Intra-operative 3D guidance and XXXX detection in prostate brachytherapy using a non-isocentric C-arm.

@entity1 @entity4 @entity263 @entity5
PURPOSE: Brachytherapy (radioactive seed insertion) has emerged as one of the most effective treatment options for @entity1 with @entity263 , with the added benefit of a convenient outpatient procedure. The main limitation in contemporary brachytherapy is faulty seed placement, predominantly due to the presence of intra-operative @entity4 (tissue expansion). Though currently not available, the capability to intra-operatively monitor the seed distribution, can make a significant improvement in @entity5 control. We present such a system here. METHODS: Intra-operative measurement of @entity4 in prostate brachytherapy requires localization of inserted radioactive seeds relative to the prostate. Seeds were reconstructed using a typical non-isocentric C-arm, and exported to a commercial brachytherapy treatment planning system. Technical obstacles for 3D reconstruction on a non-isocentric C-arm include pose-dependent C-arm calibration; distortion correction; pose estimation of C-arm images; seed reconstruction; and C-arm to TRUS registration. RESULTS: In precision-machined hard phantoms with 40-100 seeds and soft tissue phantoms with 45-87 seeds, we correctly reconstructed the seed implant shape with an average 3D precision of 0.35 mm and 0.24 mm, respectively. In a DoD Phase-1 clinical trial on six @entity1 with 48-82 planned seeds, we achieved intra-operative monitoring of seed distribution and dosimetry, correcting for dose inhomogeneities by inserting an average of over four additional seeds in the six enrolled @entity1 (minimum 1; maximum 9). Additionally, in each @entity1 , the system automatically detected intra-operative seed migration induced due to @entity4 (mean 3.84 mm, STD 2.13 mm, Max 16.19 mm). CONCLUSIONS: The proposed system is the first of a kind that makes intra-operative detection of @entity4 (and subsequent re-optimization) possible on any typical non-isocentric C-arm, at negligible additional cost to the existing clinical installation. It achieves a significantly more homogeneous seed distribution, and has the potential to affect a paradigm shift in clinical practice. Large scale studies and commercialization are currently underway.
