acceptance and is an efficient triage examination for patients with a positive FIT.

The clinical value of ferric ammonium citrate: A positive oral contrast agent for T1‐weighted MR imaging of the upper abdomen

This study was undertaken to determine whether ferric ammonium citrate (FAC), a positive magnetic resonance (MR) contrast agent, is of clinical value in demonstrating or excluding pathology of the upper gastrointestinal tract. A retrospective review was performed of pre‐ and post‐FAC studies of MR examinations in 203 patients from phase II and III clinical trials in whom final diagnoses had been established based on the results of biopsy, surgery, or independent imaging procedures. Two independent reviewers made randomized and blinded assessments of the stomach, duodenum, and pancreas. FAC significantly increased the certainty of diagnosis for normal studies of the stomach and duodenum for both readers (P < 0.001) and for abnormal studies of the stomach for one reader (P = 0.004). FAC also significantly increased the certainty of diagnosis for normal pancreas for one reader (P < 0.001). FAC significantly (P < 0.001) increased accuracy and specificity for diagnoses involving the stomach and duodenum for both readers and for one reader for the pancreas. There was significant improvement in sensitivity for gastric diagnoses (P = 0.013) for one reader but not for the duodenum or pancreas. We conclude that FAC is helpful in demonstrating and excluding upper gastrointestinal pathology on MR. J. Magn. Reson. Imaging 2000;12:702–707.

Safety and efficacy of a novel hepatobiliary MR contrast agent, Gd-DTPA-DeA: Results of phase I and phase II clinical trials

To assess the safety, effective dose, and efficacy of a novel hepatobiliary MR contrast agent Gd‐DTPA‐DeA for imaging liver tumors, from the clinical phase I and phase II trials in Japan.

Metabolic alterations in implanted human tumors after combined radiation and hyperthermia therapy measured by in vivo 31P MRS

The bioenergetics of human lung tumors grown subcutaneously in KSN nude mice, were studied in vivo using 31P NMR spectroscopy up to 27 days following radiotherapy and/or hyperthermia. Six tumors were treated with radiation (20 Gy, single fraction) and hyperthermia (44 degrees C, 10 min). There was a significant increase in the ratio of inorganic phosphate to beta-nucleoside triphosphate (Pi/beta-NTP) 24 h after radiation plus hyperthermia (p < .01), but a significant decrease 6 days after the treatment (p < .05) relative to untreated controls. Furthermore, the combined therapy produce significant acidosis at 24 h post therapy followed by significant alkalosis at 6 days compared to no treatment. This biphasic pattern was also significant in comparison with the pretreatment values of Pi/beta-NTP and pH. The combined therapy produced not only tumor decline at 24 h indicated by increased Pi/beta-NTP ratio and acidic pH shift, but also metabolic activation of tumor cells at 6 days indicated by decreased Pi/beta-NTP ratio and alkalotic pH shift. The tumor blood flow estimated by hydrogen ion clearance curves were completely depleted at 24 h and fully recovered to pretreatment level at 6 days. Reasonable close negative correlation between the blood flow and Pi/beta-NTP ratio (r = -0.59, p < .01) indicated that the two contrasting physiological states were closely related to tumor perfusion status. The 31P spectra of tumors following the combined therapy were concluded to demonstrate additive physiological effects of hyperthermia and radiation.