CT guided Technetium-99m Macroaggregated albumin injection for lung nodule localization prior to video-assisted thoracoscopic surgery: A single institutional experience

301 Objectives: To evaluate the success rate of CT guided injection of Technetium-99m macroaggregated albumin (Tc-99m MAA) for pre-operative lung nodule localization and subsequent surgical excision by video-assisted thoracoscopic surgery (VATS). We present the demographic data, procedural details including procedure related complications and pitfalls from our single institutional cohort. Methods: We retrospectively evaluated 147 patients who underwent CT guided injection of Tc-99m MAA for localizing lung nodule(s) due to expected difficulty in identifying them during planned VATS. Our early experience with this technique has been previously reported (1). The following data from the CT guided radiotracer injection procedure were recorded including number of nodules injected in a patient, size, density, lobar location and closest distance of the nodule(s) from pleural surface, needle tip position relative to the nodule before radiotracer injection, post procedural complication, procedure time, radiation dose and interval between CT guided injection and VATS surgical incision. Anterior and lateral planar images acquired on a gamma camera to assess for adequacy of the radiotracer injection were also retrospectively evaluated for the number of tracer foci visualized per injection (at or remote from the nodule). Intra-operative data of successful localization of the tracer injection site using gamma probe, palpability of the nodule, successful wedge resection of the nodule and surgical pathology results were also recorded. Results: 164 nodules were pre-operatively localized using Tc-99m MAA injection in 147 patients (Female, n=87; Mean age of 62y, range 6-85y). The average size of the nodule was 10.4mm; average distance from the nearest pleural surface was 18.2mm; 97 were solid, 37 were ground-glass, 25 were sub-solid and 5 were cystic nodules. The average CT procedure time was 78 minutes with average whole-body effective radiation dose of about 6.72mSv. The final needle position before radiotracer injection was deep to the nodule in 79, at the level of nodule in 51 and superficial to nodule in 34. 21 patients developed pneumothorax after the procedure with only 1 requiring a drainage placement before VATS procedure. More than expected pulmonary hemorrhage was noted in 7 nodules but did not require intervention. In 6 out of 164 nodules, wedge procedure was not completed in spite of successful CT guided injection and intra-operative localization for various reasons. An overall success rate of the procedure in the remaining 158 nodules culminating in a successful wedge resection with positive histopathology was 95.5% (151 out of 158). A primary radiotracer injection failure was recorded in 3 nodules due to pleural leak, split tracer injection within the same lobe and injection into an unintended nodule respectively. Intra-operative localization failure was recorded for 3 nodules in spite of successful tracer injection due to surgeon-reported diffuse activity and gamma probe malfunction. In 1 nodule, in spite of successful radiotracer injection and localization both by planar imaging and intra-operative probe, histopathology of the wedge resection reported “normal lung” with a persistent biopsy proven metastatic nodule in follow up imaging. The nodule was non-palpable at surgery. Conclusions: CT guided Tc-99m MAA injection for pre-operative lung nodule localization prior to VATS is a robust and relatively safe procedure with high success rate based on experience at our institution. However, it is important to be aware of the pitfalls of the procedure that can potentially lead to an unsuccessful VATS wedge resection.