Prostate cancer: contouring target and organs at risk by kilo- and mega-voltage computed tomography and magnetic resonance imaging in patients with and without hip prostheses.

In radiotherapy (RT) treatment planning target volume and organs at risk are contoured on kilovoltage computed tomography (kVCT) images. Unlike magnetic resonance images (MRI), kVCT does not provide precise information on target volume extension.

Since neither kVCT nor MRI may be suitable for contouring in patients with ferrous hip prostheses this study evaluated whether megavoltage CT (MVCT) reduced inter-observer variability.

2 patients without and 1 (patient 3) with hip prostheses were enrolled. Six radiation oncologists contoured prostate, rectum and bladder on kVCT (patients 1 and 3), magnetic resonance (MRI) (patient 2) and MVCT images (patient 3). MVCT was acquired with fine, normal and coarse modalities. Inter-observer variability for each organ was analyzed using Conformity Index (CI) e Coefficient of Variation (CV).

In patients without hip prostheses CIs were higher in prostate contouring with MRI than kVCT, indicating lower inter-observer variability with MRI. Very slight variations were seen in rectum and bladder contouring. In the patient with hip prostheses (No 3), contouring on kVCT lowered CI and increased CV in the prostate, bladder and rectum. The differences were more marked in the prostate. Only fine modality MVCT reduced inter-observer variability and only for the prostate.

Even though greater noise and less soft-tissue contrast increase contouring variability with MVCT compared with kVCT, lack of artifacts on MVCT could provide better image definition by this modality in hip prosthesis patients in which MRI is precluded. Advances in knowledge: We recommend the fine MVCT modality for contouring hip prostheses patients.

The British journal of radiology. 2015 Oct 14 [Epub ahead of print]

Lorenzo Falcinelli, Isabella Palumbo, Valentina Radicchia, Fabio Arcidiacono, Valentina Lancellotta, Giampaolo Montesi, Fabio Matrone, Claudio Zucchetti, Marta Marcantonini, Vittorio Bini, Cynthia Aristei

1 Radiation Oncology Division, Perugia General Hospital, Perugia, Italy. , 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy. , 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy. , 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy. , 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy. , 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy. , 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy. , 3 Perugia General Hospital, Medical Physics Unit, Perugia, Italy. , 3 Perugia General Hospital, Medical Physics Unit, Perugia, Italy. , 4 Perugia General Hospital, Internal Medicine Endocrine and Metabolic Sciences Section, Perugia, Italy. , 2 Radiation Oncology Section, Department of Surgical and Biomedical Sciences, University of Perugia and Perugia General Hospital, Perugia, Italy.

PubMed