Apparent Diffusion Coefficient (ADC) as a quantitative parameter in diffusion weighted MR imaging in gynecologic cancer: Dependence on b-values used

Abstract

Background. Diffusion weighted imaging (DWI) has gained interest as an imaging modality for assessment of tumor extension and response to cancer treatment. The purpose of this study is to assess the impact of the choice of b-values on the calculation of the Apparent Diffusion Coeffi cient (ADC) for locally advanced gynecological cancer and to estimate a stable interval of diffusion gradients that allows for best comparison of the ADC between patients and institutions. Material and methods. Six patients underwent a high resolution single shot EPI based DWI scan with 16 different diffusion gradients on a 3 Tesla Philips Achieva MR-scanner. Data analysis was performed by applying a monoexponential and a biexponential model to the acquired data. The biexponential function models the effect of both perfusion and diffusion. Results and conclusion. ADC changes of up to 40% were seen with the use of different b-values. Using a lower b-value Ն 150 s/mm 2 and an upper b-value Ն 700 s/mm 2 limited the variation to less that 10% from the reference ADC value. By eliminating the contribution of perfusion the uncertainty of quantitative ADC values were signifi cantly reduced.

Variation in apparent diffusion coefficient measurements among women with locally advanced cervical cancer

“…In vivo, the b-values often contribute to variance, because of perfusion bias at b-values less than 150 s/mm 2 , and slowed signal attenuation at high diffusion weighting [17,23]. Regression to only intermediate b-values, or with a biexponential decay, may reduce b-value effects.…”

“…Lower ADC indicates increased cellularity and differentiates malignant from benign tissues [8][9][10][11], and the extent of ADC change following chemoradiation has correlated with tumor response and disease-free survival [7,12,13]. However, the measured ADC can depend on technical factors, including field strength, region-of-interest (ROI), and b-value selection [14][15][16][17][18][19]. For example, linear regression may not hold when b is very low or high [15,16], plus b-value sets are not standardized across anatomic sites or institutions [20].…”

Estimation of optimalb-value sets for obtaining apparent diffusion coefficient free from perfusion in non-small cell lung cancer

“…For monoexponential assessments of ADC values, the use of two b-values (>100 and between 500 and 1000 µs/µm 2 ) has been recommended to avoid perfusion effects and to obtain accurate ADC values (Padhani et al 2009). In this respect, there have been a number of studies of normal tissues from various body sites such as kidney (Freiman et al 2012), liver (Freiman et al 2012), and spleen (Freiman et al 2012) as well as malignant tumours such as cervix cancer (Kallehauge et al 2010) to establish opt imal b-value sets to obtain the monoexponential ADC values close to reference-standard perfusion-insensitive IVIM model ADC (ADC IVIM ). Malignant tumours have in general higher cellularity and therefore less diffusion compared to normal tissue of similar density.…”

Diffusion-weighted MR imaging in gynecologic cancers

“…DWI has been shown to be capable of detecting early or subtle changes within the brain before any visible abnormality appears on conventional imaging [8]. DWI has been prone to severe motion sensitivity due to the long scan times, because this will limit the effects of patient motion artifacts [9]. However, recent developments in fast magnetic resonance image (MRI) techniques have helped to overcome the difficulties, respiratory and bowel peristaltic motion, of abdominal and pelvic DWI and have increased the role and potential of MRI in evaluating the abdomen and pelvis [1].…”

“…However, recent developments in fast magnetic resonance image (MRI) techniques have helped to overcome the difficulties, respiratory and bowel peristaltic motion, of abdominal and pelvic DWI and have increased the role and potential of MRI in evaluating the abdomen and pelvis [1]. Although performing DWI in the body is challenging because the inhomogeneity of the magnetic field over a large imaging area and susceptibility to motion artifacts related to respiratory and bowel peristaltic motion arising from different organs conspire to degrade image quality [9,10]. …”