Technical aspects of the deep inspiration breath-hold technique in the treatment of thoracic cancer

Purpose: The goal of this paper is to describe our initial experience with the deep inspiration breath-hold (DIBH) technique in conformal treatment of non-small-cell lung cancer with particular emphasis on the technical aspec ts required for implementation. Methods and Materials: In the DIBH technique, the patient is verbally coach ed through a modified slow vital capacity maneuver and brought to a reprodu cible deep inspiration breath-hold level. The goal is to immobilize the tum or and to expand normal lung out of the high-dose region. A physicist or th erapist monitors and records patient breathing during simulation, verificat ion, and treatment using a spirometer with a custom computer interface. Exa mination of internal anatomy during fluoroscopy over multiple breath holds establishes the reproducibility of the DIBH maneuver for each patient. A re ference free-breathing CT scan and DIBH planning scan are obtained. To prov ide an estimate of tumor motion during normal tidal breathing, additional s can sets are obtained at end inspiration and end expiration. These are also used to set the spirometer action levels for treatment. Patient lung infla tion is independently verified over the course of treatment by comparing th e distance from the isocenter to the diaphragm measured from the DIBH digit ally reconstructed radiographs to the distance measured on the portal films . Patient breathing traces obtained during treatment mere examined retrospe ctively to assess the reproducibility of the technique. Results: Data from the first 7 patients, encompassing over 250 treatments, were analyzed. The inferred displacement of the centroid of gross tumor vol ume from its position in the planning scan, as calculated from the spiromet er records in over 350 breath holds was 0.02 +/- 0.14 cm (mean and standard deviation). These data are consistent with the displacements of the diaphr agm (-0.1 +/- 0.4 cm; range, from -1.2 to 1.1 cm) relative to the isocenter , as measured on the (92) portal films. The latter measurements include the patient setup error. The patient averaged displacement of the tumor during free breathing, determined from the tumor displacement between end inspira tion and end expiration, was 0.8 +/- 0.5 cm in both the superior-inferior a nd anterior-posterior directions and 0.1 cm (+/- 0.1 cm) medial-laterally. Conclusion: Treatment of patients with the DIBH technique is feasible in a clinical setting. With this technique, consistent lung inflation levels are achieved in patients. as judged by both spirometry and verification films. Breathing-induced tumor motion is significantly reduced using DIBH compare d to free breathing, enabling better target coverage. (C) 2000 Elsevier Sci ence Inc.