Nobukazu Abe

Role of perfusion-weighted imaging at 3 T in the histopathological differentiation between astrocytic and oligodendroglial tumors

OBJECTIVE The differentiation of oligodendroglial tumors from astrocytic tumors is important clinically, because oligodendroglial tumors are more chemosensitive than astrocytic tumors. This study was designed to clarify the usefulness of 3T MR perfusion imaging (PWI) in the histopathological differentiation between astrocytic and oligodendroglial tumors. This is because there is a growing interest in the diagnostic performance of 3T MR imaging, which has the advantages of a higher signal-to-noise ratio (SNR) and greater spatial and temporal resolution. MATERIALS AND METHODS This study retrospectively included 24 consecutive patients with supratentorial, WHO grade II and III astrocytic and oligodendroglial tumors (7 astrocytic, 10 oligoastrocytic, and 7 oligodendroglial tumors) that were newly diagnosed and resected between November 2006 and December 2009 at Hiroshima University Hospital. These patients underwent dynamic susceptibility contrast-enhanced (DSC) PWI relative cerebral blood volume (rCBV) measurements before treatment. Astrocytic tumors were designated as the astrocytic group, and oligoastrocytic and oligodendroglial tumors as the oligodendroglial group. The regions of interest with the maximum rCBV values within the tumors were normalized relative to the contra-lateral white matter (rCBVmax). RESULTS The average rCBVmax of astrocytic tumors (2.01±0.68) was significantly lower than that of the oligoastrocytic (4.60±1.05) and oligodendroglial tumors (6.17±0.867) (P<0.0001). A cut-off value of 3.0 allowed to differentiate the oligodendroglial group from the astrocytic group at 100% sensitivity and 87.5% specificity. CONCLUSION The rCBVmax values obtained from 3T MR PWI may be useful as an adjunct to the postoperative histopathological diagnosis of glioma patients.

Glioblastoma treated with postoperative radio-chemotherapy : Prognostic value of apparent diffusion coefficient at MR imaging

PURPOSE To retrospectively evaluate whether the mean, minimum, and maximum apparent diffusion coefficient (ADC) of glioblastomas obtained from pretreatment MR images is of prognostic value in patients with glioblastoma. MATERIALS AND METHODS The institutional review board approved our study and waived the requirement for informed patient consent. Between February 1998 and January 2006, 33 patients (24 males, 9 females; age range 10-76 years) with supratentorial glioblastoma underwent pretreatment magnetic resonance (MR) imaging. The values of the mean, minimum, and maximum ADC (ADC(mean), ADC(MIN), and ADC(MAX), respectively) of each tumor were preoperatively determined from several regions of interest defined in the tumors. After surgical intervention, all patients underwent irradiation and chemotherapy performed according to our hospital protocol. The patient age, symptom duration, Karnofsky performance scale score, extent of surgery, and ADC were assessed using factor analysis of overall survival. Prognostic factors were evaluated using Kaplan-Meier survival curves, the log-rank test, and multiple regression analysis with the Cox proportional hazards model. RESULTS Likelihood ratio tests confirmed that ADC(MIN) was the strongest among the three prognostic factors. Total surgical removal was the most important predictive factor for overall survival (P<0.01). ADC(MIN) was also statistically correlated with overall survival (P<0.05) and could be used to classify patients into different prognostic groups. Interestingly, ADC(MIN) was also the strongest prognostic factor (P<0.01) in the group of patients in whom total tumor removal was not possible. CONCLUSION The ADC(MIN) value obtained from pretreatment MR images is a useful clinical prognostic biomarker in patients with glioblastoma.

Role of PROPELLER diffusion-weighted imaging and apparent diffusion coefficient in the evaluation of pituitary adenomas

OBJECTIVE The relationship between tumor consistency and apparent diffusion coefficient (ADC) values is controversial. We evaluated the role of the ADC using an advanced diffusion-weighted imaging (DWI) technique. We employed periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) DWI acquired on a 3-T magnetic resonance imaging (MRI) scanner to assess the consistency of pituitary adenomas and examined the relationship between the ADC and the hormone secretion status of the tumors and their MIB-1 labeling index (MIB-1 LI). MATERIALS AND METHODS The study protocol was approved by our institutional review board. We retrospectively studied 24 operated patients with pituitary adenomas who had undergone PROPELLER DWI on a 3-T MRI scanner. Conventional MRI findings were expressed as the ratio of the signal intensity (SI) in the lesions to the SI of the normal white matter and the degree of contrast enhancement. Minimum-, mean-, and maximum ADC (ADCmin, ADCmean, ADCmax) values were calculated. The consistency of the tumors was determined by neurosurgeons. All surgical specimens were submitted for histological study to calculate the MIB-1 LI and the percent collagen content. Preoperative MRI-, intraoperative-, and histological findings were analyzed by a statistician. RESULTS Our study included 15 soft-, 5 fibrous-, and 4 hard tumors. Tumor consistency was strongly associated with the percent collagen content. However, neither the tumor consistency nor the percent collagen content was correlated with MRI findings or ADC values. The SI of growth hormone-producing adenomas on T2-WI was lower than of the other pituitary adenomas studied (p<0.01); no other significant difference was found in the ADC or on conventional MRI between pituitary adenomas with different secretory functions. The MIB-1 LI of pituitary adenomas was not correlated with their appearance on conventional MRI or their ADC values. CONCLUSION Using the PROPELLER DWI technique we confirmed that the ADC was not correlated with the consistency of pituitary adenomas. We also demonstrate that the ADC was not associated with the hormone-secreting status or the MIB-1 LI of pituitary adenomas.

Role of PROPELLER diffusion weighted imaging and apparent diffusion coefficient in the diagnosis of sellar and parasellar lesions

OBJECTIVE To evaluate the role of the apparent diffusion coefficient (ADC) using periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion weighted imaging (DWI) in the differentiation between sellar and parasellar mass lesions. MATERIALS AND METHODS The study protocol was approved by our institutional review board. We retrospectively studied 60 patients with sellar and parasellar lesions who had undergone PROPELLER DWI on a 3-T MR imager. Conventional MRI findings were expressed as the ratio of signal intensity (SI) in the lesions to the normal white matter and the degree of contrast enhancement. ADC values were calculated as the minimum (ADC-MIN), mean (ADC-MEAN), and maximum (ADC-MAX). All patients underwent surgery and all specimens were examined histologically. Logistic discriminant analysis was performed by using the SI ratios on T1- and T2-weighted images (T1-WI, T2-WI), the degree of enhancement, and absolute ADC values as independent variables. RESULTS ADC-MIN of hemorrhagic pituitary adenomas was lower than of the other lesions with similar appearance on conventional MRI (non-hemorrhagic pituitary adenomas, craniopharyngiomas, Rathkes cleft cysts; accuracy 100%); the useful cut-off value was 0.700 x 10(-3)mm(2)/s. ADC-MAX of meningiomas was lower than of non-hemorrhagic pituitary adenomas (accuracy 90.3%; p<0.01). ADC-MIN of craniopharyngiomas was lower than of Rathkes cleft cysts (accuracy 100%; p<0.05). CONCLUSION As PROPELLER DWI is less sensitive to susceptibility artifacts than single-shot echoplanar DWI, it is more useful in the examination of sellar and parasellar lesions. Calculation of the ADC values helps to differentiate between various sellar and parasellar lesions.

Effects of myocardial perfusion abnormalities on the accuracy of left ventricular volume and ejection fraction measured by thallium-201 gated single-photon emission tomography: comparison with echocardiography as the reference standard.

BackgroundWe assessed the accuracy of left ventricular end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) using quantitative gated single-photon emission computed tomography (QGS) in comparison with echocardiography as the reference standard. We also assessed the effects of total perfusion deficit (TPD) on the accuracy of QGS measurements. MethodsA total of 258 patients underwent single-photon emission computed tomography and transthoracic echocardiography within 4 weeks of each investigation for evaluating coronary artery disease. Patients were divided into four groups according to TPD scores. ResultsThere were 138 patients with no/minimal TPD, 64 patients with small TPD, 35 patients with middle TPD, and 21 patients with large TPD. There were good correlations and agreements in EDV (r=0.87, 0.90, 0.71, and 0.94, respectively), ESV (r=0.92, 0.94, 0.79, and 0.94, respectively), and EF (r=0.61, 0.79, 0.61, and 0.83, respectively) between QGS and echocardiography in patients with any TPD. QGS significantly underestimated EDV and ESV in patients with no/minimal or small TPD, and significantly overestimated ESV in patients with large TPD. QGS significantly underestimated EF in patients with middle or large TPD. ConclusionOur results suggest that QGS is a useful tool for assessing the left ventricular volume and function in patients with any TPD, but myocardial perfusion abnormalities should be taken into consideration when interpreting QRS measurements.

Evaluation of dural arteriovenous fistulas of cavernous sinus before and after endovascular treatment using time-resolved MR angiography

Digital subtraction angiography (DSA) is the preferred method for confirming dural arteriovenous fistulas (DAVFs), but it has the disadvantage of being invasive. In contrast, time-resolved magnetic resonance angiography (TR-MRA) is a useful, noninvasive imaging technique. The aim of this study was to compare the evaluation of DAVFs of the cavernous sinus (CS) using TR-MRA and DSA. TR-MRA and DSA were obtained in six patients with CS-DAVFs treated with endovascular surgery. TR-MRA and DSA before and after treatment were reviewed by one neuroradiologist without previous knowledge of the existence of CS-DAVFs for the detection and characterization (feeding artery and venous drainage) of CS-DAVFs. DSA showed six CS-DAVFs in the six patients. TR-MRA demonstrated a hyperintensity area in the CS at the arterial phase in six patients. DSA revealed feeding arteries and a drainage vein in all CS-DAVFs. In contrast, the feeding arteries could not be identified with TR-MRA. The details regarding venous drainage could only be speculated upon with TR-MRA as it was only partly visible on the TR-MRA images. DSA after embolization showed no CS-DAVFs in any of the six patients. TR-MRA showed no hyperintensity areas in the CS at the arterial phase in any of the six patients, and with no coil artifacts. In summary, TR-MRA could detect and diagnose CS-DAVF. However, the detail regarding anatomical feeders and draining veins remains poorly visualized by TR-MRA. In this small number of cases, TR-MRA can be a useful screening tool to detect CS-DAVF and possibly also to confirm persistent obliteration following definitive treatment.

[Evaluation of Resolution Correction in Single Photon Emission Computed Tomography Reconstruction Method Using a Body Phantom: Study of Three Different Models].

PURPOSE The aim of this study was to evaluate the resolution recovery techniques of Flash3D, Astonish, and Evolution in single photon emission computed tomography(SPECT) using a body phantom. METHODS We scanned a National Electrical Manufactures Association body phantom filled with 99mTc. The body of the phantom with radioactive sphere and background was filled with either water or radioactive solution. We investigated image quality using profile curves, recovery coefficient, and image contrast. RESULTS The profile curve at the edge of the hot sphere showed artifact due to Gibbs oscillation for all techniques, and also over estimation of recovery coefficient was seen in the hot sphere, as had been previously reported in a simulation study. These phenomena were more remarkable than Evolution in the Flash3D and Astonish techniques. For the contrast between hot sphere and background, the contrast recover was enough for the <17-mm hot spheres. These results showed that the effect of contrast correction was less as the radius of rotation diameter became large. CONCLUSION In the present study using the body phantom, overestimated counts and edge artifacts due to Gibbs oscillation were shown. These phenomena were different by each resolution correction algorithms. Also, there were limitation regarding image quality improvement by resolution correction depending on sphere size and length of radius of rotation.