gms | German Medical Science

Objective: Many patients with shunt for hydrocephalus have to undergo repeated radiographic shunt series, resulting in a relatively high cumulative radiation exposure, with a recently reported dose of 1.57 ± 0.60 mSv per shunt series. In some cases even an additional regular CT is necessary. Especially in children, there is a high risk of long-term effects of ionizing radiation. The purpose of our study was to evaluate whether unenhanced low-dose-CT scan from head to abdomen could provide acceptable image quality, provide required information, and without radiation doses higher than with conventional standard imaging.

Method: 56 patients (mean age: 60 (0.5 to 85) yrs; 22 female and 34 male) were included. VP shunt surgery of hydrocephalus was due to various etiologies (22 normal pressure hydrocephalus, 16 posthemorrhagic, 12 congenital, 2 posttraumatic, 2 after stroke, 1 tumor-related, and 1 unknown). All patients had a routine postoperative low-dose-CT from head to abdomen using a 16-slice MD-CT scanner (Toshiba).19 low-dose-CTs were additionally performed in the later course to exclude shunt malformation. Whole body dose of 75 CT was calculated with an established computer model (Benchmarking MSCT). The axial and three dimensional (volume rendering technique) vp shunt visualisation was independently evaluated by one neuroradiologist (criteria of diagnostic image quality: excellent, satisfactory, insufficient) and one neurosurgeon.

Results: 60 (80%) of CT series were judged excellent and 15 (20%) satisfactory, none was insufficient, no repeated exam necessary. The average effective whole body dose was 1,56 ± 0,3 mSv in 75 low-dose-CT. More than the required information was obtained: beside a reliably evaluation of the shunt continuity early after surgery, one intracerebral hemorrhage was found. In the later course, 3 disconections and one case with abdominal cysts were found in 19 CT exams.

Conclusions: Low-dose head to abdomen CT scan provides diagnostically excellent or acceptable images without increasing the overall radiation exposure. It improves the diagnostic yield (hemorrhage, cysts, catheter placement, etc.) compared to plain x-ray shunt series. One disadvantage is that adjustment of some valves cannot be documented by CT, however, alternative non-invasive techniques are meanwhile available for most systems.