Sander B

Gd-DTPA enhanced MRI of breast: the most sensitive method for detecting multicentric carcinomas in female breast?

The first publications on the use of magnetic resonance for breast imaging (MRBI) appeared more than 10 years ago. According to the literature between 14% and 47% of all breast carcinomas are multicentric carcinoma (MCC), a substantial number of which are not detected by conventional mammography. In a prospective study our purpose was to establish a clinically relevant procedure with MRBI for women with a single suspect lesion on mammography. Eight (32%) of 25 patients with histologically confirmed carcinoma had an MCC. Seven MCC were detected with MRBI and only one was diagnosed by mammography; one was discovered with neither MRBI nor mammography. MRBI proved to be the superior technique, with a sensitivity of 0.88 compared with 0.13 for mammography.

MAGNETIC RESONANCE PERFUSION IMAGING WITH GADOLINIUM-DTPA: A QUANTITATIVE APPROACH FOR THE KINETIC ANALYSIS OF FIRST-PASS RESIDUE CURVES

RATIONALE AND OBJECTIVESTo present a mathematic approach for the analysis of first-pass gadolinium (Gd)-DTPA kinetics and to validate the numerical tools using simulated and measured kinetics. METHODSIn a capillary plasma filter, pulsatile flow was varied between 7.4 and 12.6 mL/second. After contrast bolus injection, the arterial input curve and the residue curve were recorded simultaneously. Signal intensity versus time curves were converted to concentration versus time curves. By deconvolution of these curves and tracer kinetic analysis, the mean transit time of the contrast medium through the organ model was calculated. RESULTSA satisfactory correlation (r = 0.98) between the inverse of mean transit time and flow measured volumetrically was demonstrated. CONCLUSIONSThe kinetic analysis of first-pass curves in an organ model indicates that this approach might be useful for in vivo assessment of organ blood flow.

Applications of specialized coils for high-resolution MRI on a whole-body scanner

To investigate the application of a mini-coil surface system for high-resolution MRI, 60 volunteers were examined in a 1.5-T whole-body scanner. Two replaceable probe heads were available: a circular 2.5-cm coil and a quadratic 5-cm coil, both of which were placed directly on the skin. The skin layers, Achilles tendon and finger joints were examined with the 2.5-cm coil and a FOV of 25 × 25 mm2. A matrix of 256 × 256 pixels resulted in a pixel size of 0.098 × 0.098 mm2. For imaging of the carpal tunnel, the 5-cm coil was used in transverse orientation. The FOV was 50 × 50 mm2 so that a matrix of 256 × 256 pixels led to a pixel size of 0.195 × 0.195 mm2. The resulting spatial resolution permitted visualization of the epidermis, dermis and subcutis, resulting in clear definition of anatomical detail of the musculoskeletal system. MRI measurement of skin-layer thickness did not correlate with histometric data (p<0.05). This discrepancy was due in part to shrinkage of the tumor specimen on histologic preparation. Other causes include the motion artifacts and the limited accuracy of determining thickness on the MRI display unit.

Regional cerebral blood volume of intracranial tumors determined by MRI

The aim of this study was to characterize intracranial tumors based on MR measurements of regional cerebral blood volume. In 8 patients without intracranial pathology and 42 patients with intracranial tumors a T2*-weighted image series was acquired during bolus injection of gadolinium-DTPA, and regional cerebral blood volume maps were calculated. The regional cerebral blood volume index (rCBVi) of vital tumor was expressed in percent of the value measured in contralateral gray matter. In extra-axial tumors (meningiomas) rCBVi was higher (124 ± 110%), and in low-grade intra axial tumors rCBVi was lower (79 ± 65%), than in contralateral cortex. In malignant intra-axial tumors the distribution of rCBV was heterogenous: high in vital tumor (glioblastomas: rCBVi = 165 ± 85%; metastases: rCBVi = 106 ± 79%), but low in necrosis (rCBVi = 33% of contralateral white matter) and edema (rCBVi = 53% of contralateral white matter). rCBVi was highest in arteriovenous malformations (1053 ± 584% of contralateral gray matter). We conclude that the regional cerebral blood volume distribution is useful to characterize intracranial tumors, although the large biological variability of individual tumor entities indicates limitations.

Computational Aspects of Blood Flow Measurement by First-Pass Gadolinium-DTPA Enhanced Magnetic Resonance Imaging

After an intravenous bolus injection of a paramagnetic contrast agent such as gadolinium-DTPA, the first cerebral passage of the contrast agent can be recorded in the brain tissue by a rapid T2*-weighted pulse sequence. From the recorded data, concentration-time-curves of the contrast medium can be calculated on a pixel-by-pixel basis. The area of the concentration-time-curve is proportional to regional cerebral blood volume. For the computation of regional cerebral blood flow, the mean transit time of the contrast bolus through the brain is required. This mean transit time, however, can not be directly obtained because the tissue concentration-time-curve is affected by the transit of the contrast medium through the brain and through veins, the heart and the lungs. To eliminate the latter, a concentration-time-curve must be recorded simultaneously in an artery that supplies the brain (inlet curve) and in the brain tissue. Numerical deconvolution (on a pixel-by-pixel basis) of the inlet curve and the tissue curve yields the transport function of the brain for the contrast agent. On the basis of that transport function the mean transit time through the brain is calculated.

Time-reduced T2-weighted celebral MRI with optimized flip angles

This study was set up to see whether lowering the flip angle in proton density- and T2-weighted double-spin echo sequences allows for shortening of repetition time (TR) and imaging time without significant change of image quality. Ten patients with celebral white matter lesions were investigated with an 1.5 T MR scanner using a conventional long- TR double-spin echo sequence (TR = 2500 ms, TE = 15 and 70 ms) and reduced-TR double-spin echo sequences (TR = 1900 ms, TE = 15 and 70 ms) at flip angles of 90°, 80°, 70°, 60°, and 50°. Lowering the flip angle resulted in less T1-contrast and a relative increase of T2-contrast. At a flip angle of 70°, contrast-to noise ratios (NNRs) between lesions and brain, as well as image artifacts of the reduced-TR sequence (CNR: 22.4) were similar to the conventional long-TR sequence (CNR:21.1), while imaging time was shortened by about 25%.

Gadolinium DTPA-enhanced MRI of degenerative cervical spine disease*

Thirty-two patients with 30 disc herniations and 5 bony stenoses were investigated together with 5 control subjects, using plain and contrast-enhanced Magnetic resonance imaging. Compared with the control group, additional non-enhancing epidural tissue was found in all patients. The enhancing epidural structures demostrated characteristics change. Compared with plain images, disease definition was improved in 7 of 35 cases after contrast administration. This was especially true for lateral and intraforaminal disc herniations, whereas no diagnostic benefit was seen in cases of posterior and posterolateral herniations or bony changes.