3D catheter reconstruction in HDR prostate brachytherapy for pre-treatment verification using a flat panel detector. (July 2017)

• Record Type: Journal Article
• Authors: Smith, Ryan L.; Haworth, Annette; Panettieri, Vanessa; Millar, Jeremy L.; Franich, Rick D.
• Is Part Of: Physica medica. Volume 39(2017)
• Page Start: 121
• Page End: 131
• Publication Date: 2017-07
• Subjects: HDR brachytherapy -- Pre-treatment imaging -- Pre-treatment verification -- Prostate -- Flat panel detector; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2017.06.008
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: Demonstration of a method to reconstruct (3D) HDR prostate catheters, for position verification. Performed in the treatment bunker immediately prior to treatment delivery. Provides a method to directly compare and validate catheter positions against the treatment plan. A clinically relevant catheter displacement detection threshold of 2.2 mm was demonstrated. Can be combined with in vivo dosimetry improving confidence in existing error detection regimes. Abstract: Purpose: High dose rate prostate brachytherapy is a widely-practiced treatment, delivering large conformal doses in relatively few treatment fractions. Inter- and intra-fraction catheter displacements have been reported. Unrecognized displacement can have a significant impact on dosimetry. Knowledge of the implant geometry at the time of treatment is important for ensuring safe and effective treatment. In this work we demonstrate a method to reconstruct the catheter positions pre-treatment, using a 'shift' imaging technique, and perform registration with the treatment plan for verification relative to the prostate. Methods: Two oblique 'shift' images were acquired of a phantom containing brachytherapy catheters, representing the patient immediately pre-treatment. Using a back projection approach, the catheter paths were reconstructed in 3D and registered with the planned catheter paths. The robustness of the reconstruction and registration process was investigated as a function of phantom rotation. Catheter displacement detection was performed and compared to known applied displacements. Results: Reconstruction of the implant geometry in 3D immediately prior to treatment was achieved. A mean reconstruction uncertainty of 0.8 mm was determined for all catheters with a mean registration uncertainty of 0.5 mm. A catheter displacement detection threshold of 2.2 mm was demonstrated. Catheter displacements were all detected to within 0.5 mm of the applied displacements. Conclusion: This technique is robust and sensitive to assess catheter displacements throughout the implant volume. This approach provides a method to detect, in 3D, changes in catheter positions relative to the prostate. The method has sufficient sensitivity to enable clinically significant decisions immediately prior to treatment delivery.