Diffusion-weighted magnetic resonance imaging and its application to cancer

Abstract

Diffusion-weighted magnetic resonance imaging (DW-MRI) provides image contrast through measurement of the diffusion properties of water within tissues. Application of diffusion sensitising gradients to the MR pulse sequence allows water molecular displacement over distances of 1-20 µm to be recognised. Diffusion can be predominantly unidirectional (anisotropic) or not (isotropic). Combining images obtained with different amounts of diffusion weighting provides an apparent diffusion coefficient (ADC) map. In cancer imaging DW-MRI has been used to distinguish brain tumours from peritumoural oedema. It is also increasingly exploited to differentiate benign and malignant lesions in liver, breast and prostate where increased cellularity of malignant lesions restricts water motion in a reduced extracellular space. It is proving valuable in monitoring treatment where changes due to cell swelling and apoptosis are measurable as changes in ADC at an earlier stage than subsequent conventional radiological response indicators.

Diffusion weighted imaging in prostate cancer

“…Potentially benign conditions that may falsely lower ADC include: (1) various abnormal conditions, such as prostatitis and the compact fibromuscular stroma seen in benign prostatic hyperplasia [10,44], (2) susceptibility artefact at tissue boundaries [45] and at areas of haemorrhage (Fig. 6), (3) elevated vascular flow associated with tumour [29], as well as (4) organ motion [24].…”

Magnetic resonance imaging as a biomarker in renal cell carcinoma

“…85 An ability of DWI to function as a biomarker to predict and monitor tumor response to targeted and/or antiangiogenic therapy has been described. 85,86 Preclinical and clinical studies have demonstrated some correlation between ADC values and tumor cellularity and grade. 87 Baseline ADC values may predict the likelihood that a patient will respond to therapy.…”

Characterization of a parietal lesion detected by diffusion weighted MRI, NaF18-PET/CT and CT

“…This technique has great versatility because it can be used for making a primary diagnosis and prognosis prediction, following the treatment response after chemotherapy or radiation and restaging of tumors. Cancerous lesions have higher cell density, fibrous tissue and areas of necrosis compared to surrounding normal tissues [2] . Thus, tumors present a greater barrier to water diffusion than normal tissues.…”

“…However, there are limitations for this type of imaging. It is very prone to artifacts such as motion and breathing artifacts [2] . The standard 1.5 T MRI used in our case is best for DW MRI protocol because it can reduce the background noises.…”

“…Bone metastases may be asymptomatic or may produce pain, swelling, and pathologic fracture [1] . DW MRI method relies on the diffusion of water molecules across cells and tissues for imaging [2] . It can detect physiological abnormalities even before structural changes are apparent.…”