Significant Difference In Apparent Diffusion Coefficient Values Research Articles

MR Diffusion Weighted Imaging for Evaluation of Radiotherapeutic Effects on Rabbit VX2 Tumor Model

To investigate the feasibility of magnetic resonance (MR) diffusion weighted imaging (DWI) for evaluation of radiotherapeutic effects on rabbit VX2 tumor model. Sixteen New Zealand white rabbits received a subcutaneous implantation of VX2 tumor cell suspension 0.5 mL (4 x 10(7) cells/mL) in their right thighs to set up tumor model. And 2 weeks later they were randomly divided into therapy group (Group T, n = 10) and control group (Group C, n = 6). Group T received radiotherapy at a single dose of 10 Gy. MR imaging (MRI) scan including short TI inversion recovery echo-planar imaging DWI, T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI) sequences were performed 1 day prior to as well as 1 day, 2 days, 3 days and 7 days after radiotherapy. Group C received only MRI scan at the same time points without any treatment. MRI appearance on T2WI, T1WI, and DWI images was compared and tumor volume was calculated. Apparent diffusion coefficient (ADC) values of the tumor were evaluated in all cases. HE staining was used for pathological study. Necrosis (n = 8) and hemorrhage (n = 2) were seen gradually on T2WI and T1WI images of Group T after time point of day 2 after irradiation. In Group C, no obvious necrosis was found until day 7. There was no significant difference in tumor volume between the two groups before radiotherapy. After radiotherapy, tumors in Group T showed a gradual growth but not as obvious as Group C. There was a significant difference in tumor volume between the two groups from day 2 on (P < 0.05). ADC value changed dramatically right from the 1st day after radiotherapy in Group T [(0.99 +/- 0.15) x 10(-3) mm2/s for 1 day before radiotherapy, (1.23 +/- 0.08) x 10(-3), (1.45 +/- 0.07) x 10(-3), (1.63 +/- 0.06) x 10(-3), and (2.02 +/- 0.18) x 10(-3) mm2/s for day 1, 2, 3, and 7]; and ADC value had no significant changes after radiotherapy in Group C except day 7 [(1.07 +/- 0.08) x 10(-3) mm2/s for 1 day before radiotherapy, (1.03 +/- 0.04) x 10(-3), (1.05 +/- 0.02) x 10(-3), (1.05 +/- 0.05) x 10(-3), and (0.95 +/- 0.07) x 10(-3) mm2/s for day 1, 2, 3, and 7]. There was significant difference in ADC value between the two groups for each time point after radiotherapy (P < 0.01). Pathological study showed that the number of viable tumor cells in Group T decreased 1 day after radiotherapy, and the inflammatory cell infiltration was marked and almost all viable tumor cells disappeared by day 7 after radiotherapy. DWI is a new promising technique for monitoring radiotherapy outcomes. ADC value may give a prior clue on physiological changes of radiotherapy before routine MRI could tell.

ADC value and diffusion tensor imaging of prostate cancer: Changes in carbon‐ion radiotherapy

To assess the apparent diffusion coefficient (ADC) value and diffusion tensor image (DTI) including fractional anisotropy (FA) of the noncancerous prostate and prostate cancer before and after carbon-ion radiotherapy (CIRT). Nine patients with biopsy-proven prostate cancer underwent 1.5T magnetic resonance (MR) examinations. One patient with benign prostatic hypertrophy and one healthy volunteer were also examined as references. The changes in ADC values and DTI of the entire prostate calculated from b-values of 0 and 700 (s/mm(2)) were estimated between before and after CIRT. ADC values of prostate cancer significantly increased after CIRT by paired t-test (P < 0.01) but those of noncancerous inner gland (IG) and peripheral zone (PZ) showed no significant change. By analysis of variance, significant differences in ADC values were observed among prostate cancer and noncancerous IG and PZ before CIRT (P < 0.05). After CIRT, those significant differences had disappeared. FAs showed no significant differences in any comparisons. DTI showed changes in the direction of the main axis of the tensor in prostate cancer after CIRT. There were changes in ADC and DTI in prostate cancer after CIRT. They may be useful for monitoring prostatic structural changes under radiotherapy.

Characteristics of typical and atypical meningiomas on ADC maps with respect to schwannomas

The differences in apparent diffusion coefficient (ADC) between typical and atypical meningiomas and schwannomas were investigated, with 41 patients included in the study. There were no significant differences in ADC values or ADC ratios between typical and atypical meningiomas. The discrimination between schwannomas and the typical and atypical meningiomas on ADC maps was reliable, with significant differences in ADC values and ratios and with the narrow range of ADC values in meningiomas.

Apparent Diffusion Coefficient is Increased in Children with Tuberous Sclerosis Complex Personal Experience and Review of the Literature

Diffusion-weighted imaging (DWI) provides information on tissue integrity and shows increased sensivity in detecting brain white matter disease compared to traditional T2-weighted MRI. We compared apparent diffusion coefficient (ADC) values in brain lesions and normal appearing white matter (NAWM) in patients with tuberous sclerosis complex (TSC) to normal brain tissue in the control group. MRI and DWI were performed in 14 patients with TSC (age range 7-16 years) and in 18 age-matched normal control subjects. ADC values measured from 44 supratentorial cortical tubers, 37 white matter lesions, 80 NAWM were compared to those in control subjects. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U tests. The highest ADCs were measured in cortical tubers (mean ADC, 1.24×10-3 mm(2)/s), followed in descending order by WM lesions (mean ADC, 1.07×10-3 mm(2)/s), NAWM (mean ADC, 0.83×10-3 mm(2)/s). We found a significant difference in ADC values of gray, WM lesions and NAWM in TSC patients compared to the control group (p<0,0001). Elevated ADC values in NAWM in TSC patients may be caused by subtle depletion of myelin sheaths and looseness of structures within the brain parenchyma due to underlying migration disorders.

Apparent diffusion coefficient of pituitary macroadenoma evaluated with line-scan diffusion-weighted imaging

Objective The goal of this study was to evaluate the consistency of pituitary macroadenoma using apparent diffusion coefficient (ADC) with line-scan diffusion-weighted imaging (LSDWI). Methods Patients with pituitary macroadenoma ( n = 19) were studied prospectively. The LSDWI was performed using a maximum b factor of 1000 s/mm 2. The consistency of macroadenoma was rated as soft, intermediate or hard at transsphenoidal surgery. The ADC values of tumors were compared with the tumor-consistency ratings. Results A soft consistency was found at surgery in 13 patients (mean ADC: 0.84 ± 0.1 × 10 −3 mm 2/s); an intermediate consistency was observed in six patients (mean ADC: 0.81 ± 0.16 × 10 −3 mm 2/s). No tumors of hard consistency were found. There was no significant difference in ADC values between tumors of soft consistency compared with tumors of intermediate consistency ( P = 0.37). Conclusions A relationship between tumor consistency and the ADCs of soft and intermediate macroadenomas was not shown in this study using LSDWI.

Cerebral and cerebellar ADC values during a migraine attack

We investigated the diffusion-weighted MRI changes, apparent diffusion coefficient (ADC) values, and conventional MRI findings in specific brain areas during migraine attacks in patients with and without aura. Included in the study were 22 patients (2 male, 20 female) aged between 17 and 49 years who were diagnosed as having migraine according to the diagnostic criteria of the International Headache Society. Also included in the study were 18 age- and sex-matched healthy volunteers. Hyperintense lesions were evaluated in conventional MR images. Heavily diffusion-weighted images, ADC maps, and segmented ADC maps generated for regional ADC (rADC) measurements, were also studied. ADC values from specific brain areas were used with appropriate region of interests (ROI). Migraine with aura was diagnosed in 13 patients and migraine without aura was diagnosed in 9 patients. A total of 23 hyperintense lesions within the periventricular white matter and deep white matter were detected in five patients (21.8%). All of these hyperintense lesions were seen in migraine patients with aura. In only one patient did a hyperintense lesion show an increased diffusion pattern on diffusion-weighted images and ADC maps. One hyperintense lesion was detected in the control group (5.5%). There was no significant difference in ADC values between the migraine and control groups. T2-weighted hyperintense lesions were significantly more frequent in migraine patients especially in those with aura than in the control group. No diffusion alterations in diffusion-weighted images were detected in the infra- and supratentorial brain areas during migraine attacks in patients with and without aura.

Apparent diffusion coefficient in malignant lymphoma and carcinoma involving cavernous sinus evaluated by line scan diffusion‐weighted imaging

To evaluate the apparent diffusion coefficient (ADC) of malignant lymphomas and carcinomas involving cavernous sinus by line scan diffusion-weighted imaging (LSDWI) and to determine the usefulness of this method for differentiating between the two tumors. Four patients with malignant lymphomas and six patients with carcinomas were prospectively studied. LSDWI images were obtained with two different b values of 5 seconds/mm(2) and 1000 seconds/mm(2) in the coronal plane. The ADC values of the two types of tumors were calculated and compared. LSDWI provided diagnostic images with minimum susceptibility artifacts and enabled measurement of the ADC. The ADC value (mean +/- SD) was 0.51 +/- 0.06 x 10(-3) mm(2)/second in malignant lymphomas and 0.99 +/- 0.08 x 10(-3) mm(2)/second in carcinomas. A significant difference in ADC values was found between the two (P < 0.01). Malignant lymphomas showed significantly lower ADC value than carcinomas. ADC provides additional useful information about differentiation between these tumors.

Dorsolateral Prefrontal Cortex and Anterior Cingulate Cortex White Matter Alterations in Late-Life Depression

The dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC) are critical for mood regulation. Alterations in the white matter connections of these regions may impair their role in mood regulation and increase the risk of developing depression. This study used diffusion tensor imaging to examine for white matter microstructural abnormalities of these regions and of central white matter structures in late-life depression. One hundred six elderly depressed subjects and eighty-four elderly nondepressed subjects underwent clinical assessment and diffusion tensor imaging. The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were measured in regions of interest placed in the white matter of the DLPFC, ACC, corpus callosum, and internal capsule. Differences between groups were assessed, controlling for age, sex, and total cerebral volume. After controlling for covariates, depressed subjects had significantly lower FA values in white matter of the right ACC, bilateral superior frontal gyri, and left middle frontal gyrus. There were no significant differences in ADC values. Lower FA, representing lower tissue organization, is observed in depressed elders in the DLPFC and right ACC. These findings support the hypothesis that altered connectivity between brain regions contributes to the risk of depression.

Magnetic resonance diffusion–weighted imaging: extraneurological applications

Diffusion-weighted (Dw) imaging has for a number of years been a diagnostic tool in the field of neuroradiology, yet only since the end of the 1990s, with the introduction of echoplanar imaging (EPI) and the use of sequences capable of performing diffusion studies during a single breath hold, has it found diagnostic applications at the level of the abdomen. The inherent sensitivity to motion and the magnetic susceptibility of Dw sequences nonetheless still create problems in the study of the abdomen due to artefacts caused by the heartbeat and intestinal peristalsis, as well as the presence of various parenchymal-gas interfaces. With regard to focal liver lesions, a review of the literature reveals that Dw imaging is able to differentiate lesions with high water content (cysts and angiomas) from solid lesions. With regard to the latter, although there are differences between benign forms [focal nodular hyperplasia (FNH), adenoma] and malignant forms [metastasis, hepatocellular carcinoma (HCC)] in their apparent diffusion coefficient (ADC) in the average values for histological type, there is a significant overlap in values when lesions are assessed individually, with the consequent problem of their correct identification. One promising aspect is the possibility of quantifying the degree of fibrosis in patients with chronic liver disease and cirrhosis given that the deposit of collagen fibres "restricts" the motion of water molecules and therefore reduces ADC values. However, even in this field, studies can only be considered preliminary and far from real clinical applications. The retroperitoneum is less affected by motion artefacts and similarly deserves the attention of Dw imaging. Here it is possible to differentiate mucin-producing tumours of the pancreas from pseudocystic forms on the basis of ADC values even though the limited spatial resolution of Dw imaging does not enable the identification of small lesions. Dw imaging may be applied to the study of the kidney to differentiate hydronephrosis from pyonephrosis and with regard to tumours, solid from pseudocystic forms. In addition, given that renal parenchyma has significantly variable ADC values on the basis of the anatomic section and physiological conditions, the possibility of assessing functional alterations is currently being studied. Indeed, a good correlation has been found between ADC values and glomerular filtration rate. With regard to musculoskeletal applications, the absence of motion artefacts in the regions studied has enabled the development of sequences less sensitive to magnetic susceptibility and with greater spatial resolution than EPI. Attempts have therefore been made to use Dw imaging in the characterization of soft-tissue tumours although the findings so far have been disputed. Greater agreement has been found regarding sensitivity of the technique in assessing response of these tumours to chemotherapy: tumour necrosis is thought to increase ADC whereas the persistence of vital neoplastic tissue tends to lower it. One of the most promising applications of Dw imaging is without doubt the assessment of vertebral collapse where a high ADC has been shown to be associated with an osteoporotic cause and a low ADC with a neoplastic cause. Nonetheless, even here, a moderate overlap between ADC values of the two types has been encountered. Dw imaging has also been used in the assessment of bone marrow cellularity: areas of tightly packed cells show a higher ADC value than hypocellular areas. In particular, no significant difference in ADC is noted between normal hypercellular bone marrow and hypercellular bone marrow secondary to lymphomatous infiltration whereas this difference is significant between hypocellular, normocellular and haematopoietic hypercellular bone marrow. With regard to the study of joints, the limited structure dimensions, particularly cartilage, creates technical difficulties related to spatial resolution and an adequate signal-to-noise ratio, problems that can only be solved by further technological developments. Lastly, a significant difference in ADC values between degenerative and inflammatory effusion has been found, a fact that may be explained as the result of the activity of hyaluronidase present in inflammatory forms, which causes a reduction in the concentration of hyaluronic acid with a consequent decrease in viscosity.

Diffusion-Weighted Imaging of Edema following Traumatic Brain Injury in Rats: Effects of Secondary Hypoxia

Hypoxia and edema are frequent and serious complications of traumatic brain injury (TBI). Therefore, we examined the effects of hypoxia on edema formation after moderate lateral fluid percussion (LFP) injury using NMR diffusion-weighted imaging (DWI). Adult Sprague-Dawley rats were separated into four groups: sham uninjured (S), hypoxia alone (H), trauma alone (T), and trauma and hypoxia (TH). Animals in Groups T and TH received LFP brain injury, with Groups H and TH undergoing 30 min of moderately severe hypoxia (FiO2 = 0.11) immediately after surgery or TBI (respectively). DWIs were obtained at 2, 4, and 24 h and at 1 week post injury, and apparent diffusion coefficient (ADC) maps were constructed. Animals in Groups T and TH showed an early decrease (p < 0.001) in ADC values in the cortex ipsilateral to TBI 4 hr post injury, followed by elevated ADCs 1 week later (p < 0.05). No significant differences in ADC values were seen between T and TH groups in the ipsilateral cortex. In contrast, the ipsilateral hippocampus for Group TH showed only increasing ADC values. This hyperintensity in the ADC map began at 2 h after TBI, was significant by 24 h (p < 0.05), and reached a maximum at 1 week. This hyperintensity was not observed in Group T. Histopathology seen in TBI animals corresponded well with the pathology observed with MRI. Midline shifts reflecting edema were only observed in TBI animals with little difference between normoxic (T) and hypoxic animals (TH). In sum, this study demonstrates that the development and extent of brain edema following TBI can be examined in vivo in rats using DWI technology. TBI resulted in an early decrease in ADC values indicating cytotoxic edema in the cortex that was followed at 1 week by an increase in the ADC that was associated with decreased tissue cellularity. Histopathology corresponded well to the regions of brain injury and edema visualized by T2 and DWI procedures. Overall, the addition of hypoxia to brain injury resulted in a small increase in the magnitude of edema in hippocampus and cortex over that seen with trauma alone.

Normal and transplanted rat kidneys: diffusion MR imaging at 7 T.

To investigate the feasibility of obtaining reproducible apparent diffusion coefficient (ADC) maps of normal rat kidneys by using respiratory-triggered spin-echo diffusion-weighted magnetic resonance (MR) imaging, to investigate the sensitivity of ADC maps in the evaluation of renal blood flow, and to use this technique to monitor acute graft rejection in transplanted rat kidneys. Spin-echo diffusion-weighted MR imaging measurements were performed in 20 normal rats and nine rats that had undergone transplantation (six rats had received allografts; three had received isografts) at 7 T. To evaluate the effect of alteration in blood flow and water transport function, angiotensin II was infused in six normal rats and a series of spin-echo diffusion-weighted MR images was obtained at five time points. Transplanted kidneys were monitored by obtaining spin-echo diffusion-weighted MR images and gradient-echo MR images every 2 hours for 8 hours on postoperative day 4. Statistical analysis was performed with repeated-measures multivariate analysis of variance and the paired t test. No significant differences in ADC values were observed between right and left kidneys in all three orthogonal directions; however, a small difference was observed between the cortex and medulla. ADC values in the cephalocaudal and mediolateral directions were higher than those in the anteroposterior direction (P <.01 for all). ADC values in the cortex and medulla decreased significantly (by >35%, P <.01) during angiotensin II-induced reduction in renal blood flow. No significant signal intensity change was observed between native and transplanted kidneys on gradient-echo MR images. Allografts exhibited decreased ADC values (P <.01) and isografts exhibited similar ADC values compared with native kidneys. These findings suggest that reproducible renal ADC maps can be obtained in rats by using spin-echo diffusion-weighted MR imaging at 7 T. Spin-echo diffusion-weighted MR imaging may have potential as a noninvasive tool for monitoring early graft rejection after kidney transplantation.