Glyn A. Coutts

Increased acquisition efficiency has been achieved by exciting several slices simultaneously. The mixed data were unfolded to produce separate slices using the spatial encoding information inherent in a multicoil receiver system. Each coil yields a linear combination of signals from all excited slices weighted by the sensitivity of each coil. A matrix inversion provides a solution to unfold these images.

BACKGROUND: Extracellular matrix expansion is a key element of ventricular remodeling and a potential therapeutic target. Cardiovascular magnetic resonance (CMR) T1-mapping techniques are increasingly used to evaluate myocardial extracellular volume (ECV); however, the most widely applied methods are without histological validation. Our aim was to perform comprehensive validation of (1) dynamic-equilibrium CMR (DynEq-CMR), where ECV is quantified using hematocrit-adjusted myocardial and blood T1 values measured before and after gadolinium bolus; and (2) isolated measurement of myocardial T1, used as an ECV surrogate. METHODS AND RESULTS: Whole-heart histological validation was performed using 96 tissue samples, analyzed for picrosirius red collagen volume fraction, obtained from each of 16 segments of the explanted hearts of 6 patients undergoing heart transplantation who had prospectively undergone CMR before transplantation (median interval between CMR and transplantation, 29 days). DynEq-CMR-derived ECV was calculated from T1 measurements made using a modified Look-Locker inversion recovery sequence before and 10 and 15 minutes post contrast. In addition, ECV was measured 2 to 20 minutes post contrast in 30 healthy volunteers. There was a strong linear relationship between DynEq-CMR-derived ECV and histological collagen volume fraction (P<0.001; within-subject: r=0.745; P<0.001; r(2)=0.555 and between-subject: r=0.945; P<0.01; r(2)=0.893; for ECV calculated using 15-minute postcontrast T1). Correlation was maintained throughout the entire heart. Isolated postcontrast T1 measurement showed significant within-subject correlation with histological collagen volume fraction (r=-0.741; P<0.001; r(2)=0.550 for 15-minute postcontrast T1), but between-subject correlations were not significant. DynEq-CMR-derived ECV varied significantly according to contrast dose, myocardial region, and sex. CONCLUSIONS: DynEq-CMR-derived ECV shows a good correlation with histological collagen volume fraction throughout the whole heart. Isolated postcontrast T1 measurement is insufficient for ECV assessment.

Proton magnetic resonance spectroscopy (1H MRS) was used to investigate intracranial tumours in vitro and in vivo. Biopsy specimens were studied from 47 patients, 11 of whom were also examined in vivo. Analysis was based on the signals from N-acetylaspartate (NAA), phosphocreatine plus creatine (Cr), choline-containing compounds (Cho), alanine (Ala), and lactate. Biopsy data from 26 astrocytomas showed that the NAA/Cr ratio differs significantly in all grades from its value in normal white matter and that the Cho/Cr ratio differs significantly in grade IV tumours from its value in the other grades. Meningiomas have an unusually high Ala/Cr ratio. Spectra obtained in vivo are consistent with in vitro results from the same patients, and their lactate signal provides additional information about abnormal metabolism. We conclude that 1H MRS has a clear role in the diagnosis and biochemical assessment of intracranial tumours and in the evaluation and monitoring of therapy.

MR imaging of the anal sphincter in multiparous women using an endoanal coil: correlation with in vitro anatomy and appearances in fecal incontinence.N M deSouza, R Puni, A Zbar, D J Gilderdale, G A Coutts and T KrauszAudio Available | Share

PURPOSE: The objective of our study was to compare MRI of fistulas-in-ano using an endoanal coil with that using a pelvic phased array coil and to assess the value of a combined approach by correlating the findings with those at surgery. METHOD: Twenty consecutive patients with clinical suspicion of perianal sepsis were studied using an endoanal coil immediately followed by a phased array coil. T1 weighted and STIR images in transverse and coronal planes were made with each coil and analysed by noting the presence and site of a collection and primary track, the position of any internal opening, and subcutaneous or supralevator extension. Operative findings were similarly recorded. RESULTS: Of 20 patients with suspected fistulas, 8 had simple fistulas, 8 had complex fistulas, and 4 had no current evidence of infection. The concordance between MR and surgery for identifying the presence and site of the collection, the primary track, and the internal opening in both simple and complex cases was superior using the endoanal coil as compared with the phased array. Both coils together reflected the findings of the endoanal coil used alone. However, for supralevator/subcutaneous extension, concordance was superior using the phased array compared with the endoanal coil, and a combined approach reflected the values of the phased array coil used alone. CONCLUSION: Endoanal MRI is highly sensitive in the delineation of fistulas-in-ano. In combination with phased array techniques, it provides valuable preoperative assessment in both simple and complex cases.