CT Navigation for Percutaneous Needle Placement: How I Do It

CT navigation (CTN) has recently been developed to combine many of the advantages of conventional CT and CT-fluoroscopic guidance for needle placement. CTN systems display real-time needle position superimposed on a CT dataset. This is accomplished by placing electromagnetic (EM) or optical transmitters/sensors on the patient and needle, combined with fiducials placed within the scan field to superimpose a known needle location onto a CT dataset. Advantages of CTN include real-time needle tracking using a contemporaneous CT dataset with the patient in the treatment position, reduced radiation to the physician, facilitation of procedures outside the gantry plane, fewer helical scans during needle placement, and needle guidance based on diagnostic-quality CT datasets. Limitations include the display of a virtual (vs actual) needle position, which can be inaccurate if the needle bends, the fiducial moves, or patient movement occurs between scans, and limitations in anatomical regions with a high degree of motion such as the lung bases. This review summarizes recently introduced CTN technologies in comparison to historical methods of CT needle guidance. A "How I do it" section follows, which describes how CT navigation has been integrated into the study center for both routine and challenging procedures, and includes step-by-step explanations, technical tips, and pitfalls.

Impact of physician practice on patient radiation dose during CT guided biopsy procedures

PURPOSE

Patient radiation dose during Computed Tomography (CT) guided biopsy procedures is determined by both acquisition technical parameters and physician practice. The potential effect of the physician practice is of concern. This study is to investigate the effects of those intangibles on patient radiation dose.

METHODS

Patient radiation dose from 252 patients who underwent CT guided biopsy from 2009 to 2010 were retrospectively studied. Ten physicians who used conventional intermittent shots, low mA dose saving feature, or both were included in the study. The patient dose reports were retrieved and the total dose length products (DLPs) were analyzed. Linear regression analysis performed between various variables and reported dose. Patient detriment index (PDI) was developed, which sets threshold (standard of practice) for comparing physician practice with their peers. Odds ratio was calculated to determine odds of a group of patients receiving dose above threshold when compared to another group.

RESULTS

Median DLP among ten physicians was 1194 mGy-cm. There was a significant difference (p< 0.01) between reported DLPs doses when physicians used dose saving feature vs. when feature not used (539.8 ± 169.4 mGy-cm vs. 1269.7 ± 659.0 mGy-cm). In general, physicians who used dose saving feature had lower relative PDIs (< 1) compared to the PDIs (> 1) without the dose feature. Odds ratio estimate of 7.7 at 95% confidence level indicates that the odds of a group receiving a high dose depends on practitioner.

CONCLUSION

Adjustments of practice habits, use of dose saving features or both may be needed to improve patient care for CT biopsy.