Nandita M. deSouza

An investigation into the use of sensitivity-encoded techniques to increase temporal resolution in dynamic contrast-enhanced breast imaging

Gadolinium‐enhanced dynamic magnetic resonance (MR) imaging is playing an increasingly important diagnostic role in patients with breast cancer. Because of the multi‐focal nature of the disease, it is mandatory to cover all of both breasts, not only in the initial scan, but also at subsequent follow‐up. This requires volume acquisitions with a temporal resolution limited to 60–80 seconds, which is insufficient to clearly discriminate malignant from benign rates of contrast uptake. In this work, we performed sensitivity‐encoded imaging using a commercially available four‐channel breast coil (MRI Devices Corporation) on a commercial 0.5‐T scanner with moderate gradient performance to give increased temporal resolution in these dynamic contrast‐enhanced scans. A two‐fold increase in temporal resolution was readily achievable with this coil. Image reconstruction was robust and image quality was assessed qualitatively to be good. We also investigated higher speed‐up factors using two directions of sensitivity‐encoded reduction and discussed some of the potential artifacts associated with such imaging. J. Magn. Reson. Imaging 2001;14:329–335.

Magnetic resonance imaging of the primary site in stage I cervical carcinoma: A comparison of endovaginal coil with external phased array coil techniques at 0.5T

Objective: To compare endovaginal with pelvic phased array coil magnetic resonance imaging (MRI) in detection of Stage I cervical carcinoma by correlating the findings with histopathology. Patients and Methods: Forty consecutive patients with Stage I cervical carcinoma confirmed histologically were studied using an endovaginal coil alone immediately followed by a pelvic phased array coil. T1‐W transverse and T2‐W FSE sagittal images made with each coil were analyzed independently by two radiologists noting the presence and size of a mass within the cervix and any parametrial extension or involvement of adjacent organs. Tumor volumes were measured using the electronic calliper to compute tumor area on each slice and multiplying by the slice thickness. Thirty patients underwent radical hysterectomy, one a trachylectomy, one simple hysterectomy and four extended cone biopsies. Four patients had radiotherapy to the primary tumor. Following surgery, histopathologic findings were recorded and tumor volumes measured. Results: Tumor volumes ranged from 0–106 cm3(median 1.4 cm3, mean 9 ± 19.4 cm3). Thirty‐six patients had correlation of the primary site with the surgical specimen. Agreement between observers was excellent for both endovaginal (k = 0.90) and pelvic phased array (k = 0.96) techniques. Combined sensitivity and specificity for both observers of endovaginal MR imaging for detection of tumor was 96% and 70%, respectively; for pelvic phased array imaging sensitivity was substantially less at 54%. Specificity was higher at 83.7%, probably because small abnormalities were seldom visible. In patients treated surgically, early parametrial involvement in four women on endovaginal MRI was confirmed histologically in two. Pelvic phased array imaging showed early parametrial involvement in four women and was confirmed in one. Conclusion: Endovaginal MRI adds substantially to information from pelvic phased array images in the preoperative assessment of patients with early cervical cancer. J. Magn. Reson. Imaging 2000;12:1020–1026.

Endovascular stents and stent-grafts: is heparin coating desirable?

Heparins are glycosaminoglycans that, in addition to their anticoagulant activity, have interactions with growth factors and other glycoproteins. These interactions may stimulate neointimal hyperplasia when heparin is delivered locally on stents and stent-grafts. Modifying the structure of heparin to retain anticoagulant activity while minimizing these stimulatory effects on the vascular endothelium is desirable and may be achieved by understanding the relationships between the structure and function of the various parts of the heparin molecule.

High-resolution magnetic resonance imaging of the anal sphincter using a dedicated endoanal receiver coil.

Abstract. The use of a surface coil in MR imaging improves signal-to-noise ratio of adjacent tissues of interest. We therefore devised an endoanal receiver coil for imaging the anal sphincter. The probe is solid and re-usable: it comprises a saddle geometry receiver with integral tuning, matching and decoupling. It is placed in the anal canal and immobilised externally. Both in vitro and in vivo normal anatomy is identified. The mucosa is high signal intensity, the submucosa low signal intensity, the internal sphincter uniformly high signal intensity and the external sphincter low signal intensity on T1- and T2-weighted images. In females, the transverse perineal muscle bridges the inferior part of the external sphincter anteriorly. In perianal sepsis, collections and the site of the endoanal opening are identified. In early-onset fecal incontinence following obstetric trauma/surgery, focal sphincter defects are demonstrated; in late-onset fecal incontinence external sphincter atrophy is seen. In fecally incontinent patients with scleroderma, forward deviation of the anterior sphincter musculature with descent of rectal air and feces into the anal canal is noted. The extent of sphincter invasion is assessed in low rectal tumours. In children with congenital anorectal anomalies, abnormalities of the muscle components are defined using smaller-diameter coils. Such information is invaluable in the assessment and surgical planning of patients with a variety of anorectal pathologies.

Pre‐polarized saline: an in vivo feasibility study of a potential contrast agent

The potential for using pre‐polarized liquids as contrast agents in vivo is investigated and the feasibility of the method demonstrated. In this study we show the enhancement obtained following intravenous delivery of pre‐polarized saline into the antecubital vein of a volunteer. This form of contrast agent provides signal gain on time scales commensurate with its T1 and allows repeated doses to be administered, thus making alternate acquisitions of data with and without enhancement practicable. Copyright