Ultrasound versus Cone-beam CT image-guided radiotherapy for prostate and post-prostatectomy pretreatment localization.

To evaluate the accuracy of an intra-modality trans-abdominal ultrasound (TA-US) device against soft-tissue based Cone-Beam Computed tomography (CBCT) registration for prostate and post-prostatectomy pre-treatment positioning.

The differences between CBCT and US shifts were calculated on 25 prostate cancer patients (cohort A) and 11 post-prostatectomy patients (cohort B), resulting in 284 and 106 paired shifts for cohorts A and B, respectively. As a second step, a corrective method was applied to the US registration results to decrease the systematic shifts observed between TA-US and CBCT results. This method consisted of subtracting the mean difference obtained between US and CBCT registration results during the first 3 sessions from the US registration results of the subsequent sessions. Inter-operator registration variability (IOV) was also investigated for both modalities.

After initial review, about 20% of the US images were excluded because of insufficient quality. The average differences between US and CBCT were: 2. 8 ± 4. 1 mm, -0. 9 ± 4. 2 mm, 0. 4 ± 3. 4 mm for cohort A and 1. 3 ± 5. 0 mm, -2. 3 ± 4. 6 mm, 0. 5 ± 2. 9 mm for cohort B, in the anterior-posterior (AP), superior-inferior (SI) and lateral (LR) directions, respectively. After applying the corrective method, only the differences in the AP direction remained significant (p < 0. 05). The IOV values were between 0. 6-2. 0 mm and 2. 1-3. 5 mm for the CBCT and TA-US modalities, respectively.

Based on the obtained results and on the image quality, the TA-US imaging modality is not safely interchangeable with CBCT for pre-treatment repositioning. Treatment margins adaptation based on the correction of the systematic shifts should be considered.

Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB). 2015 Sep 25 [Epub ahead of print]

Marie Fargier-Voiron, Benoît Presles, Pascal Pommier, Alexandre Munoz, Simon Rit, David Sarrut, Marie-Claude Biston

CREATIS, Université de Lyon, Lyon, France; CNRS UMR5220, Lyon, France; Inserm U1044, Lyon, France; INSA-Lyon, Lyon, France; Université Lyon 1, Lyon, France; Centre Léon Bérard, Lyon, France. , CREATIS, Université de Lyon, Lyon, France; CNRS UMR5220, Lyon, France; Inserm U1044, Lyon, France; INSA-Lyon, Lyon, France; Université Lyon 1, Lyon, France; Centre Léon Bérard, Lyon, France. , Léon Bérard Cancer Center, University of Lyon, F-69373 Lyon, France. , Léon Bérard Cancer Center, University of Lyon, F-69373 Lyon, France. , CREATIS, Université de Lyon, Lyon, France; CNRS UMR5220, Lyon, France; Inserm U1044, Lyon, France; INSA-Lyon, Lyon, France; Université Lyon 1, Lyon, France; Centre Léon Bérard, Lyon, France. , CREATIS, Université de Lyon, Lyon, France; CNRS UMR5220, Lyon, France; Inserm U1044, Lyon, France; INSA-Lyon, Lyon, France; Université Lyon 1, Lyon, France; Centre Léon Bérard, Lyon, France. , CREATIS, Université de Lyon, Lyon, France; CNRS UMR5220, Lyon, France; Inserm U1044, Lyon, France; INSA-Lyon, Lyon, France; Université Lyon 1, Lyon, France; Centre Léon Bérard, Lyon, France.  

PubMed