MR anatomy and small lesions of the eye: improved delineation with a special surface coil

To develop an improved investigation protocol for MRI studies of intraocular lesions, imaging with a small surface coil (diameter 6 cm) was compared with a standard surface coil (diameter 11 cm). Both coils were assessed initially on an eye phantom and then by studying 22 patients with uveal melanoma and similar lesions of the eye. The influence of bandwidth and field or view (FOV) were systematically studied and evaluated quantitatively. A smaller bandwidth improved image quality independent of surface coil size. The subsequent secondary increase in chemical shift artefact was acceptable. Smaller FOVs (60–80 mm) necessitated the use of a smaller surface coil. A smaller bandwidth also proved to be advantageous with the use of the smaller surface coil. In conclusion, a smaller-diameter surface coil improves MR imaging of ocular lesions. Pulse sequences with a small bandwidth maintain an acceptable signal-to-noise ratio when the FOV is reduced. Received 27 December 1995; Revision received 29 July 1996; Accepted 3 September 1996     

Local staging of prostate carcinoma with endorectal coil MRI: correlation with whole-mount radical prostatectomy specimens

The purpose of this study was to investigate the accuracy of endorectal coil MRI in the local staging of prostate carcinoma. A total of 73 patients with biopsy-proven prostate carcinoma were examined at 0.5 T prior being submitted to radical prostatectomy. The gold standard was provided in all patients by findings at whole-mount sectioning of the surgical specimens. At pathology 28 patients had stage T2, 30 had stage T3a/b, and 15 had stage T3c lesions. Overall accuracy of endorectal coil MRI in defining local tumor stage was 82% (60 of 73 patients). Of 73 patients, 5 (7%) were underestimated and 8 (11%) overestimated. The sensitivity and the specificity of endorectal coil MRI in diagnosing capsular penetration were 95% and 82%, respectively. Seminal vesicle invasion was detected with 80% sensitivity and 93% specificity. Our data indicate that endorectal coil MRI is an accurate method for local staging of prostate cancer.Correspondence to: C. Bartolozzi     

Anatomical and metabolic assessment of prostate using a 3-Tesla MR scanner with a custom-made external transceive coil: healthy volunteer study

PURPOSE: To examine the possibility of using a 3 Tesla (T) magnetic resonance (MR) scanner with a custom-made external coil to obtain ductal details of the prostate, high-quality spectra, and metabolite mapping corresponding to prostate zonal anatomy in healthy volunteers. MATERIALS AND METHODS: MRI and two-dimensional (2D) chemical shift imaging (CSI) were performed in 16 healthy volunteers using a 3T scanner with a custom-made external transmit-receive (transceive) coil. Visualization of the prostatic duct-like structure was analyzed on T2-weighted (T2W) images. The resolution of the metabolite peaks and the distribution of metabolites in CSI were also assessed. RESULTS: In the axial plane, 3-mm-thick images were better than 4-mm-thick images with the same voxel volume for assessing duct-like structures and prostatic urethra. Differentiation between inner and outer citrate (Cit) peaks was frequently observed (29 out of 30). The mean peak area ratio of choline (Cho) plus creatine (Cr) over Cit in the peripheral zone (PZ) was significantly lower than in the transition zone (TZ) (P = 0.014). CONCLUSION: 3T MR examinations of the prostate using an external coil allow information to be collected about the details of duct-like structures, the high-quality spectra of Cit, and the zone-specific distribution of metabolites.     

Whole-body MR angiography using a novel 32-receiving-channel MR system with surface coil technology: first clinical experience

PURPOSE: To demonstrate the feasibility of detecting atherosclerotic vascular disease using an innovative magnetic resonance angiography (MRA) protocol in combination with a dedicated whole-body MR scanner with new surface coil technology. MATERIALS AND METHODS: A total of 10 volunteers and eight patients with peripheral arterial occlusive disease (PAOD) were examined at 1.5 T. Conventional digital subtraction angiography (DSA) of the symptomatic region was available as a reference standard in all eight patients. Depending on subjects' size, four to five three-dimensional data sets were acquired using an adapted injection protocol. Images were assessed independently by two readers for vascular pathology. Additionally, signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were measured. RESULTS: Whole-body MRA yielded excellent sensitivity and specificity of more than 95% for both readers with high interobserver agreement (k = 0.93). Surface coil signal reception rendered a high SNR (mean 151.28 +/- 54.04) and CNR (mean 120.75 +/- 46.47). Despite lower SNR and CNR of the cranial and cervical vessels, a two-step injection protocol exhibited less venous superposition and therefore proved to be superior compared to single-bolus injection. CONCLUSION: Our approach provides accurate noninvasive high-resolution imaging of systemic atherosclerotic disease, covering the arterial vasculature from intracranial arteries to distal runoff vessels. The recently introduced MR scanner and coil technology is feasible to significantly increase the performance of whole-body MRA.     

Evaluation of reconstructed orbital wall fractures: high-resolution MRI using a microscopy surface coil versus 16-slice MSCT

We evaluated high-resolution magnetic resonance imaging (MR) using a 47-mm microscopy surface coil in comparison to 16-slice multislice CT (MSCT) for postsurgical imaging of reconstructed orbital walls. Twenty-five patients with 27 internal orbital wall fractures were imaged prospectively after reconstruction with resorbable polydioxanone sulfate (PDS) sheets. Coronal high-quality T1- and T2-weighted MR images were obtained with an in-plane resolution of 350 m within a measure time of 6–7 min for each sequence. Nineteen symptomatic patients underwent MSCT as the current gold standard. In MRI the PDS foil appears in T1- and T2-weighted images as a thin, low-signal-intensity linear structure. In CT it appears hyperdense in comparison to soft tissue and slightly hypodense in comparison to cortical bone. PDS foils could be clearly depicted in 20 out of 25 patients (80%) with MRI and in 13 out of 19 patients (68%) with MSCT. An inadequate foil position or size could be diagnosed in eight patients with MRI and in only three patients with MSCT. In ten symptomatic patients secondary surgery could be avoided because of regular MRI findings except mild hematoma and muscle edema. High-resolution MRI of the orbit using a 47-mm microscopy coil is a promising method to accurately demonstrate normal and pathologic conditions in symptomatic patients after orbital wall reconstruction with PDS foils.     

High-resolution magnetic resonance of the extracranial facial nerve and parotid duct: demonstration of the branches of the intraparotid facial nerve and its relation to parotid tumours by MRI with a surface coil

AIM: To investigate the usefulness of high-resolution MR imaging in the evaluation of the extracranial facial nerve, compared with surgical findings. MATERIALS AND METHODS: Thirteen patients with benign parotid tumours were studied on a 1.5-T MR system with a 3 in circular surface coil. High-resolution T1-weighted spin-echo, T2-weighted fast spin-echo, and three-dimensional gradient-recalled acquisition in the steady state (GRASS) images were obtained in the axial planes. Oblique reformatted images were generated. Tumours, parotid ducts and facial nerves were identified on these images. The relationship of the tumours to the facial nerves was confirmed at surgery. RESULTS: Facial nerves appeared as linear structures of low intensity on all pulse sequences. The main trunks and cervicofacial and temporofacial divisions of the facial nerves were identified in 100%, 84.1% and 53.8% of GRASS images, respectively. Parotid ducts appeared as structures of low intensity on T1-weighted (66.6%) and GRASS images (81.8%), and as structures of very high intensity on T2-weighted images (91.7%). The relationships of the tumours to the facial nerves were correctly diagnosed in 11 (91.7%) of 12 cases. CONCLUSION: High-resolution MR imaging depicts the extracranial facial nerve and the parotid duct, and is useful for preoperative evaluation of parotid gland tumours.