Reconstruction of applicator positions from multiple-view images for accurate superficial hyperthermia treatment planning

In the current clinical practice, prior to superficial hyperthermia treatments (HT), temperature probes are placed in tissue to document a thermal dose. To investigate whether the painful procedure of catheter placement can be replaced by superficial HT planning, we study if the specific absorption rate (SAR) coverage is predictive for treatment outcome. An absolute requirement for such a study is the accurate reconstruction of the applicator setup. The purpose of this study was to investigate the feasibility of the applicator setup reconstruction from multiple-view images. The accuracy of the multiple-view reconstruction method has been assessed for two experimental setups using six lucite cone applicators (LCAs) representing the largest array applied at our clinic and also the most difficult scenario for the reconstruction. For the two experimental setups and 112 distances, the mean difference between photogrametry reconstructed and manually measured distances was 0.25 +/- 0.79 mm (mean +/- 1 standard deviation). By a parameter study of translation T (mm) and rotation R (degrees) of LCAs, we showed that these inaccuracies are clinically acceptable, i.e. they are either from +/- 1.02 mm error in translation or +/- 0.48. in rotation, or combinations expressed by 4.35R(2) + 0.97T(2) = 1. We anticipate that such small errors will not have a relevant influence on the SAR distribution in the treated region. The clinical applicability of the procedure is shown on a patient with a breast cancer recurrence treated with reirradiation plus superficial hyperthermia using the six-LCA array. The total reconstruction procedure of six LCAs from a set of ten photos currently takes around 1.5 h. We conclude that the reconstruction of superficial HT setup frommultiple-view images is feasible and only minor errors are found that will have a negligible influence on treatment planning quality

Impact of silicone and metal port-a-cath implants on superficial hyperthermia treatment quality

Purpose: A port-a-cath is a device implanted under the skin for continuous drug administration. It is composed of a catheter and a silicone or metal reservoir. A simulation study was done to assess the impact of a port-a-cath implant on the quality of superficial hyperthermia treatments applied using the Lucite cone applicator (LCA). Methods: Specific absorption rate (SAR) and temperature distributions were predicted using SEMCAD-X (version 14.8). We simulated 72 arrangements: two LCA-implant set-ups (central port-a-cath or at an edge below the LCA footprint), six translations of the LCA per set-up, two LCA orientations (Parallel or perpendicular electric field direction) per set-up, two implant materials (silicon or metal) and a control without port-a-cath. Treatment quality was quantified by the average 1 g SAR coverage (CV25%), i.e. volume within the 25% iso-SAR surface, and the volume within the 40 degrees C iso-temperature surface (CV40 degrees C). Results: CV25% reduced with a silicon port-a-cath located below the LCA footprint. In the worst scenario, only 64% of the CV25% of the control set-up was achieved. For a metal port-a-cath below the LCA aperture, dramatic reductions of CV25% were predicted: worst scenario down to 12.1% of the control CV25%. For the CV40 degrees C the worst case values were 74.5% and 6.5%, for silicon and metal implants, respectively. Conclusions: A silicone port-a-cath below the LCA had a smaller effect on treatment quality than a metal implant. Based on this study we recommend verifying heating quality by 3D patient-specific treatment planning when a port-a-cath is located below the footprint of the applicator

Reirradiation combined with hyperthermia in breast cancer recurrences: Overview of experience in Erasmus MC

For superficial hyperthermia a custom-built multi-applicator multi-amplifier superficial hyperthermia system operating at 433MHz is utilised. Up to 6 Lucite Cone applicators can be used simultaneously to treat an area of 600cm(2). Temperatures are measured continuously with fibre optic multi-sensor probes. For patients with non-standard clinical problems, hyperthermia treatment planning is used to support decision making with regard to treatment strategy. In 74% of our patients with recurrent breast cancer treated with a reirradiation scheme of 8 fractions of 4 Gy in 4 weeks, combined with 4 or 8 hyperthermia treatments, a complete response is achieved, approximately twice as high as the CR rate following the same reirradation alone. The CR rate in tumours smaller than 30mm is 80-90%, for larger tumours it is 65%. Hyperthermia appears beneficial for patients with microscopic residual tumour as well. To achieve high CR rates it is important to heat the whole radiotherapy field, and to use an adequate heating technique