| Objective1. To explore the veracity of diffusion-weighted imaging (DWI) and enhanced T1 high resolution isotropic volume examination (e-THRIVE) in combination with high resolution T2-weighted imaging respectively for the T-staging of rectal cancer.2. To assess the correlation of perfusion between intravoxel incoherent motion (I VIM) and T1-weighted imaging dynamic contrast enhancement (DCE-T1WI) on rectal cancer.3. To explore the multi-directional contrast-enhanced MRI characteristics of adenomatous polyp canceration (APC).Materials and Methods1. The HR-T2WI, DWI and e-THRIVE dynamic contrast enhancement (DCE) findings of rectal adenocarcinoma with pathological proved were analyzed. T-staging of rectal cancer diagnosed by HR-T2WI alone, DWI with HR-T2WI, and e-THRIVE-DCE with HR-T2WI were performed a comparison with pathology.2. The integrated DCE-T1WI and DWI were performed in 15 patients from December 2013 to December 2014 with pathological proved rectal cancer after endoscopic biopsy or surgery using different b-value (0,10,50,80,100,200, 300,500,800s/mm2). Time intensity curves (TICs) of group a, b, and c, as well as Tp, Emax, Erise, wash in rate (WIR) of group a, were reconstructed by Basic T1 Perfusion package in workstation. The diffusion coefficient D, perfusion fraction f, and pseudodiffusion coefficient D* derived from intravoxel incoherent motion with bi-exponential model, apparent diffusion coefficient (ADC) derived from mono-exponential model with b=0 s/mm2 and b=800 s/mm2 in rectal cancer group (group a) and normal rectal wall group (group b) were calculated and compared. The correlational analyses between f and DCE-T1WI parameters were performed by Spearman correlation analysis after defining the frequency variables from 1 to 3 according to their data range. Receiver operating characteristics (ROC) curves of IVIM and DCE parameters for diagnosing rectal cancer were analyzed.3. The 56 cases pelvic MR examination were excuted on the patients who were diagnosed as rectal mass through digital rectal examination from September 2013 to December 2014. There were 8 cases (totally ten focus) of rectal polypoid lesions. One of them companied with polypoid lesions from sigmoid. The pathological findings by synchronous endoscopic biopsy were tubulovillous adenoma or villus-tubiform adenoma. There were 3 males and 5 females,51-88 years old, with the average age of 66. Totally ten focus that had oblique-coronal, sagittal, and axial contrast-enhanced MRI of 8 cases rectal adenomatous polyp (AP) and APC were observed and correlated with pathological results by total mesorectal excision or local excision.Results1. T-staging of rectal cancer diagnosed by HR-T2WI alone, DWI with HR-T2WI and e-THRIVE-DCE with HR-T2WI agreed with pathological stage was 79.2%, 70.8% and 95% respectively (k=0.710,0.597, and 0.930 respectively).2. The mean D, f, D*, and ADC in group a and b were (77±25)×10-2mm2/s, (10.90±5.55)%, (13509±6902)×10-2mm2/s, (83±27)×10-2mm2/s, (157±39)×10-2mm2/s, (20.60±14.03)%, (12056±6325)×10-2 mm2/s, (165±19)×10-2 mm2/s respectively. Mean tumor D, f, and ADC were significantly different when comparing with group b. The mean D and ADC were significantly different in group a with mean D was smaller than ADC. There was no significantly different when comparing mean D and ADCs in group b.3. The Tp, Emax, Erise, WIR of group a were 96.05±41.96s,1245.48 ±910.50(%), 1463.23 ±917.89(%),82.98±57.59(1/s) respectively. Of group b were 94.82± 49.44s,851.92 ± 559.23(%),1469.19 ± 1072.72(%),74.43 ± 53.97(1/s) respectively.4. In group a,10 cases were platform type curves, in which 7 cases were stage T1-2, 3 cases were advanced stage. Three cases were resistant type curves, in which 2 cases were stage T2,1 case was stage T4a. Two cases were washout type curves (both were stage T2). The curves showed platform type (11cases) and washout type (2cases) in group b. For group c, they were all washout type curves. The time intervals of WIR were between dynamic 4 and 5 in both group a and b, for group c between dynamic 3 and 4.5. Correlation analysis between IVIM and DCE-T1WI of rectal cancer:the correlation coefficients of f and Erise, f and WIR were 0.585,0.571 respectively. The difference was statistically significant. Erise, WIR and f was moderate positive correlation. But D, D* had no significant correlation with DCE-T1WI parameters.6. The ROC curves showed D and f had diagnostic efficiency on rectal cancer with the cut-off lower than 103.79×10-2 mm2/s,< 19.59% respectively.7. There were nine pedicle polyps and one sessile configuration. In pathology, there were one tubular adenoma, four villioustublar adenoma and five adenomatous polyp with partial canceration. After administration of contrast agents, four AP showed tricyclic reinforcement while APC manifest fried egg reinforcement (four cases) and paving stone reinforcement (one case).Conclusion1. The addition of e-THRIVE-DCE can provide better accuracy of preoperative T-staging and should become an important efficient means in preoperative T-staging of rectal cancer. DWI has limited value in preoperative T-staging of stage I (T1-2) rectal cancer.2. The mean D, f and ADC are significantly different in rectal cancer group without any treatment when comparing with normal rectal wall, but D* had no significant difference. ADCs derived from mono-exponential model of multi b-value DWI are larger than D derived from IVIM with bi-exponential model in rectal cancer group, but the two of normal rectal wall group have no significant difference.3. Compared to the washout type curves of iliac artery on the same plane with rectal cancer, the types of rectal cancer are variable. But platform type is still most in common, so as to the normal rectal wall. Whereas, the higher WIR and Emax of rectal cancer may provide strong proof in distinguishing cancer and non-cancer.4. The perfusion parameter f derived from IVIM can reflect the perfusion characteristics of rectal cancer. The f has a good correlation between WIR and Erise.5. It can remind the diagnosis of rectal cancer when D lower than 103.79×10-2mm2/s, f lower than 19.59%. Furthermore, D has the higher diagnostic efficiency than f.6. We should pay close attention to whether fried egg-like enhancement of rectal cancer is characteristic on contrast enhancement MRI. |
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