The role of diffusion-weighted imaging and the apparent diffusion coefficient (ADC) values for breast tumors.

OBJECTIVE: We wanted to evaluate the role of diffusion-weighted imaging (DWI) and the apparent diffusion coefficient (ADC) for detecting breast tumors, as compared with the T1- and T2-weighted images. MATERIALS AND METHODS: Forty-one female patients underwent breast MRI, and this included the T1-, T2-, DWI and dynamic contrast-enhanced images. Sixty-five enhancing lesions were detected on the dynamic contrast-enhanced images and we used this as a reference image for detecting tumor. Fifty-six breast lesions were detected on DWI and the histological diagnoses were as follows: 43 invasive ductal carcinomas, one mucinous carcinoma, one mixed infiltrative and mucinous carcinoma, seven ductal carcinomas in situ (DCIS), and four benign tumors. First, we compared the detectability of breast lesions on DWI with that of the T1- and T2-weighted images. We then compared the ADCs of the malignant and benign breast lesions to the ADCs of the normal fibroglandular tissue. RESULTS: Fifty-six lesions were detected via DWI (detectability of 86.2%). The detectabilities of breast lesions on the T1- and T2-weighted imaging were 61.5% (40/65) and 75.4% (49/65), respectively. The mean ADCs of the invasive ductal carcinoma (0.89+/-0.18 x 10(-3)mm(2)/second) and DCIS (1.17+/-0.18 x 10(-3)mm(2)/ second) are significantly lower than those of the benign lesions (1.41+/-0.56 x 10(-3)mm(2)/second) and the normal fibroglandular tissue (1.51+/-0.29 x 10(-3)mm(2)/ second). CONCLUSION: DWI has a high sensitivity for detecting breast tumors, and especially for detecting malignant breast tumors. DWI was an effective imaging technique for detecting breast lesions, as compared to using the T1- and T2-weighted images.     

Role of diffusion weighted imaging in differentiation of intracranial tuberculoma and tuberculous abscess from cysticercus granulomas-a report of more than 100 lesions

Restricted diffusion is noted in a large number of non-stroke conditions including tuberculoma. The purpose of this study was to demonstrate spectrum of diffusion weighted imaging (DWI) abnormalities in tuberculomas and tuberculous abscess and to distinguish these from degenerating neurocysticercosis. Seventy tuberculomas and tuberculous abscesses in 30 patients were categorized in three groups depending on the intensity in the core of the lesion on T2 weighted images. Mean apparent diffusion coefficient (ADC) was calculated from the core as well as from the wall of the lesions. Forty-five lesions of neurocysticercosis in different stage of evolution in 12 patients were also included for comparison. The mean ADC value from the core of the T2 hypointense lesions was significantly higher compared to the wall ((1.24+/-0.32)x10(-3) and (1.06+/-0.15)x10(-3)mm(2)/s, respectively), while mean ADC value from the core of mildly T2 hyperintense lesions was significantly lower compared to the wall ((0.80+/-0.08)x10(-3) and (1.08+/-0.13)x10(-3)mm(2)/s, respectively). Truly T2 hyperintense lesions were divided into two subgroups, tuberculomas and tuberculous abscesses; ADC values from the core and the wall of these lesions were (0.74+/-0.13)x10(-3), (0.61+/-0.08)x10(-3) and (1.03+/-0.14)x10(-3), (1.08+/-0.14)x10(-3)mm(2)/s, respectively, and was significantly lower in core as compared to the wall. However, there was no significant difference between ADC values of the tuberculous abscess and the hyperintense tuberculomas. Vesicular and degenerating stages of cysticercus cysts from the core showed ADC values of (1.66+/-0.29)x10(-3) and (1.51+/-0.23)x10(-3)mm(2)/s, respectively, and were significantly higher than the core of all groups of tuberculomas and tuberculous abscess. We conclude that addition of DWI to routine imaging protocol may help in differentiation of tuberculous lesions from degenerating cysticercus granuloma.     

Diffusion-weighted MRI features of brain abscess and cystic or necrotic brain tumors: comparison with conventional MRI

BACKGROUND AND PURPOSE: The purpose of this study was to determine whether diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) can be used to distinguish brain abscesses from cystic or necrotic brain tumors, which are difficult to distinguish by conventional magnetic resonance imaging (MRI) techniques. METHODS: Eleven consecutive patients with brain abscesses [10 pyogenic and 1 toxoplasmosis (in an AIDS patient)] and 15 with cystic or necrotic brain gliomas or metastases were enrolled in this study. None of these lesions had apparent hemorrhage based on T1-weighted image (T1WI). The DWI was performed using a 1.5-T system, single-shot spin-echo echo-planar pulse sequence with b=1000 s/mm(2). The ADC was calculated using a two-point linear regression method at b=0 and b=1000 s/mm(2). The ratio (ADCR) of the lesion ADC to control region ADC was also measured. RESULTS: Increased signal was seen in all of the pyogenic abscess cavities to variable degrees on DWI. In vivo ADC maps showed restricted diffusion in the abscess cavity in all pyogenic abscesses [0.65+/-0.16 x 10(-3) (mean+/-S.D.) mm(2)/s, mean ADCR=0.63]. The case with multiple toxoplasmosis abscesses showed low signal intensity on DWI and high ADC values (mean 1.9 x 10(-3) mm(2)/s, ADCR=2.24). All cystic or necrotic tumors but one showed low signal intensity on DWI and their cystic or necrotic areas had high ADC values (2.70+/-0.31 x 10(-3) mm(2)/s, mean ADCR=3.42). One fibrillary low-grade astrocytoma had a high DWI signal intensity and a low ADC value in its central cystic area (0.44 x 10(-3) mm(2)/s, ADCR=0.49). Postcontrast T1WIs yielded a sensitivity of 60%, a specificity of 27.27%, a positive predictive value (PPV) of 52.94%, and a negative predictive value (NPV) of 33.33% in the diagnosis of necrotic tumors. DWI yielded a sensitivity of 93.33%, a specificity of 90.91%, a PPV of 93.33%, and a NPV of 90.91%. The area under receiver operating characteristic (ROC) curves for postcontrast T1WI was 0.44 and DWI was 0.92. Analysis of these areas under the ROC curves indicates significant difference between postcontrast T1WI and DWI (P<.001). CONCLUSION: With some exceptions, DWI is useful in providing a greater degree of confidence in distinguishing brain abscesses from cystic or necrotic brain tumors than conventional MRI and seems to be a valuable diagnostic tool.     

Apparent diffusion coefficient of subcutaneous epidermal cysts in the head and neck comparison with intracranial epidermoid cysts

RATIONALE AND OBJECTIVES: Subcutaneous epidermal cysts and intracranial epidermoid cysts are pathologically identical. Although diffusion-weighted imaging (DWI) studies of intracranial epidermoid cysts have been numerously reported, those of subcutaneous epidermal cysts have not been sufficiently investigated. Our hypothesis for this study is that the apparent diffusion coefficient (ADC) values of subcutaneous epidermal cysts and intracranial epidermoid cysts are not different. This study was intended to evaluate the ADC of subcutaneous epidermal cysts of the head and neck in comparison with that of intracranial epidermoid cysts. MATERIALS AND METHODS: The MR studies were performed in 14 patients with head and neck subcutaneous epidermal cysts and 10 patients with intracranial epidermoid cysts using line scan DWI (LSDWI). The ADC was measured and compared between the two types of cyst. RESULTS: The ADC values (mean +/- SD) were 0.81 +/- 0.14 x 10(-3) mm(2)/s in subcutaneous epidermal cysts and 1.06 +/- 0.12 x 10(-3) mm(2)/s in intracranial epidermoid cysts. A significant difference was found in ADC values between the two types (P = .0019). CONCLUSION: Our preliminary study has shown that the ADC provides useful information regarding tissue characterization of subcutaneous epidermal cysts. However, the ADC of subcutaneous epidermal cysts was significantly lower than that of intracranial epidermoid cysts.     

Characterization of benign and metastatic vertebral compression fractures with quantitative diffusion MR imaging

BACKGROUND AND PURPOSE: Conventional imaging techniques cannot be used to unambiguously and reliably differentiate malignant from benign vertebral compression fractures. Our hypothesis is that these malignant and benign vertebral lesions can be better distinguished on the basis of tissue apparent diffusion coefficients (ADCs). The purpose of this study was to test this hypothesis by using a quantitative diffusion imaging technique. METHODS: Twenty-seven patients with known cancer and suspected metastatic vertebral lesions underwent 1.5-T conventional T1-weighted, T2-weighted, and contrast-enhanced T1-weighted imaging to identify the lesions. Diffusion-weighted images of the areas of interest were acquired by using a fast spin-echo diffusion pulse sequence with b values of 0-250 s/mm(2). The abnormal regions on the diffusion-weighted images were outlined by using the conventional images as guides, and the ADC values were calculated. On the basis of pathologic results and clinical findings, the cases were divided into two categories: benign compression fractures and metastatic lesions. The ADC values for each category were combined and plotted as histograms; this procedure was followed by statistical analysis. RESULTS: The patient group had 12 benign fractures and 15 metastases. The mean ADC values, as obtained from the histograms, were (1.9 +/- 0.3) x 10(-4) mm(2)/s and (3.2 +/- 0.5) x 10(-4) mm(2)/s for metastases and benign fractures, respectively. CONCLUSION: Our results indicate that quantitative ADC mapping, instead of qualitative diffusion-weighted imaging, can provide valuable information in differentiating benign vertebral fractures from metastatic lesions.     

Chronic cystic lesion of the sacrum: characterisation with diffusion-weighted MR imaging

PURPOSE: Sacral bone remodelling with abnormal dilatation of intervertebral foramina is usually associated with Tarlov cysts but can be caused by slow-growth lesions, which also may present cerebrospinal-fluid (CSF)-like signal or density. We describe three patients with a similar history of lower back pain presenting CSF-like density/signal lesions with extensive sacral bone remodelling who were affected by a Tarlov cyst, an epidermoid cyst and a giant neurofibroma, respectively. MATERIALS AND METHODS: Magnetic resonance imaging (MRI) studies were performed with 1.0-T magnet; axial and sagittal pre- and postcontrast T1-and T2-weighted images were obtained. Moreover, axial and sagittal diffusion-weighted (DWI) echoplanar images were produced, and corresponding apparent diffusion coefficient (ADC) values were calculated. ADC values were measured within the lesions on axial images. RESULTS: All lesions presented a CSF-like signal on conventional MRI. The Tarlov cyst was hypointense on DWI with high ADC values (2,793 s/mm(2)+/-137). The epidermoid cyst proved to be markedly hyperintense on DWI, with reduced ADC values (855 s/mm(2)+/-109). The neurofibroma was isointense on DWI, with ADC values not compatible with CSF (1,467 s/mm(2)+/-130). CONCLUSIONS: DWI and ADC values seem to be able to clearly differentiate Tarlov cysts from slow-growth lesions, allowing for adequate treatment.     

Malignant renal neoplasms: correlation between ADC values and cellularity in diffusion weighted magnetic resonance imaging at 3 T

PURPOSE: This study aimed at exploring the feasibility of high-field diffusion-weighted magnetic resonance imaging (DW-MRI) (3 T) and to correlate apparent diffusion coefficient (ADC) values with tumour cellularity in renal malignancies. MATERIALS AND METHODS: Thirty-seven patients (ten healthy volunteers and 27 patients with suspected renal malignancy) underwent T1-, T2-weighted and T1-weighted contrast-enhanced magnetic resonance imaging (MRI). Diffusion-weighted images were obtained with a single-shot spin-echo echo-planar imaging (SE-EPI) sequence with a b value of 500 s/mm(2). All lesions were surgically resected, and mean tumour cellularity was calculated. Comparison between tumour cellularity and mean ADC value was performed using simple linear regression analysis. RESULTS: The mean ADC value in normal renal parenchyma was 2.35+/-0.31 x 10(-3) mm(2)/s, whereas mean ADC value in renal malignancies was 1.72+/-0.21 x 10(-3) mm(2)/s. In our population, there were no statistically significant differences between ADC values of different histological types. The analysis of mean ADC values showed an inverse linear correlation with cellularity in renal malignancies (r=-0.73, p<0.01). CONCLUSIONS: DW-MRI is able to differentiate between normal and neoplastic renal parenchyma on the basis of tissue cellularity.     

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.     

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.     

Pituitary macroadenomas: preoperative evaluation of consistency with diffusion-weighted MR imaging--initial experience

PURPOSE: To prospectively evaluate use of diffusion-weighted (DW) magnetic resonance (MR) images and apparent diffusion coefficient (ADC) maps for determination of the consistency of macroadenomas. MATERIALS AND METHODS: The study protocol was approved by the institutional ethics committee, and informed consent was obtained from all patients. Twenty-two patients with pituitary macroadenoma (10 men, 12 women; mean age, 54 years +/- 17.09 [standard deviation]; range, 21-75 years) were examined. All patients underwent MR examination, which included T1-weighted spin-echo and T2-weighted turbo spin-echo DW imaging with ADC mapping and contrast material-enhanced T1-weighted spin-echo imaging. Regions of interest (ROIs) were drawn in the macroadenomas and in normal white matter on DW images, ADC maps, and conventional MR images. Consistency of macroadenomas was evaluated at surgery and was classified as soft, intermediate, or hard. Histologic examination was performed on surgical specimens of macroadenomas. Mean ADC values, signal intensity (SI) ratios of tumor to white matter within ROIs on conventional and DW MR images, and degree of enhancement were compared with tumor consistency and with percentage of collagen content at histologic examination by using analysis of variance for linear trend. RESULTS: The mean value of ADC in the soft group was (0.663 +/- 0.109) x 10(-3) mm(2)/sec; in the intermediate group, (0.842 +/- 0.081) x 10(-3) mm(2)/sec; and in the hard group, (1.363 +/- 0.259) x 10(-3) mm(2)/sec. Statistical analysis revealed a significant correlation between tumor consistency and ADC values, DW image SI ratios, T2-weighted image SI ratios, and percentage of collagen content (P < .001, analysis of variance). No other statistically significant correlations were found. CONCLUSION: Findings in this study suggest that DW MR images with ADC maps can provide information about the consistency of macroadenomas.     

Diffusion-weighted imaging of the prostate at 3 T for differentiation of malignant and benign tissue in transition and peripheral zones: preliminary results

OBJECTIVE: To evaluate prospectively the use of apparent diffusion coefficients (ADCs) for the differentiation of malignant and benign tissue in the transition (TZ) and peripheral (PZ) zones of the prostate diffusion-weighted imaging (DWI) at 3 T magnetic resonance imaging (MRI) using a phased-array coil. METHODS: The DWI at 3-T MRI was performed on a total of 35 patients before radical prostatectomy. A single-shot echo-planar imaging DWI technique with b = 0 and b = 1000 s/mm2 was used. The ADC values were measured in both benign and malignant tissues in the PZ and TZ using regions of interest. Differences between PZ and TZ ADC values were estimated using a paired Student t test. Presumed ADC cutoff values in the PZ and TZ for the diagnosis of cancer were assessed by receiver operating characteristic analysis. RESULTS: The ADC values of malignant tissues were significantly lower than those of benign tissues in the PZ and TZ (P < 0.001; 1.32 +/- 0.24 x 10(-3) mm2/s vs 1.97 +/- 0.25 x 10(-3) mm2/s, and 1.37 +/- 0.29 x 10(-3) mm2/s vs 1.79 +/- 0.19 x 10(-3) mm2/s, respectively). For tumor diagnosis, cutoff values of 1.67 x 10(-3) mm2/s (PZ) and 1.61 x 10(-3) mm2/s (TZ) resulted in sensitivities and specificities of 94% and 91% and 90% and 84%, respectively. CONCLUSIONS: The DWI of the prostate at 3T MRI using a phased-array coil was useful for the differentiation of malignant and benign tissues in the TZ and PZ.     

Quantitative magnetic resonance techniques in the evaluation of intracranial tuberculomas

PURPOSE: To evaluate intracranial tuberculomas using quantitative magnetic resonance (MR) techniques such as T2 relaxometry, magnetization transfer (MT), and diffusion-weighted imaging (DWI). MATERIAL AND METHODS: Thirty-three patients with intracranial tuberculomas (histologically confirmed in 22) were evaluated using proton density/T2-weighted, T1-weighted (with and without MT), and echo-planar diffusion-weighted imaging sequences. T2 relaxation times, MT ratios (MTR), and apparent diffusion coefficient (ADC) values were calculated from the center of the lesion, the periphery, perilesional edema, and contralateral normal white matter. The mean and standard deviation values of each variable were calculated and correlated using Pearson's test (P = 0.05). RESULTS: The measured mean values of T2 relaxation time, MTR, and ADC in the center of lesions were 155.5 ms, 14.1, and 1.27 x 10(-3) mm(2)/s, respectively, compared to 117 ms, 23.72, and 0.74 x 10(-3) mm(2)/s in normal white matter, and a T2 relaxation time of 187.45 ms in normal gray matter. Significant inverse correlations were noted between T2 relaxation values and MTR (P<0.001) and between MTR and ADC (P = 0.046). Significant positive correlation was seen between T2 relaxation and ADC values (P = 0.03). CONCLUSION: Intracranial tuberculomas are characterized by relatively short T2 relaxation times (compared to normal gray matter), decreased MTR, and mostly no restriction of diffusion. A combination of these quantitative parameters could be of help in the noninvasive diagnosis of tuberculomas.     

Diffusion-weighted imaging of normal and malignant prostate tissue at 3.0T

PURPOSE: To measure the apparent diffusion coefficient (ADC) of normal and malignant prostate tissue at 3.0T using a phased-array coil and parallel imaging, and determine the utility of ADC values in differentiating tumor from normal peripheral zone (PZ). MATERIALS AND METHODS: ADC values were calculated for 49 patients (tumor and PZ) with evidence of prostate cancer. Additionally, for nine asymptomatic volunteers, ADC values were determined for apparently normal central gland and PZ. A single-shot EPI diffusion-weighted imaging (DWI) technique with b = 0 and 500 seconds/mm2 was employed. RESULTS: ADC values were significantly lower for tumor (1.38 +/- 0.32 x 10(-3) mm2/second) than for patient PZ (1.95 +/- 0.50 x 10(-3) mm2/second, P < 0.001) and volunteer PZ (1.60 +/- 0.25 x 10(-3) mm2/second, P = 0.031). A considerable overlap of ADC values was noted between patient tissue types. CONCLUSION: DWI of the prostate at 3.0T in conjunction with a phased-array coil and parallel imaging allows ADC calculation of the prostate. ADC values were lower for tumors compared to normal-appearing PZ; however, there was considerable intersubject variability.     

Quantitative diffusion imaging in breast cancer: a clinical prospective study

PURPOSE: To study the correlation between apparent diffusion coefficient (ADC) and pathology in patients with undefined breast lesion, to validate how accurately ADC is related to histology, and to define a threshold value of ADC to distinguish malignant from benign lesions. MATERIALS AND METHODS: Seventy-eight patients (110 lesions) were referred for positive or dubious findings. Three-dimensional fast low-angle shot (3D-FLASH) with contrast injection was applied. EPI diffusion-weighted imaging (DWI) with fat saturation was performed, and ROIs were selected on subtraction 3D-FLASH images before and after contrast injection, and copied on an ADC map. Inter- and intraobserver analyses were performed. RESULTS: At pathology 22 lesions were benign, 65 were malignant, and 23 were excluded. The ADCs of malignant and benign lesions were statistically different. In malignant tumors the ADC was (mean +/- SEM) 0.95 +/- 0.027 x 10(-3)mm(2)/second, and in benign tumors it was 1.51 +/- 0.068 x 10(-3)mm(2)/second. According to receiver operating characteristic (ROC) curves, we found a threshold between malignant and benign lesions for highest sensitivity and specificity (both 86%) around 1.13 +/- 0.10 x 10(-3)mm(2)/second. For a threshold of 0.95 +/- 0.10 x 10(-3)mm(2)/second, specificity was 100% but sensitivity was very low. Inter- and intraobserver studies showed good reproducibility. CONCLUSION: The ADC may help to differentiate benign and malignant lesions with good specificity, and may increase the overall specificity of breast MRI.     

Characterization of soft tissue masses: can quantitative diffusion weighted imaging reliably distinguish cysts from solid masses?

Objective

To investigate the accuracy of quantitative diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping for characterizing soft tissue masses (STMs) as cysts or solid masses.

Materials and methods

This IRB-approved retrospective study included 36 subjects with 37 STMs imaged by conventional MRI (T1-weighted, T2-weighted, contrast-enhanced T1-weighted sequences) and DWI (b-values 50, 400, 800 s/mm²) with ADC mapping. STMs were defined as non-solid cysts by histology or clinical follow-up, and as solid by histology. For each STM, ADC values (range, mean) were recorded by two observers. Differences between ADC values in cysts and solid STMs were compared using Wilcoxon rank-sum and receiver-operating characteristic (ROC) analysis.

Results

There were higher minimum (1.65 vs 0.68, p?=?0.003) and mean (2.31 vs 1.45, p?=?0.005) ADC values in cysts than solid STMs respectively. Areas under the ROC for minimum and mean ADC values were 0.82 and 0.81 respectively. Using threshold ADC values of 1.8 (minimum) or 2.5 (mean) yielded a sensitivity of 60 % and 80 % respectively, and a specificity of 100 % for classifying a STM as a cyst; for tumors with high fluid–signal intensity, the performance of these threshold values was maintained.

Conclusion

Diffusion-weighted imaging with ADC mapping provides a non-contrast MRI alternative for the characterization of STMs as cysts or solid masses. Threshold ADC values exist that provide 100 % specificity for differentiating cysts and solid STMs, even for tumors of high fluid–signal intensity on T2-weighted images.     

Differentiation of clinically benign and malignant breast lesions using diffusion-weighted imaging

PURPOSE: To evaluate the value of diffusion-weighted imaging (DWI) in distinguishing between benign and malignant breast lesions. MATERIALS AND METHODS: Fifty-two female subjects (mean age = 58 years, age range = 25-75 years) with histopathologically proven breast lesions underwent DWI of the breasts with a single-shot echo-planar imaging (EPI) sequence using large b values. The computed mean apparent diffusion coefficients (ADCs) of the breast lesions and cell density were then correlated. RESULTS: The ADCs varied substantially between benign breast lesions ((1.57 +/- 0.23) x 10(-3) mm(2)/second) and malignant breast lesions ((0.97 +/- 0.20) x 10(-3) mm(2)/second). In addition, the mean ADCs of the breast lesions correlated well with tumor cellularity (P < 0.01, r = -0.542). CONCLUSION: The ADC would be an effective parameter in distinguishing between malignant and benign breast lesions. Further, tumor cellularity has a significant influence on the ADCs obtained in both benign and malignant breast tumors.     

Diffusion tensor MR imaging of high-grade cerebral gliomas

BACKGROUND AND PURPOSE: Optimizing high-grade glioma treatment requires the delineation of edematous and normal brain from tumor, perhaps by using potential differences in the absolute diffusion parameters of water. Our purpose was to determine whether mean diffusivity and diffusion anisotropic MR imaging data help in this differentiation. METHODS: Nine patients with high-grade cerebral glioblastoma underwent contrast-enhanced structural and diffusion tensor MR imaging before therapy. Tumor, edematous brain, and apparently normal white matter regions were determined on T2-weighted and contrast-enhanced T1-weighted structural images. Fractional anisotropy (FA) and were measured in each tissue type. Differences in these values among the tissue types were assessed with a standard analysis of variance. RESULTS: was highest in the necrotic tumor core (1825.38 +/-404.06) x 10(-6) mm(2)/s, followed by edematous brain (1411.23 +/- 322.31) x 10(-6) mm(2)/s, enhancing tumor core (1308.67 +/- 292.50) x 10(-6) mm(2)/s, enhancing tumor margin (1229.80 +/- 206.80) x 10(-6) mm(2)/s, and normal brain (731.53 +/- 35.21) x 10(-6) mm(2)/s. FA was highest in normal brain (0.47 +/- 0.08) and lowest in the necrotic core (0.09 +/- 0.03). was significantly different in enhancing tumor margins and edematous brain in all patients; FA was significantly different in only seven. These values were significantly different from those of normal brain in all cases in which they were measurable. CONCLUSION: values can be used to differentiate normal white matter, edematous brain, and enhancing tumor margins. Diffusion anisotropic data added no benefit to tissue differentiation. Further studies are required to determine if a value that corresponds to the limit of tumor invasion can be identified.     

Perfusion and diffusion MR imaging in enhancing malignant cerebral tumors

OBJECTIVE: Common contrast-enhancing malignant tumors of the brain are glioblastoma multiforme (GBMs), anaplastic astrocytomas (AAs), metastases, and lymphomas, all of which have sometimes similar conventional MRI findings. Our aim was to evaluate the role of perfusion MR imaging (PWI) and diffusion-weighted imaging (DWI) in the differentiation of these contrast-enhancing malignant cerebral tumors. MATERIALS AND METHODS: Forty-eight patients with contrast-enhancing and histologically proven brain tumors, 14 AAs, 17 GBMs, nine metastases, and eight lymphomas, were included in the study. All patients have undergone routine MR examination where DWI and PWI were performed in the same session. DWI was performed with b values of 0, 500, and 1000 mm(2)/s. Minimum ADC values (ADC(min)) of each tumor was later calculated from ADC map images. PWI was applied using dynamic susceptibility contrast technique and maximum relative cerebral blood volume (rCBV(max)) was calculated from each tumor, given in ratio with contralateral normal white matter. Comparisons of ADC(min) and rCBV(max) values with the histological types of the enhancing tumors were made with a one-way analysis of variance and Bonferroni test. A P value less than 0.05 indicated a statistically significant difference. RESULTS: The ADC(min) values (mean+/-S.D.) in GBMs, AAs, lymphomas, and metastases were 0.79+/-0.21 (x10(-3)mm(2)/s), 0.75+/-0.21 (x10(-3)mm(2)/s), 0.51+/-0.09 (x10(-3)mm(2)/s), and 0.68+/-0.11 (x10(-3)mm(2)/s), respectively. The difference in ADC(min) values were statistically significant between lymphomas and GBMs (P<0.05). It was also statistically significant between lymphomas and AAs (P<0.03). However, there were no differences between lymphomas and metastasis, and between GBMs, AAs, and metastasis. The rCBV(max) ratio (mean+/-S.D.) in GBMs were 6.33+/-2.03, whereas it was 3.66+/-1.79 in AAs, 2.33+/-0.68 in lymphomas, and 4.45+/-1.87 in metastases. These values were statistically different between GBMs and AAs (P<0.001), GBMs and lymphoma (P<0.0001). Although there seemed to be difference between GBMs and metastases, it was not statistically significant (P<0.083). CONCLUSION: Combination of DWI and PWI, with ADC(min) and rCBV(max) calculations, may aid routine MR imaging in the differentiation of common cerebral contrast-enhancing malignant tumors.     

Warthin tumor of the parotid gland: diagnostic value of MR imaging with histopathologic correlation

BACKGROUND AND PURPOSE: The purpose of our study was to describe the MR imaging appearance of Warthin tumors multiple MR imaging techniques and to interpret the difference in appearance from that of malignant parotid tumors. METHODS: T1-weighted, T2-weighted, short inversion time inversion recovery, diffusion-weighted, and contrast-enhanced dynamic MR images of 19 Warthin tumors and 17 malignant parotid tumors were reviewed. MR imaging results were compared with those of pathologic analysis. RESULTS: Epithelial stromata and lymphoid tissue with slitlike small cysts in Warthin tumors showed early enhancement and a high washout rate (> or =30%) on dynamic contrast-enhanced images, and accumulations of complicated cysts showed early enhancement and a low washout ratio (< 30%). The areas containing complicated cysts showed high signal intensity on T1-weighted images, whereas some foci in those areas showed low signal intensity on short tau inversion recovery images. The mean minimum signal intensity ratios (SIRmin) of Warthin tumor on short tau inversion recovery (0.29 +/- 0.22 SD) (P < .01) and T2-weighted images (0.28 +/- 0.09) (P < .05) were significantly lower than those of malignant parotid tumors (0.53 +/- 0.19, 0.48 +/- 0.19). The average washout ratio of Warthin tumors (44.0 +/- 20.4%) was higher than that of malignant parotid tumors (11.9 +/- 11.6%). The mean apparent diffusion coefficient of Warthin tumors (0.96 +/- 0.13 x 10(-3)mm2/s) was significantly lower (P < .01) than that of malignant tumors (1.19 +/- 0.19 x 10(-3)mm2/s). CONCLUSION: Detecting hypointense areas of short tau inversion recovery and T2-weighted images or low apparent diffusion coefficient values on diffusion-weighted images was useful for predicting whether salivary gland tumors were Warthin tumors. The findings of the dynamic contrast-enhanced study also were useful.     

Bone marrow diffusion in osteoporosis: evaluation with quantitative MR diffusion imaging

PURPOSE: To determine the diffusion of vertebral body marrow with quantitative MR diffusion imaging and to examine whether differences exist between subjects with postmenopausal osteoporosis and premenopausal control subjects. MATERIALS AND METHODS: A total of 44 consecutive women (mean age, 70 years) with documented bone mineral density (BMD) measured by dual energy x-ray absorptiometry (T-score) and 20 normal subjects (mean age, 28 years) were examined with echo-planar diffusion imaging at 1.5 T using b values of 0, 20, 40, 60, 80, 100, 200, 300, 400, and 500 seconds/mm2. Extravascular diffusion (D) and apparent diffusion coefficient (ADC) were calculated and results from both groups compared. RESULTS: Both D and ADC values tended to decrease with decreasing BMD. Mean D values were significantly lower in postmenopausal women with reduced BMD (0.42 +/- 0.12 x 10(-3) mm2/second) than normal premenopausal women (0.50 +/- 0.09 x 10(-3) mm2/second). Mean ADC values were significantly lower both in subjects with reduced BMD (0.41 +/- 0.10 x 10(-3) mm2/second) and normal BMD (0.43 +/- 0.08 x 10(-3) mm2/second) compared to normal controls (0.49 +/- 0.07 x 10(-3) mm2/second). CONCLUSION: Accumulation of fatty bone marrow associated with osteoporosis is reflected by a decrease in D and ADC. Diffusion imaging may prove useful in the study of osteoporosis.