Dataset Information

Elastography and diffusion-weighted MRI in patients with rectal cancer.

ABSTRACT:

Objective

The current literature has described the usefulness of elastography and diffusion-weighted MRI in patients with cancer, but to the best of our knowledge so far none of them has compared the two new methods. The tumour cell density is related to the MRI-measured apparent diffusion-weighted coefficient (ADC). The purpose of the present study was to compare quantitative elastography based on ultrasound shear wave measurements with MRI ADC.

Methods

We prospectively examined 52 patients with histopathologically proven rectal cancer. The mean age was 67 years (range 42-90 years). Males: 39, females: 13. Tumour elasticity was measured transgluteally using the acoustic radiation force impulse (ARFI) to generate information on the mechanical properties of the tissue. The objective quantitative elastography shear wave velocity was blindly compared with the ADC measurements using a 1.5-T MRI system.

Results

The mean tumour elasticity was 3.05 m s(-1) [standard deviation (SD): 0.79], and the mean ADC was 0.69 × 10(-3) mm(2) s(-1) (SD: 0.27). Elasticity was inversely strongly correlated with ADC, r = -0.65 (Salkin scale). ARFI = 4.392 - 1.949 × ADC, R(2) = 0.43, p < 0.0001. Intercept = 4.392 (95% CI: 3.92 to 4.86), slope = -1.949 (95% CI: -1.31 to -2.59), p < 0.0001.

Conclusion

Elasticity correlates with the estimated diffusion restriction by MRI ADC measurements in rectal tumours. The relationship between ARFI and ADC measurement was linear in our study population.

Advances in knowledge

This work describes a correlation between tissue elasticity and diffusion in rectal cancer.

SUBMITTER: Rafaelsen SR

PROVIDER: S-EPMC4984932 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Publications

Elastography and diffusion-weighted MRI in patients with rectal cancer.

Rafaelsen Søren R SR Vagn-Hansen Chris C Sørensen Torben T Lindebjerg Jan J Pløen John J Jakobsen Anders A

The British journal of radiology 20150924 1056

<h4>Objective</h4>The current literature has described the usefulness of elastography and diffusion-weighted MRI in patients with cancer, but to the best of our knowledge so far none of them has compared the two new methods. The tumour cell density is related to the MRI-measured apparent diffusion-weighted coefficient (ADC). The purpose of the present study was to compare quantitative elastography based on ultrasound shear wave measurements with MRI ADC.<h4>Methods</h4>We prospectively examined ...[more]

PMID: 26402215

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Project description:PurposeThe purpose of this study was to compare the performance of four diffusion models, including mono and bi-exponential both Gaussian and non-Gaussian models, in diffusion weighted imaging of rectal cancer.Material and methodsNineteen patients with rectal adenocarcinoma underwent MRI examination of the rectum before chemoradiation therapy including a 7 b-value diffusion sequence (0, 25, 50, 100, 500, 1000 and 2000 s/mm2) at a 1.5T scanner. Four different diffusion models including mono- and bi-exponential Gaussian (MG and BG) and non-Gaussian (MNG and BNG) were applied on whole tumor volumes of interest. Two different statistical criteria were recruited to assess their fitting performance, including the adjusted-R2 and Root Mean Square Error (RMSE). To decide which model better characterizes rectal cancer, model selection was relied on Akaike Information Criteria (AIC) and F-ratio.ResultsAll candidate models achieved a good fitting performance with the two most complex models, the BG and the BNG, exhibiting the best fitting performance. However, both criteria for model selection indicated that the MG model performed better than any other model. In particular, using AIC Weights and F-ratio, the pixel-based analysis demonstrated that tumor areas better described by the simplest MG model in an average area of 53% and 33%, respectively. Non-Gaussian behavior was illustrated in an average area of 37% according to the F-ratio, and 7% using AIC Weights. However, the distributions of the pixels best fitted by each of the four models suggest that MG failed to perform better than any other model in all patients, and the overall tumor area.ConclusionNo single diffusion model evaluated herein could accurately describe rectal tumours. These findings probably can be explained on the basis of increased tumour heterogeneity, where areas with high vascularity could be fitted better with bi-exponential models, and areas with necrosis would mostly follow mono-exponential behavior.

Project description:The purpose of this work was (1) to develop a magnetic resonance elastography (MRE) system for imaging of the ex vivo human prostate and (2) to assess the diagnostic power of mono-frequency and multi-frequency MRE and diffusion weighted imaging (DWI) alone and combined as correlated with histopathology in a patient study. An electromagnetic driver was designed specifically for MRE studies in small-bore MR scanners. Ex vivo prostate specimens (post-fixation) of 14 patients who underwent radical prostatectomy were imaged with MRE at 7 T (nine cases had DWI). In six patients, the MRE examination was performed at three frequencies (600, 800, 1000 Hz) to extract the power-law exponent Gamma. The images were registered to wholemount pathology slides marked with the Gleason score. The areas under the receiver-operator-characteristic curves (AUC) were calculated. The methods were validated in a phantom study and it was demonstrated that (i) the driver does not interfere with the acquisition process and (ii) the driver can generate amplitudes greater than 100 µm for frequencies less than 1 kHz. In the quantitative study, cancerous tissue with Gleason score at least 3 + 3 was distinguished from normal tissue in the peripheral zone (PZ) with an average AUC of 0.75 (Gd ), 0.75 (Gl ), 0.70 (Gamma-Gd ), 0.68 (apparent diffusion coefficient, ADC), and 0.82 (Gd + Gl + ADC). The differentiation between PZ and central gland was modest for Gd (p < 0.07), Gl (p < 0.06) but not significant for Gamma (p < 0.2). A correlation of 0.4 kPa/h was found between the fixation time of the prostate specimen and the stiffness of the tissue, which could affect the diagnostic power results. DWI and MRE may provide complementary information; in fact MRE performed better than ADC in distinguishing normal from cancerous tissue in some cases. Multi-frequency (Gamma) analysis did not appear to improve the results. However, in light of the effect of tissue fixation, the clinical implication of our results may be inconclusive and more experiments are needed.

Dataset Information

Elastography and diffusion-weighted MRI in patients with rectal cancer.

Objective

Methods

Results

Conclusion

Advances in knowledge

Publications

Elastography and diffusion-weighted MRI in patients with rectal cancer.

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