Cone-beam CT-guidance in Interventional Radiology

Abstract

OBJECTIVE.

CBCT-guidance (CBCT-guidance) is a new stereotactic technique for needle interventions, combining 3D soft-tissue cone-beam CT, needle planningsoftware, and real-time fluoroscopy. Our objective was to evaluate the use, feasibility and outcome of this technique. To determine the effective dose for the patient and operator during these procedures and to use the merging modality of this sytems is to quantify the kidney movement by transfer the patient from supine to prone position.

MATERIALS AND METHODS.

All procedures were performed using a flat-panel based fluoroscopy-system capable of acquiring cone-beam CT-images with dedicated needle path planning software. In the data set, a needle trajectory is determined and, after co-registration, a fusion image is created from fluoroscopy and a slice from the data set, enabling the needle to be positioned in real-time.

In a spine phantom we analyzed the outcome of randomized CBCT-guidance and fluoroscopy-guided vertebroplasty procedures. Another phantom was used to compare CBCT-guidance and CT-guidance for inplane, angulated and double angulated needle paths. Multiple studies were performed to evaluate CBCT-guidance in clinical setting (e.g. general (N=145), lungbiopsies (N=84), kidneybiopsies (N=41), type-II endoleak treatment (N=5)). Based on 92 procedures the patient dose was calculated and compared to the dose of 137 CT-guided procedures. The operator dose (hand, collar and gonad region) was measured in a model and during clinical casus. Leaddrapes and ceiling/couch-shielding were used to measure the effect of shielding. By merging a supine-CT with a prone-CBCT the needle planningsoftware was used to determine the movement of the kidney.

RESULTS.

The mean accuracy using CBCT-guidance is 93%. All procedures have a 100% technical success. The mean proceduretime is 25.2 minutes and the fluoroscopytime is 169.5 seconds. CBCT-guidance has a significant better accuracy then fluoroscopy. Compared to CT-guidance, CBCT-guidance has a significantly better accuracy in complex procedures. The mean outcome for sensitivity, specificity, PPV, NPV, and accuracy was 90.9%, 100%, 100%, 78.1%, and 93.4% respectively. Total mean effective doses with cone-beam CT guidance was between 7.6-16.1 depending of the anatomical location. Effective doses with CT-guidance was 13.0-20.4 mSv. CBCT-guidance results in a significant effective dose reduction of 13%–42%. The mean doses for the hand were 34.2 and 54.6 µSv (thoracic/abdominal respectively). The doses for thyroid and gonad regions were 83.2 and 34.3 µSv in the thoracic, and 66.2 and 47.2 µSv in the abdominal group. Combined shielding reduced dose by 98.2-98.9% (p<0.05). Merging previous CT-data with CBCT is feasible. There is a significant change of the kidney after the transfer from supine to prone position.

CONCLUSION.

CBCT-guidance is an accurate and safe method for needle interventions, especially usefull in hard-to-reach locations. This technique results in a significant dose reduction for patients compared with conventional CT-guidance. Also the operator dose in CBCT-guidance without shielding is quite low. Approximately 240 cases can be performed staying below the yearly limit. The best significant dose reduction is achieved by a combination of shielding. Training in CBCT-guidance is essential to achieve a better outcome. Merging previous data is feasible but organ movement should be taken into account.