Assessment Of T2 Relaxation Times Research Articles

MRI T2 mapping assessment of T2 relaxation time in desmoid tumors as a quantitative imaging biomarker of tumor response: preliminary results.

Because size-based imaging criteria poorly capture biologic response in desmoid-type fibromatosis (DF), changes in MRI T2 signal intensity are frequently used as a response surrogate, but remain qualitative. We hypothesized that absolute quantification of DF T2 relaxation time derived from parametric T2 maps would be a feasible and effective imaging biomarker of disease activity. This IRB-approved retrospective study included 11 patients with DF, managed by observation or systemic therapy, assessed by 3T MRI. Tumor maximum diameter, volume, and T2-weighted signal intensity were derived from manual tumor segmentations. Tumor:muscle T2 signal ratios were recorded. Two readers measured tumor T2 relaxation times using a commercial T2 scanning sequence, manual ROI delineation and commercial calculation software enabling estimation of reader reliability. Objective response rates based on RECIST1.1 and best responses were compared between size-based and signal-based parameters. Median patient age was 52.6 years; 8 subjects were female (73%). Nine patients with longitudinal assessments were followed for an average of 314 days. Median baseline tumor diameter was 7.2 cm (range 4.4 - 18.2 cm). Median baseline T2 was 65.1 ms (range 40.4 - 94.8 ms, n=11); median at last follow-up was 44.3 ms (-32% from baseline; range 29.3 - 94.7 ms, n=9). T2 relaxation times correlated with tumor:muscle T2 signal ratios, Spearman p=0.78 (p<0.001). T2 mapping showed high inter-reader reliability, ICC=0.84. The best response as a percentage change in T2 values was statistically significant (mean -17.9%, p=0.05, paired t-test) while change in diameter was not (mean -8.9%, p=0.12). Analysis of T2 relaxation time maps of DF may offer a feasible quantitative biomarker for assessing the extent of response to treatment. This approach may have high inter-reader reliability.

МР–РЕЛАКСОМЕТРИЯ В ДИАГНОСТИКЕ РАБДОМИОЛИЗА

Purpose. Assessing the possibilities of quantitative MRI in the diagnosis and monitoring of the course of rhabdomyolysis of various etiologies. Materials and methods. The results of MRI performed by 80 patients with clinical manifestations of rhabdomyolysis were analyzed. The diagnosis of rhabdomyolysis was confirmed by measuring the level of myoglobin (more than 70 μg/l) and CPK (more than 1000 IU/l) in the absence of laboratory and instrumental signs of myocardial damage. Scanning was carried out using T1, T2, STIR protocols, as well as the developed pulse sequences for calculating the relaxation times T1, T2 and T2*. Patients underwent MR examination at least 3 times during the course of the disease. Results. In 48 cases was detected a hyperintensive signal from muscle tissue on the T2 and STIR protocols. In 25 cases were identified MR signs of rhabdomyolysis, 16 of which were confirmed by laboratory methods and or biopsy of the affected muscle. One patient with a blood myoglobin level (577 ng/ml) showed no pathological changes in MR images. Thus, in the analyzed group, the sensitivity and specificity were 94% and 71%. Quantification protocols obtained relaxation times for the affected muscle tissue. The ROC analysis method determined cutoff thresholds for rhabdomyolysis: T1 greater than 1152 ms, T2 greater than 63 ms and T2* greater than 48 ms with sensitivity and specificity, respectively: 94% and 73%, 94% and 84%, 88% and 85%. Dynamic changes in the relaxation time during the recovery of patients had correlation relationships of high and medium strength with the main laboratory markers of rhabdomyolysis. The highest values of the correlation coefficient were found between T2 and the activity of CPK, ALS, and AST (rs = 0.805, 0.813, and 0.803; p &lt;0.05). Conclusion. An improved technique for muscle MRI with a quantitative assessment of T2 relaxation time has high sensitivity and specificity (94% and 82%) in the diagnosis of rhabdomyolysis. Recovery of

Temporal course of perfusion in human masseter muscle during isometric contraction assessed by arterial spin labeling at 3T

Examination of blood perfusion in the masseter muscle in the course of repetitive isometric contraction by arterial spin-labeling (ASL) MR imaging and additional T2 relaxation time measurements during and after masseter muscle activation. Anatomical and ASL imaging was performed (3 T) in the masseter muscle of seven healthy volunteers before and after sustained clenching (30s) at maximum voluntary contraction (MVC). Several cycles of clenching were repeated in an overall period of 11 min. ASL imaging was performed by an adapted FAIR-TrueFISP technique. Time to peak and time to baseline were systematically analyzed in recorded perfusion curves. T2 relaxation times were estimated using a multi-echo spin-echo sequence. The influence of MVC on T2 was statistically analyzed. In all cases, perfusion imaging and assessment of T2 relaxation time was feasible. Mean perfusion values at rest calculated from all volunteers were 97.9 ± 17.1 ml/min/100 g (right masseter) and 83.0 ± 18.1 ml/min/100 g (left masseter). The percentage mean perfusion increase in all volunteers immediately after clenching ranged between 114 and 154%. Mean time to peak was 13.7 s (range: 8.0-26.7 s; SD 5.6 s), and mean time to baseline was 25.6 s (range: 18.7-37.0 s; SD 5.4 s). No significant influence of MVC on T2 relaxation time was found, although a tendency to T2 increase after each clenching stress was observed. Clear contraction-related perfusion changes of the masseter muscle could be assessed in high spatial and temporal resolution by means of ASL. In contrast, no significant T2 changes were measured. ASL imaging could serve as supplementing tool for studying masticatory function and dysfunction.

Noninvasive MRI-SERS Imaging in Living Mice Using an Innately Bimodal Nanomaterial

We report a novel nanomaterial (AuMN-DTTC) that can be used as a bimodal contrast agent for in vivo magnetic resonance imaging (MRI) and Raman spectroscopy. The probe consists of MRI-active superparamagnetic iron oxide nanoparticles, stably complexed with gold nanostructures. The gold component serves as a substrate for a Raman active dye molecule to generate a surface-enhanced Raman scattering (SERS) effect. The synthesized probe produces T2 weighted contrast and can be used as a SERS active material both in silico (in aqueous solution) and in vivo. A quantitative assessment of T2 relaxation times was obtained using multiecho MRI analysis. The T2 relaxation times of AuMN-DTTC and MN (dextran-coated iron oxide nanoparticles) were 29.23 + 1.45 and 31.58 + 1.7 ms, respectively. The SERS signature of AuMN-DTTC revealed peaks at 508, 629, 782, 844, 1080, 1108, 1135, and 1242 cm(-1). Intramuscular administration of the probe resulted in a decrease of the T2 relaxation time of muscle from 33.4 + 2.5 to 20.3 + 2.2 ms. SERS peaks were observed at 508, 629, 782, 844, 1080, 1108, 1135, and 1242 cm(-1), consistent with the in silico results. Our studies illustrate for the first time the design and in vivo application of a contrast agent, whose component modalities include MRI and SERS. The value of this agent lies in its innately bimodal nature and its application in vivo for molecular imaging applications.

Single-subject voxel-based relaxometry for clinical assessment of temporal lobe epilepsy

T2 relaxometry, quantitative assessment of T2 relaxation time in magnetic resonance (MR) data, typically uses manually drawn regions of interest (ROIs). This approach is limited by its subjectivity and its restricted scope of investigation. A recently developed approach called voxel-based relaxometry (VBR) provides an unbiased statistical analysis of the whole brain. Our objective was to assess the clinical utility of single-subject VBR for patients with temporal lobe epilepsy (TLE). Forty-five patients with TLE confirmed by history, EEG, and structural MRI and 25 control subjects were scanned at 3T using a modified Carr-Purcell-Meiboom-Gill MR sequence. ROIs were drawn for each patient and control subject, and measurements were made on unregistered T2 maps. VBR was performed on a single-subject basis at a significance level of alpha=0.05. Patients were grouped according to seizure focus (left mesial, right mesial, other), and whether structural MR imaging was normal or abnormal. Up to 85% of patients in the temporal lobe groups demonstrated T2 abnormalities. VBR detected abnormalities either in equal numbers or in more patients (up to 23% more) than ROI analysis for each group. The number of detected abnormalities per patient was higher using VBR (3.38 versus 2.04, p<0.05). VBR also identified abnormalities that were missed by ROI analysis. The rate of VBR detection of abnormalities was higher for patients than controls (76% versus 36%). VBR can be performed on single subjects with TLE and it detects considerably more abnormalities than ROI analysis. VBR may be a clinically useful tool for the detection of T2 abnormalities at the seizure focus and sites remote from it.