Apparent diffusion coefficient and fractional anisotropy of newly diagnosed grade II gliomas.
ABSTRACT: Distinguishing between low-grade oligodendrogliomas (ODs) and astrocytomas (AC) is of interest for defining prognosis and stratifying patients to specific treatment regimens. The purpose of this study was to determine if the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) from diffusion imaging can help to differentiate between newly diagnosed grade II OD and AC subtypes and to evaluate the ADC and FA values for the mixed population of oligoastrocytomas (OA). Fifty-three patients with newly diagnosed grade II gliomas were studied using a 1.5T whole body scanner (23 ODs, 16 ACs, and 14 OAs). The imaging protocol included post-gadolinium T1-weighted images, T2-weighted images, and either three and/or six directional diffusion imaging sequence with b = 1000 s/mm(2). Diffusion-weighted images were analyzed using in-house software to calculate maps of ADC and for six directional acquisitions, FA. The intensity values were normalized by values from normal appearing white matter (NAWM) to generate maps of normalized apparent diffusion coefficient (nADC) and normalized fractional anisotropy (nFA). The hyperintense region in the T2 weighted image was defined as the T2All region. A Mann-Whitney rank-sum test was performed on the 25th, median, and 75th nADC and nFA among the three subtypes. Logistic regression was performed to determine how well the nADC and nFA predict subtype. Lesions diagnosed as being OD had significantly lower nADC and significantly higher nFA, compared to AC. The nADC and nFA values individually classified the data with an accuracy of 87%. Combining the two did not enhance the classification. The patients with OA had nADC and nFA values between those of OD and AC. This suggests that ADC and FA may be helpful in directing tissue sampling to the most appropriate regions for taking biopsies in order to make a definitive diagnosis.
Project description:The aim was to evaluate diffusion-weighted imaging (DWI) as a tool for measuring treatment response in adolescents with enthesitis-related arthropathy (ERA).Twenty-two adolescents with ERA underwent routine MRI and DWI before and after TNF inhibitor therapy. Each patient's images were visually scored by two radiologists using the Spondyloarthritis Research Consortium of Canada system, and sacroiliac joint apparent diffusion coefficient (ADC) and normalized ADC (nADC) were measured for each patient. Therapeutic clinical response was defined as an improvement of ? 30% physician global assessment and radiological response defined as ? 2.5-point reduction in Spondyloarthritis Research Consortium of Canada score. We compared ADC and nADC changes in responders and non-responders using the Mann-Whitney-Wilcoxon test.For both radiological and clinical definitions of response, reductions in ADC and nADC after treatment were greater in responders than in non-responders (for radiological response: ADC: P < 0.01; nADC: P = 0.055; for clinical response: ADC: P = 0.33; nADC: P = 0.089). ADC and nADC could predict radiological response with a high level of sensitivity and specificity and were moderately sensitive and specific predictors of clinical response (the area under the receiver operating characteristic curves were as follows: ADC: 0.97, nADC: 0.82 for radiological response; and ADC: 0.67, nADC: 0.78 for clinical response).DWI measurements reflect the response to TNF inhibitor treatment in ERA patients with sacroiliitis as defined using radiological criteria and may also reflect clinical response. DWI is more objective than visual scoring and has the potential to be automated. ADC/nADC could be used as biomarkers of sacroiliitis in the clinic and in clinical trials.
Project description:Diffusion and diffusion tensor imaging techniques (DTI) are widely available and used both in central nervous system and body imaging, including gynecological diseases.The aims of this study were to assess the capability of DTI of uterine zones in relation to the menstrual cycle and ascertain the normal apparent diffusion coefficient and fractional anisotropy values at 3T magnetic resonance imaging (MRI).Prospective clinical study.A total of 13 young reproductive and 12 postmenopausal healthy volunteers were included in the study. MRI examination included sagittal T2-weighted and single-shot echo planar imaging DTI obtained under free breathing. Fractional anisotropy (FA) values of the endometrium, junctional zone, and myometrium were determined.The median (minimum-maximum) FA of the endometrium, myometrium, and junctional zone of the reproductive group were 0.31 (0.260-0.465), 0.42 (0.302-0.664), and 0.58 (0.420-0.745), respectively, in the proliferative phase and 0.26 (0.180-0.413), 0.48 (0.357-0.656), and 0.59 (0.490-0.675)], respectively, in the secretory phase. In the postmenopausal group, the FA values of the endometrium, myometrium, and junctional zone were 0.275 (0.136-0.425), 0.255 (0.191-0.553), and 0.27 (0.129-0.397), respectively. Apparent diffusion coefficient (ADC) values of the endometrium, myometrium, and junctional zone of the reproductive group were 1.25±0.254 (0.970-1.463), 1.67 (1.213-1.854), and 1.23 (0.853-1.301), respectively, in the proliferative phase and 1.32±0.283 (1.165-1.706), 1.55 (1.360-1.791), and 1.17 (1.163-1.705), respectively, in the secretory phase. In the postmenopausal group, the ADC values of the endometrium, myometrium, and junctional zone were measured as 1.100±0.192 (0.850-1.302), 1.14 (0.864-1.283), and 1.09 (0.912-1.291). The FA values of the endometrium and myometrium were lower in the secretory phase of the reproductive group, while ADC values were higher. However, both the FA and ADC values were lower in the postmenopausal group.The present study showed that uterine DTI is feasible when used quantitatively. While FA values tend to decrease, ADC values increase significantly in all zones in the secretory phase except the junctional zone. Zonal FA and ADC values of postmenopausal women are lower in comparison to those in young women.
Project description:To develop a diffusion-tensor-imaging (DTI) protocol that is sensitive to the complex diffusion and perfusion properties of the healthy and malignant pancreas tissues.Twenty-eight healthy volunteers and nine patients with pancreatic-ductal-adenocacinoma (PDAC), were scanned at 3T with T2-weighted and DTI sequences. Healthy volunteers were also scanned with multi-b diffusion-weighted-imaging (DWI), whereas a standard clinical protocol complemented the PDAC patients' scans. Image processing at pixel resolution yielded parametric maps of three directional diffusion coefficients ?1, ?2, ?3, apparent diffusion coefficient (ADC), and fractional anisotropy (FA), as well as a ?1-vector map, and a main diffusion-direction map.DTI measurements of healthy pancreatic tissue at b-values 0,500 s/mm² yielded: ?1?=?(2.65±0.35)×10?³, ?2?=?(1.87±0.22)×10?³, ?3?=?(1.20±0.18)×10?³, ADC?=?(1.91±0.22)×10?³ (all in mm²/s units) and FA?=?0.38±0.06. Using b-values of 100,500 s/mm² led to a significant reduction in ?1, ?2, ?3 and ADC (p<.0001) and a significant increase (p<0.0001) in FA. The reduction in the diffusion coefficients suggested a contribution of a fast intra-voxel-incoherent-motion (IVIM) component at b?100 s/mm², which was confirmed by the multi-b DWI results. In PDACs, ?1, ?2, ?3 and ADC in both 0,500 s/mm² and 100,500 s/mm² b-values sets, as well as the reduction in these diffusion coefficients between the two sets, were significantly lower in comparison to the distal normal pancreatic tissue, suggesting higher cellularity and diminution of the fast-IVIM component in the cancer tissue.DTI using two reference b-values 0 and 100 s/mm² enabled characterization of the water diffusion and anisotropy of the healthy pancreas, taking into account a contribution of IVIM. The reduction in the diffusion coefficients of PDAC, as compared to normal pancreatic tissue, and the smaller change in these coefficients in PDAC when the reference b-value was modified from 0 to 100 s/mm², helped identifying the presence of malignancy.
Project description:BACKGROUND AND PURPOSE:Baseline diffusion or apparent diffusion coefficient (ADC) characteristics have been shown to predict outcome related to DIPG, but the predictive value of post-radiation ADC is less well understood. ADC parametric mapping (FDM) was used to measure radiation-related changes in ADC and compared these metrics to baseline ADC in predicting progression-free survival and overall survival using a large multi-center cohort of DIPG patients (Pediatric Brain Tumor Consortium-PBTC). MATERIALS AND METHODS:MR studies at baseline and post-RT in 95 DIPG patients were obtained and serial quantitative ADC parametric maps were generated from diffusion-weighted imaging based on T2/FLAIR and enhancement regions of interest (ROIs). Metrics assessed included total voxels with: increase in ADC (iADC); decrease in ADC (dADC), no change in ADC (nADC), fraction of voxels with increased ADC (fiADC), fraction of voxels with decreased ADC (fdADC), and the ratio of fiADC and fdADC (fDM Ratio). RESULTS:A total of 72 patients were included in the final analysis. Tumors with higher fiADC between baseline and the first RT time point showed a trend toward shorter PFS with a hazard ratio of 6.44 (CI 0.79, 52.79, p?=?0.083). In contrast, tumors with higher log mean ADC at baseline had longer PFS, with a hazard ratio of 0.27 (CI 0.09, 0.82, p?=?0.022). There was no significant association between fDM derived metrics and overall survival. CONCLUSIONS:Baseline ADC values are a stronger predictor of outcome compared to radiation related ADC changes in pediatric DIPG. We show the feasibility of employing parametric mapping techniques in multi-center studies to quantitate spatially heterogeneous treatment response in pediatric tumors, including DIPG.
Project description:Navigated transcranial magnetic stimulation (nTMS) combined with diffusion tensor imaging (DTI) is used preoperatively in patients with eloquent-located brain lesions and allows analyzing non-invasively the spatial relationship between the tumor and functional areas (e.g. the motor cortex and the corticospinal tract [CST]). In this study, we examined the diffusion parameters FA (fractional anisotropy) and ADC (apparent diffusion coefficient) within the CST in different locations and analyzed their interrater reliability and usefulness for predicting the patients' motor outcome with a precise approach of specific region of interest (ROI) seeding based on the color-coded FA-map.Prospectively collected data of 30 patients undergoing bihemispheric nTMS mapping followed by nTMS-based DTI fiber tracking prior to surgery of motor eloquent high-grade gliomas were analyzed by 2 experienced and 1 unexperienced examiner. The following data were scrutinized for both hemispheres after tractography based on nTMS-motor positive cortical seeds and a 2nd region of interest in one layer of the caudal pons defined by the color-coded FA-map: the pre- and postoperative motor status (day of discharge und 3 months), the closest distance between the tracts and the tumor (TTD), the fractional anisotropy (FA) and the apparent diffusion coefficient (ADC). The latter as an average within the CST as well as specific values in different locations (peritumoral, mesencephal, pontine).Lower average FA-values within the affected CST as well as higher average ADC-values are significantly associated with deteriorated postoperative motor function (p = 0.006 and p = 0.026 respectively). Segmental analysis within the CST revealed that the diffusion parameters are especially disturbed on a peritumoral level and that the degree of their impairment correlates with motor deficits (FA p = 0.065, ADC p = 0.007). No significant segmental variation was seen in the healthy hemisphere. The interrater reliability showed perfect agreement for almost all analyzed parameters.Adding diffusion weighted imaging derived information on the structural integrity of the nTMS-based tractography results improves the predictive power for postoperative motor outcome. Utilizing a second subcortical ROI which is specifically seeded based on the color-coded FA map increases the tracking quality of the CST independently of the examiner's experience. Further prospective studies are needed to validate the nTMS-based prediction of the patient's outcome.
Project description:To evaluate the feasibility of differentiating between hepatocellular carcinomas (HCC) and healthy liver using diffusion tensor imaging (DTI).All subjects underwent an abdominal examination on a 3.0T MRI scanner. Two radiologists independently scored the image quality (IQ). An optimal set of DTI parameters was obtained from a group of fifteen volunteers with multiple b-values (100, 300, 500, and 800 s/mm2) and various diffusion-encoding directions (NED = 6, 9, and 12)using two way ANOVA analysis. Eighteen Patients with HCC underwent DTI scans with the optimized parameters. Fractional anisotropy(FA) and average apparent diffusion coefficient (ADC) values were measured. The differences of FA and ADC values between liver healthy region and HCC lesion were compared through paired t tests.There were no significant changes in liver IQ and FA/ADC values with increased NED(P >0.05), whereas the liver IQ and FA/ADC values decreased significantly with increased b-values(P <0.05). Good IQ, acceptable scan time and reasonable FA/ADC values were acquired using NED = 9 with b-value of (0,300) s/mm2. Using the optimized DTI sequence, ADC value of the tumor lesion was significantly lower than that of the healthy liver region (1.30 ± 0.34×10-3 vs 1.52 ± 0.27×10-3 mm2/s, P = 0.013), whereas the mean FA value of the tumor lesion (0.42 ± 0.11) was significantly higher than the normal liver region (0.32 ± 0.10) (P = 0.004).Either FA or ADC value from DTI can be used to differentiate HCC from healthy liver. HCC lead to higher FA value and lower ADC value on DTI than healthy liver.
Project description:To evaluate the feasibility of differentiating between acute pancreatitis (AP) and healthy pancreas using diffusion tensor imaging (DTI) and correlate apparent diffusion coefficient (ADC) /fractional anisotropy (FA) values with the severity of AP.66 patients diagnosed with AP and 20 normal controls (NC) underwent DTI sequences and routine pancreatic MR sequences on a 3.0T MRI scanner. Average ADC and FA values of the pancreatic were measured. Differences of FA and ADC values between the AP group and the NC group with AP and healthy pancreas were compared by two-sample independent t-test. The severity of AP on MRI was classified into subgroups using MR severity index (MRSI), where the mean FA and ADC values were calculated. Relationship among the FA values, ADC values and MRSI were analyzed using Spearman's rank correlation coefficients.The pancreatic mean ADC value in the AP group (1.68 ± 0.45×10-3mm2/s) was significantly lower than in the NC group (2.09 ± 0.55×10-3mm2/s) (P = 0.02); the same as mean FA value (0.39 ± 0.23 vs 0.54 ± 0.12, P = 0.00). In the subgroup analysis, the pancreatic ADC and FA value of edema AP patients was significantly higher than necrosis AP patients with P = 0.000 and P = 0.001respectively. In addition, as severity of pancreatitis increased according to MRSI, lower pancreatic ADC (r = -0.635) and FA value (r = -0.654) were noted.Both FA and ADC value from DTI can be used to differentiate AP patients from NC. Both ADC and FA value of pancreas have a negative correlation with the severity of AP.
Project description:We evaluated the feasibility of using the kinetic of diffusion-weighted MRI (DWI) and the normalized apparent coefficient diffusion (ADC) map value as an early biomarker in patients treated by external beam radiotherapy (EBRT). Twelve patients were included within the frame of a multicenter phase II trial and treated for intermediate risk prostate cancer (PCa). Multiparametric MRI was performed before treatment (M0) and every 6 months until M24. Association between nADC and PSA or PSA kinetic was evaluated using the test of nullity of the Spearman correlation coefficient. The median rates of PSA at the time of diagnosis, two years and four years after EBRT were 9.29?ng/ml (range from 5.26 to 17.67), 0.68?ng/ml (0.07-2.7), 0.47?ng/ml (0.09-1.39), respectively. Median nADC increased from 1.14?×?10-3 mm2/s to 1.59?×?10-3 mm2/s between M0 and M24. Only one patient presented a decrease of nADC (1.35?×?10-3?mm2/s and 1.11?×?10-3?mm2/s at M0 and M12 respectively). The increase in nADC at M6 was correlated with PSA decrease at M18, M24 and M30 (p?<?0.05). The increase in nADc at M12 was correlated with PSA decrease at M36 (p?=?0.019). Early nADC variation were correlated with late PSA decrease for patients with PCa treated by EBRT.
Project description:OBJECTIVE: To assess rhabdomyolysis-associated skeletal muscle changes induced by complete ischaemia in rabbits using MRI. METHODS: Acute ischaemia was induced in the right hind limb of 34 New Zealand white rabbits by arterial ligation. MRI of vastus lateralis was carried out pre-operatively and every hour post-operatively up to 7 h. T1 weighted images, T2 weighted images with fat suppression, T2 maps and diffusion tensor scans were obtained. The correlation of MRI findings with histopathological changes in biopsies of vastus lateralis was examined. RESULTS: Histopathology demonstrated early cellular oedema 1 h post ischaemia and irreversible injuries by 7 h, including loss of striation and broken muscle fibres. T2 weighted images with fat suppression showed inhomogeneous high signal intensity of vastus lateralis, which progressively increased from 2 h following ischaemia. The T2 relaxation rate of ischaemic vastus lateralis was significantly greater than normal muscle (p<0.001) and demonstrated a linear increase with time following ischaemia. A similar linear increase was also found in the ischaemic vastus lateralis apparent diffusion coefficient (ADC) 1-5 h post ischaemia (p=0.006). Both the T2 ADC and fractional anisotropy (FA) were significantly higher on the ischaemic side 7 h post ischaemia (for T2, p=0.02; for ADC, p=0.004). CONCLUSION: Muscle oedema is detectable on MR images and is reflected well by T2, ADC and FA values. MRI may have value in clinical evaluation of rhabdomyolysis. ADVANCES IN KNOWLEDGE: Ischaemic changes detected by MRI may have value in the diagnosis of rhabdomyolysis.
Project description:To evaluate correlations between tumour response to definitive chemoradiotherapy (CRT) in oesophageal squamous cell carcinoma (SCC) and histogram-derived apparent diffusion coefficient (ADC) parameters on diffusion-weighted MR images.Forty patients with clinical T3-4 oesophageal SCC underwent concurrent CRT. MR examination at 3 T was performed 1-3 days prior to CRT. Readout-segmented echo-planar diffusion imaging was used to acquire ADC maps. Pre- and post-treatment CT examinations were performed. Histogram parameters (mean, 10th, 25th, 50th, 75th, 90th percentiles, skewness and kurtosis) of the ADC values were compared with post-treatment disease status based on RECIST and the tumour regression ratio.None of the ADC parameters showed significant correlation with post-treatment status (range of Spearman's ? values - 0.19 to 0.14, range of p values 0.22-0.47) or tumour regression ratio (range of Spearman's ? values - 0.045 to 0.18, range of p values 0.26-0.96). Neither progression-free survival (PFS) (p = 0.17) nor overall survival (OS) (p = 0.15) was significantly different between the two groups corresponding to the lower (< median) and upper arms (? median) of the mean ADC values.Histogram-derived pretreatment ADC parameters were not predictive imaging biomarkers for tumour response to CRT in patients with oesophageal SCC.• Apparent diffusion coefficient (ADC) values are derived from diffusion-weighted MR imaging. • High-resolution diffusion-weighted images are generated by readout-segmented echo-planar diffusion imaging. • Readout-segmented echo-planar diffusion-weighted imaging enabled evaluation of ADC parameters. • Pretreatment ADC parameters do not predict chemoradiotherapy response in patients with oesophageal carcinoma.