Clinical Value And Study Of High Resolution And Functional MR Imaging For Preoperative Staging Of Rectal Cancer

Part one:Value of high-resolution MRI of rectal cancer with radiologic-pathologic correlation for evaluation of T and N stagingObjective To determine the accuracy of high-resolution magnetic resonance imaging of T,N staging and mesorectal fascia infiltration in rectal cancer using T₂ weighted turbo spin-echo(T₂W-TSE) before operation.Materials and Methods:Eighty patients with primary rectal cancer were undergone 1.5T MRI with phased-array coil. Initial axial and sagittal T₂WI obtained were used to plan T₂W-TSE high-resolution angled oblique scans,which were always perpendicular to the long axis of the rectum. For the lower tumors,additional oblique coronal scans were also acquired.The assessment of MRI were compared with postoperative histopathologic findings. Sensitivity,specificity,accuracy,positive predictive value(PPV),and negative predictive value(NPV) were evaluated.Result:The overall accuracy was 85%for T staging and 70%for N staging.MR sensitivity,specificity,accuracy,PPV and NPV was 72.7%,96.6%,90%,88.9%,90.3%for≤T2 tumors;88.5%,78.6%,85%,88.5%, 78.6%for T3 tumors;and 100%,94.6%,95%,60%,100%for T4 tumors;73%, 85.7%,77.5%,90.5%,63.1%for N0 tumors;55.6%,77.4%,72.5%,41.7%,85.7% for N1 tumors;80%,91.4%,87.5%,57.1%,97%for N2 tumors;82.4%,90.5%, 88.8%,70%,95%for predicting mesorectal fascia involvement respectively. Conclusion:High-resolution MRI is an accurate technique for preoperative T,N staging and mesorectal fascia infiltration in rectal cancer in order to determine suitable patients for preoperative neoadjuvant treatment..Part two:Clinical value of diffusion-weighted MRI in rectal cancerOne Investigation of optimized b factor with diffusion-weighted MRI in detection of rectal cancer.Objective:To assess the image quality of various b factor of diffusion-weighted magnetic resonance imaging and determine appropriate b factor in depicting rectal cancer.Materials and Methods:Forty-five patients with primary rectal cancer were undergone high resolution T₂WI and diffusion-weighted single-shot spin-echo echo-planar imaging(SE-EPI) with breath-holding.The b factors used were 500,800,1000 and 1200s/mm² respectively.The detection of tumors were assessed, and signal-to-noise ratio(SNR)of tumors,contrast-to-noise ratios(CNRs)of tumor-fat, tumor-muscle were calculated and compared.SNR,CNRs with subjective visual evaluation were used to assess the image quality.Results:Diffusion-weighted imaging depicted all rectal cancers as hyperintense areas with various b factors.The image quality scores were increased with increasing b factor,but the SNR of tumors and CNRs of tumor-fat,tumor-muscle were decreased.The SNR of tumors and CNRs of tumor-fat,tumor-muscle in the DWI with b=800,1000 s/mm² differed statistically significantly with the others,which showed no significant difference between various b factors each other.Conclusion:For DWI of rectal cancer on a 1.5T scanner,there may be the appropriate way with b=800 s/mm² or 1000 s/mm².Two The value of diffusion-weighted imaging in combination with T₂-weighted imaging for detection of rectal cancerObjective:To evaluate the clinical value of diffusion-weighted imaging(DWI) in combination with T₂-weighted imaging(T₂WI) for the detection of rectal cancer as compared with T₂WI alone.Materials and Methods:Fifty-five patients with rectal cancer and 30 without rectal cancer were undergone T₂WI and DWI(b=1000 s/mm²) with parallel imaging on a 1.5T scanner.Images were independently reviewed by 2 experienced radiologists who were blinded to the results and made the evaluation about the detectability of rectal cancer.The detectability of T₂W imaging without and with DW imaging was assessed by means of receiver operating characteristic analysis. Grades 4 and 5 were accepted as positive for the presence of rectal cancer and the sensitivity,specificity,positive predictive value(PPV),and negative predictive value(NPV) were calculated.The interobserver agreement between the two radiologists was calculated with kappa statistics.Results:The ROC analysis showed that each of two radiologists achieved more accurate results with T₂W imaging combined with DW imaging than with T₂W imaging alone significantly.The A_Z values for the two radiologists for each T₂WI and T₂WI combined with DWI were 0.9218 versus 0.9900(p=0.0276),0.9360 versus0.9963(p=0.0313),respectively.The mean sensitivity,specificity,PPV,NPVwere 80%,90%,93.6%,71.1%for T₂WI and 90%,98.35%,99%,84.3%for T₂WI combined with DWI.The values of kappa were 0.827 for T₂WI and 0.820 for T₂WI combined with DWI between the two radiologists.Conclusion:The DW imaging in combined with T₂W imaging impoves detection rate for rectal cancer.Part three:Assessment of liver metastases using functional MRI(DWI and PWI) in rectal cancerOne Comparative study of DWI with routine MRI for detection of rectal liver metastasesObjective:To compare the diagnostic accuracy of routine MR imaging and diffusion-weighted imaging(DWI),alone and in combination,for detecting rectal liver metastases.Materials and Methods:Twenty-five consecutive patients with rectal liver metastases underwent routine MR imaging(T₂WI+Dynamic enhanced T₁WI) and DWI(b=500 s/mm²) with parallel imaging on a 1.5T scanner.Three image sets(routine MRI,DWI and combined routine MRI and DWI) were reviewed independently by two observers.The lesions detection and diagnostic accuracy were calculated for each image set and compared.Results:For the detection of all lesions and liver metastases,the combined set significantly higher than that of routine MRI or DWI set.Using the combined set resulted in the highest diagnostic accuracy (94.2%),with improved sensitivity of liver metastases diagnosis compared with the routine MRI set(96.9%vs 85.7%)and DWI set(96.9%vs 81.5%),but the specificity were 85.7%for both combined set and routine MRI set and 66.7%for DWI set.The image quality of DW images was affected by T₂ shine-through effect, cardiac motion and susceptibility artifacts of air.Conclusion:Combination of routine MR imaging and DWI resulted in the highest diagnostic accuracy and can increase sensitivity without loss in specificity of liver metastases. Two Application of MR whole liver perfusion weighted imaging in detection of rectal liver metastases.Objective:To assess whether MRI measurements can depict liver hemodynamic changes in patients with and without rectal liver metastases.Materials and Methods: Forty-six(16 with rectal liver metastases and 30 without liver metastases) underwent 1.5T MRI using a modified volume-interpolated breath-hold examination sequence (VIBE),which were obtained every 3s for 90 s during the injection of 0.1 mmol kilogram of body weight of contrast medium at 4ml/s.The sequence was acquired while the patient breathed gently.Time signal intensity curve(TIC) of the aorta,portal vein,liver and spleen were used to calculate relative hepatic arterial perfusion(HAP), hepatic portal vein perfusion(HPP),and hepatic perfusion index(HPI).Results: Significant differences were seen between the relative HPP and HPI for the patient with and without metasases(p＜0.005),with patients demonstrating reduced portal perfusion(0.976 vs 1.332)and increased HPI relative to controls(0.387 vs 0.285).The patients with metasases showed slightly increased relative HAP(0.565 vs 0.535),but this trend did not reach significance(p＞0.05).Conclusion:MR whole liver perfusion weighted imaging enabled quantification of perfusion parameters of liver hemodynamic changes and may contribute to the early detection of liver metastases.