Compartmentation of intracellular water in multicellular tumor spheroids: diffusion and relaxation NMR.

Diffusion and relaxation of water in C6 glioma and MLS human ovarian carcinoma spheroids were measured from 1D projections acquired using a 2D diffusion-relaxation correlation pulse sequence and processed by non-negative least-square (NNLS) analysis. Systematic underestimation of I(s) and ADC(s) were observed for I(s)/(I(s) + I(f)) < 0.001. In the presence of spheroids, two apparent diffusion coefficient (ADC) compartments were observed, where ADC(f), ADC(s), and I(f), I(s) are the respective ADCs and signal intensities of the fast and slow compartments. These compartments differed also in their T(2) relaxation (ADC(s) = 0.5-0.74 x 10(-5) cm(2)/s, T(2) = 36-45 ms; and ADC(f) = 2.2-2.8 x 10(-5) cm(2)/s, T(2) = 280-316 ms). The two ADC compartments and the slow T(2) compartment were consistent with slow exchange. The fast T(2) compartment showed a drift with diffusion weighting, suggesting that it represents water exchanging between compartments that differ in their ADC and T(2). Both ADC(s) and I(s) were markedly attenuated with increasing diffusion time (Delta) for Delta < 100 ms, and increased at longer Delta. These results are consistent with restricted diffusion and fast relaxation of intracellular water for short diffusion time (T(1)' = 46.6 ms), and with predominant extracellular contribution to ADC(s) at longer diffusion times. Magn Reson Med 46:68-77, 2001.     

Diffusion-weighted magnetic resonance imaging: a potential non-invasive marker of tumour aggressiveness in localized prostate cancer

AIM: To evaluate diffusion-weighted magnetic resonance imaging (DW-MRI) as a marker for disease aggressiveness by comparing tumour apparent diffusion coefficients (ADCs) between patients with low- versus higher-risk localized prostate cancer. METHOD: Forty-four consecutive patients classified as low- [n = 26, stageT1/T2a, Gleason score < or = 6, prostate-specific antigen (PSA)< 10 (group 1)] or intermediate/high- [n = 18, stage > or = T2b and/or Gleason score > or = 7, and/or PSA > 10 (group 2)] risk, who subsequently were monitored with active surveillance or started neoadjuvant hormone and radiotherapy, respectively, underwent endorectal MRI. T2-weighted (T2W) and DW images (5 b values, 0-800 s/mm(2)) were acquired and isotropic ADC maps generated. Regions of interest (ROIs) on T2W axial images [around whole prostate, central gland (CG), and tumour] were transferred to ADC maps. Tumour, CG, and peripheral zone (PZ = whole prostate minus CG and tumour) ADCs (fast component from b = 0-100 s/mm(2), slow component from b = 100-800 s/mm(2)) were compared. RESULTS: T2W-defined tumour volume medians, and quartiles were 1.2 cm(3), 0.7 and 3.3 cm(3) (group 1); and 6 cm(3), 1.3 and 16.5 cm(3) (group 2). There were significant differences in both ADC(fast) (1778 +/- 264 x 10(-6) versus 1583 +/- 283 x 10(-6) mm(2)/s, p = 0.03) and ADC(slow) (1379 +/- 321 x 10(-6) versus 1196 +/- 158 x 10(-6) mm(2)/s, p = 0.001) between groups. Tumour volume (p = 0.002) and ADC(slow) (p = 0.005) were significant differentiators of risk group. CONCLUSION: Significant differences in tumour ADCs exist between patients with low-risk, and those with higher-risk localized prostate cancer. DW-MRI merits further study with respect to clinical outcomes.     

MR microscopy of multicomponent diffusion in single neurons.

This study examines multicomponent diffusion in isolated single neurons and discusses the implications of the results for macroscopic water diffusion in tissues. L7 Aplysia neurons were isolated and analyzed using a 600 MHz Bruker wide-bore instrument with a magnetic susceptibility-matched radiofrequency microcoil. Using a biexponential fit, the apparent diffusion coefficients (ADCs) from the cytoplasm (with relative fraction) were 0.48 +/- 0.14 x 10(-3) mm2 x s(-1) (61 +/- 11%) for the fast component, and 0.034 +/- 0.017 x 10(-3) mm2 x s(-1) (32 +/- 11%) for the slow component (N = 10). Diffusion in the nucleus appears to be primarily monoexponential, but with biexponential analysis it yields 1.31 +/- 0.32 x 10(-3) mm2 x s(-1) (89 +/- 6%) for the fast component and 0.057 +/- 0.073 x 10(-3) mm2 x s(-1) (11 +/- 6%) for the slow (N = 5). The slow component in the nucleus may be explained by cytoplasmic volume averaging. These data demonstrate that water diffusion in the cytoplasm of isolated single Aplysia neurons supports a multiexponential model. The ADCs are consistent with previous measurements in the cytoplasm of single neurons and with the slow ADC measurement in perfused brain slices. These distributions may explain the multiple compartments observed in tissues, greatly aiding the development of quantitative models of MRI in whole tissues.     

Apparent diffusion coefficient: a quantitative parameter for in vivo tumor characterization

PURPOSE: The purpose of the this study was to evaluate the potential of diffusion weighted imaging (DWI) to distinguish different tissue compartments in early, intermediate and advanced tumor stages. MATERIALS AND METHODS: Twenty-two male mice were induced with squamous cell tumor (SCCVII) and scanned with a clinical 1.5 T scanner. T1-SE, T2-FSE, diffusion weighted Line-Scan-MRI and contrast enhanced T1-SE were obtained from mice with early (tumor volume 10-100 mm(3)), intermediate (200-600 mm(3)), advanced tumors (600-1000 mm(3)) and tumor necrosis (>1500 mm(3)). The apparent diffusion coefficient (ADC) of different tumor compartments was calculated offline with a pixel-by-pixel method. The animals were sacrificed immediately after scanning and histopathologic correlation was performed. RESULTS: In early stages of tumor development, tumors appeared homogeneous on diffusion weighted images with an ADC of 0.64+/-0.06 x 10(-3) mm(2)/s. With tumor progression the ADC in the rim areas of tumor increased significantly (intermediate stage: 0.70+/-0.11 x 10(-3) mm(2)/s; advanced stage: 0.88+/-0.11 x 10(-3) mm(2)/s; tumor necrosis 1.03+/-0.06 x 10(-3) mm(2)/s), whereas the ADC in viable tumor remained constant. Histologically the areas with an increased ADC correlated well with areas of necrosis (reduced cell density). CONCLUSION: The ADC is a non-invasive technique to monitor changes in the biological structure of tumor tissue during tumor progression. Thus, DWI is a potential diagnostic tool for in-vivo tissue characterization.     

Diffusion MRI findings in Wilson's disease.

Six patients having Wilson's disease were studied with diffusion MRI in order to characterize cerebral lesions. Diffusion MRI was obtained using the spin-echo, echo-planar sequence with a gradient strength of 30 mT/m. The trace protocol was used in the axial imaging plane. Heavily diffusion-weighted (b=1000s/mm(2)) images, and the ADC (apparent diffusion coefficient) values from automatically generated ADC maps were studied. The ADC values of the normal brain parenchyma were available in 17 age-matched cases for comparison (ADC values, 0.85+/-0.11 x 10(-3)mm(2)/s). In Wilson's disease two distinct diffusion MRI patterns were observed by quantitative evaluations of the ADC maps; cytotoxic edema-like (ADC values, 0.52+/-0.03 x 10(-3)mm(2)/s), and vasogenic edema-like (ADC values, 1.42+/-0.17 x 10(-3)mm(2)/s) patterns. Diffusion imaging appears to be a promising sequence to evaluate the changes in the brain tissue in Wilson's disease at least by revealing two different patterns.     

Simultaneous diffusion MRI measurements from multiple perfused rat hippocampal slices.

Rat brain slices provide a controllable tissue model in which to investigate the biophysical basis of diffusion-weighted magnetic resonance (MR) signal changes observed clinically in nervous tissue after ischemic injury. This study describes a new multislice perfusion chamber that allows for the simultaneous acquisition of diffusion-weighted MR images from multiple perfused rat hippocampal slices (eight slices in the present study). These images had a signal-to-noise ratio (SNR) of 48 +/- 3 at b = 8080 s/mm(2), which was sufficient to analyze the multicomponent diffusion properties of water in rat hippocampal slices. The tissue water diffusion parameters (f(fast) = 0.527 +/- 0.041, D(fast) = 1.268 +/- 0.087 x 10(-3) mm(2)/s, and D(slow) = 0.060 +/- 0.003 x 10(-3) mm(2)/s) were stable for at least 8 hr after slice procurement (ANOVA, P > 0.05), suggesting that it may be possible to study the acute temporal evolution of diffusion changes in multiple brain slices following experimental perturbation.     

Apparent diffusion coefficient in pancreatic cancer: characterization and histopathological correlations

PURPOSE: To clarify the components primarily responsible for diffusion abnormalities in pancreatic cancerous tissue. MATERIALS AND METHODS: Subjects comprised 10 patients with surgically confirmed pancreatic cancer. Diffusion-weighted (DW) echo-planar imaging (b value = 0, 500 s/mm(2)) was employed to calculate the apparent diffusion coefficient (ADC). ADC values of cancer and noncancerous tissue were calculated. Furthermore, ADC values of the cancer were compared with histopathological results. RESULTS: The mean (+/-standard deviation) ADC value was significantly lower for tumor (1.27 +/- 0.52 x 10(-3) mm(2)/s) than for noncancerous tissue (1.90 +/- 0.41 x 10(-3) mm(2)/s, P < 0.05). Histopathological examination showed similar proportions of fibrotic area, cellular component, necrosis, and mucin in each case. Regarding the density of fibrosis in cancer, three cases were classified in the loose fibrosis group and the remaining seven cases were classified in the dense fibrosis group. The mean ADC value was significantly higher in the loose fibrosis group (1.88 +/- 0.39 x 10(-3) mm(2)/s) than in the dense fibrosis group (1.01 +/- 0.29 x 10(-3) mm(2)/s, P < 0.05). In quantitative analysis, ADC correlated well with the proportion of collagenous fibers (r = -0.87, P < 0.05). CONCLUSION: Collagenous fibers may be responsible for diffusion abnormalities in pancreatic cancer.     

Discrimination of metastatic cervical lymph nodes with diffusion-weighted MR imaging in patients with head and neck cancer

BACKGROUND AND PURPOSE: Metastasis to the regional cervical lymph nodes may be associated with alterations in water diffusivity and microcirculation of the node. We tested whether diffusion-weighted MR imaging could discriminate metastatic nodes. METHODS: Diffusion-weighted echo-planar and T1- and T2-weighted MR imaging sequences were performed on histologically proved metastatic cervical lymph nodes (25 nodes), benign lymphadenopathy (25 nodes), and nodal lymphomas (five nodes). The apparent diffusion coefficient (ADC) was calculated by using two b factors (500 and 1000 s/mm(2)). RESULTS: The ADC was significantly greater in metastatic lymph nodes (0.410 +/- 0.105 x 10(-3) mm(2)/s, P <.01) than in benign lymphadenopathy (0.302 +/- 0.062 x 10(-3) mm(2)/s). Nodal lymphomas showed even lower levels of the ADC (0.223 +/- 0.056 x 10(-3) mm(2)/s). ADC criteria for metastatic nodes (>/= 0.400 x 10(-3) mm(2)/s) yielded a moderate negative predictive value (71%) and high positive predictive value (93%). Receiver operating characteristic analysis demonstrated that the criteria of abnormal signal intensity on T1- or T2-weighted images (A(z) = 0.8437 +/- 0.0230) and ADC (A(z) = 0.8440 +/- 0.0538) provided similar levels of diagnostic ability in differentiating metastatic nodes. The ADC from metastatic nodes from highly or moderately differentiated cancers (0.440 +/- 0.020 x 10(-3) mm(2)/s, P <.01) was significantly greater than that from poorly differentiated cancers (0.356 +/- 0.042 x 10(-3) mm(2)/s). CONCLUSION: Diffusion-weighted imaging is useful in discriminating metastatic nodes.     

The effect of aging on the apparent diffusion coefficient of normal-appearing white matter

OBJECTIVE: The purpose of our study was to test the hypothesis that the apparent diffusion coefficient (ADC) of normal-appearing white matter increases with advancing age. SUBJECTS AND METHODS: We selected 38 patients with normal MR imaging findings from 332 patients undergoing clinical MR imaging. Diffusion-weighted MR imaging was performed with diffusion gradients applied in three orthogonal directions. For each patient, the average ADC on trace-weighted diffusion images of white matter at prespecified regions of interest and at the thalamus were compared with the patient's age. RESULTS: For the white matter, ADC sorted by patient age in decades increased with advancing age. Patients at least 60 years old had significantly higher ADC (0.769 +/- 0.019 mm(2)/sec x 10(-3)) than patients less than 60 years old (0.740 +/- 0.013 mm(2)/sec x 10(-3)) (p < 0.001). Comparison of individual white matter ADC and age showed a significant increase with advancing age (p < 0.0001). For the thalamus, the average ADC among patients at least 60 years old (0.766 +/- 0.015 mm(2)/sec x 10(-3)) exceeded the average ADC for patients less than 60 years old (0.745 +/- 0.022 mm(2)/sec x 10(-3)) (p < 0.05). However, comparison of individual thalamic ADC and patient ages, although showing a trend to higher ADC with increasing age, did not reach statistical significance (p = 0.06). CONCLUSION: Advancing age is associated with a small but statistically significant increase of water diffusibility in human white matter. A similar trend was present in the thalamus. These increases may reflect mild structural changes associated with normal aging.     

Monitoring of gustatory stimulation of salivary glands by diffusion-weighted MR imaging: comparison of 1.5T and 3T

BACKGROUND AND PURPOSE: Our aim was to compare different field strengths monitoring physiologic changes due to oral stimulation of parotid glands by using diffusion-weighted (DW) echo-planar imaging (EPI). MATERIALS AND METHODS: Twenty-seven healthy volunteers were examined with a DW-EPI sequence at 1.5T and 3T before and after oral stimulation with commercially available lemon juice. The b factors used were 0, 500, and 1000 s/mm(2). Apparent diffusion coefficient (ADC) maps were evaluated with a manually placed region of interest including the entire parotid gland. For comparison of results, a Student t test was used on the basis of the mean of the volunteer median values. To compare both field strengths, we calculated the Pearson correlation coefficient (r). RESULTS: DW-EPI MR imaging visualized the parotid glands of all volunteers. With 1.5T, the mean ADC before stimulation was 1.12 x 10(-3) mm(2)/s +/- 0.08 x 10(-3) mm(2)/s. After stimulation with lemon juice, the ADC increased to 1.18 x 10(-3) mm(2)/s +/- 0.09 x 10(-3) mm(2)/s. For 3T, the ADC before stimulation was 1.14 x 10(-3) mm(2)/s +/- 0.04 x 10(-3) mm(2)/s, with an increase to 1.17 x 10(-3) mm(2)/s +/- 0.05 x 10(-3) mm(2)/s after stimulation. For both field strengths, the increase in ADC after stimulation was significant (P < .001). High correlations between both field strengths were found pre- and poststimulation (r = 0.955, and 0.936, respectively). CONCLUSION: DW-EPI MR imaging allows monitoring of physiologic changes due to oral stimulation of parotid glands by using DW imaging with high correlation between 1.5T and 3T.     

Usefulness of the apparent diffusion coefficient in line scan diffusion-weighted imaging for distinguishing between squamous cell carcinomas and malignant lymphomas of the head and neck

BACKGROUND AND PURPOSE: Squamous cell carcinoma (SCC) and lymphoma are common malignant tumors of the head and neck. The purpose of this study was to determine whether the apparent diffusion coefficient (ADC) in line scan diffusion-weighted imaging (LSDWI) is useful for distinguishing between SCC and lymphoma of the head and neck. METHODS: LSDWI was prospectively performed in 39 patients with SCC and in 14 patients with lymphoma. Images were obtained with a diffusion-weighted factor (b factor) of 5 and 1000 s/mm(2), and ADC maps were generated. ADC values were measured for the two types of tumor. RESULTS: Mean ADC values were 0.96 +/- 0.11 x 10(-3) mm(2)/s for SCC and 0.65 +/- 0.09 x 10(-3) mm(2)/s for lymphoma; the difference was significant (P < .001). All but one of the patients with lymphoma had ADC values lower than the lowest ADC (0.76 x 10(-3) mm(2)/s) in patients with SCC. When an ADC of 0.76 x 10(-3) mm(2)/s was used to distinguish between SCC and lymphoma, accuracy was 98% (52 of 53 lesions). CONCLUSION: ADC values appear to be useful for distinguishing between SCC and lymphoma in the head and neck.     

Tuberous sclerosis: diffusion MRI findings in the brain

Diffusion MRI has mainly been used for detection of acute ischemia, and for distinction of cytotoxic and vasogenic edema. We applied diffusion MRI in patients with tuberous sclerosis in order to evaluate diffusion imaging characteristics of parenchymal changes. Five children with known tuberous sclerosis were included in this study. The MRI examinations were performed on a 1.5-T MR unit. Diffusion MRI was obtained using the echo-planar imaging sequence. Apparent diffusion coefficient (ADC) values from the abnormal brain parenchyma were calculated directly from automatically generated ADC maps. Seven normal children were available for comparison. In this control group the mean ADC value of the normal white matter was 0.84 +/- 0.12 x 10(-3) mm(2)/s. In tuberous sclerosis patients the mean ADC value of the white matter hamartomas ( n=20) was apparently high (1.52 +/- 0.24 x 10(-3) mm(2)/s) compared with that of normal white matter. The ADC value of calcified hamartomas was "zero". The ADC value within a giant cell tumor was 0.89 x 10(-3) mm(2)/s, similar to that of normal cerebral white matter. The ADC maps were superior to b=1000 s/mm(2) (true diffusion) images with respect to lesion evaluation, and they provided mathematical information on tissue integrity. With respect to detection of the exact numbers and sizes of the parenchymal hamartomas fluid-attenuated inversion recovery images were superior to ADC maps. It is believed that diffusion MRI can be useful in evaluation of various parenchymal changes associated with tuberous sclerosis. Further studies on tuberous sclerosis, and on various brain lesions, would provide increasing data on this relatively new MRI sequence.     

Time course of the apparent diffusion coefficient after cerebral infarction

The purpose of this study was to evaluate quantitative apparent diffusion changes in the center of infarction by measurement of the apparent diffusion coefficient (ADC), and to investigate the influence of ischemia on the contralateral hemisphere. By diffusion echo-planar imaging (EPI) 52 patients showing cerebral infarction were studied within 5 h to >12 months after onset of clinical symptoms. Using three diffusion gradient strengths (b1=30 s/mm(2); b2=300 s/mm(2), b3=1100 s/mm(2)) ADC maps were generated. After onset of ischemia, ADC in the center of infarction was lower than in the contralateral regions of human brain. At first ADC declined for approximately 28 h to a minimum of approximately 150x10(-8) cm(2)/s. Then the ADC reincreased and reached a "pseudonormalization" after approximately 5 days. Chronic infarctions did show much higher ADC values (2000x10(-8) cm(2)/s) than unaffected areas. Neither localization nor size of infarctions showed a significant influence on this time course. In the center of infarction diffusion is isotropic. Even brain regions of the contralateral hemisphere are influenced by cerebral ischemia. In these regions ADC is higher than for physiological conditions. The ADC also declines especially for the first 2-3 days after onset of symptoms, also followed by reincrease. The ADC calculation enables determination of the onset of infarction more exactly than is possible using only diffusion-weighted imaging. Diffusion in the center of infarction is isotropic; hence, orientation of the diffusion gradients has no significant influence on sensitivity of measurements. The calculation of the ADC ratio based on data derived from the center of infarction and the contralateral hemisphere seems to be critical because the ADC in the unaffected contralateral hemisphere also changes.     

Diffusion MRI in neurofibromatosis type 1: ADC evaluations of the optic pathways, and a comparison with normal individuals.

In a control group of 12 normal children (ages ranging from 9 months to 3 years; mean=1.6 years) the mean apparent diffusion coefficient (ADC) value of the normal white matter, obtained from automatically generated ADC maps, was 0.84 +/- 0.14 x 10(-3)mm(2)/s. A patient with neurofibromatosis type 1 with bilateral optic gliomas, and extensive optic pathway involvement was evaluated by diffusion MRI. Multiple measurements of ADC values throughout the involved optic radiations revealed a higher mean value: 1.16 +/- 0.06 x 10(-3)mm(2)/s than that of the normal white matter, suggesting relatively high molecular motion in these regions, probably representing myelin vacuolization. ADC evaluation of a thalamic hamartoma revealed a lower value (=1.06 x 10(-3)mm(2)/s) than this. The mean ADC value obtained from multiple measurements of the enlarged optic chiasm, and intraorbital portions of the nerve was similar (=0.81+/- 0.09 x 10(-3)mm(2)/s) to that of the normal cerebral white matter of the control cases. It appears that diffusion imaging can be useful in evaluation of optic pathway involvement in NF1, and might contribute to differentiating optic gliomas from hamartomas, and myelin vacuolization, however, further studies will be required for assessing the role of diffusion imaging in such lesions.     

Water diffusion measurements in perfused human hippocampal slices undergoing tonicity changes.

Diffusion MRI has the potential to probe the compartmental origins of MR signals acquired from human nervous tissue. However, current experiments in human subjects require long diffusion times, which may confound data interpretation due to the effects of compartmental exchange. To investigate human nervous tissue at shorter diffusion times, and to determine the relevance of previous diffusion studies in rat hippocampal slices, water diffusion in 20 perfused human hippocampal slices was measured using a wide-bore 17.6-T magnet equipped with 1000-mT/m gradients. These slices were procured from five patients undergoing temporal lobectomy for epilepsy. Tissue viability was confirmed with electrophysiological measurements. Diffusion-weighted water signal attenuation in the slices was well-described by a biexponential function (R(2) > 0.99). The mean diffusion parameters for slices before osmotic perturbation were 0.686 +/- 0.082 for the fraction of fast diffusing water (F(fast)), 1.22 +/- 0.22 x 10(-3) mm(2)/s for the fast apparent diffusion coefficient (ADC), and 0.06 +/- 0.02 x 10(-3) mm(2)/s for the slow ADC. Slice perturbations with 20% hypotonic and 20% hypertonic artificial cerebrospinal fluid led to changes in F(fast) of -8.2% and +10.1%, respectively (ANOVA, P < 0.001). These data agree with previous diffusion studies of rat brain slices and human brain in vivo, and should aid the development of working models of water diffusion in nervous tissue, and thus increase the clinical utility of diffusion MRI.     

Diffusion-weighted MR imaging in normal human brains in various age groups

BACKGROUND AND PURPOSE: Few studies have concerned the absolute apparent diffusion coefficient (ADC) values in the normal human brain and the effect of aging on diffusion. Therefore, our purpose was to determine whether the average ADC (ADC(av)) values in the various regions of the brain differ with age, sex, or hemisphere and to establish reference values of the absolute ADC(av) for further studies. METHODS: Subjects (40 men and 40 women) were chosen from a healthy population; age groups were 20-34, 35-49, and 50-64 years and 65 years or older (n = 20 each). All subjects were examined with MR imaging, including conventional and diffusion-weighted imaging in three orthogonal directions with two b values (0 and 1000 s/mm(2)) at 1.5 T. Bilateral ADC(av) values were determined in 36 regions of interest encompassing the entire brain. RESULTS: ADC(av) values were highest in the cortical gray matter ([0.89 +/- 0.04] x 10(-3) mm(2)/s; range, 0.78-1.09 x 10(-3)), lower in the deep gray matter ([0.75 +/- 0.03] x 10(-3) mm(2)/s; range, 0.64-0.83 x 10(-3)), and lowest in the white matter ([0.70 +/- 0.03] x 10(-3) mm(2)/s; range, 0.62-0.79 x 10(-3)). The ADC(av) values did not significantly change with aging, except for an increase in the lateral ventricles. No difference was observed between women and men or between the hemispheres. CONCLUSION: The data reported herein are representative, and the ADC(av) values can be used for reference in future studies and in clinical settings.     

Diffusion-weighted imaging of soft tissue tumors: usefulness of the apparent diffusion coefficient for differential diagnosis

PURPOSE: We evaluated the efficacy of using the apparent diffusion coefficient (ADC) to differentiate soft tissue tumors. MATERIALS AND METHODS: We examined 88 histologically proven tumors (44 benign, 8 intermediate, 36 malignant) using diffusion-weighted magnetic resonance images. Images of the tumors were obtained using a single-shot, spin-echo type echo-planar imaging sequence. The tumors were classified histologically as myxoid or nonmyxoid. We then compared the ADC values of the myxoid and nonmyxoid tumors; the benign and malignant myxoid tumors; and the benign, intermediate, and malignant nonmyxoid tumors. RESULTS: The mean ADC value of the myxoid tumors (2.08 +/- 0.51 x 10(-3) mm(2)/s) was significantly greater than that of the nonmyxoid tumors (1.13 +/- 0.40 x 10(-3) mm(2)/s) (P < 0.001). There was no significant difference in the mean ADC values between benign myxoid tumors (2.10 +/- 0.50 x 10(-3) mm(2)/s) and malignant myxoid tumors (2.05 +/- 0.58 x 10(-3) mm(2)/s). The mean ADC value of benign nonmyxoid tumors (1.31 +/- 0.46 x 10(-3) mm(2)/s) was significantly higher than that of malignant nonmyxoid tumors (0.94 +/- 0.25 x 10(-3) mm(2)/s) (P < 0.001). CONCLUSION: The ADC value might be useful for diagnosing the malignancy of nonmyxoid soft tissue tumors.     

MR imaging of salivary duct carcinoma

BACKGROUND AND PURPOSE: Salivary duct carcinoma (SDC) is regarded as a high-grade malignancy in the current classification of salivary gland neoplasms. The aim of our study was to describe the MR imaging features of SDC. METHODS: Nine patients with SDC underwent MR imaging study. The apparent diffusion coefficient (ADC) values of SDCs were measured from diffusion-weighted images. Time-signal intensity curves (TICs) of the tumors on dynamic MR images were plotted, and washout ratios were also calculated. TICs were divided into four types: type A, curve peaks <120 seconds after administration of contrast material with high washout ratio (> or =30%); type B, curve peaks <120 seconds with low washout ratio (<30%); type C, curve peaks >120 seconds; type D, nonenhanced. We correlated the MR findings of SDC with the pathologic findings. RESULTS: All tumors had ill-defined margins and showed low to moderately high signal intensity for contralateral parotid gland on T2-weighted images. The average of the ADC values of the SDCs was 1.16 +/- 0.14 [SD] x 10(-3)mm(2)/s. Seven of nine (78%) tumors had type B enhancement. On the other hand, six of nine (67%) tumors with rich fibrotic tissue also had type C enhancement. CONCLUSION: The findings of ill-defined margin, early enhancement with low washout ratio (type B), and low ADC value (1.22 x 10(-3)mm(2)/s) were useful for suggesting malignant salivary gland tumors. Although it was reported that type C enhancement was specific for pleomorphic adenoma, SDC frequently has type C-enhanced focus.     

Diffusion magnetic resonance imaging of solid vestibular schwannomas

Six patients with solid vestibular schwannomas were studied by diffusion magnetic resonance imaging to assess if this modality adds new information for these tumors, because there is no previous report in the relevant literature. The sizes of the tumors ranged from 2.2 to 4.7 cm with respect to their largest diameters. They were isointense to the normal brain parenchyma on b = 1,000 s/mm2 images. The apparent diffusion coefficient (ADC) values in the tumors were high (range: 1.14-1.72 x 10(-3) mm2/s, mean = 1.42 +/- 0.17 x 10(-3) mm2/s) compared with normal brain parenchyma ADC values (mean = 0.80 +/- 0.11 x 10(-3) mm2/s). High ADC values of solid vestibular schwannomas were in conformity with increased diffusion rates, indicating the presence of increased amounts of extracellular water (a relatively loose tissue) in the tumor matrix.     

Head and neck lesions: characterization with diffusion-weighted echo-planar MR imaging

PURPOSE: To evaluate whether apparent diffusion coefficients (ADCs) calculated from diffusion-weighted echo-planar magnetic resonance (MR) images can be used to characterize head and neck lesions. MATERIALS AND METHODS: Diffusion-weighted echo-planar MR imaging was performed with a 1.5-T MR unit in 97 head and neck lesions in 97 patients. Images were obtained with a diffusion-weighted factor, factor b, of 0, 500, and 1,000 sec/mm(2), and an ADC map was constructed. The ADCs of lesions, cerebrospinal fluid, and spinal cord were calculated. RESULTS: Acceptable images for ADC measurement were obtained in 81 (84%) patients. The mean ADC of malignant lymphomas, (0.66 +/- 0.17[SD]) x 10(-3) mm(2)/sec (n = 13), was significantly smaller (P <.001) than that of carcinomas. The mean ADC of carcinomas, (1.13 +/- 0.43) x 10(-3) mm(2)/sec (n = 36), was significantly smaller (P =.002) than that of benign solid tumors. The mean ADC of benign solid tumors, (1.56 +/- 0.51) x 10(-3) mm(2)/sec (n = 22), was significantly smaller (P =.035) than that of benign cystic lesions, (2.05 +/- 0.62) x 10(-3) mm(2)/sec (n = 10). No significant differences were seen in the mean ADC of cerebrospinal fluid and of spinal cord among four groups of lesions. When an ADC smaller than 1.22 x 10(-3) mm(2)/sec was used for predicting malignancy, the highest accuracy of 86%, with 84% sensitivity and 91% specificity, was obtained. CONCLUSION: Measurement of ADCs may be used to characterize head and neck lesions.