| Objective To investigate the feasibility of MR diffusion-weighted imaging (DWI) on normal, inflammatory and VX2 carcinoma metastatic lymph nodes in rabbit model and the potential use for discrimination. Materials and Methods 20 New-Zealand White rabbits were divided randomly into 2 groups. Complete Freund adjuvant was injected into the left dorsal footpads of 10 rabbits so as to set up ipsilateral lymphadenitis model, while the right legs were measured as normal control. The left 10 rabbits received a subcutaneous implantation of VX2 tumor cell suspension (4×107 cells/ml) in fight thighs. STIR-EPI-DWI (short TI inversion recovery, STIR), T1-weighted and T2-weighted images were performed 14 days after the injection. Apparent diffusion coefficient (ADC) value of the lymph nodes was evaluated in all cases. The size of the lymph nodes on T2WI, DWI and pathological examination was measured and compared. Pathological study was made after lymph nodes resection and hematoxylin-eosin (HE) staining. Results Normal, inflammatory and VX2 carcinoma metastatic lymph nodes in animal models could be demonstrated clearly with STIR-DWI sequence without fat contamination or significant distortion. There was no statistically difference among the size of the lymph nodes measured on T2WI, DWI and pathological examination(normal group F=0.88, P=0.43; inflammatory group F=0.38, P=0.69; metastatic group F=0.64, P=0.53). The size of inflammatory lymph nodes was almost the same as VX2 carcinoma metastatic groups, while they were much larger than normal group. All lymph nodes appeared isointense on T1WI and hyperintense on T2WI and DWI. The mean ADC value of normal, inflammatory and metastatic nodes was (1.35±0.15)×10-3mm2/s, (1.14±0.02)×10-3mm2/s and (0.78±0.07)×10-3mm2/s respectively, the distinction between each group was significant (F=112.12, P＜0.01). Conclusion High quality images can be obtained using STIR-EPI-DWI sequence in rabbit model. DWI is a new promising technique for differentiating inflammatory from metastatic lymph nodes. The addition of DWI to routine MR sequence provides more useful physiological and functional information for diagnosis. Objective To investigate the feasibility of MR diffusion-weighted imaging (DWI) for evaluating radiotherapeutic effect on rabbit VX2 tumor model. Materials and Methods 16 New-Zealand White rabbits received a subcutaneous implantation of VX2 tumor cell suspension(4×107/ml) in their right thighs. 2 weeks later they were divided randomly into therapy group (Group T, n=10) and control group (Group C, n=6). Group T received radiotherapy at a single dose of 10Gy. MRI scan including STIR-EPI-DWI (short TI inversion recovery, STIR), T1WI and T2WI were performed pretreatment, 1 day, 2 days, 3 days and 7 days after treatment. Group C received only MRI scan at the same time points without any treatment. Apparent diffusion coefficient (ADC) values of the tumor were evaluated in all cases. Volume of the tumors was calculated and its MRI appearance on the T2WI and T1WI image was compared. Results There was no significant difference between the tumor volume of two groups at base line. After radiotherapy, tumors in Group T showed a gradual growth but not as obvious as Group C. There was a statistical difference from Day 2 on (p＜0.01). Necrosis (n=8) and hemorrhage (n=2) were seen gradually on T2WI and T1WI image of group T also after time point of Day 2. In Group C, no obvious necrosis was found until Day 7. ADC value changed dramatically fight from the first day after radiotherapy [Group T: ADC=(1.23±0.08)×10-3mm2/s, (1.45±0.07)×10-3mm2/s, (1.63±0.06)×10-3mm2/s, (2.02±0.18)×10-3mm2/s for day 1, 2, 3 and 7; Group C: ADC=(1.03±0.04)×10-3mm2/s; (1.05±0.02)×10-3mm2/s; (1.05±0.05)×10-3mm2/s; (0.95±0.07)×10-3mm2/s for day 1, 2, 3, and 7]. There was significant difference between these two groups for each time points except base line (p＜0.01). Pathological study showed that the number of viable tumor cells in the Group T decreased 1 day after radiotherapy and that inflammatory cell infiltration was marked and almost all viable tumor cells had disappeared by day 7 after radiotherapy. Conclusion DWI is a new promising technique for monitoring radiotherapy outcomes. ADC value may give a prior clue on physiological changes of radiotherapy before routine MRI could tell. Objective To optimize the free breathing whole body diffusion weighted imaging (WB-DWI) protocol by using short TI inversion recovery diffusion weighted echo planar imaging (STIR-EPI-DWI) sequence and build-in body coil. And to evaluate the feasibility of WB-DWI in tumor patient screening. Materials and Methods 1) Comparison of SE-EPI-DWI and STIR-EPI-DWI sequence: In 5 patients who had an abdominal MR scan, the STIR-EPI-DWI sequence and SE-EPI-DWI sequence were compared in terms of their CNR (contrast noise ratio), SNR (signal to noise ratio) and the degree of background fat suppression. 2) Prescan technical improvement: 30 volunteers underwent WB-DWI and the central frequency of each location of each volunteer was recorded. The imaging quality obtained by auto-CF process and fixed CF was compared. The optimal combinations of determining uniform CF for whole body scan procedure was chosen. The receiving gain was also modified, only "transmission gain" and "gradient shimming" were kept. 3) Feasibility evaluation: Thirty patients with histological proven malignant diseases were scanned under the final protocol by using STIR-EPI-DWI sequence with free breathing and build in body coil. Total scan time was 30 minutes for 5 stations covering from head to thigh with b values of 0 and 800 s/mm2. Each station composed of 39 slices with 7mm thickness and lmm overlap. Conventional FSE T2-weighted image was also performed at same location as a reference. Results CNR(contrast noise ratio) and SNR(signal to noise ratio) were significantly higher in the STIR-EPI-DWI sequence than SE-EPI-DWI sequence (30.10±11.82, 12.10±6.87; 56.22±17.69, 43.30±19.83). Images obtained by fixed CF were superior to those obtained by auto-CF process. The averaged CF between abdomen and head location was most close to the averaged CF of all station with a standard deviation of 13.2 Hz. Free breathing WB-DWI was successfully performed in this patients group, without slice misregistration, fat contamination, significant distortion or non-uniformity. The reconstructed 3D-MIP images were adequate to depict the malignant lesions on the total 30 patients. Conclusion Stable and high resolution WB-DWI can be obtained with these technical improvements. WB-DWI might have an important clinical application value in the detection of primary and whole body metastasis lesions of malignancies. The potential in diagnosis and therapeutic assessment of tumors has to be further assessed in a larger patient cohort. Objective To establish quantitative reference standard of apparent diffusion coefficient (ADC) values in various human normal organs and to evaluate the effect of aging, gender and laterality on diffusion. Materials and Methods 50 healthy volunteers were included. Age groups(group 1-5) were 15-30yrs, 31-40 yrs, 41-50 yrs, 51-60 yrs and 61 yrs or older (n=10 each, 5 male and 5 female). WB-DWI was performed by using STIR-DWEPI sequence with b values of 0 and 800s/mm2. ADC values were calculated in 30 regions of interest encompassing the whole body on ADC map. Results The ADC values of different organs were: gray matter: 1.09±0.07; white matter: 0.86±0.09; caudate nucleus: 0.75±0.05; putamen: 0.794±0.08; thalamus: 0.80±0.07; pons: 0.64±0.05; submandibular glands: 1.33±0.14; parotid gland: 1.17±0.11; left cardiac ventricle: 2.18±0.28; gastric wall: 1.85±0.28; liver: 1.22±0.05; spleen: 0.834±0.08; pancreatic head: 1.72±0.05; kidney: 1.98±0.12; ascending colon: 1.18±0.07; rectum: 1.28±0.18; prostate central zone: 1.44±0.18; prostate peripheral zone: 1.64±0.15; breast: 1.56±0.22, body of uterus: 1.64±0.13; cavity of uterus: 1.264±0.14; T8 vertebra: 0.30±0.08; T8-9 intervertebral disc: 1.27±0.13; L2 vertebrae: 0.34±0.08; L2-3 intervertebral disc: 1.40±0.15. White matter showed higher ADC value in Group 5 than Group 1(p=0.02). ADC value of prostate central zone in Group 5 were statistically different with other groups (p=0.00-0.02), while in Group 1 that was significantly lower than Group 4 (p=0.02); the prostate peripheral zone ADC value of group 5 was higher than group 1, 2, 3 (p=0.04, 0.01, 0.02). Cavity of uterus showed higher ADC value in Group 5 than Group 1, 2 (p=0.00, 0.02). In the intervertebral lumbar disc, the ADC value of Group 1 and 2 were higher than Group 4 and 5 (p=0.01, 0.00, 0.00, 0.00). ADC values showed correlation with aging in the white matter, prostate central and peripheral zone, cavity of uterus and lumbar intervertebral disc. Correlation coefficient was 0.413, 0.699, 0.757, 0.632, -0.626 respectively. There was no statistically difference between left and right sides of the parotid, submandibular glands, kidney and breast (p=0.436-0.916). No regions showed significant difference between different gender (p=0.251-0.966). Conclusion: With the exception of the white matter, prostate, cavity of uterus and lumbar intervertebral disc, the ADC values were not affected by aging. The symmetrical organs had similar ADC values in the left and right. Gender factor had no effect on ADC values. The ADC values of normal organs obtained in this study can be used as reference for evaluation and semiquantify analysis in future studies. Objective To compare the accuracy in staging of various malignant tumors with whole-body diffusion-weighted MR imaging (WB-DWI) and [18F]-fluoro-2-deoxy-D-glucose positron emission tomography (18F-FDG-PET). Materials and Methods 16 patients (9 male, 7 female, age 35-82 years) with various oncological diseases underwent tumor staging by WB-DWI and PET within three weeks. Correct classification of the primary tumor, regional lymph nodes and distant metastasis (overall TNM stage) were assessed for both modalities in a separate consensus reading. Different ADC value (lymph node 1.1×10-3mm2/s, hepatic metastasis 1.2×10-3mm2/s and bone metastasis 0.6×10-3mm2/s) and SUV (standard uptake value) of 2.5 were used as a threshold value for differentiating malignant from benign lesions. The sensitivity, specificity, positive predictive value, negative predictive value, accuracy and the accordance of both modalities were evaluated with histological results and other radiological follow up within 6 months as the standard of reference. Results WB-DWI identified 80 pathological lesions in 11 cases, while PET demonstrated 77 lesions in 13 cases. Concordance between WB-DWI and PET occurred in 12 of 16 patients (75%). There was no statistically difference between the two modalities (X2=0.607, P=0.437). The sensitivity, specificity, positive predictive value, negative predictive value, accuracy of PET were 91.67%(11/12), 50%(2/4), 84.6%(11/13), 66.7%(2/3), 81.3%(13/16), those of WB-DWI were 91.67%(11/12), 100%(4/4), 100%(11/11), 80%(4/5) and 93.75%(15/16). One prostate cancer was missed with PET, while WB-DWI missed one remaining lesion in one NHL case after chemotherapy. Separate assessment of N-stage revealed a sensitivity/specificity of 100% and 75% for PET and 100% for WB-DWI. In two cases looking for primary tumor, WB-DWI showed more lymph nodes than PET in the cervial and iliac region. Among 51 lesions of distant metastases, PET detected 45 lesions with a sensitivity of 88.2%, while WB-DWI revealed 47 lesions with a sensitivity of 92.2%. WB-DWI proved to be more reliable in the detection of cerebral metastases, while PET was more accurate in detecting lung and spleen metastases. Conclusion WB-DWI and PET are reliable imaging modalities for tumor staging. Superior performance overall TNM staging suggests WB-DWI is a valuable technology for whole-body tumor screening. Objective To evaluate the clinical impact of whole body diffusion weighted MR imaging (WB-DWI) for the diagnosis, staging and treatment assessment in patients with Hodgkin's disease (HD) and Non-Hodgkin's lymphoma (NHL). Materials and Methods WB-DWI was performed in 55 patients with lymphoma or suspected lymphoma. The WB-DWI images were analyzed in qualitative and semi-quantitative ways. The results of WB-DWI were compared with pathological examination and other conventional imaging modalities. The mean ADC value of different kinds of lymph nodes was compared either. Results Among 31 newly diagnosed cases, WB-DWI was positive in all 18 cases with lymphoma, 5 cases with metastatic lymph nodes and 4 of 8 benign lymphadenopathy. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of WB-DWI was 100% (18/18), 30.8% (4/13), 71.0% (22/31), 66.7% (18/27) and 100% (4/4). The mean ADC value of lymphomatous, metastatic and benign lymph nodes was (0.874±0.17)×10-3mm2/s, (0.98±0.09)×10-3mm2/s and (1.20±0.10)×10-3mm2/s. There was statistically different between benign lymph nodes and other groups (P=0.00). When an ADC value of 1.085×10-3mm2/s was used as a threshold value for differentiating malignant from benign lymph nodes, the best results were obtained with an sensitivity of 87.8% and specificity of 91.3%. 16 of 18 cases (88.9%) were accurately staged in accordance with clinical staging. For 24 patients after chemotheraphy or radiotheraphy, 4 cases were complete remission (CR) and WB-DWI was negative. WB-DWI was positive in 14 of 17 cases with recurrent or remnant tumor. For 3 patients with suspected partial remission (PR), WB-DWI indicated necrosis in 2 cases and inactive in 1 case. Repeated WB-DWI examination was performed in 13 cases, tumors were eradicated in 6 cases, improved in 4, expanded in 2. A new colon carcinoma besides its primary lesion was found in 1 case. The results of WB-DWI were all concordant with other clinical tests. Conclusion WB-DWI is a sensitive, but less specific method for diagnosis of lymphoma. It is difficult to differentiate lymphomatous from metastatic lymph nodes. ADC value may provide help in diagnosis of lymph nodes malignancy. WB-DWI could detect the recurrent and remnant tumor accurately. It has great value in staging, guiding therapy and treatment efficiency evaluation.
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