Joachim Graessner

Diffusion-Weighted Echo-Planar MR Imaging of Primary Parotid Gland Tumors: Is a Prediction of Different Histologic Subtypes Possible?

BACKGROUND AND PURPOSE: Our aim was to determine the value of echo-planar diffusion-weighted MR imaging (epiDWI) in differentiating various types of primary parotid gland tumors. MATERIALS AND METHODS: One hundred forty-nine consecutive patients with suspected tumors of the parotid gland were examined with an epiDWI sequence by using a 1.5T unit. Image analysis was performed by 2 radiologists independently, and the intraclass correlation coefficient was computed. Histologic diagnosis was obtained in every patient. For comparison of apparent diffusion coefficients (ADCs), a paired 2-tailed Student t test with a Bonferroni correction was used. RESULTS: In 136 patients, a primary parotid gland tumor was confirmed by histology. Among the observers, a high correlation was calculated (0.98). ADC values of pleomorphic adenomas were significantly higher than those of all other entities, except for myoepithelial adenomas (P = .054). ADC values of Warthin tumors were different from those of myoepithelial adenomas, lipomas, and salivary duct carcinomas (P < .001, 0.013, and .037, respectively). Mucoepidermoid carcinomas, acinic cell carcinomas, and basal cell adenocarcinomas were not differentiable from Warthin tumors (P = .094, .396, and .604, respectively). CONCLUSION: epiDWI has the potential to differentiate pleomorphic adenoma and myoepithelial adenomas from all other examined entities. Due to an overlap not only within the group of benign and malignant lesions but also between groups, diagnoses should not be addressed on the basis of ADC values solely. Therefore, further studies combining DWI, morphologic criteria, and probably other MR imaging techniques seem warranted.

Magnetic resonance imaging of prostate cancer: diffusion-weighted imaging in comparison with sextant biopsy.

Purpose: To retrospectively evaluate the impact of diffusion-weighted imaging (DWI) on the detection of prostate cancer in comparison with sextant biopsy. Materials and Methods: Fifty patients with clinical suspicion of prostate cancer underwent a combined endorectal-body-phased array magnetic resonance imaging examination at a 1.5 T magnetic resonance imaging (Siemens, Erlangen, Germany). The DWI was performed using b values of 50, 400, 800 s/mm2. The prostate was divided into sextants, including the apex, the middle aspect, and the base for the left and right sides, separately. Regions of interest were placed in the peripheral zone of each sextant to evaluate the apparent diffusion coefficient (ADC) values. The results of the DWI were compared side by side with the findings of the histological examination of endorectal sonographically guided sextant biopsy. The sensitivity and specificity of ADC for the identification of the tumor tissue were computed for variable discrimination thresholds to evaluate its receiver operating characteristic. An association between ADC and Gleason score was tested for both the whole study group and on an individual basis using the nonparametric Spearman &rgr; test and the Pearson correlation, respectively. Results: Histopathology identified tumor tissue in 21 (42%) of the 50 patients. The ADC value was 1.65 ± 0.32 mm2/s 10−3 in normal tissue and 0.96 ± 0.24 mm2/s 10−3 in tumor tissue (mean ± 1 SD). The area under the receiver operating characteristic curve was 0.966. Using the discrimination threshold 1.21 mm2/s 10−3, for example, the ADC value provided a sensitivity of 0.92 and a specificity of 0.93. There was a highly significant negative correlation between the ADC value and the Gleason score in the tumor-positive tissue probes (n = 62, &rgr; = −0.405, P = 0.001) in the whole study group. On the individual patient basis, the Pearson correlation revealed a mean coefficient of r = −0.89 (SD ± 0.12) with a P < 0.001. Conclusions: Diffusion-weighted imaging of the prostate can be used to differentiate benign from malignant tissue in the peripheral zone. In the present study, ADC values were significantly lower in prostate cancer than in benign tissue.

Diffusion-weighted imaging of the healthy pancreas: apparent diffusion coefficient values of the normal head, body, and tail calculated from different sets of b-values.

To evaluate differences in apparent diffusion coefficient (ADC) values between head, body, and tail regions and the impact of sets of b‐values used in diffusion weighted imaging (DWI) of the normal pancreas.

Age-related distribution of vertebral bone-marrow diffusivity

PURPOSE To determine age-related diffusivity changes of the lumbar bone marrow by measurement of apparent diffusion coefficient (ADC) values. MATERIALS AND METHODS The local ethics committee approved this study and written informed consent was obtained. The study group comprised 88 individuals including 75 healthy volunteers and 13 patients (48 female, 40 male; mean age 36 years, range 0-84 years). The pediatric cases were recruited from patients. Echo-planar diffusion weighted imaging (DWI) was performed with b-values of 50, 400 and 800 s/mm(2). ADC-values were calculated and measured in the 1st and 2nd vertebral body of the lumbar spine. Correlation between age and ADC-values was analyzed with Spearmans rho test. RESULTS The ADC values of the vertebral bone marrow of the lumbar spine showed a significant negative correlation with age (rho=-0.398, p=0.001). The mean ADC values (×10(-3)mm(2)/s) in the age groups 0-29 years (mean age 18.0 years, n=42) and 30-88 years (mean age 51.6 years, n=46) were 0.54 ± 0.07 and 0.47 ± 0.08, respectively (p<0.001, T-test). No significant differences were found between children and young adults. CONCLUSION Bone marrow ADC values of the lumbar spine show a linear decrease with growing age and thereby reflect the gradual changes of cell composition occurring during marrow conversion.

Diffusion-weighted imaging of the healthy pancreas: ADC values are age and gender dependent

To investigate the healthy pancreas with diffusion‐weighted imaging (DWI) for characterization of age and gender‐related differences in apparent diffusion coefficient (ADC) values.

Pancreatic iron and fat assessment by MRI-R2* in patients with iron overload diseases.

To determine the pancreatic iron (R2*) and fat content (FC) in comparison to hepatic and cardiac R2* in patients with iron overload disorders like β‐thalassemia major (TM), Diamond‐Blackfan anemia (DBA) or hereditary hemochromatosis.

Contrast-enhanced magnetic resonance angiography: evaluation of the high relaxivity low diffusible gadolinium-based contrast agent P846 in comparison with gadoterate meglumine in rabbits at 1.5 Tesla and 3.0 Tesla.

Objectives:To evaluate the gadolinium-based contrast agent P846 and compare it with gadoterate meglumine (Gd-DOTA) for contrast-enhanced magnetic resonance angiography (MRA) in rabbits at 1.5 T and 3.0 T, respectively. Materials and Methods:Five rabbits underwent contrast-enhanced MRA of the abdominal vasculature applying gadolinium doses of 0.025 mmoL/kg for P846 and 0.1 mmoL/kg for Gd-DOTA, respectively. All animals were examined on a 1.5-T and 3.0-T MR system. Image data were acquired during the first-pass arterial phase and repeatedly over 10 minutes. Contrast-to-noise-ratio (CNR) was determined in the aorta, the inferior vena cava, and the renal cortex. Image quality of arterial phase MR angiograms was consensually judged on a 5-point scale (5 = high). Results:Contrast-enhanced MRA was successful in all cases with both contrast agents. CNR values consistently proved statistically significantly higher for P846 compared with Gd-DOTA. CNR values in the aorta during the arterial phase were 46.0 ± 3.7 (P846) and 28.0 ± 3.2 (Gd-DOTA) at 1.5 T (P < 0.05), and correspondingly 89.3 ± 12.7 (P846) and 64.1 ± 15.0 (Gd-DOTA) at 3.0 T (P < 0.05). Image quality of arterial phase MR angiograms was rated with scores of 4.8 ± 0.4 (P846) and 4.0 ± 0.0 (Gd-DOTA) at 1.5 T (P = 0.06), and 5.0 ± 0.0 (P846) and 4.8 ± 0.4 (Gd-DOTA) at 3.0 T (P = 0.42), respectively. Conclusions:The contrast agent P846 provides high contrast enhancement and image quality for contrast-enhanced MRA in rabbits at 1.5 T and 3.0 T with a 4-fold lower gadolinium dose compared with a standard extracellular contrast agent.

Assessment of aortic root dimensions in patients with suspected Marfan syndrome: intraindividual comparison of contrast-enhanced and non-contrast magnetic resonance angiography with echocardiography.

PURPOSE Our purpose was to evaluate intraindividually the performance of contrast-enhanced magnetic resonance angiography (MRA) and non-contrast MRA for aortic root diameter measurements and to compare the results with routinely performed echocardiography in patients with suspected Marfan syndrome. METHODS AND MATERIALS Aortic roots were examined prospectively in 51 consecutive patients with suspected Marfan syndrome by using contrast-enhanced MRA and non-contrast MRA at 1.5 T. Two readers independently measured aortic root diameters at the annulus, sinuses of Valsalva and sinutubular junction in both data sets and compared results with echocardiographic data. Intraclass correlation coefficient, Pearson correlation coefficient, Bland-Altman, and two-sided t-test were used to assess agreement between observers and methods. RESULTS 38 (74.5%) of the 51 patients (25 female, 26 male; mean age 37.1 ± 13.7 years) had Marfan syndrome. Both, contrast-enhanced MRA and non-contrast MRA measurements of the sinuses of Valsalva revealed a strong correlation with echocardiography (r=0.850 and r=0.893, respectively). Intraclass correlation was markedly better for non-enhanced MRA (r=0.904) when compared to contrast-enhanced MRA (r=0.690). Image quality (p<0.001) as well as interobserver agreement (p<0.0042) of measurements of the sinuses of Valsalva was significantly better for non-enhanced MRA than for contrast-enhanced MRA. CONCLUSION Non-contrast MRA was more reliable and more valid than contrast-enhanced MRA for assessment of aortic root dimensions in patients with suspected Marfan syndrome. Therefore contrast agents can be omitted for establishing the diagnosis of aortic involvement in Marfan syndrome.

Balanced steady-state free precession vs. segmented fast low-angle shot for the evaluation of ventricular volumes, mass, and function at 3 Tesla

To compare balanced steady‐state free precession (SSFP) and segmented fast low angle shot (FLASH) for quantification of left and right ventricular volumes and function and for left ventricular mass at high field (3 Tesla).

Black-blood imaging of the human heart using rapid stimulated echo acquisition mode (STEAM) MRI

To develop a rapid stimulated echo acquisition mode (STEAM) MRI technique for “black‐blood” imaging of the human heart that overcomes the single‐slice limitation and partially compromised blood suppression associated with double inversion‐recovery techniques.