1. A Villanueva, J Broncano, J Arias, A Benito, I Vivas, M J Garcia Velloso, J M Subtil, R Martínez-Monge Department of Radiology. Clínica Universidad de Navarra. Madrid. Spain. Departments of Radiology, Nuclear Medicine, Radiotherapy and Digestive Diseases (Endoscopy). Clínica Universidad de Navarra. Pamplona. Spain Thoracic permanent interstitial brachytherapy: MDCT and PET- CT findings

2. Background Permanent interstitial brachytherapy (PIB) consists of treating neoplastic lesions by implanting seeds of radioactive material inside the tumor. PIB is a well established radiotherapy modality in the management of various malignant diseases, such as low- risk prostate cancer. Encouraging results have been published from groups of patients with thoracic tumors treated with PIB (1-5).

3. Background PIB is performed to treat lung and thoracic malignancies in patients who are technically operable but cannot tolerate the operative procedure or the expected reduction in lung function after resection. The response is usually evaluated by MDCT and PET- CT. To our knowledge, no studies have been published specifically on MDCT and PET-CT findings from thoracic tumors treated using PIB. Here we present the MDCT signs from 20 patients with thoracic tumors treated using PIB (Tables 1 and 2).

4. Number20 Sex17 W/ 3M Age16 - 92 years (mean 65.3) Table 1.Number, sex and age of patients presented in this educational presentation Background

5. Table 2.Type of thoracic neoplasm treated by PIB presented in this exhibit TypeNumber Primary pulmonary neoplasm stage I8 Primary pulmonary neoplasm stage II or more3 Thoracic relapse of pulmonary neoplasm5 Thoracic relapse of non-pulmonary neoplasm3 Total20

6. Radioactive Seeds (RS) were implanted intraoperatively with or without ultrasonographic guide (N = 10) (Fig 1), with CT guide (N = 8) (Fig 2) and by transoesophageal endoscopic-ultrasonography-guided procedures (N = 2) (Fig 3). Mini-Mick or standard 20 cm Mick needles were used. Background Fig 1.- 46-year-old man with mediastinal relapse of pulmonary neoplasm (marks at A) located between the ascending aorta (Ao) ) and the superior vena cava (SVC) before PIB. During the intraoperative ultrasonography-guided procedure, the seeds of I 125 are identified as echogenic points within the tumor (arrow head at B). Some present reverberation (arrow at B). The tumor is not well delineated at B. A Ao SVC B

7. Fig 2. Pulmonary neoplasm of stage IB (arrow at A). It was treated by implanting I 125 seeds (arrows at B) percutaneously using CT guidance. The tumor appeared to increase in size in the images obtained during the procedure (B). AB

8. Fig 3. Fig 3. Two images captured on video during a transoesophageal endoscopic-ultrasonography-guided procedure in a 60-year-old patient with recurrence of lung cancer with lymph node involvement in the aorto-pulmonary window. A hyperechogenic line and some fat, more echogenic dots can be seen. The line represents the route of the needle (arrow), and the dots are the seeds (arrowhead). When the seeds are inserted, air bubbles enter the adenopathy, which appears to be poorly defined in the image. The edges of the adenopathy that had been irradiated cannot be clearly identified.

9. 1) Early post procedure findings 2) Late findings 3) Complications MDCT findings Classification MDCT Findings were classified as follows.