SU-E-T-516: Evaluation of the Effects of Total Lung Volume, Age, and Body Mass Index on Breath-Hold Level for Left Breast Cancer Patients

Abstract

Purpose: To determine if abdominal height displacement between free- breathing and breath-hold correlates with change in total lung volume (TLV). Correlation between abdominal height during breath-hold versus patient age and body mass index (BMI) was also investigated. Methods: The study involved 35 patients, each with free-breathing and breath-hold CT scans. The RPM System (Varian Oncology Systems, Palo Alto, Ca) was used to measure abdominal height. Abdominal height displacement was defined as the distance from end of normal inspiration to the average breath- hold level during simulation. Breathing data for each patient was exported from the RPM system and analyzed. Free-breathing and breath-hold scans were fused by matching the field borders, scar, excision cavity, and left breast skin. One physician performed all contouring and image fusions. TLV was calculated by the planning system. Box displacement was plotted against change in TLV, patient age, and BMI. Correlation coefficients (r) were calculated for each comparison. Results: An r-value of 0.59 was calculated for TLV versus breath-hold level. The relationship showed larger TLV changes with greater abdominal height displacement. Comparing box displacement against all ages the r-value was 0.48. Separating by age, patients 70 years and older had an r-value of 0.91 with box displacement decreasing with age. For the remaining age groups (30–49, 50–59, and 60– 69), r-values were 0.30, 0.33, and 0.07, respectively. For BMI, the r-value was 0.35. Conclusions: The data in this investigation was plotted between patients, therefore only inter-patient trends can be described. Younger patients generally achieve deeper breath-holds as measured by abdominal motion than older patients. It can be concluded that abdominal height carries a moderate predictive value for change in TLV for patients under age 70, regardless of BMI. However, a strong correlation exists for patients over age 70.