Dynamic MRI and CAD vs. Choline MRS: Where is the detection level for a lesion characterisation in prostate cancer?

Abstract

Purpose: To evaluate the role of pre-interventional fused high resolution T2-weighted images with parametrically analysed dynamic contrast enhanced T1-weighted magnetic resonance (MR) images (DCE-MRI) and 1H magnetic resonance spectroscopy (MRS) for a precise biopsy for the detection of prostate cancer and for the delineation of intraprostatic subvolumes for intensity modulated radiation therapy (IMRT).Materials and methods: Inclusion criteria: Pathological prostate-specific antigen values (PSA) and/or previously negative transrectal ultrasound guided biopsy. Standardised biopsy of the prostate divided into 20 regions. Image fusion of coloured parametric maps derived from DCE-MRI and MRS (single voxel spectroscopy, SVS; chemical shift imaging, CSI) with T2 images for morphological localisation using the MR-workstation, a separate CAD-workstation (CAD: computer aided diagnosis) or a radiation treatment planning system. Correlation of these intraprostatic subvolumes with histology and cytokeratin-positive areas in prostatectomy species.Results: DCE-MRI: Sensitivity 82%, specificity 89%, accuracy 88%, positive predictive value 61%, negative predictive value 96%. SVS: Sensitivity 55%, specificity 62%. CSI: Sensitivity 68%, specificity 67%. False positive findings due to prostatitis, adenomatous hyperplasia, false negative findings due to low signal (PIN (prostatic intraepithelial neoplasia), cut-off level for DCE-MRI: lesions smaller 3 mm and less than 30% cancer cells, for SVS: lesions smaller 8 mm and less than 50% cancer cells), for CSI: lesions smaller 4 mm and less than 40% cancer cells. Our MR data are correlated with published choline PET/CT data (PET/CT: hybrid scanner of positron emission tomography and computed tomography).Conclusions: DCE-MRI and MRS are helpful for a precise biopsy of the prostate. The European Society for Therapeutic Radiology and Oncology (ESTRO) guidelines 2006 for radiation treatment planning of the prostate have to be revised, if the standardised biopsy will be replaced by a lesion-orientated biopsy. Until now it is unclear, if the parametric maps of DCE-MRI and MRS can be used for radiation treatment planning of the prostate.