Quantitative Predictive Imaging Biomarkers of Lumbar Intervertebral Disc Degeneration

STUDY DESIGN: Observational comparative study. PURPOSE: To compare fractional anisotropy (FA) maps with T2 values of the nucleus pulposus (NP) and annulus fibrosus (AF) of intervertebral discs in healthy volunteers and patients to develop a predictive disc health scale. OVERVIEW OF LITERATURE: T2-weighted magnetic resonance imaging (MRI) is not sensitive to early morphological changes and provides no quantitative biomarker profile for early degeneration. METHODS: We examined 59 healthy controls and 59 patients with back pain by MRI using T2 relaxometry and diffusion tensor imaging (DTI). Each group was divided into three age subgroups: A (50 years, n=21). We obtained FA values for AF and NP and T2 values for NP for each intervertebral disc. Furthermore, we calculated the FA (AF/NP) ratios. RESULTS: We categorized 590 intervertebral discs from 118 participants, 566 of which were analyzed with T2 relaxometry and DTI. The T2 values were as follows: subgroup A, 55.8±4.4 ms; B, 48.5±6.9 ms; C, 45.8±8.7 ms (p120 ms, 90–100 ms, and 70 ms, respectively (p<0.001). Control subgroup A had higher T2 values and AF/NP ratios than subgroups B and C; the AF values were not significantly different. Control subgroup B had higher T2 values and AF/NP ratios than subgroup C but lower FA (NP). CONCLUSIONS: FA maps of the AF/NP ratio and T2 values of NP are potential microstructure biomarkers of normal and degenerating discs and can help detect early degeneration using a predictive disc health score on a continuous scale.

Application of Synthetic MRI for Direct Measurement of Magnetic Resonance Relaxation Time and Tumor Volume at Multiple Time Points after Contrast Administration: Preliminary Results in Patients with Brain Metastasis

OBJECTIVE: The purpose of this study was to investigate the time-dependent effects of contrast medium on multi-dynamic, multi-echo (MDME) sequence in patients with brain metastases. MATERIALS AND METHODS: This study included 7 patients with 15 brain metastases who underwent magnetic resonance (MR) examination which included MDME sequences at 1 minute, 10 minutes and 20 minutes after contrast injection. Two volumes of interests, covering an entire tumor (whole tumor) and the enhancing portion of the tumor, were derived from post-contrast synthetic T1-weighted images. Statistical comparisons were performed for three different time delays for histogram parameters of the longitudinal relaxation rate (R1) and the transverse relaxation rate (R2), and lesion volumes. RESULTS: The mean and the median of R1 and the mean of R2 in both the whole tumor and the inner enhancing portion were larger on the 10 minutes delayed images than on the 1 minute or 20 minutes delayed images (mean of R1 in the whole tumor on the 1 minute, 10 minutes, and 20 minutes delayed images: 1.26 ms, 1.39 ms, and 1.37 ms; mean of R1 in the inner enhancing portion: 1.43 ms, 1.53 ms and 1.44 ms; all p < 0.017). The volumes of the whole tumor and the inner enhancing portion were significantly larger in the 10 minutes and 20 minutes delayed images than on the 1 minute delayed images (all p < 0.017). CONCLUSION: Magnetic resonance relaxation times and the volumes of the whole tumor and the inner enhancing portion were measured larger on the 10 minutes or 20 minutes delayed images than on the 1 minute delayed images. The MDME sequence immediately after contrast injection cannot fully reflect the effects of gadolinium-based contrast agent leakage in the tissue.

Volumetric T1 and T2 magnetic resonance brain toolkit for relaxometry mapping simulation

Abstract Introduction Relaxometry images are an important magnetic resonance imaging (MRI) technique in the clinical routine. Many diagnoses are based on the relaxometry maps to infer abnormal state in the tissue characteristic relaxation constant. In order to study the performance of these image processing approaches, a controlled simulated environment is necessary. However, a simulated relaxometry image tool is still lacking. This study proposes a computational anatomical brain phantom for MRI relaxometry images, which aims to offer an easy and flexible toolkit to test different image processing techniques, applied to MRI relaxometry maps in a controlled simulated environment. Methods A pipeline of image processing techniques such as brain extraction, image segmentation, normalization to a common space and signal relaxation decay simulation, were applied to a brain structural ICBM brain template, on both T1 and T2 weighted images, in order to simulate a volumetric brain relaxometry phantom. The FMRIB Software Library (FSL) toolkits were used here as the base image processing needed to all the relaxometry reconstruction. Results All the image processing procedures are performed using automatic algorithms. In addition, different artefact levels can be set from different sources such as Rician noise and radio-frequency inhomogeneity noises. Conclusion The main goal of this project is to help researchers in their future image processing analysis involving MRI relaxometry images, offering reliable and robust brain relaxometry simulation modelling. Furthermore, the entire pipeline is open-source, which provides a wide collaboration between researchers who may want to improve the software and its functionality.

T2 Relaxometry Using 3.0-Tesla Magnetic Resonance Imaging of the Brain in Early- and Late-Onset Restless Legs Syndrome

BACKGROUND AND PURPOSE: Previous T2 relaxometry studies have provided evidence for regional brain iron deficiency in patients with restless legs syndrome (RLS). Measurement of the iron content in several brain regions, and in particular the substantia nigra (SN), in early- and late-onset RLS patients using T2 relaxometry have yielded inconsistent results. In this study the regional iron content was assessed in patients with early- and late-onset RLS using magnetic resonance imaging (MRI), and compared the results with those in controls. METHODS: Thirty-seven patients with idiopathic RLS (20 with early onset and 17 with late onset) and 40 control subjects were studied using a 3.0-tesla MRI with a gradient-echo sampling of free induction decay and echo pulse sequence. The regions of interest in the brain were measured independently by two trained analysts using software known as medical image processing, analysis, and visualization. The results were compared and a correlation analysis was conducted to investigate which brain areas were related to RLS clinical variables. RESULTS: The iron index in the SN was significantly lower in patients with late-onset RLS than in controls (p=0.034), while in patients with early-onset RLS there was no significant difference. There was no significant correlation between the SN iron index of the late-onset RLS group and clinical variables such as disease severity. CONCLUSIONS: Late-onset RLS is associated with decreased iron content in the SN. This finding supports the hypothesis that regional brain iron deficiency plays a role in the pathophysiology of late-onset RLS.

Fluid-Attenuated Inversion Recovery Hypointensity of the Pulvinar Nucleus of Patients with Alzheimer Disease: Its Possible Association with Iron Accumulation as Evidenced by the T2* Map

OBJECTIVE: We hypothesized that prominent pulvinar hypointensity in brain MRI represents the disease process due to iron accumulation in Alzheimer disease (AD). We aimed to determine whether or not the pulvinar signal intensity (SI) on the fluid-attenuated inversion recovery (FLAIR) sequences at 3.0T MRI differs between AD patients and normal subjects, and also whether the pulvinar SI is correlated with the T2* map, an imaging marker for tissue iron, and a cognitive scale. MATERIALS AND METHODS: Twenty one consecutive patients with AD and 21 age-matched control subjects were prospectively included in this study. The pulvinar SI was assessed on the FLAIR image. We measured the relative SI ratio of the pulvinar to the corpus callosum. The T2* values were calculated from the T2* relaxometry map. The differences between the two groups were analyzed, by using a Student t test. The correlation between the measurements was assessed by the Pearson's correlation test. RESULTS: As compared to the normal white matter, the FLAIR signal intensity of the pulvinar nucleus was significantly more hypointense in the AD patients than in the control subjects (p < 0.01). The pulvinar T2* was shorter in the AD patients than in the control subjects (51.5 +/- 4.95 ms vs. 56.5 +/- 5.49 ms, respectively, p = 0.003). The pulvinar SI ratio was strongly correlated with the pulvinar T2* (r = 0.745, p < 0.001). When controlling for age, only the pulvinar-to-CC SI ratio was positively correlated with that of the Mini-Mental State Examination (MMSE) score (r = 0.303, p < 0.050). Conversely, the pulvinar T2* was not correlated with the MMSE score (r = 0.277, p = 0.080). CONCLUSION: The FLAIR hypointensity of the pulvinar nucleus represents an abnormal iron accumulation in AD and may be used as an adjunctive finding for evaluating AD.

Multi-Component Relaxation Study of Human Brain Using Relaxographic Analysis

PURPOSE: To demonstrate that the relaxographic method provides additional information such as the distribution of relaxation times and water content which are poentially applicable to clinical medicine. MATERIALS AND METHODS: First, the computer simulation was performed with the generated relaxation data to verify the accuracy and reliablility of the relaxographic method (CONTIN). Secondly, in order to see how well the CONTIN quantifies and resolves the two different T1 environments, we calculated the oil to water peak area ratios and identified peak positions of T1-distribution curve of the phantom solutions, which consist of four centrifugal tubes (10ml) filled with the compounds of 0, 10, 20, 30% of corn oil and distilled water, using CONTIN. Finally, inversion recovery MR images for a volunteer are acquired for each TI ranged from 40 to 1160 msec with TR/TE=2200/20 msec. From the 3 different ROIs (GM, WM, CSF), CONTIN analysis was performed to obtain the T1-distribution curves, which gave peak positions and peak area of each ROI location. RESULTS: The simulation result shows that the errors of peak positions were less in the higher peak (centered T1=600 msec) than in the lower peak (centered T1=150 msec) for all SNR but the errors of peak areas were larger in the higher peak than in the lower peak. The CONTIN analysis of the measured relaxation data of phantoms revealed two peaks between 20 and 60 msec and between 500 and 700 msec. The analysis gives the peak area ratio as oil 10%: oil 20%: oil 30%=1:1.3:1.9, which is different from the exact ratio, 1:2:3. For human brain, in ROI 3 (CSF), only one component of -distributions was observed whereas in ROI 1 (GM) and in ROI 2 (WM) we observed two components of T1-distribution. For the WM and CSF there was great agreement between the observed T1-relaxation times and the reported values. CONCLUSION: we demonstrated that the relaxographic method provided additional information such as the distribution of relaxation times and water content, which were not available in the routine relaxometry and T1/T2 mapping techniques. In addition, these additional information provided by relaxographic analysis may have clinical importance.

The Relationship between Hippocampal Damage on MRI and Secondarily Generalized Tonic Clonic Seizures in Temporal Lobe Epilepsy : Quantitative and Qualitative MRI Study / 대한간질학회지

PURPOSE: It has been suggested that recurrent seizures may cause the hippocampal formation (HF) damage in temporal lobe epilepsy (TLE). To evaluate whether secondarily generalized tonic clonic seizure (SGTC) is related to the degree of the HF damage on MRI we performed this study. METHODS: We found 42 patients with TLE who had HS on qualitative MRI from epilepsy database. They were divided into unilateral HS (UHS) and bilateral HS (BHS) on qualitative MRI by visual analysis. We performed HF volumetry in 20 and T2 relaxometry in 22 (17 patients were lateralized by quantitative MRI and ictal or interictal EEG). RESULTS: The frequency of status epilepticus and SGTCs in BHS were significantly higher than that in UHS (14% vs 3%, p<0.05 and 60% vs 6%, p<0.05 respectively). Of 17 patients who were lateralized, the frequency of SGTCs was significantly correlated to the ipsilateral (r=0.58, p<0.05) and contralateral (r=0.35, p<0.05) T2 relaxometry as well as inversely to the ipsilateral (r=-0.59, p<0.05) and contralateral (r=-0.52, p<0.05) HF volume. CONCLUSIONS: BHS has the higher frequency of status epilepticus and SGTCs, and the frequency of SGTCs was related to the HF damage.

Clinical Usefulness of T2 Relaxometry in Temporal Lobe Epilepsy

BACKGROUND: Quantitative measurement of hippocampal T2 relaxation time is an objective means of determining the frequency and severity of signal abnormalities. To evaluate the diagnostic properties of T2 relaxometry in temporal lobe epilepsy(TLE), we measured T2 relaxation time of bilateral hippocampi in pathology-proven TLE patients and normal controls. METHODS: We investigated 10 TLE patients who had temporal lobectomy with MR T2 relaxation mapping. All patients underwent in phase I or II studies, and had pathologic diagnosis. Also we measured T2 relaxation time in 10 normal volunteers. RESULTS: The pathologic findings of 10 TLE patients were followings: 8 hippocampal sclerosis (including dual pathology of necrotic granuloma), 1 calcified fibrous nodule, and 1 normal hippocampus. The mean T2 relaxation time of normal controls is 67.5msec, which is lower value than previous reports. All patients with hippocampal sclerosis in pathology showed increased T2 time greater than 2 SD of mean value of normal controls. But, the T2 values are upper normal range in non-hippocampal sclerosis. The lateralizing value of T2 relaxometry is 50% in TLE patients, and 62.5% in pathology-proven hippocampal sclerosis groups. CONCLUSIONS: There is a clear distinction of T2 relaxation time between the patients of hippocampal sclerosis and normal controls or non-hippocampal sclerosis. These findings suggest that the T2 relaxation time is a reliable objective measurement of hippocampal pathology, especially hippocampal sclerosis in TLE.