(Sunday, 7/14/2019) 5:00 PM - 6:00 PM
Room: Stars at Night Ballroom 4
Purpose: To demonstrate the challenges of post-implant dosimetry on prostatectomy CivaSheetᵀᴹ (CivaTech) and to develop a systematic workflow to perform the task.
Methods: BrachyVisionᵀᴹ (Varian) was used to perform CivaSheet post-implant dosimetry. A 3mm slice thickness CT scan of the pelvic region was used to determine the position of each source (CivaDot). Multiple angle projections (AP, RAO, LAO, and RL) kV images were also taken to decipher the orientation of each CivaDot. A computer program was created to determine the alignment of each CivaDot by matching its cross section on 4 different kV projections.
Results: Although custom cut CivaSheets were placed flat on prostate bed during prostatectomy, after the reconstruction of the bladder neck and suturing, the sources clumped together. The 3D position of each CivaDot can be located using the CT scan, but the orientation is almost indecipherable based on the original placement. The kV projections provide sufficient additional information to align the CivaDots. This process is essential to accurately determine the PID of the CivaSheet, as it is a mono-directional source with highly heterogeneous angular dependence.
Conclusion: Determining the orientation of implanted CivaDots using only a CT and the original placement of the sources is a difficult for a prostatectomy. Using kV projections to reconstruct the spatial orientation is feasible and can be used to improve the process.
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