Diffusion-Weighted MRI in the Genitourinary System

Abstract

Diffusion weighted imaging (DWI) constitutes a major functional parameter performed in Magnetic Resonance Imaging (MRI). The DW sequence is performed by acquiring a set of native images described by their b-values, each b-value representing the strength of the diffusion MR gradients specific to that sequence. By fitting the data with models describing the motion of water in tissue, an apparent diffusion coefficient (ADC) map is built and allows the assessment of water mobility inside the tissue. The high cellularity of tumors restricts the water diffusion and decreases the value of ADC within tumors, which makes them appear hypointense on ADC maps. The role of this sequence now largely exceeds its first clinical apparitions in neuroimaging, whereby the method helped diagnose the early phases of cerebral ischemic stroke. The applications extend to whole-body imaging for both neoplastic and non-neoplastic diseases. This review emphasizes the integration of DWI in the genitourinary system imaging by outlining the sequence’s usage in female pelvis, prostate, bladder, penis, testis and kidney MRI. In gynecologic imaging, DWI is an essential sequence for the characterization of cervix tumors and endometrial carcinomas, as well as to differentiate between leiomyosarcoma and benign leiomyoma of the uterus. In ovarian epithelial neoplasms, DWI provides key information for the characterization of solid components in heterogeneous complex ovarian masses. In prostate imaging, DWI became an essential part of multi-parametric Magnetic Resonance Imaging (mpMRI) to detect prostate cancer. The Prostate Imaging–Reporting and Data System (PI-RADS) scoring the probability of significant prostate tumors has significantly contributed to this success. Its contribution has established mpMRI as a mandatory examination for the planning of prostate biopsies and radical prostatectomy. Following a similar approach, DWI was included in multiparametric protocols for the bladder and the testis. In renal imaging, DWI is not able to robustly differentiate between malignant and benign renal tumors but may be helpful to characterize tumor subtypes, including clear-cell and non-clear-cell renal carcinomas or low-fat angiomyolipomas. One of the most promising developments of renal DWI is the estimation of renal fibrosis in chronic kidney disease (CKD) patients. In conclusion, DWI constitutes a major advancement in genitourinary imaging with a central role in decision algorithms in the female pelvis and prostate cancer, now allowing promising applications in renal imaging or in the bladder and testicular mpMRI.

Combined radiomics-clinical model to predict platinum-sensitivity in advanced high-grade serous ovarian carcinoma using multimodal MRI

“…Therefore, it is essential to search for adequate predictive markers that can be easily performed in clinical practice to identify patients who can maximally benefit from treatment. Previous studies have demonstrated that radiomic information from MRI can improve the efficiency of precise diagnosis by leveraging high-resolution morphological images and providing various functional information, such as tissue oxygenation, perfusion, or diffusion (35)(36)(37)(38). In addition, recent studies have demonstrated that radiomics information from MRI can be used to predict the treatment response to platinum, risk of recurrence, and residual disease in patients with ovarian HGSC (39)(40)(41).…”

Clinical significance of MRI-DWI and PWI scans in identifying benign prostatic hyperplasia and prostate cancer

“…Together with the incessant proliferation of tumor cells, this results in the extrusion and deformation of the extracellular space. Consequently, the movement of water molecules within the tumor becomes restricted, leading to a decrease in ADC values during DWI scans [14][15][16]. This phenomenon serves as the pathological foundation for the diagnostic utility of DWI in the identification of malignant tumors.…”

Fibrosis in Chronic Kidney Disease: Pathophysiology and Therapeutic Targets

“…A quantitative parameter that integrates both the random diffusion and directional movement of water is the apparent diffusion coefficient (ADC). The ADC provides insight into the extent of water diffusion in extracellular/extravascular spaces and capillary perfusion [31,60]. Both preclinical and clinical studies have demonstrated lower renal ADC values in dysfunctional renal transplants and native renal pathologies.…”