Diffusion-weighted magnetic resonance imaging of breast lesions: first experiences at 3 T.

PURPOSE: Dynamic contrast-enhanced magnetic resonance imaging (MRI) has been established as a valuable tool for the detection of breast cancer. There is evidence suggesting that diffusion-weighted imaging (DWI) may be useful to distinguish between malignant and benign breast lesions. We seek to evaluate the ability of DWI to differentiate between malignant and benign breast lesions at 3 T. METHODS: Dynamic contrast-enhanced MRI and DWI of the breasts were performed in 31 female patients (age: mean, 46 years; range, 34-69 years) with suspected breast lesions on mammography and ultrasound using a 3-T scanner (MAGNETOM Tim Trio; Siemens Medical Solutions, Erlangen, Germany). Each lesion was assigned as either malignant or benign, blinded to the results of mammography and ultrasound, according to their imaging characteristics on contrast-enhanced MRI, DWI, and apparent diffusion coefficient (ADC) measurements. Tissue samples were obtained from all lesions by either needle or excision biopsy. Using histological results as the gold standard, the diagnostic accuracies of the dynamic contrast-enhanced MRI, DWI, and ADC were calculated and compared. RESULTS: All breast lesions (n = 31) were identified on both the dynamic contrast-enhanced MRI and DWI scans. The threshold ADC value was determined to be 0.00121 mm2/s, below which a lesion was considered malignant. The sensitivities/specificities of the dynamic contrast-enhanced MRI, qualitative DWI, and quantitative ADC were 95%/91%, 95%/63.6%, and 90%/91%, respectively. The differences in sensitivities, specificities, positive and negative predictive values, and diagnostic accuracies between the 3 examinations were statistically insignificant. CONCLUSIONS: Diffusion-weighted imaging at 3 T is highly sensitive in the detection of malignant breast lesions even with qualitative assessment alone, whereas ADC measurement offers quantitative assessment and increases the specificity to more than 90%. Further studies involving a larger cohort size and a wider spectrum of breast lesions are indicated.

Magnetic resonance whole body imaging at 3 Tesla: feasibility and findings in a cohort of asymptomatic medical doctors.

OBJECTIVES: To evaluate the feasibility of whole body imaging using a 3 Tesla magnetic resonance scanner without a contrast agent, and to study the prevalence of abnormal findings among a cohort of asymptomatic doctors. DESIGN: Prospective study. SETTING: Private hospital, Hong Kong. PARTICIPANTS: A total of 132 asymptomatic medical doctors (111 men, 21 women), with a mean age of 56 (range, 38-82) years, volunteered for the study. They underwent corresponding whole body imaging at our hospital between October 2005 and February 2006. Imaging involved a 3 Tesla magnetic resonance scanner with 32 channels, parallel imaging, Total Imaging Matrix technology, a maximum gradient amplitude of 40 mT/m and a slew rate of 200 mT/m/ms (Magnetom Tim Trio, Siemens Medical Solution, Erlangen, Germany). The use of matrix coils enabled coverage of the whole body. No contrast agent was used. MAIN OUTCOME MEASURES: Detection of abnormalities in asymptomatic, apparently healthy adults. RESULTS: All examinations were completed successfully. The mean scan time per subject was 33 (standard deviation, 4) minutes. All subjects tolerated the examination well and overall imaging quality was satisfactory. A total of 124 (94%) subjects had positive findings, of whom 24 (18%) had further workup. Five (4%) subjects were found to have tumours, of which two (1.5%) were proven malignant. Our cancer detection rate was comparable to that of other reported whole body screening studies using contrast magnetic resonance imaging and positron emission tomography. CONCLUSION: We demonstrated the feasibility of performing whole body imaging in 30 minutes, using 32-channel magnetic resonance imaging at 3 Tesla without a contrast agent or any ionising radiation.

Rapid assessment of left ventricular segmental wall motion, ejection fraction, and volumes with single breath-hold, multi-slice TrueFISP MR imaging.

BACKGROUND AND OBJECTIVE: To reduce imaging time and complexity, we sought to determine whether single breath-hold, multi-slice TrueFISP (SB-MST) magnetic resonance imaging (MRI) method is comparable to standard multi-breath-hold, multi-slice TrueFISP (MB-MST) for assessment of left ventricular (LV) wall motion abnormality (WMA), volumes, and ejection fraction (EF). METHODS AND RESULTS: We studied 62 patients having cardiac MRI at 1.5-Tesla. After acquiring standard MB-MST (one slice per breath-hold), SB-MST was performed, acquiring 3 short- and 2 long-axis views over only 20 heartbeats. Using both techniques, wall motion was scored using a 6-point, 17-segment LV model for all scans (62 patients x 2 techniques/patient = 124 scans) on two separate occasions. Separately, EF and ventricular volumes were evaluated using both MB-MST and SB-MST. For all analyses, MB-MST was considered the standard against which SB-MST was compared. Twenty-six of 62 patients exhibited at least one segmental WMA by MB-MST. Exact agreement for wall motion was found in 965/1054 segments (92%, kappa = 0.74, p < 0.001), and agreement was within 1 score point in 1010/1054 segments (96%). Considering a score >1 abnormal, exact agreement for presence of WMA was found in 131/193 segments (68%) abnormal by MB-MST and for absence of WMA in 838/861 segments (97%) normal by MB-MST. Agreement within 1 score point occurred in 167/193 abnormal (87%) and in 843/861 normal segments (98%). There were no significant differences in agreement between first and second read of the data. Variability of SB-MST on read one versus read two was small (5%, 996/1054 segments read identically, p = ns) and statistically identical to variability of MB-MST on read one versus read two (4%, 1007/1054 segments read identically, p = ns). For end-diastolic volumes, end-systolic volumes, and EF using SB-MST compared to MB-MST, mean differences were 9 +/- 15 ml, 6 +/- 12 ml, and 2 +/- 5%, and correlations were r = 0.97, 0.98 and 0.95, respectively. CONCLUSION: SB-MST accurately assesses wall motion, volumes and EF. This approach may serve as a screening exam for assessment of WMA and, under select circumstances, may substitute for standard multi-breath-hold method in situations requiring rapid accurate assessments of LV function.

Direct quantitative in vivo comparison of calcified atherosclerotic plaque on vascular MRI and CT by multimodality image registration.

PURPOSE: To investigate direct volumetric in vivo correspondence of calcified atherosclerotic plaque lesions in MRI and CT images of the thoracic aorta by multimodality image registration and fusion. MATERIALS AND METHODS: Twelve CT (11 noncontrast and one contrast) and MRI (TruFISP, contrast T1-weighted volumetric interpolated breath-hold examination (VIBE)) data sets were co-registered by approximate segmentation of the aorta and subsequent automatic co-registration by maximization of mutual information (MI). We quantitatively assessed 22 co-registered calcified plaque lesions on CT and MRI. RESULTS: The three-dimensional registration consistency and accuracy were 1.74 +/- 1.3 mm, and 2.42 +/- 1.65 mm, respectively. The ratio of CT/MRI calcified plaque volume decreased asymptotically with MRI volume, and correlated with average CT lesion density (r = 0.72) for small lesions (<25 mm(3)). The average calcified plaque volume, circumferential extent, and maximal radial width by MRI were significantly smaller compared to CT (35%, 68%, and 53%, respectively; P < 0.05). CONCLUSION: Software co-registration allowed precise, direct, and voxel-based comparison of calcified atherosclerotic plaque lesions imaged by MRI and CT. In comparison with co-registered MRI, overestimation of calcified plaque in aortic CT due to "blooming" correlates with the average lesion density for small plaques, and is greater for small plaques.