Computer Aided Diagnosis of Prostate Cancer with Magnetic Resonance Imaging
Promotor: N. Karssemeijer and J. O. Barentsz Copromotor: H. Huisman Radboud University, Nijmegen 2011
Prostate cancer is the most commonly diagnosed cancer among men and remains the second leading cause of cancer death in men. In 2010, more than 217,000 men in the United States (US) were diagnosed with prostate cancer . The American Cancer Society estimated that approximately 32,000 men died from the disease in the US in 2010. In Europe, more than 338,00 males were diagnosed with prostate cancer in 2008 and almost 71000 men died because of prostate cancer. The growth of the population and, more importantly, the aging population is a major cause of the high number of prostate cancer cases and will contribute to an increase in cancer burden. For that reason, there is a ongoing debate whether screening for prostate cancer should be performed. Screening can help find cancers in an early stage when they are more easily cured. An important trial to determine the effect of screening for breast cancer was performed between 1977 and 1984 in Sweden. The trial showed that after seven years of follow up a reduction of 31% in breast cancer mortality was achieved when screening was applied. This led to the introduction of breast cancer screening in most western countries. Recently, several studies have been performed that looked at whether prostate cancer screening with the prostate-specific antigen (PSA) blood test saves lives. For example, the European Randomized Study of Screening for Prostate Cancer (ERSPC) has shown significant reductions in PCa mortality in an intention-to-screen analysis. The reduction in mortality comes, however, at the price of over-diagnosis and over-treatment. In the study of Schröder et al. the authors specifically warn that, in order to prevent one death from prostate cancer, 1410 men would need to be screened and 48 additional cases of prostate cancer would need to be treated. Hence, controversy still exists regarding the effectiveness of prostate cancer screening. The ongoing debate is essentially a public demand for a more reliable, non-invasive method that has a sufficiently high specificity in detecting prostate cancer. Magnetic resonance imaging (MRI) has evolved this decade to a competitive imaging modality for the localization of prostate cancer. The non-invasive nature and ability to provide structural, functional and metabolic information in a single examination makes the technique suitable to improve specificity when screening for prostate cancer. Many studies showed that multiparametric MRI, consisting of high resolution 3D T2-weighted sequences, 3D dynamic contrast enhanced MRI, 3D diffusion weighted imaging or spectroscopic imaging, leads to a sufficiently high accuracy for prostate cancer detection. Unfortunately, multiparametric MRI analysis requires a high level of expertise, suffers from observer variability and is a labor intensive procedure. For that reason the technique is considered cost inefficient and, as a result, has not been implemented in a screening environment. Computer aided diagnosis (CAD) can be of benefit to improve the consistency and accuracy of interpreting radiographic images by the radiologist. Additionally, it can speed up the reading time considerably. CAD research has been successfully pursued in other diagnostic areas such as mammography, CT chest, CT colonography as well as retinal imaging. However, published literature on prostate CAD research is still relatively immature. The motivation of this thesis was therefore to research state of the art CAD methods that can assist in a better diagnosis of prostate cancer, reduce the observer variability and be of benefit to a more efficient workflow for the radiologist.