PO103

Abstract

Purpose Dupuytren's contracture (DC) is an inflammatory disorder of the palm resulting in fascia thickening into nodules and cords. Although typically not painful, the cords can cause increased fixed flexion of one or more fingers (usually the 4th or 5th digits) to remain bent towards the palm. Prospective clinical trials have shown radiation's ability to stabilize or even improve symptoms in the majority of cases. Brachytherapy can be used to target the affected region while providing a rapid dose falloff to spare healthy tissue, and can also easily modulate treatment depth within the field. In some MRI sequences the cords yield a characteristic signal. This study examines if MR imaging in combination with surface applicator brachytherapy (SABT) may allow accurate targeting of the fibrosed region. Materials and Methods Five patients with DC, one with bilateral disease, underwent MR-guided surface applicator brachytherapy in our clinic. For each of the six hands, a CT simulation was performed followed immediately by MR scans. At simulation, the hand was palpated to locate the nodules and cords to be treated; up to a 2 cm margin was then applied and marked with a non-ferrous CT wire. A flap applicator was laid on top of the treatment region and secured with Coban wrap. A CT scan was acquired with the patient's hand stretched out over the head in swimmer's position, if tolerable. After CT and before unwrapping the applicator, the patient underwent MRI with a T1-weighted DIXON VIBE sequence, while in the same positioning. At treatment planning the catheters were reconstructed on the CT scan, which was then fused to the T1 DIXON VIBE in-phase scan for target evaluation. Treatment extent marked by CT wire was compared to MRI, and treatment depth was determined by the MRI findings. Patients received daily 3 Gy x 10 fxs, with a 6-8 week break following fraction 5, a common dose regime used in published literature. Results All six courses of radiation were well tolerated with no acute grade I toxicities. MRI target regions were all contained within the 2 cm margin marked at simulation. For CT-only treatment planning, our clinic prescribes to a uniform depth of 3 mm; however, the MRI showed localized increased depth of fibrosis up to a maximum of 8.5 mm, which was accounted for during treatment planning. The in-phase DIXON images were selected for treatment planning to avoid the phase cancellation artifact present at fat-water interfaces on the opposed-phase DIXON images, which nevertheless demonstrated higher flap applicator visibility. The possibility of MR-only SABT by combining different MR sequences and contrasts is being separately investigated. One patient was unable to accommodate the swimmer's position during simulation, and had his hand placed on his abdomen. That patient's MR was partially affected by motion artifacts but was still useful in target delineation. Conclusions MR-guided SABT for DC is feasible and well tolerated. MR information was used to deliver dose to the full extent of the fibrosis, and after further study may be used to individually adjust margins used on the skin surface. MR-only SABT is also under investigation. A clinical trial is necessary to evaluate any difference in treatment outcomes related to MR-guidance. Dupuytren's contracture (DC) is an inflammatory disorder of the palm resulting in fascia thickening into nodules and cords. Although typically not painful, the cords can cause increased fixed flexion of one or more fingers (usually the 4th or 5th digits) to remain bent towards the palm. Prospective clinical trials have shown radiation's ability to stabilize or even improve symptoms in the majority of cases. Brachytherapy can be used to target the affected region while providing a rapid dose falloff to spare healthy tissue, and can also easily modulate treatment depth within the field. In some MRI sequences the cords yield a characteristic signal. This study examines if MR imaging in combination with surface applicator brachytherapy (SABT) may allow accurate targeting of the fibrosed region. Five patients with DC, one with bilateral disease, underwent MR-guided surface applicator brachytherapy in our clinic. For each of the six hands, a CT simulation was performed followed immediately by MR scans. At simulation, the hand was palpated to locate the nodules and cords to be treated; up to a 2 cm margin was then applied and marked with a non-ferrous CT wire. A flap applicator was laid on top of the treatment region and secured with Coban wrap. A CT scan was acquired with the patient's hand stretched out over the head in swimmer's position, if tolerable. After CT and before unwrapping the applicator, the patient underwent MRI with a T1-weighted DIXON VIBE sequence, while in the same positioning. At treatment planning the catheters were reconstructed on the CT scan, which was then fused to the T1 DIXON VIBE in-phase scan for target evaluation. Treatment extent marked by CT wire was compared to MRI, and treatment depth was determined by the MRI findings. Patients received daily 3 Gy x 10 fxs, with a 6-8 week break following fraction 5, a common dose regime used in published literature. All six courses of radiation were well tolerated with no acute grade I toxicities. MRI target regions were all contained within the 2 cm margin marked at simulation. For CT-only treatment planning, our clinic prescribes to a uniform depth of 3 mm; however, the MRI showed localized increased depth of fibrosis up to a maximum of 8.5 mm, which was accounted for during treatment planning. The in-phase DIXON images were selected for treatment planning to avoid the phase cancellation artifact present at fat-water interfaces on the opposed-phase DIXON images, which nevertheless demonstrated higher flap applicator visibility. The possibility of MR-only SABT by combining different MR sequences and contrasts is being separately investigated. One patient was unable to accommodate the swimmer's position during simulation, and had his hand placed on his abdomen. That patient's MR was partially affected by motion artifacts but was still useful in target delineation. MR-guided SABT for DC is feasible and well tolerated. MR information was used to deliver dose to the full extent of the fibrosis, and after further study may be used to individually adjust margins used on the skin surface. MR-only SABT is also under investigation. A clinical trial is necessary to evaluate any difference in treatment outcomes related to MR-guidance.