LightSpeed® VCT XT evaluation system. allows the user the flexibility of performing 4 cm or 8 cm data acquisition for Cerebral Brain Perfusion. The increased flexibility and coverage means that small focal abnormalities are more likely to be imaged and, Cerebral Blood Volume (CBV), Cerebral Blood Flow (CBF) and Mean Transit Time (MTT) can be precisely estimated(1).

LightSpeed® VCT XT evaluation system and the GE exclusive axial shuttle mode feature provides a full 8cms of coverage for Cerebral Perfusion. (Fig. 1)
The patient is positioned in the gantry as for a Brain Study, with careful immobilisation of the head as the table will move allowing for 13 or more passess over the area of interest to collect perfusion data.

The following 3 cases studies demonstrate the use of VolumeShuttleTM on LightSpeed® VCT XT evaluation system:

Patient 1:

A 65 year old female, known to have a colloid cyst of the third ventricle. She presented with sudden collapse, and on waking was found to have a mild hemiparesis. Initial CT scan was at 2 hours after ictus, and so a Perfusion scan was carried out to look for an acute brain infarct.
She made a fairly rapid recovery over the next 12 hours without treatment.

Patient 2:

A 48 year old female with migraine. She presented with a typical headache but a left hemiparesis, which was unusual for her migraine attacks. The scan was at 3 hours after ictus, and a Perfusion study ( Fig 3) was performed to evaluate her cerebral condition and helped the doctor exclude a cerebral thrombo-embolic event.

She made a complete recovery over 24 hours and a diagnosis of Hemiplegic Migraine was made.

Patient 3:

The patient is a 56 year old male who presented with a large frontal haematoma and SAH from rupture of an ACom aneurysm. He was referred to our hospital on day 4 after the bleed, by which time he had developed bilateral leg weakness, clinically due to delayed ischaemia / vasospasm. His leg power graded 2-3/5 and slowly improved to grade 4 with medical therapy by day 11, when the Perfusion study was done to obtain information to help the doctor determine how best to proceed.

The perfusion study demonstrated reduced perfusion in the medial high frontal lobes.
CTA data was extracted from the 0.625mm images, choosing the optimal arterial opacification from the cine perfusion scans.

The information from the CTA was used to confirm severe spasm in both the proximal and distal anterior cerebral arteries bilaterally, and a decision was taken to postpone treatment for another few days. 5 days later, the aneurysm was successfully coiled with no clinical sequelae.

The usefulness of the VolumeShuttle™ perfusion study in this patient is that it allowed the user to look higher in the frontal lobes than a conventional perfusion study would have allowed. Extraction of the CTA data permits a full vascular and perfusion work up with a single contrast injection and potentially less time without dose penalty than the conventional separate CTA and CT Perfusion studies.

The VolumeShuttle™ perfusion examination was performed on all these patients covering 8cms. This was very useful in these the first two patients (case studies 1 & 2) to help the physician rule out brain infarction. Migraine can be associated with high cortical infarction, and it was very useful to have the 8cm coverage of the VolumeShuttle™ exam, so that a small lesion could be more easily imaged in the larger scan area.

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The VolumeShuttle™ mode provides a volume data set through the arterial phase and therefore it is possible to post process the data with Volume Rendering techniques to produce an Angio. (case study 3) Being able to extract the angio is also really helpful as there is only a single contrast injection with no dose penalty, by obtaining the benefit of 2 examinations in one rather than the conventional single slab technique. In addition, this new scanning paradigm should make examinations shorter since the usual wait between the CTA and perfusion study could be avoided.

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