Reduction of the estimated radiation dose and associated patient risk with prospective ECG-gated 256-slice CT coronary angiography.

Computed tomography (CT) coronary angiography has been widely used since the introduction of 64-slice scanners and dual-source CT technology, but high radiation doses have been reported. Prospective ECG-gating using a 'step-and-shoot' axial scanning protocol has been shown to reduce radiation exposure effectively while maintaining diagnostic accuracy. 256-slice scanners with 80 mm detector coverage have been currently introduced into practice, but their impact on radiation exposure has not been adequately studied. The aim of this study was to assess radiation doses associated with CT coronary angiography using a 256-slice CT scanner. Radiation doses were estimated for 25 patients scanned with either prospective or retrospective ECG-gating. Image quality was assessed objectively in terms of mean CT attenuation at selected regions of interest on axial coronary images and subjectively by coronary segment quality scoring. It was found that radiation doses associated with prospective ECG-gating were significantly lower than retrospective ECG-gating (3.2 +/- 0.6 mSv versus 13.4 +/- 2.7 mSv). Consequently, the radiogenic fatal cancer risk for the patient is much lower with prospective gating (0.0176% versus 0.0737%). No statistically significant differences in image quality were observed between the two scanning protocols for both objective and subjective quality assessments. Therefore, prospective ECG-gating using a 'step-and-shoot' protocol that covers the cardiac anatomy in two axial acquisitions effectively reduces radiation doses in 256-slice CT coronary angiography without compromising image quality.

Recurrence of trigeminal neuralgia due to an acquired arachnoid cyst.

We present the case of a 55-year-old female with pain recurrence after microvascular decompression for trigeminal neuralgia due to development of an arachnoid cyst. Radioimaging studies were inconclusive for vascular compression but showed evidence of fifth nerve distortion. The patient underwent surgical re-exploration, and a cystic lesion of thickened arachnoid containing cerebrospinal fluid was identified and excised. Postoperatively, the patient obtained pain relief. Arachnoid cyst formation may be a possible reason for pain recurrence after microvascular decompression for trigeminal neuralgia, especially when repeat neuroimaging does not show clear evidence of fifth nerve vascular compression. Direct compression from the cyst or arterial pulsation transmission through the cyst to the nerve may be the cause of recurrence.

Giant dumbbell-shaped middle cranial fossa trigeminal schwannoma with extension to the infratemporal and posterior fossae.

We present a 38-year-old female with a giant dumbbell-shaped trigeminal neurinoma originating primarily in the middle cranial fossa, extending to the infratemporal and posterior fossae through the foramen ovale and Meckel's cave, respectively. Because of the large tumour extension into the Infratemporal Fossa, a combined skull base approach (zygomatic infratemporal - transmandibular) was utilised for tumour removal, with a subsequent excellent outcome. An extensive literature review since 1935, revealed 580 cases of surgically treated trigeminal neurinomas. Among these, only three were located in three distinct compartments, making this the rarest developmental pattern for trigeminal neurinomas.

Use of a single semilinear incision in Deep Brain Stimulation for movement disorders.

This technical note presents the authors experience in using a single semilinear incision for bilateral implantation of Deep Brain Stimulation electrodes in the treatment of movement disorders, in order to avoid some of the hardware and skin related complications of this procedure. The advantages and disadvantages of this technique are presented and discussed.