Comparison of ventricular drain location and infusion test in hydrocephalus.

OBJECTIVES: Suspected cerebrospinal fluid shunt (CSF) dysfunction in hydrocephalic patients poses a diagnostic uncertainty. The clinical picture can be non-specific and CT imaging alone is not always pathognomonic. Infusion tests are an increasingly used investigation for real-time hydrodynamic assessment of shunt patency. We report the correlation between infusion test results with the quality of ventricular drain placement on CT scans in a large retrospective group of hydrocephalic patients. MATERIALS & METHODS: Three hundred and six infusion test results performed in 200 patients were correlated with 306 corresponding CT head scans. Nominal logistic regression was used to correlate shunt catheter position on CT imaging to patency of ventricular drain as determined by infusion tests. RESULTS: Infusion test results of shunt patency are statistically congruent with the analysis of shunt catheter position on CT head scans. Catheter tips completely surrounded by either parenchyma or CSF on CT imaging are strongly associated with evidence of occlusion or patency from infusion tests, respectively (χ² = 51.68, P < 0.0001, n = 306 and χ² = 31.04, P < 0.0001, n = 306). CONCLUSIONS: The most important anatomical factor for shunt patency is the catheter tip being completely surrounded by CSF. Infusion tests provide functional and reliable assessment of shunt patency in vivo and are strongly correlated with the position of the ventricular catheter on CT imaging.

Tracking camera control in endoscopic dacryocystorhinostomy surgery.

OBJECTIVES: Poor camera control during endoscopic dacryocystorhinostomy (EnDCR) surgery can cause inadequate visualisation of the anatomy and suboptimal surgical outcomes. This study investigates the feasibility of using computer vision tracking in EnDCR surgery as a potential formative feedback tool for the quality of endoscope control. DESIGN: A prospective cohort analysis was undertaken comparing junior versus senior surgeons performing routine EnDCR surgery. Computer vision tracking was applied to endoscopic video footage of the surgery: Total number of movements, camera path length in pixels and surgical time were determined for each procedure. A Mann-Whitney U-test was used to test for a significant difference between juniors and seniors (P < 0.05). SETTING: Operating theatre. PARTICIPANTS: Ten junior surgeons (<20 completed procedures) and 10 senior surgeons (>100 completed procedures). MAIN OUTCOME MEASURES: Total number of movements of the endoscope per procedure. Path length of the endoscope per procedure. RESULTS: Twenty videos, 10 from junior surgeons and 10 from senior surgeons were analysed. Feasibility of our tracking system was demonstrated. Mean camera path lengths were significantly different at 119,329px (juniors) versus 43,697px (seniors), P ≪ 0.05. The mean number of movements was significantly different at 9134 (juniors) versus 3690 (seniors), P ≪ 0.05. These quantifiable differences demonstrate construct validity for computer vision endoscope tracking as a measure of surgical experience. CONCLUSIONS: Computer vision tracking is a potentially useful structured and objective feedback tool to assist trainees in improving endoscope control. It enables juniors to examine how their pattern of endoscope control differs from that of seniors, focusing in particular on sections where they are most divergent.