Diffusion-weighted magnetic resonance imaging in cancer: Reported apparent diffusion coefficients,in-vitro and invivo reproducibility

There is considerable disparity in the published apparent diffusion coefficient(ADC) values across different anatomies. Institutions are increasingly assessing repeatability and reproducibility of the derived ADC to determine its variation,which could potentially be used as an indicator in determining tumour aggressiveness or assessing tumour response. In this manuscript,a review of selected articles published to date in healthy extracranial body diffusion-weighted magnetic resonance imaging is presented,detailing reported ADC values and discussing their variation across different studies. In total 115 studies were selected including 28 for liver parenchyma,15 for kidney(renal parenchyma),14 for spleen,13 for pancreatic body,6 for gallbladder,13 for prostate,13 for uterus(endometrium,myometrium,cervix) and 13 for fibroglandular breast tissue. Median ADC values in selected studies were found to be 1.28 × 10-3 mm2/s in liver,1.94 × 10-3 mm2/s in kidney,1.60 × 10-3 mm2/s in pancreatic body,0.85 × 10-3 mm2/s in spleen,2.73 × 10-3 mm2/s in gallbladder,1.64 × 10-3 mm2/s and 1.31 × 10-3 mm2/s in prostate peripheral zone and central gland respectively(combined median value of 1.54×10-3 mm2/s),1.44 × 10-3 mm2/s in endometrium,1.53 × 10-3 mm2/s in myometrium,1.71 × 10-3 mm2/s in cervix and 1.92 × 10-3 mm2/s in breast. In addition,six phantom studies and thirteen in vivo studies were summarized to compare repeatability and reproducibility of the measured ADC. All selected phantom studies demonstrated lower intra-scanner and inter-scanner variation compared to in vivo studies. Based on the findings of this manuscript,it is recommended that protocols need to be optimised for the body part studied and that system-induced variability must be established using a standardized phantom in any clinical study. Reproducibility of the measured ADC must also be assessed in a volunteer population,as variations are far more significant in vivo compared with phantom studies.

Value of Apparent Diffusion Coefficient(ADC) of Diffusion eighted Magnetic Resonance Imaging in Common Renal Disease Diagnosis

Objective：To find the value of the apparent diffusion coefficient （ADC） of diffusion weighted magnetic resonance imaging of common renal diseases. Methods： There were 30 healthy subjects and 81 patients with renal lesions （56 cases of renal carcinoma, 18 lesions of 12 cases of renal angiomyolipomal and 21 lesions of 13 cases of renal cysts）. Conventional magnetic resonance imaging and diffusion weighted magnetic resonance imaging were carried out. We measured the average ADC value of the renal lesions and normal kidneys. ADC maps from different b values were generated by a statistical package. Results： The ADC values of normal kidneys with three different motion-probing gradients（b=500, 800, 1000 sec/mm^2） were 2.78 ± 0.14 × 10^-3mm^2s^-1, 2.45 ± 0.13 × 10^3mm^2s^-1, 2.13 ± 0.14 × 10^-3mm^2s^-1, respectively. The ADC values of renal cell carcinoma with three different motion-probing gradients（b=500, 800, 1000 sec/mm^2） were 1.63 ± 0.14 × 10^3mm^2s^-1, 1.31 ± 0.18 × 10^3mm^2s^-, 1.07 ± 0.15 × 10^-3mm^2s^-1, respectively. Among the renal cell carcinoma, the ADC value of clear cell type were 1.67 ± 0.09 × 10^3mm^2s^-1, 1.36 ± 0.13 × 10^3mm^2s^-1, 1.15 ± 0.14 × 10^3mm^2s^-1,respectively; the ADC values of granular cell type were 1.59±0.19 × 10^3mm^2s^-1, 1.25 ± 0.22 × 10^3mm^2s^-1, 0.97 ± 0.12 × 10^3mm^2s^-1, respectively. The ADC values of renal angiomyolipoma with three different motion-probing gradients（b=500, 800,1000 sec/mm^2） were 0.88 ± 0.08 × 10^3mm^2s^-1, 0.63 ± 0.07 × 10^3mm^2s^-1, 0.43 ± 0.04 × 10^3mm^2s^-1, respectively. The ADC values of renal cystic lesions with three different motionprobing gradients（b=500, 800, 1000 sec/mm^2） were 3.73 ± 0.18 × 10^3mm^2s^-1, 3.44 ± 0.13 × 10^3mm^2s^-1, 3.09± 0.21 × 10^3mm^2s^-1, respectively. Statistically significant differences exists between the ADC values of normal kidney, renal carcinomas, renal angiomyolipomas and renal cysts when the b value is the same. Among the different cell types of renal carcinomas, the ADC value of granular cell carcinoma is lower than that of clear cell carcinomas. Conclusion： It is of benefit in diagnosing and distinguishing between benign and malignant renal tumors to know the ADC values in diffusion weighted magnetic resonance imaging. Furthermore, these values help to know the internal structure of the tumor and the tumor typel, which is helpful to the treatment and in predicting the patient＇ s prognosis.

Image Quality Stability of Whole-body Diffusion Weighted Imaging

Objective To assess the reproducibility of whole-body diffusion weighted imaging(WB-DWI) technique in healthy volunteers under normal breathing with background body signal suppression.Methods WB-DWI was performed on 32 healthy volunteers twice within two-week period using short TI inversion-recovery diffusion-weighted echo-planar imaging sequence and built-in body coil.The volunteers were scanned across six stations continuously covering the entire body from the head to the feet under normal breathing.The bone apparent diffusion coefficient(ADC) and exponential ADC(eADC) of regions of interest(ROIs) were measured.We analyzed correlation of the results using paired-t-test to assess the reproducibility of the WB-DWI technique.Results We were successful in collecting and analyzing data of 64 WB-DWI images.There was no significant difference in bone ADC and eADC of 824 ROIs between the paired observers and paired scans(P>0.05).Most of the images from all stations were of diagnostic quality.Conclusion The measurements of bone ADC and eADC have good reproducibility.WB-DWI technique under normal breathing with background body signal suppression is adequate.

Prediction of different stages of rectal cancer: Texture analysis based on diffusion-weighted images and apparent diffusion coefficient maps

BACKGROUND It is evident that an accurate evaluation of T and N stage rectal cancer is essential for treatment planning.It has not been extensively investigated whether texture features derived from diffusion-weighted imaging(DWI)images and apparent diffusion coefficient(ADC)maps are associated with the extent of local invasion(pathological stage T1-2 vs T3-4)and nodal involvement(pathological stage N0 vs N1-2)in rectal cancer.AIM To predict different stages of rectal cancer using texture analysis based on DWI images and ADC maps.METHODS One hundred and fifteen patients with pathologically proven rectal cancer,who underwent preoperative magnetic resonance imaging,including DWI,were enrolled,retrospectively.The ADC measurements(ADCmean,ADCmin,ADCmax)as well as texture features,including the gray level co-occurrence matrix parameters,the gray level run-length matrix parameters and wavelet parameters were calculated based on DWI(b=0 and b=1000)images and the ADC maps.Independent sample t-tests or Mann-Whitney U tests were used for statistical analysis.Multivariate logistic regression analysis was conducted to establish the models.The predictive performance was validated by receiver operating characteristic curve analysis.RESULTS Dissimilarity,sum average,information correlation and run-length nonuniformity from DWIb=0 images,gray level nonuniformity,run percentage and run-length nonuniformity from DWIb=1000 images,and dissimilarity and run percentage from ADC maps were found to be independent predictors of local invasion(stage T3-4).The area under the operating characteristic curve of the model reached 0.793 with a sensitivity of 78.57%and a specificity of 74.19%.Sum average,gray level nonuniformity and the horizontal components of symlet transform(SymletH)from DWIb=0 images,sum average,information correlation,long run low gray level emphasis and SymletH from DWIb=1000 images,and ADCmax,ADCmean and information correlation from ADC maps were identified as independent predictors of nodal involvement.The area under the operating characteristic curve of the model reached 0.802 with a sensitivity of 80.77%and a specificity of 68.25%.CONCLUSION Texture features extracted from DWI images and ADC maps are useful clues for predicting pathological T and N stages in rectal cancer.

Correlation of magnetic resonance imaging quantitative parameters and apparent diffusion coefficient value with pathological breast cancer

BACKGROUND China ranks 120th worldwide for the incidence of breast cancer and 163rd for mortality.Early screening,diagnosis,and timely determination of the optimal treatment plan can help ensure clinical efficacy and prognosis.AIM To investigate the relationship between quantitative magnetic resonance imaging parameters,apparent diffusion coefficient value,pathological immunohistochemical status,and patient prognosis.METHODS A total of 108 patients with breast cancer(breast cancer group)and 110 patients with benign breast tumors(benign group)confirmed by pathological examination at our Hospital from September 2013 to August 2016 were selected.All patients had undergone preoperative magnetic resonance imaging(MRI)examinations,and the quantitative parameters of MRI and apparent diffusion coefficient(ADC)values for the two groups were compared.The MRI quantitative parameters and ADC values of patients with different estrogen receptor(ER),progesterone receptor,and human epidermal growth factor receptor-2 expression were statistically analyzed.The relationship between the quantitative parameters of MRI and ADC values and patient recurrence was analyzed using receiver operating curves.RESULTS The measured values of the quantitative parameters of MRI-Ktrans,Kep,and Ve in the breast cancer group were higher than those in the benign group;the ADC value in the breast cancer group was lower than that in the benign group,and the difference was statistically significant(P<0.05).The Ktrans,Ve,and ADC values in patients with ER-positive breast cancer were significantly lower than those in patients with negative ER expression(P<0.05).After 5 years of follow-up,22 patients with breast cancer experienced postoperative recurrence.The Kep,Ve,and ADC values of the recurrence group were significantly lower than those of the non-recurrence group,and the difference was statistically significant(P<0.05).CONCLUSION MRI quantitative parameters and ADC are related to the expression of breast cancer-related immunological receptor factors and have certain clinical value in assessing postoperative recurrence in patients.

Diffusion weighted imaging in the liver

Diffusion weighted magnetic resonance imaging (DWI) is an imaging technique which provides tissue contrast by the measurement of diffusion properties of water molecules within tissues. Diffusion is expressed in an apparent diffusion coefficient (ADC), which reflects the diffusion properties unique to each type of tissue. DWI has been originally used in neuroradiology. More recently, DWI has increasingly been used in addition to conventional unenhanced and enhanced magnetic resonance imaging (MRI) in other parts of the body. The reason for this delay was a number of technical problems inherent to the technique, making DWI very sensitive to artifacts, which had to be overcome. With assessment of ADC values, DWI proved to be helpful in characterization of focal liver lesions. However, DWI should always be used in conjunction to conventional MRI since there is considerable overlap between ADC values of benign and malignant lesions. DWI is useful in the detection of hepatocellular carcinoma in the cirrhotic liver and detection of liver metastases in oncological patients. In addition, DWI is a promising tool in the prediction of tumor responsiveness to chemotherapy and the follow-up of oncological patients after treatment, as DWI may be capable of detecting recurrent disease earlier than conventional imaging.This review focuses on the most common applications of DWI in the liver.

PRELIMINARY APPLICATION OF WHOLE BODY DIFFUSION WEIGHTED IMAGING IN SCREENING METASTASIS

Objective To investigate the feasibility of whole body diffusion weighted imaging (WB-DWI) in screening metastasis. Methods WB-DWI was performed in 24 patients diagnosed with various types of primary tumors. The three-dimensional maximum intensity projection reconstruction and black-and-white flip technique were used to observe metastatic lesions, and the results were compared with those of bone scintigraphy. Results By WB-DWI scanning sequence at b = 800 s/mm2, all the bone lesions found by bone scintigraphy in the cohort were well identified, and other lesions of soft tissue and organs were also well demonstrated. Its screening capability was equivalent with bone scintigraphy in screening metastases in bones (P = 0.062). Conclusion WB-DWI was practicable with the parameter settings attempted in metastases screening.

FEASIBILITY OF DIAGNOSING AND STAGING LIVER FIBROSIS WITH DIFFUSION WEIGHTED IMAGING

Objective To assess the clinical feasibility of diagnosing and staging liver fibrosis by apparent diffusion coefficient (ADC). Methods Totally, 43 patients (mean age 29.3 years) with chronic hepatitis by liver biopsy and 7 healthy controls (mean age 39.9 years) underwent liver diffusion weighted imaging (DWI) with four b values: 0, 200, 500, and 1000 s/mm2 respectively. The liver fibrosis was staged according to Ishak fibrosis stage. The ADC value of liver fibrosis patients and healthy controls was compared. The correlation of ADC value and liver fibrosis staging was analyzed. Result The histological staging showed 8 stage 1 patients, 10 stage 2 patients, 6 stage 3 patients, 9 stage 4 patients, 8 stage 5 patients and 2 stage 6 patients. The mean ADC value of liver fibrosis patients was significantly lower than that of healthy controls except for stage 1 group (P < 0.05). There was a negative correlation between liver fibrosis staging and ADC value (r = -0.697 with b=500 s/mm2, P < 0.01). Receiver operating characteristic (ROC) curve of ADC value of advanced liver fibrosis (Ishak stage F3 and higher) showed that area under curve = 0.913, 0.825, and 0.794 with b = 500, 1000, and 200 s/mm2, respectively (95% confidence interval: 83.6%-99.0%, 70.7%-94.3%, 66.5%- 92.4%; P < 0.05). When b value was 500 s/mm2, the sensitivity (84%) and specificity (80%) of DWI for diagnosis of advanced liver fibrosis were the highest. Conclusion DWI is proved to be a useful clinical tool in the quantitative evaluation of liver fibrosis and in the prediction of the process of liver fibrosis with the recommendable b value (500 s/mm2).

Diffusion weighted imaging for the detection and evaluation of cholesteatoma

Cholesteatoma is a collection of keratinous debris and stratified squamous epithelium.It is trapped in the middle ear and can lead to bony erosion.The disease is treated surgically often followed by a second-look procedure to check for residual tissue or recurrence.Cholesteatoma has specific signal-intensity characteristics on magnetic resonance imaging with very high signal intensity on diffusion weighted imaging(DWI).Various DWI techniques exist:Echo-planar imaging(EPI)-based and non-EPI-based techniques as well as new approaches like multi-shot EPI DWI.This article summarizes all techniques,discusses the significance in detecting cholesteatoma and mentions actual studies.Further recommendations for daily clinical practise are provided.

Magnetic resonance imaging apparent diffusion coefficient before and after neoadjuvant chemotherapy in patients with breast cancer and its correlation with tumor load

Objective:To study the magnetic resonance imaging apparent diffusion coefficient (ADC) before and after neoadjuvant chemotherapy in patients with breast cancer and its correlation with tumor load.Methods: Patients with stage II-III breast cancer who intended to receive radical operation for breast cancer in our hospital between May 2015 and February 2018 were selected and divided into the experimental group who accepted neoadjuvant chemotherapy and the control group who received surgery directly according to the adoption of preoperative neoadjuvant chemotherapy or not in the history data. Experimental group underwent magnetic resonance imaging before and after neoadjuvant chemotherapy to measure the ADC, and control group underwent magnetic resonance imaging before surgery to measure the ADC;the tumor tissues surgically removed from the two groups of patients were collected to measure the expression of oncogenes and invasion genes.Results:ADC value of experimental group after neoadjuvant chemotherapy was higher than that before neoadjuvant chemotherapy, ADC value of experimental group before neoadjuvant chemotherapy was not significantly different from that of control group whereas ADC value after neoadjuvant chemotherapy was significantly higher than that of control group;MCM3, CyclinD1, TC-1,β-catenin, YAP and MMP2 mRNA expression levels in surgically removed tumor tissues of experimental group were significantly lower than those of control group whereas CCN5, ARID1A and PDCD4 mRNA expression levels were significantly higher than those of control group;MCM3, CyclinD1, TC-1,β-catenin, YAP and MMP2 mRNA expression levels in tumor tissues with high ADC value were significantly lower than those in tumor tissues with low ADC value whereas CCN5, ARID1A and PDCD4 mRNA expression levels were significantly higher than those in tumor tissues with low ADC value.Conclusion:The increase of ADC after breast cancer neoadjuvant chemotherapy is related to the activity of cancer cell proliferation and invasion, and can be used to evaluate the changes of tumor load before and after chemotherapy.

FEASIBILITY OF WHOLE BODY DIFFUSION WEIGHTED IMAGING IN DETECTING BONE METASTASIS ON 3.0T MR SCANNER

Objective To evaluate the feasibility of whole body diffusion weighted imaging (DWI) in bone metastasis detection using bone scintigraphy as comparison. Methods Forty-five patients with malignancy history were enrolled in our study. All the patients received the whole body DWI and bone scintigraphy scan within 1 week. The magnetic resonance (MR) examination was performed on 3.0T MR scanner using embedded body coil. The images were reviewed separately by two radiologists and two nuclear medicine physicians, who were blinded to the results of the other imaging modality. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the two techniques for detecting bone metastasis were analyzed. Results A total of 181 metastatic lesions in 77 regions of 34 patients were detected by whole body DWI, and 167 metastatic lesions in 76 regions of 31 patients were identified by bone scintigraphy. The patient-based sensitivity and PPV of whole body DWI and bone scintigraphy were similar (89.5% vs. 81.6%, 97.1% vs. 91.2%), whereas, the patient-based specificity and NPV of whole body DWI were obviously higher than those of bone scintigraphy (85.7% vs. 57.1%, 60.0% vs. 36.4%). Ten regions negative in scintigraphy but positive in whole body DWI, mainly located in spine, pelvis, and femur; nine regions only detected by scintigraphy, mainly located in skull, sternum, clavicle, and scapula. The region-based sensitivity and specificity of whole body DWI were slightly higher than those of bone scintigraphy (89.5% vs. 88.4%, 95.6% vs. 87.6%). Conclusion Whole body DWI reveals excellent concordance with bone scintigraphy regarding detection of bone metastasis, and the two techniques are complementary for each other.

AGE-RELATED CHANGES OF BONE MARROW OF NORMAL ADULT MAN ON DIFFUSION WEIGHTED IMAGING

Objective To investigate the signal intensity and apparent diffusion coefficient (ADC) of bone marrow of normal adult man on diffusion weighted imaging (DWI). Methods Fifteen healthy volunteers and thirty-eight patients with benign prostatic hyperplasia or normal prostate were enrolled in this study, with age range 28-82 years old (mean 55.26 ± 18.05 years). All people were examined with large field DWI on a 3.0T magnetic resonance scanner, which ranges from the top of head to the lower limb. The signal-to-noise ratio (SNR) on the DWI and ADC of lumber vertebra at renal hilum level, left ilium and superior segment of left femur were measured. The measured SNR and ADC value of the above sites were compared by one way analysis of variance and their correlations with age were investigated by Pearson's correlation analysis. Results The SNR of lumber vertebra, left ilium and left femur showed no significant difference (F = 0.271, P = 0.763). The SNR of lumber vertebra (r = 0.309, P = 0.024) and left ilium (r = 0.359, P = 0.008) showed positive correlation with age, while the SNR of left femur showed no correlation with age (r = -0.163, P = 0.283). The ADC of lumber vertebra [(0.617 ± 0.177) ×10-3 mm2/s] was significantly higher than that of left ilium [(0.404 ± 0.112) ×10-3 mm2/s, P < 0.001] and left femur [(0.362 ± 0.092) ×10-3 mm2/s, P < 0.001], while the ADC of left ilium and left femur had no significant difference. The ADC of lumber vertebra, left ilium and left femur showed no correlation with age. Conclusion Understanding of age-related changes of normal adult bone marrow on DWI is very important to differentiate the normal bone marrow and abnormal lesions.

Clinical Value of Whole-body Magnetic Resonance Diffusion Weighted Imaging on Detection of Malignant Metastases

Objective To evaluate the value of whole-body diffusion weighted imaging （WB-DWI） on detection of malignant metastasis. Methods Forty-six patients with malignant tumors underwent WB-DWI examinations between April 2007 and August 2007 in our hospital. Before WB-DWI examination, the primary cancers of all the patients were confirmed by pathology, and the TNM-stage was assessed with conventional magnetic resonance imaging （MRI） or computed tomography （CT）. WB-DWI was performed using short TI inversion recovery echo-planar imaging （STIR-EPI） sequence. Abnormal high signal intensities on WB-DWI were considered as metastases. The results of WB-DWI were compared with other imaging modalities. For the assessment of the diagnostic capability of WB-DWI, WB-DWI were compared with CT for demonstrating mediastinal lymph node metastases and lung metastases, and with conventional MRI for demonstrating metastases in other locations. Results WB-DWI demonstrated 143 focuses, 14 routine imaging. The number of bone metastases depicted of which were diagnosed to be benign lesions in on WB-DWI and routine imaging was 85 and 86; lymph node metastases was 17 and 18; liver metastases was 14 and 14; lung metastases was 4 and 8; and brain metastases was 6 and 8, respectively. WB-DWI failed to detect 12 metastatic lesions including 3 osteoplastic bone metastases, 4 lung metastases, 3 mediastinal lymph node metastases, and 2 brain metastases Four metastatic lesions including 2 deltopectoral lymph nodes and 2 rib metastases were detected with WB-DWI alone, all of which evolved greatly during clinical follow-up for more than 6 months. WB-DWI had higher detection rates for metastatic lesions in liver, bone, and lymph nodes than those in lung and brain （ X^2=30, P〈0.001）. Conclusions WB-DWI could detect most of metastatic lesions that were diagnosed with conventional MRI and CT. The limitations of WB-DWI might be had high false-positive rate and low efficiency in detecting mecliastinal lymph node, brain, and lung metastases.

PRELIMINARY STUDY OF FEASIBILITY OF WHOLE BODY DIFFUSION WEIGHTED IMAGING IN DIAGNOSIS OF METASTASIS OF TUMOR

Objective To evaluate the feasibility of whole body diffusion weighted imaging (DWI) in the diagnosis of metastatic tumor. Methods Fifty-six patients (40 males and 16 females, age ranging from 29 to 84 years with a mean age of 57 years) with a variety of primary tumors were investigated by whole body DWI combined with computed tomography (CT) and/or conventional magnetic resonance imaging (MRI) scans. Twelve patients underwent positron emission tomography. The final diagnosis was made on the basis of CT or high resolution CT result for lung lesion and MRI or CT result for skull, abdomen and other parts. All tumors were classified into four groups by their diameter: below 1.0 cm, 1.0-1.9 cm, 2.0-2.9 cm, and above 3.0 cm. The sensitivity and specificity of whole body DWI in the detection of metastatic tumor were analyzed. Results The sensitivities of whole body DWI for screening metastasis of the four groups were 38%, 75%, 97%, and 100%, respectively. Whole body DWI showed the highest sensitivity and specificity for detecting metastasis of the skeletal system. It was difficult to find metastatic tumor whose diameter was below 1.0 cm, or lymph nodes located in the pelvis with diameter below 2.0 cm. Conclusions Whole body DWI is a promising method in the diagnosis of metastastic tumors. With the perfection of scanning parameter, whole body DWI should be a new effective whole body technique for tumor detection.

DIAGNOSTIC VALUE OF WHOLE BODY DIFFUSION WEIGHTED IMAGING FOR SCREENING PRIMARY TUMORS OF PATIENTS WITH METASTASES

Objective To evaluate the values of whole body diffusion weighted imaging （DWI） in screenmg pnmary unknown tumor in patients with metastases. Methods Totally, 34 patients with metastases of primary unknown tumors were scanned with whole body DWI, and conventional magnetic resonance （MR） imaging was performed if suspected lesions were detected. All the metastases including 27 cases of osseous metastases, 2 brain metastases, 2 liver metastases, 1 pulmonary multiple metastasis, 1 neck metastasis and 1 malignant ascites, were diagnosed by computed tomography, single photon emission computed tomography, or MR imaging. For the proven primary tumors diagnosed by biopsy or pathology of surgical specimens, apparent diffusion coefficient （ADC） values of the primary and metastatic lesions were measured respectively. The sensitivity and specificity of this technique for screening primary tumors were cvaluated. Results We found 24 cases with suspected primary lesions, in which 23 lesions were proved to be primary tumors, and 1 was proved to be benign lesion. And no definite primary lesion was found in 10 cases on whole body DWI, but in which 1 case was diagnosed with primary tumor by biopsy later, and the other 9 cases remained unknown within follow-up of over halfa year. The difference was not significant in ADC values between primary and metastatic lesions （P〉0.05）. The sensitivity and specificity of whole body DWI for searching primary tumors was 95.8% and 90.0%, respectively. Conclusion Combined with conventional MR scanning, whole body DWI can help to search primary lesions of patients with metastases.

NORMAL APPEARANCE OF LARGE FIELD DIFFUSION WEIGHTED IMAGING ON 3.0T MRI

Objective To evaluate the normal appearance of large field diffusion weighted imaging (DWI) on 3.0T magnetic resonance imaging (MRI). Methods Twenty healthy volunteers and thirty patients with benign prostate hyperplasia were included in this study. All patients were examined with large field DWI on 3.0T MRI. Normal tissue appearance was analyzed and apparent diffusion coefficient (ADC) of normal tissue with high signal intensity was measured. The ADC values of bilateral symmetrical tissue were also compared. The ADC values of intervertebral disks of healthy people younger than 50 years and exceeding 50 years were compared. Results Salivary gland, spleen, kidney, gallbladder, bladder, prostate, seminal vesicle, testis, intervertebral disk, liquid in articular cavity and lymph node showed high signal intensity on large field DWI, while lung, liver and bone showed hypo-signal intensity. The mean ADC values of partial hyperintensity tissue were as followed: parotid gland (1.088 ± 0.114) ×10-3 mm2/s, submaxillary gland (1.309 ± 0.189) ×10-3 mm2/s, kidney (1.909 ± 0.143) ×10-3 mm2/s, seminal vesicle (1.669 ± 0.168) ×10-3 mm2/s, testis (1.028 ± 0.075) ×10-3 mm2/s, spleen (0.963 ± 0.108) ×10-3 mm2/s, bladder (2.898 ± 0.267) ×10-3 mm2/s, prostate (1.448 ± 0.132) ×10-3 mm2/s, intervertebral disks (1.360 ± 0.140) ×10-3 mm2/s. No statistical significance was found between the ADC values of bilateral symmetrical tissues. The difference of ADC values of intervertebral disks of healthy people younger than 50 years [(1.372 ± 0.142) ×10-3 mm2/s] and exceeding 50 years [(1.344 ± 0.134) ×10-3 mm2/s] showed statistical significance (P = 0.040). Conclusion Understanding the high signal intensity of normal tissue on large field DWI may help to differentiate the normal tissues and abnormal ones.

Magnetic resonance-based total liver volume and magnetic resonance-diffusion weighted imaging for staging liver fibrosis in mini-pigs

AIM:To determine whether and how magnetic resonance imaging(MRI)-based total liver volume(TLV) and diffusion weighted imaging(DWI) could predict liver fibrosis.METHODS:Sixteen experimental mature mini-pigs(6 males,10 females),weighing between 20.0 and 24.0 kg were prospectively used to model liver fibrosis induced by intraperitoneal injection of 40% CCl4 dissolved in fat emulsion twice a week for 16 wk,and by feeding 40% CCl4 mixed with maize flour twice daily for the subsequent 5 wk.All the survival animals underwent percutaneous liver biopsy and DWI using b = 300,500 and 800 s/mm2 followed by abdominal gadolinium-enhanced MRI at the 0,5th,9th,16th and 21st weekend after beginning of the modeling.TLV was obtained on enhanced MRI,and apparent diffusion coefficient(ADC) was obtained on DWI.Hepatic tissue specimens were stained with hematoxylin and Masson' s trichrome staining for staging liver fibrosis.Pathological specimens were scored using the human METAVIR classification system.Statistical analyses were performed to determine whether and how the TLV and ADC could be used to predict the stage of liver fibrosis.RESULTS:TLV increased from stage 0 to 2 and decreased from stage 3(r = 0.211;P < 0.001).There was a difference in TLV between stage 0-1 and 2-4(P = 0.03) whereas no difference between stage 0-2 and 3-4(P = 0.71).TLV could predict stage ≥ 2 [area under receiver operating characteristic curve(AUC) = 0.682].There was a decrease in ADC values with increasing stage of fibrosis for b = 300,500 and 800 s/mm2(r =-0.418,-0.535 and-0.622,respectively;all P < 0.001).Differences were found between stage 0-1 and 2-4 in ADC values for b = 300,500 and 800 s/mm2,and between stage 0-2 and 3-4 for b = 500 or 800 s/mm2(all P < 0.05).For predicting stage ≥ 2 and ≥ 3,AUC was 0.803 and 0.847 for b = 500 s/mm2,and 0.848 and 0.887 for b = 800 s/mm2,respectively.CONCLUSION:ADC for b = 500 or 800 s/mm2 could be better than TLV and ADC for b = 300 s/mm2 to pre-dict fibrosis stage ≥ 2 or ≥ 3.

1H magnetic resonance spectroscopy and diffusion weighted imaging findings of medulloblastoma in 3.0T MRI A retrospective analysis of 17 cases

1H magnetic resonance spectroscopy and diffusion weighted imaging features of the cerebellar vermis in 17 medulloblastoma patients were retrospectively analyzed, and 17 healthy volunteers were selected as controls. 1H magnetic resonance spectroscopy showed that in all 17 medulloblastoma patients, N-acetyl aspartate and creatine peaks were significantly decreased, the choline peak was significantly increased, and there was evidence of a myo-inositol peak. Further, 11 patients showed a low taurine peak at 3.4 ppm, five patients showed a lipid peak at 0.9-1.3 ppm, and three patients showed a negative lactic acid peak at 1.33 ppm. Compared with the control group, the ratios of N-acetyl aspartate/choline and N-acetyl aspartate/creatine were significantly decreased, and the ratio of choline/creatine was increased, in medulloblastoma patients. Diffusion weighted imaging displayed hyperintensity and decreased apparent diffusion coefficient in medulloblastoma patients. These findings indicate that 1H magnetic resonance spectroscopy and diffusion weighted imaging are useful for qualitative diagnosis of medulloblastoma.

EXPERIMENTAL STUDY OF INFLAMMATORY AND METASTATIC LYMPH NODES WITH DIFFUSION WEIGHTED IMAGING ON ANIMAL MODEL: COMPARISON WITH CONVENTIONAL METHODS

Objective To investigate the feasibility of magnetic resonance （MR） diffusion weighted imaging （DWI） in discriminating inflammatory from VX2 carcinoma metastatic lymph nodes in rabbit model. Methods Twenty New Zealand white rabbits were randomly divided into 2 groups. Complete Freund＇s adjuvant was injected into the bilateral dorsal footpads to set up ipsilateral lymphadenitis model （n = 10）, and the other 10 rabbits received a subcutaneous implantation of VX2 tumor cell suspension （1.5×10^7 cells/mL） in both thighs to set up metastatic lymph node model. MR imaging scan covering the popliteal fossa and lilac fossa including short time inversion recovery echo-planar imaging DWI （STIR-EPI-DWI）, Tl-weighted imaging （T1WI） and T2-weighted imaging （T2WI） was performed 2 weeks after injection. T2WI signal intensity （SI）, DWI SI, long/short axial ratio （LSR） and apparent diffusion coefficient （ADC） values of the lymph nodes were evaluated in all cases. Right after MR imaging scan, popliteal and iliac fossa lymph nodes were collected for hematoxylin-eosin staining. Results Totally 33 lymph nodes larger than 5 turn, including 22 inflammatory and 11 metastatic ones, were successfully isolated and taken into pathological analysis. LSR showed no significant difference between the inflammatory and malignant lymph nodes （P 〉 0.05）. Both benign and malignant lymph nodes appeared iso-intense on TlWI and hyperintense on both T2WI and DWI images with an even lower TlWI and higher T2WI SI core at the hilum. Both T2WI and DWI SI showed no significant difference between two pathological groups （P 〉 0.01） in popliteal fossa. The mean ADC value of inflammatory nodes [（1.199±0.281） ×10^-3 mm^2/s] was significantly higher than that of metastatic nodes [（0.858 ± 0.090） ×10^-3 mm^2/s, P 〈 0.01]. On ADC map, a high ADC value central area could be seen in most of the lymph nodes no matter benign or malignant. ADC value gave out the largest area under curve （AUCADC = 0.955） compared with other three indexes （AUCLsR = 0.488; AUCT2WI SI = 0.727; AUCDDWISI = 0.822） and gave the best sensitivity and specificity in lymph node differential diagnosis compared with the other three indexes. Conclusions High quality DWI image can be obtained using STIR-EPI-DWI sequence in rabbit model. DWI is a new promising technique for differentiating inflammatory from metastatic lymph nodes. Compared with routine MR sequence, DWI could provide more useful physiological and functional information for diagnosis.

Value of whole body diffusion weighted imaging in diagnostic and therapeutic evaluation of malignant lymphoma

Objective:The aim was to evaluate the role of whole body diffusion weighted imaging(WB-DWI) of magnetic resonance in the diagnosis and efficacy evaluation of malignant lymphoma.Methods:The clinical manifestation of whole body diffusion weighted imaging of 47 patients with malignant lymphoma being pathologically proved were carried on by retrospective analysis and to compare with 10 healthy volunteers.There were 8 cases of Hodgkin's lymphoma(HD) patients,of which WB-DWI examination of 5 cases were carried out before and after treatment and 3 cases were done after treatment.There were 39 cases of non-Hodgkin's lymphoma(NHL) patients,of which WB-DWI examination in 19 cases were acted before treatment,11 cases were done before and after treatment and 9 cases done after treatment.In apparent diffusion coefficient(ADC) diagram the ADC values of lymph nodes in patients with malignant lymphoma and healthy volunteers were measured respectively,among 16 patients the ADC values of parts of lymph node being consistent with the initial inspection were determined again and compared the values before and after,and compared with healthy volunteers.Results:Whole body magnetic resonance diffusion weighted imaging(MR-DWI) showed more sensitive to lymphoma,and 372 lymph nodes greater than 1 cm were detected with MR-DWI.Before treatment,mean ADC value of 35 patients with malignant lymphoma was(0.86 ± 0.21) × 10-3 mm2/s,of which an average ADC values of 28 cases after treatment was(1.22 ± 0.31) × 10-3 mm2/s,before and after treatment difference of the average ADC values of patients was statistically significant(P < 0.05);the average ADC value of cervical lymph nodes of 10 healthy volunteers(1.29 ± 0.12) × 10-3 mm2/s and of 30 patients with malignant lymphoma before treatment was statistically significant(P < 0.05),and to compare with 28 patients after treatment difference of the ADC values was not statistically significant(P > 0.05).Conclusion:WB-DWI and ADC values being measured in the clinical diagnosis of malignant lymphoma,staging and evaluation of efficacy of monitoring is a fast and effective technology,with some clinical value.