Importance of Daily Computed Tomography Imaging with Accelerated Partial Breast Irradiation
Article Published in ABS American Brachytherapy Society magazine
Contributing Investigators: Meredith A. Semon, MS, Mohsen Isaac, MD, Natalie Furgiuele, MD, Michael J. Semon, MS. Radiation Oncology, Monongahela Valley Hospital, Monongahela, PA.
Purpose: Provide information and educate those using accelerated partial breast irradiation brachytherapy on the importance of the daily CT prior to each treatment. The following will provide a comparison between the patients from clinical experience where treatment was terminated in an effort to minimize the termination of patients in the future.
Materials and Methods: At the participating clinic, two of a total twenty-two patients were terminated from treatment due to the increase in air greater than 10% of the PTVeval. Patient 1 was a left breast tumor at a 9 o’clock position while patient 2 was a right breast tumor at a 12 o’clock position. As the clinic’s policy states, all patients receive a CT before each treatment amounting to two CT exams per day. The initial scan used for planning showed the air volume within the PTVeval to be within the accepted criterion. After the initial scan the patients are re-evaluated for the air pocket and were determined to be out of criterion. Before the termination of the treatment, different methods of minimizing the air volume were tried. Some of these methods included withdrawing volume of the balloon, massaging the breast tissue and instruction to sleep in a certain position to eliminate the air. Upon treatment time, however, no decrease of the air volume within the PTVeval occurred so the patients were then terminated from the accelerated partial breast irradiation brachytherapy treatment. If the daily CT would have not been completed these patients could have been treated violating the set criterion.
Results: Patient 1 and 2 completed a planning CT scan followed by treatment before the air volume was out of the criterion. Table 1 shows the tabular volume data obtained from the two patients over their treatment times and how the termination of treatment was determined based on the criterion.
Patient 1 was scanned on the first day and after evaluation of the air pocket size was not planned from the CT. Patient 1 returned the next day and was scanned. This scan showed acceptable criterion of being less than 10% air of the PTVeval. Comparisons were then made in an attempt to correlate why there was increasing air during treatment. The following is the observed criterion for patient 1: left breast, balloon volume of 49.78cc, surgeon A, skin distance of 8.1mm, rib distance of 15.7mm, anteriorly angled lateral catheter placement, breast density of -93HU, 9 o’clock balloon position. The following is the observed criterion for patient 2: right breast, balloon volume of 43.2cc, surgeon B, skin distance of 5.0mm, rib distance of 10.2mm, straight lateral catheter placement, breast density of -105HU, 12 o’clock balloon position. From this criterion, there was no clear correlation between the two patients.
Conclusions: Despite this study containing only two of twenty-two patients, it still provides insight as to how important the daily CT scan is before each treatment. It determines the air pocket volume and whether of not to continue with the treatment. This study will be continued with other patients that accumulate more than 10% of air within the PTVeval and will be evaluated with the same format, hoping to determine some common factors.
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