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Radiother Oncol. 2017 Jul;124(1):61-67. doi: 10.1016/j.radonc.2017.05.018. Epub 2017 Jun 21.

Intraoperative Registered Ultrasound and Fluoroscopy (iRUF) for dose calculation during prostate brachytherapy: Improved accuracy compared to standard ultrasound-based dosimetry.

Author information

1
Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, USA.
2
Department of Radiation Oncology, Indiana University, Indianapolis, USA.
3
Acoustic MedSystems Inc., Savoy, USA.
4
Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, USA.
5
Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, USA. Electronic address: dsong2@jhmi.edu.

Abstract

BACKGROUND AND PURPOSE:

Intraoperative transrectal ultrasound dosimetry during low-dose-rate prostate brachytherapy is imprecise due to sonographic distortion caused by seed echoes and needle tracks that obscure seed positions or create false signals as well as traumatic edema. Here we report the results of a pilot study comparing a combined ultrasound and fluoroscopy-based seed localization method (iRUF) to standard ultrasound-based dosimetry (USD).

MATERIAL AND METHODS:

Eighty patients undergoing permanent Pd-103 seed implantation for prostate cancer were prospectively enrolled. Seed implantation was performed using standard USD for intraoperative dose tracking. Upon implant completion, six X-ray images were intraoperatively acquired using a mobile C-arm and transverse ultrasound images of the implanted prostate were also acquired. Three-dimensional seed locations were reconstructed from X-ray images and registered to the ultrasound for iRUF dosimetry. Day 1 CT/MRI scans were performed for post-implant dosimetry. Prostate and urethral dosimetric parameters were separately calculated for analysis on iRUF, USD, and CT/MRI data sets. Differences and similarities between dosimetric values measured by iRUF, USD, and CT/MRI were assessed based on root mean squared differences, intraclass correlation coefficients (ICC), and Wilcoxon signed rank test.

RESULTS:

Data from 66 eligible patients were analyzed. Compared to CT/MRI, iRUF dosimetry showed higher correlation with overall ICC of 0.42 (0.01 for USD) and significantly smaller root mean squared differences (overall 16.5 vs 21.5 for iRUF and USD) than USD for all prostate and urethral dosimetric parameters examined. USD demonstrated a tendency to overestimate dose to the prostate when compared to iRUF.

CONCLUSIONS:

iRUF approximated post-implant CT/MRI prostate and urethral dosimetry to a greater degree than USD. A phase II trial utilizing iRUF for intraoperative dynamic plan modification is underway, with the goal to confirm capability to minimize and correct for prostate underdosage not otherwise detected.

KEYWORDS:

C-arm; Fluoroscopy; Intraoperative dosimetry; Prostate brachytherapy; Registration

PMID:
28647400
PMCID:
PMC5553286
DOI:
10.1016/j.radonc.2017.05.018
[Indexed for MEDLINE]
Free PMC Article

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