Magnetic Resonance Relaxometry for Tumor Cell Density Imaging for Glioma: An Exploratory Study via 11C-Methionine PET and Its Validation via Stereotactic Tissue Sampling.

One of the most crucial yet challenging issues for glioma patient care is visualizing non-contrast-enhancing tumor regions. In this study, to test the hypothesis that quantitative magnetic resonance relaxometry reflects glioma tumor load within tissue and that it can be an imaging surrogate for visualizing non-contrast-enhancing tumors, we investigated the correlation between T1- and T2-weighted relaxation times, apparent diffusion coefficient (ADC) on magnetic resonance imaging, and 11C-methionine (MET) on positron emission tomography (PET). Moreover, we compared the T1- and T2-relaxation times and ADC with tumor cell density (TCD) findings obtained via stereotactic image-guided tissue sampling. Regions that presented a T1-relaxation time of >1850 ms but <3200 ms or a T2-relaxation time of >115 ms but <225 ms under 3 T indicated a high MET uptake. In addition, the stereotactic tissue sampling findings confirmed that the T1-relaxation time of 1850-3200 ms significantly indicated a higher TCD (p = 0.04). However, ADC was unable to show a significant correlation with MET uptake or with TCD. Finally, synthetically synthesized tumor load images from the T1- and T2-relaxation maps were able to visualize MET uptake presented on PET.

T2-FLAIR Mismatch Sign Is Caused by Long T1 and T2 of IDH-mutant, 1p19q Non-codeleted Astrocytoma.

T2-fluid-attenuated inversion recovery images (FLAIR) mismatch sign is now known to be a specific yet insensitive image feature for IDH-mutant, 1p19q non-codeleted astrocytoma. The current study revealed that lesion presenting T2-FLAIR mismatch exhibited extremely long T1- and T2-relaxation time while T2-FLAIR matched lesions showed low to moderate values. On the other hand, IDH-wildtype tumors presented noticeably short T1- and T2-relaxation time. These different relaxation time characteristics seemed to render T2-FLAIR mismatch sign of becoming such a unique and specific image feature for IDH-mutant, 1p19q non-codeleted astrocytoma.

Transverse Relaxation Rate of Cyst Fluid Can Predict Malignant Transformation of Ovarian Endometriosis.

PURPOSE: Heme and iron accumulation due to repeated hemorrhage in endometriosis may contribute to a pivotal role in carcinogenesis. We evaluate the clinical application of MR relaxometry in a series of ovarian endometriosis (OE) and endometriosis-associated ovarian cancer (EAOC). MATERIALS AND METHODS: A prospective study of diagnostic accuracy was conducted among 82 patients (67 OE and 15 EAOC) to compare MR relaxometry and biochemical measurement of cyst fluid total iron concentration. Transverse relaxation rate R2 value was determined using a single-voxel, multi-echo MR sequence (HISTO) by a 3T-MR system. Phantom experiments were also performed to assess the correlation between the ex vivo R2 values and total iron concentrations. RESULTS: Both the results of phantom experiments and in vivo human data confirmed that in vivo R2 values were highly correlated with total iron concentrations. Compared to OE, EAOC exhibit decreased in vivo R2 values and total iron levels, regardless of their age, menopausal status and cyst size. The use of in vivo R2 values retained excellent accuracy in distinguishing EAOC versus OE (sensitivity and specificity: 86% and 94%). CONCLUSIONS: We have demonstrated that MR relaxometry provides a noninvasive predictive tool to discriminate between EAOC and OE.

Feasibility of non-contrast-enhanced four dimensional (4D) MRA in head and neck tumors, comparison with contrast-enhanced 4D MRA.

BACKGROUND: Information of tumor vascular architecture and hemodynamics is important in treating patients with head and neck tumors (HNTs). The purpose of this study is to investigate the feasibility of non-contrast-enhanced four-dimensional magnetic resonance angiography (non-CE 4DMRA) using arterial spin labeling for anatomical and hemodynamic evaluation of vascularity of head and neck tumors. RESULTS: Non-CE 4DMRA images of 15 patients with HNTs were compared with those of contrast-enhanced 4DMRA (CE 4DMRA) by two independent observers. For qualitative evaluation, overall image quality, visualization of arterial branches and main arterial tumor feeders were assessed. For hemodynamic evaluation, signal-intensity-over-time curves within the tumors were compared. The sensitivity of non-CE 4DMRA for the identification of arterial branches and the main arterial tumor feeders was 75 and 20 %, respectively (interobserver agreement, κ = 0.56 and 0.54, respectively), while that of CE 4DMRA was 99 and 95 %, respectively (interobserver agreement, κ = 0.62 and 0.70, respectively). All three arterial/hypervascularized tumors determined on CE 4DMRA showed distinct signal-intensity-over-time curve pattern on non-CE 4DMRA, with distinct peak and wash out phases. Other tumors showed no wash out on non-CE 4DMRA. CONCLUSIONS: Use of non-CE 4DMRA for the anatomical and hemodynamic evaluation of vascularity of head and neck tumors is feasible, although the technique needs to be improved.

Diffusion tensor imaging (DTI) of the normal human uterus in vivo at 3 tesla: comparison of DTI parameters in the different uterine layers.

PURPOSE: To investigate the differences in the fiber architecture and related diffusion tensor imaging (DTI) parameters among different uterine layers of the normal human uterus in vivo at 3 Tesla (T). MATERIALS AND METHODS: DTI of the uterus was performed for nine healthy women of reproductive age on a 3T scanner. A volume of interest (VOI) was drawn for the outer myometrium (OM), junctional zone (JZ), and endometrium (EM). Apparent diffusion coefficient (ADC), fractional anisotropy (FA), and maximum fiber length were compared using paired Student's t-tests. Fibers were classified into four groups and were visually evaluated. RESULTS: ADC (×10(-3) mm(2) /s) was highest for OM (1.12), followed by EM (0.97) and JZ (0.83) (OM versus JZ, P < 0.0001; JZ versus EM, P = 0.0001; OM versus EM, P = 0.0057). FA was highest for JZ (0.297), followed by OM (0.257) and EM (0.186) (OM versus JZ, P = 0.0002; JZ versus EM, P < 0.0001; OM versus EM, P < 0.0001). Fibers were longest in OM (42.0 mm), followed by JZ (34.2 mm) and EM (20.0 mm). Circularly oriented fibers were observed in 69% in OM and in 70% in JZ. CONCLUSION: DTI of the uterus in vivo revealed layer-wise differences in the microstructure of the uterus.

[Utility of sampling perfection with application optimized contrasts using different flip angle evolutions method in magnetic resonance imaging of carotid artery plaque].

In the carotid artery plaque diagnosis, it is said that properties evaluation is important. For this inspection, it is general to use electrocardiogram (ECG)-trigger-dark blood (DB)-fat suppression (fs)-turbo spin echo (TSE)-T1 weighted image (T1WI), T2WI, and magnetization prepared rapid gradient echo (MPRAGE) methods though many problems still remain. This time, a comparative study of the carotid artery plaque diagnosis that used the sampling perfection with application optimized contrasts was made. This used different flip angle evolutions method sampling perfection with application optimized contrasts using different flip angle evolutions (SPACE) method that was 3 dimension (3D) imaging procedure that used variable flip angle with the law so far. The subjects were normal volunteers, handmade phantoms changed by T1 and T2 value, and the five patients on five cases who had taken carotid endoarterectomy (CEA) (male, mean 70.6 yr). Findings by the pathologist were obtained for the CEA enforcement patient. There is an excellent result in the contrast ratio by phantom, the signal intensity ratio of a clinical patient, and the comparison with pathological findings. The SPACE method can solve various problems, be evaluated by a properties evaluation of the plaque, a grasp of the range, and an arbitrary section, and be devised as a useful imaging procedure.

Accuracy for predicting adhesion between meningioma and the brain by using brain surface motion imaging: comparison between single and double acquisition methods.

INTRODUCTION: The presence of adhesions between the brain and the meningioma is an important factor that determines the success of total surgical removal. Brain surface motion imaging enables assessment of the dynamics of brain surface motion. A subtraction image of pulse-gated heavily T2-weighted images in different phases of the cardiac cycle provides a stripe pattern on the surface of the pulsating brain. Thus, the lack of a stripe pattern on the surface of extraaxial tumor indicates the presence of tumor-brain adhesion. The purpose of the present experiment was to evaluate the accuracy of predicting tumor-brain adhesion using the original double acquisition method and the improved single acquisition method. METHODS: The subjects were 67 meningioma cases patients who were surgically treated after brain surface motion imaging. Thirty-three cases were evaluated using the double acquisition method and 34 cases were evaluated with the single acquisition method. In the double acquisition method, the two sets of images are acquired as two independent scans, and in the single acquisition method, the images are acquired serially as a single scan. RESULTS: The findings for the double acquisition method agreed with the surgical findings in 23 cases (69.7 %), while findings from the single acquisition method agreed with the surgical findings in 26 cases (76.5 %). CONCLUSION: Pre-surgical evaluation for tumor-brain adhesion by brain surface motion imaging provides helpful information for meningioma surgery, especially when using the single acquisition method.

[T2 image contrast evaluation using three dimension sampling perfection with application optimized contrasts using different flip angle evolution (3D-SPACE)].

PURPOSE: Sampling perfection with application optimized contrasts using different flip angle evolution (3D-SPACE) sequence enables one to decrease specific absorption rate (SAR) by using variable flip angle refocusing pulse. Therefore, it is expected that the contrast obtained with 3D-SPACE sequences is different from that of spin echo (SE) images and turbo spin echo (TSE) images. The purpose of this study was to evaluate the characteristics of the signal intensity and central nervous system (CNS) image contrast in T(2) weighted 3D-SPACE. METHOD: Using 3 different sequences (SE, 3D-TSE and 3D-SPACE) with TR/TE=3500/70, 90 and 115 ms, we obtained T(2) weighted magnetic resonance (MR) images of inhouse phantom and five healthy volunteers' brain. Signal intensity of the phantom which contains various T(1) and T(2) value was evaluated. Tissue contrasts of white/gray matter, cerebrospinal fluid (CSF)/subcutaneous fat and gray matter/subcutaneous fat were evaluated for a clinical image study. RESULTS: The phantom study showed that signal intensity in 3D-SPACE significantly decreased under a T(1) value of 250 ms. It was markedly decreased in comparison to other sequences, as effective echo time (TE) was extended. White/gray matter contrast of 3D-SPACE was the highest in all sequences. On the other hand, CSF/fat and gray matter/fat contrast of 3D-SPACE was higher than TSE but lower than SE. CONCLUSION: CNS image contrasts of 3D-SPACE were comparable to that of SE. Signal intensity had decreased in the range where T(1) and T(2) values were extremely short.

Evaluation of left ventricular rotation by two-dimensional speckle tracking method and real-time three-dimensional echocardiography: comparison with MRI tagging method.

BACKGROUND: Recently, it has become possible to evaluate left ventricular (LV) torsion by two-dimensional (2D) speckle tracking images. However, LV torsion is a three-dimensional (3D) performance, which per se cannot be assessed by the 2D speckle tracking method. The present study investigated the accuracy of the 2D speckle tracking method and real-time 3D echocardiography in measuring LV rotation, comparing with the MRI tagging method. METHODS: We assessed LV apical rotation using the 2D speckle tracking method, real-time 3D echocardiography, and MRI tagging method in 26 normal subjects, and compared the results of these three methods. LV apical rotation was measured just before the level in which the posterior papillary muscle was absorbed into the free wall. RESULTS: The degree of LV apical rotation evaluated by the 2D speckle tracking method (Δθ 2D) was significantly smaller than that evaluated by 3D echocardiography (Δθ 3D) and the MRI tagging method (Δθ MRI) (Δθ 2D 7.3 ± 2.8°; Δθ 3D 8.8 ± 3.4°; Δθ MRI 9.0 ± 3.4°; Δθ 2D vs. Δθ 3D, p = 0.0001; Δθ 2D vs. Δθ MRI, p < 0.0001). There were good correlations among Δθ 2D, Δθ 3D, and Δθ MRI, but agreement between Δθ 3D and Δθ MRI (mean difference 0.14 ± 1.43°) was better than that between Δθ 2D and Δθ MRI (mean difference 1.68 ± 1.89°). CONCLUSION: The degree of LV apical rotation was underestimated with the 2D speckle tracking method compared with the MRI tagging method, whereas it could be precisely measured by 3D echocardiography.

[Usefulness of 3D-VIBE method in breast dynamic MRI: imaging parameters and contrasting effects].

MR imaging (MRI) has been reported to be a useful modality to characterize breast tumors and to evaluate disease extent. Contrast-enhanced dynamic MRI, in particular, allows breast lesions to be characterized with high sensitivity and specificity. Our study was designed to develop three-dimensional volumetric interpolated breath-hold examination (3D-VIBE) techniques for the evaluation of breast tumors. First, agarose/Gd-DTPA phantoms with various concentrations of Gd-DTPA were imaged using 3D-VIBE and turbo spin echo (TSE). Second, one of the phantoms was imaged with 3D-VIBE using different flip angles. Finally, water excitation (WE) and a chemical shift-selective (CHESS) pulse were applied to the images. Each image was analyzed for signal intensity, signal-to-noise ratio (1.25*Ms/Mb) (SNR), and contrast ratio [(Ms1-Ms2)/[(Ms1+Ms2)/2]]. The results showed that 3D-VIBE provided better contrast ratios with a linear fit than TSE, although 3D-VIBE showed a lower SNR. To reach the best contrast ratio, the optimized flip angle was found to be 30 degrees for contrast-enhanced dynamic study. Both WE and CHESS pulses were reliable for obtaining fat-suppressed images. In conclusion, the 3D-VIBE technique can image the entire breast area with high resolution and provide better contrast than TSE. Our phantom study suggests that optimized 3D-VIBE may be useful for the assessment of breast tumors.

[Fundamental study of the relation between flow velocity and signal intensity in the TrueFISP sequence].

The purpose of this study was to evaluate the effect of inflow phenomenon on TrueFISP. We created a phantom using a vinyl tube and distilled water, and applied a pump-oxygenator to the phantom to obtain stationary flow. First, to evaluate the effect of inflow and the dephase phenomenon on signal intensity, the phantom was measured for the signal intensity of variable flow velocity. Second, the relation of TR/TE with signal intensity was analyzed. The results showed that a flow velocity of less than 15 cm/sec did not participate in signal reduction; however, signal intensity was reduced when flow velocity was more than 30 cm/sec. Moreover, the reduction of signal intensity was remarkable with a flow velocity of 50-100 cm/sec, which corresponds with arterial flow velocity. In the analysis of TR/TE, signal intensity was increased when TR of less than 5 ms was applied to the slow velocity of 15 cm/sec. Signal intensity was decreased when the same TR was applied to the high velocity of 50-100 cm/sec. When TR was 6-9 ms, peak signal intensity was recognized at the high velocity of 50-100 cm/sec. This peak, however, might correspond only to the inflow phenomenon, and steady state might have already collapsed. Based on these results, we concluded that TrueFISP is suitable for the imaging of slow flow velocity. A short TR of less than 5 ms was effective for obtaining high signal intensity. Our next goal will be to apply TrueFISP to MR venography, although further investigation will be necessary.