Comparison of the diagnostic performances of diffusion parameters in diffusion weighted imaging and diffusion tensor imaging of breast lesions

Purpose

To evaluate the diagnostic efficiency of the diffusion parameters measured by conventional diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) for discrimination of malignant breast lesions from benign lesions and the normal breast.

Materials and methods

The study included 52 women with 55 breast lesions (30 malignant, 25 benign). DTI and DWI were performed complementary to dynamic contrast MRI at 3T. Apparent diffusion coefficient (ADC) of DWI, mean diffusivity (MD) and fractional anisotropy (FA) values of DTI were measured for lesions and contralateral breast parenchyma in each patient. We used b factors of 0, 50, 850, 1000 and 1500 s/mm² for DWI and b 0 and 1000 s/mm² for DTI. ADC, MD and FA values were compared between malignant and benign lesions, and the normal parenchyma by univariate and multivariate analyses.

Results

Diffusion parameters showed no difference according to menopausal status in the normal breast. ADC and MD values of the malignant lesions were significantly lower than benign lesions and normal parenchyma (p = 0.001). The FA showed no statistical significance. With the cut-off values of ≤1.23 × 10⁻³ mm²/s (b 0–1000 s/mm²) and ≤1.12 × 10⁻³ mm²/s (b 0–1500 s/mm²), ADC showed 92.85% and 96.15% sensitivity; 72.22% and 73.52% PPV, respectively. With a cut-off value of ≤1.27 × 10⁻³ mm²/s (b 1000 s/mm²), MD was 100% sensitive with a PPV of 65.90%. Comparing the diagnostic performance of the parameters in DTI with DWI, we obtained similar efficiency of ADC with b values of 0,1000 and 0,1500 s/mm² and MD with a b value of 0, 1000 s/mm² (AUC = 0.82 ± 0.07).

Conclusion

ADC of DWI and MD of DTI values provide significant discriminative factors for benign and malignant breast lesions. FA measurement was not discriminative. Supported with clinical and dynamic contrast MRI findings, DWI and DTI findings provide significant contribution to the final radiologic decision.     

Comparison of monopolar and bipolar diffusion weighted imaging sequences for detection of small hepatic metastases

Objective

To compare monopolar (MP) and bipolar (BP) diffusion weighted imaging (DWI) in detecting small liver metastases.

Materials and methods

Eighty-eight patients underwent 3-T MRI. The signal-to-noise ratios (SNR) of the liver parenchyma and lesions, the lesion-to-liver contrast-to-noise ratios (CNR), and the detection sensitivities were compared. The lesion distortion was scored (LDS) from 4 (no distortion) to 1 (excessive distortion), dichotomised as no-distortion and distortion, and the association between detected lesions for each reader in the MP or BP DWI group and the dichotomised lesion distortion degree was assessed.

Result

Forty-six hepatic metastases were confirmed. The CNR with BP images showed significantly higher values than with MP (P = 0.017). The detection sensitivities of the three readers were higher in the BP sequence than in MP, and one reader detected significantly more hepatic lesions with BP images (P = 0.04). LDS was significantly improved with BP sequence (P = 0.002). In the no-distortion group, excluding the MP DWI assessments of one reader, detection sensitivities were significantly higher than in the distortion group (P < 0.001 and P = 0.002, respectively).

Conclusion

Reduced lesion distortion improves the detection of small liver metastases, and BP is more sensitive in detecting small liver metastases than MP DWI.     

The role of MR diffusion in differentiation of malignant and benign hepatic focal lesions

Aim

To determine if focal liver masses could be differentiated as benign or malignant by DWI and ADC maps.

Methods and materials

Sixty focal liver lesions were scanned using 1.5 T MRI. DWI was performed with b 0, b 500 and b 1000 gradients with ADC measurements. Comparison of mean ADC values between each benign and malignant lesion was done. Reference standard of diagnosis was obtained by correlating DWI with histopathologic findings and imaging follow-up. The accuracies of DWI and ADC values were assessed with the Student’s t test, and cut-off values were determined with receiver operating characteristic curve analysis.

Results

When ADC value of 1.0 × 10⁻³ mm²/s was used as a threshold value for differentiation of malignant tumors from benign lesions, sensitivity was 90.3%, specificity 78.57% and accuracy 86.7%. The best result was obtained with the use of ADC cut off value (at b 500) of 1.5 × 10⁻³ mm²/s and ADC cut off value (at b 1000) of 1.0 × 10⁻³ mm²/s, with 90.3% sensitivity, 92.86% specificity, 91.1% accuracy, 96.6% positive predictive value and 81.3% negative predictive value.

Conclusion

DWI and ADC map is a useful tool in differential diagnosis of malignant from benign liver lesions.     

Diagnostic performance of conventional diffusion weighted imaging and diffusion tensor imaging for the liver fibrosis and inflammation

Objective

To evaluate the diagnostic accuracy of liver apparent diffusion coefficient (ADC) measured with conventional diffusion-weighted imaging (CDI) and diffusion tensor imaging (DTI) for the diagnosis of liver fibrosis and inflammation.

Materials and methods

Thirty-seven patients with histologic diagnosis of chronic viral hepatitis and 34 healthy volunteers were included in this prospective study. All patients and healthy volunteers were examined by 3 T MRI. CDI and DTI were performed using a breath-hold single-shot echo-planar spin echo sequence with b factors of 0 and 1000 s/mm². ADCs were obtained with CDI and DTI. Histopathologically, fibrosis of the liver parenchyma was classified with the use of a 5-point scale (0–4) and inflammation was classified with use of a 4-point scale (0–3) in accordance with the METAVIR score. Quantitatively, signal intensity and the ADCs of the liver parenchyma were compared between patients stratified by fibrosis stage and inflammation grade.

Results

With a b factor of 1000 s/mm², the signal intensity of the cirrhotic livers was significantly higher than those of the normal volunteers. In addition, ADCs reconstructed from CDI and DTI of the patients were significantly lower than those of the normal volunteers. Liver ADC values inversely correlated with fibrosis and inflammation but there was only statistically significant for inflammatory grading. CDI performed better than DTI for the diagnosis of fibrosis and inflammation.

Conclusion

ADC values measured with CDI and DTI may help in the detection of liver fibrosis. They may also give contributory to the inflammatory grading, particularly in distinguishing high from low grade.     

Characterization of head and neck lesions with diffusion-weighted MR imaging and the apparent diffusion coefficient values

Purpose

The aim of this study was to determine the role of diffusion-weighted MR imaging (DWI) and the apparent diffusion coefficient (ADC) in characterization of head and neck lesions.

Patients and methods

MR imaging including diffusion-weighted sequences was performed on 43 patients presented with head and neck lesions. Images were obtained with a diffusion-weighted factor (b factor) of 100, 500, and 1000 s/mm². ADC maps were reconstructed, and the ADC value of the lesions was calculated.

Results

The mean ADC value of malignant tumors was (1.02 ± 0.22) × 10⁻³ mm²/s (n = 31). The mean ADC value of benign tumors was (1.62 ± 0.27) × 10⁻³ mm²/s (n = 12). The mean ADC of lymphomas was significantly lower than that of carcinomas. The difference in the ADC value between the malignant tumors and benign lesions was statistically significant (p < 0.001). Selection of (1.2) × 10⁻³ mm²/s as a threshold value of ADC for differentiating benign from malignant tumors yielded the best result, with an accuracy of 94%, sensitivity of 95%, specificity of 92%, positive predictive value of 92% and negative predictive value of 94%.

Conclusion

DWI and the ADC measurement are promising, non-invasive imaging approach that can be used for characterization of head and neck lesions. It can help differentiate malignant tumors from benign lesions.     

Role of dynamic contrast-enhanced and diffusion weighted MRI in evaluation of necrosis of hepatocellular carcinoma after chemoembolization

Purpose

The purpose of this study is to evaluate the role of dynamic contrast enhanced and diffusion weighted MRI in the assessment of response and necrosis in the treatment of hepatocelluar carcinoma after transcatheter arterial chemoembolization (TACE).

Subjects and methods

Precontrast T1, T2, STIR, Dynamic contrast enhanced and respiratory triggered diffusion weighted MR images (b factor, 500, 1000 s/mm² obtained in 50 patients with hepatocellular carcinoma who underwent transarterial hepatic chemoembolization). Diffusion-weighted MR images, gadolinium-enhanced MR images after TACE were assigned confidence levels for postoperative HCC recurrence. The sensitivity, specificity, PPV, NPV and overall agreement were calculated for both the dynamic and the DWI images. Apparent diffusion coefficients (ADCs) were calculated searching for a cut off value using the ROC curve.

Results

Dynamic MRI had a sensitivity of 90.5%, a specificity of 96.6%, a positive predictive value of 95%, a negative predictive value of 93.3% and an overall agreement of 94% compared to 100%, 65.5%, 67.7%, 100% and 80% respectively of diffusion weighted imaging.The difference between the malignant and benign groups’ ADC variables was statistically significant P value 0.006.The ROC curve showed that the area under the curve is C = 0.728 with SE = 0.075 and 95% CI from 0.582 to 0.874.

Conclusion

Diffusion weighted MR imaging has lower specificity compared to dynamic MRI with increased false positives. We suggest that increase is due to intralesional hemorrhage or liquefactive necrosis causing diffusion restriction. Diffusion weighted imaging may act as a supplementary sequence to compensate the dynamic MRI in patients who could not hold their breath adequately.     

Lymphomas and glioblastomas: differences in the apparent diffusion coefficient evaluated with high b-value diffusion-weighted magnetic resonance imaging at 3T

Background and purpose

As the usefulness of the apparent diffusion coefficient (ADC) obtained from diffusion-weighted images (DWI) for the differential diagnosis between glioblastoma and primary central nervous system lymphoma is controversial, we assessed whether high b-value DWI at b 4000 s/mm² could discriminate between glioblastoma and lymphoma. We also compared the power of high- and standard b-value (b-4000, b-1000) imaging on a 3-Tesla (3 T) magnetic resonance (MR) instrument.

Materials and methods

This study was approved by our Institutional Review Board. We acquired DWI at 3 T with b = 1000 and b = 4000 s/mm² in 10 patients with lymphoma and 14 patients with glioblastoma. The ADC was measured by placing multiple regions of interest (ROI) on ADC maps of the site of enhanced lesions on contrast-enhanced T1-weighted MR images. We avoided hemorrhagic and cystic lesions by using T1-, T2-, FLAIR-, and T2* MR images. The ADC values of each tumor were determined preoperatively from several ROI and expressed as the minimum-, mean-, and maximum ADC value (ADC_MIN, ADC_MEAN, ADC_MAX). We evaluated the relationship between ADCs and histological information including tumor cellularity.

Results

All ADC values were statistically associated with tumor cellularity. ADC_MIN at b-4000 was associated with tumor cellularity more significantly than ADC_MIN at b-1000. All ADC values were lower for lymphoma than glioblastoma and the statistical difference was larger at b = 4000- than b = 1000 s/mm². According to the results of discriminant analysis, the log likelihood was greatest for ADC_MIN at b = 4000. At a cut-off value of ADC_MIN = 0.500 × 10⁻³ mm²/s at b-4000 it was possible to differentiate between lymphoma and glioblastoma (sensitivity 90.9%, specificity 91.7%).

Conclusions

Calculating the ADC value is useful for distinguishing lymphoma from glioblastoma. The lowest degree of overlapping and a better inverse correspondence with tumor cellularity were obtained with ADC_MIN at b-4000 s/mm² at 3 T MRI.     

Comparison of PET-CT and magnetic resonance diffusion weighted imaging with body suppression (DWIBS) for initial staging of malignant lymphomas

Objective

To evaluate the clinical impact of diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) in staging of malignant lymphoma.

Methods

Twenty-three patients with proven malignant lymphomas were prospectively enrolled. DWIBS (b = 0, 1000 s/mm²) examinations and PET-CT were performed respectively on an Intera 1.5 T unit and a Gyroscan PET-CT scan (Philips Medical system, Best, the Netherland). The criteria for positive node involvement were a size over 10 mm or an apparent diffusion coefficient (ADC) value under 0.75 10⁻³ mm²/s for nodes under 10 mm. For extranodal analysis, a high or heterogeneous signal on DWIBS was considered as positive. In cases of discordance, the reference standard for each region or organ was established at 6 months after the diagnosis according to all available clinical, biological information, as well as histological evidence or follow-up to prove or disprove the presence of disease.

Results

DWIBS and PET-CT results were congruent in 333 node regions on the 345 areas analyzed, with excellent agreement (κ = 0.97, P < 0.0001). From 433 organs analyzed (one patient had splenectomy) extranodal disease was detected in 22 organs on DWIBS. The two imaging techniques agreed on 430 organs (κ = 0.99, P < 0.0001). Finally, Ann Arbor stages based on DWIBS and those of PET/CT were in agreement for 23 patients.

Conclusions

For malignant lymphoma in a pre-therapeutic context, agreement between diffusion-weighted whole-body imaging and PET/CT is high for Ann Arbor staging.     

Comparison of computed tomographic urography,magnetic resonance urography and the combination of diffusion weighted imaging in diagnosis of upper urinary tract cancer

Purpose

To evaluate the performance of computed tomographic urography (CTU), static-fluid magnetic resonance urography (static-fluid MRU) and combinations of CTU, static-fluid MRU and diffusion weighted imaging (DWI) in the diagnosis of upper urinary tract cancer.

Material and Methods

Between January 2010 and June 2011, patients with suspected UUT cancer underwent CTU, static-fluid MRU and DWI (b = 1000 s/mm ²) within a 1-week period. The diagnostic performances of CTU, static-fluid MRU and combinations of CTU, static-fluid MRU and DWI for upper urinary tract cancer were prospectively evaluated. The ureteroscopic and histopathologic findings were compared with the imaging findings.

Results

Compared to static-fluid MRU alone (sensitivity: 76/75%, reader 1/reader 2), combining DWI with MRI can increase the sensitivity (sensitivity: 84/84%, p = 0.031/p = 0.016) of upper urinary tract cancer diagnosis. CTU had greater sensitivity (95/94%) and accuracy (92/91%) than both static-fluid MRU (sensitivity: p < 0.001/p < 0.001 and accuracy: 83/81%, p = 0.001/p < 0.001) and static-fluid MRU with DWI (sensitivity: p = 0.023/p = 0.039 and accuracy: 87/85%, p = 0.042/p = 0.049) for the diagnosis of upper urinary tract cancers. Compared with CTU alone, CTU with DWI did not significantly increase sensitivity, specificity or accuracy. However, the diagnostic confidence was improved when the combined technique was used (p = 0.031/p = 0.024). Moreover, there was no significant change in sensitivity, specificity, accuracy or diagnostic confidence when static-fluid MRU was used in combination with CTU and DWI.

Conclusion

Although there is a potential role for static-fluid MRU and static-fluid MRU with DWI in urinary tract imaging, CTU is still the better choice for the diagnosis of upper urinary tract cancer. Combining DWI with CTU can help improve confidence in upper urinary tract cancer diagnoses.     

The added value of diffusion-weighted MR imaging to MR cholangiopancreatography in differentiating malignant from benign extrahepatic biliary strictures

Purpose

To investigate the added value of diffusion-weighted imaging (DWI) to magnetic resonance cholangiopancreatography (MRCP) in differentiating benign from malignant extrahepatic biliary strictures.

Methods

Magnetic resonance examination including, T2-weighted imaging, MRCP and DWI using different b-values (0,500,800 s/mm²) were performed in 38 patients with suspicious extrahepatic biliary strictures. Apparent diffusion coefficient (ADC) value was calculated. The signal intensity of the lesions on DWI using b = 500 and 800 s/mm² was examined. Analysis of the DWI and MRCP images for the cause of the extrahepatic biliary stricutre was performed. Patients were further confirmed by histopathological diagnosis and follow up. Sensitivity, specificity, accuracy, positive predictive and negative predictive values were calculated for both the MRCP images and DWI.

Results

Of the 38 cases, 23 cases had malignant extrahepatic biliary strictures and 15 had benign strictures. DWI detected 21 out of the 23 malignant biliary strictures and 14 out of 15 benign biliary strictures. Malignant strictures more frequently appeared hyperintense than benign strictures on DWI using b-values of 500 and 800 s/mm². There was a significant difference in sensitivity (91.3% vs. 73%), specificity (93.3% vs. 64.7%), accuracy (92.1% vs. 73.6%), positive predictive value (95.4% vs. 81%), and negative predictive value (87.5% vs. 64.7%) between DWI and MRCP in differentiating biliary strictures.

Conclusion

Combined evaluation using DWI added to MRCP improves the differentiation of malignant from benign extrahepatic biliary strictures.     

Comparison of peritoneal tumor imaging using conventional MR imaging and diffusion-weighted MR imaging with different b values

Purpose

The aim of this study was to evaluate the utility of DW MRI with two different b values in identifying peritoneal tumors in oncology patients.

Materials and methods

Nineteen patients with known malignancy underwent abdominal and pelvic MRI before surgery. MRI included free-breathing DWI with b values of 400 and 800 s/mm², T1-weighted fat-suppressed spoiled gradient-echo, T2-weighted fat-saturated turbo spin-echo, and 5-min delayed gadolinium-enhanced imaging. Two observers reviewed images for peritoneal tumors at ten anatomic sites within consensus. The results of laparatomy and histopathological evaluation were compared with MRI results. Sensitivity, specificity, and accuracy of identifying peritoneal metastases were calculated for conventional MRI, combined DWI with a b value of 400 s/mm² and conventional MRI, and combined DWI with a b value of 800 s/mm² and conventional MRI by consensus of two observers.

Results

One-hundred and twenty-five peritoneal metastasis sites were confirmed by surgical and histopathological findings. Conventional MRI alone identified 72 peritoneal metastases (sensitivity, 0.58; specificity, 0.87; accuracy, 0.67). Combined DWI with a b value of 400 s/mm² and conventional MRI revealed 106 peritoneal metastases (sensitivity, 0.85; specificity, 0.88; accuracy, 0.85). Finally, combined DWI with a b value of 800 s/mm² and conventional MRI revealed 103 peritoneal metastases (sensitivity, 0.83; specificity, 0.94; accuracy, 0.86).

Conclusion

DWI with a high b value provides complementary information that can improve the detection of peritoneal tumors when combined with conventional MRI. We recommend combined MRI and DWI with a high b value for increasing the sensitivity and accuracy of the preoperative detection of peritoneal tumors.     

Apparent diffusion coefficient of diffusion weighted MRI in endometrial carcinoma-Relationship with local invasiveness

Objective

To evaluate the relationship between apparent diffusion coefficient (ADC) value and the local invasiveness of endometrial carcinoma.

Methods and materials

The MR imaging of seventy-three patients with endometrial carcinoma proved by post-operative pathology and sixty-four patients with healthy uteri were retrospectively reviewed. All MR examinations included axial T2WI and T1WI, sagittal T2WI and diffusion-weighted sequences (b = 0 and b = 1000 s/mm²). Tumor size, mean ADC value (ADCm) and quartile ADC (ADCq) were acquired on post-processing workstation using voxel-analysis software. Differences between the ADC values among three layers of normal uterine body and endometrial carcinomas were compared by ANOVA test. Groups were divided according to pathologic type, histologic grade, depth of myometrial infiltration, presence of cervical invasion and lymphovascular space invasion, and lymph node metastasis. Tumor size and ADC values were compared and analyzed.

Results

ADC values were different in three zones of uterine body (P < 0.001), with the lowest in junctional zone [(1.126 ± 0.190) × 10⁻³ mm²/s] and highest in outer myometrium [(1.496 ± 0.196) × 10⁻³ mm²/s]. Mean ADC value of endometrial carcinomas [(1.011 ± 0.121) × 10⁻³ mm²/s] was lower than the normal uterine body. Quartile ADC and tumor size were greater in groups with more invasive pathologic factors (P < 0.05). Deep myometrial infiltration, cervical invasion, lymphovascular space invasion and lymph node metastasis were more common as quartile ADC values and tumor sizes increased.

Conclusion

Mean ADC value was lower in endometrial carcinoma was lower than the normal uterus. Quartile ADC, representing the intra-tumor heterogeneity of water movement, had a profound relationship with invasiveness of endometrial carcinomas, while mean ADC value did not. ADC values may serve as a quantitative indicator to complement routine sequences.     

Diffusion weighted magnetic resonance imaging of kidneys in children with vesicoureteral reflux

Purpose

The apparent diffusion coefficient (ADC) which obtain from diffusion-weighted magnetic resonance imaging (DWI), is a quantitative parameter representing the renal function and parenchymal damage in some renal disorders. The primary aim of this study was to investigate whether renal tissue alterations associated with vesicoureteral reflux (VUR) can be displayed by DWI. The secondary aim was to assess how ADC values change with age in kidneys with and without VUR.

Materials and methods

This prospective study included 46 patients (8 boys, 38 girls; mean age 7.3 ± 4.2; range 1–15 years) with VUR and 54 control subjects (21 boys, 33 girls; mean age 7.7 ± 5.2; range 1–17 years). All subjects underwent DWI of the kidneys using b value of 600 s/mm² in addition to MR urography. The ADC values of 71 kidneys with VUR were compared with those of 81 kidneys without VUR.

Results

The mean ADC values were (1.93 ± 0.36) × 10⁻³ mm²/s, (1.97 ± 0.24) × 10⁻³ mm²/s, (1.83 ± 0.37) × 10⁻³ mm²/s, (1.98 ± 0.20) × 10⁻³ mm²/s and (2.08 ± 0.42) × 10⁻³ mm²/s in normal kidneys, and in those with grade 1, grade 2, grade 3 and grade 4 VUR, respectively. There was no significant difference in ADC values between kidneys with and without VUR. There was a significant positive correlation between the age and ADC values both in kidneys with and without VUR (r = 0.79, p < 0.001 and r = 0.82; p < 0.001, respectively).

Conclusion

DWI does not reveal probable parenchymal alterations in reflux nephropathy. ADC values increase with age during childhood not only in normal kidneys but also in kidneys with VUR.     

Gadoxetic acid-enhanced 3.0 T MRI for the evaluation of hepatic metastasis from colorectal cancer: Metastasis is not always seen as a “defect” on the hepatobiliary phase

Purpose

To determine specific imaging features of hepatic metastasis from colorectal cancer, focusing on the hepatobiliary phase (HBP) of gadoxetic acid-enhanced MRI.

Materials and methods

Over a 2-year period, 79 hepatic metastatic lesions were identified from 32 patients (22 men and 10 women) who proven colorectal cancer and underwent gadoxetic acid-enhanced 3.0 T MRI. Hepatic metastases were proven pathologically in 16 patients: by surgical liver resection (n = 14) and by US-guided biopsy (n = 2). The remaining 16 patients were considered to have hepatic metastasis based on imaging studies and clinical information. Two radiologists evaluated the imaging features of each MRI sequence, including high resolution T2WI, dynamic contrast enhancement study with hepatobiliary phase, and diffusion weighted image. We also compared SI of the lesions on T2WI and HBP.

Results

T2WI showed homogeneous high SI (n = 25; 31.7%), target appearance (n = 3; 3.8%), reversed target appearance (n = 2; 2.6%), and heterogeneously high SI (n = 49; 62%). On HBP, homogeneous defect were seen in 22 lesions (27.9%), target appearance in five lesions (6.4%), reversed target appearance in two lesions (2.5%), and heterogeneous defect in 50 lesions (63.3%); including reticular (70%), partially globular (26%), and diffuse GGO-like (4%) patterns. According to the imaging features on HBP, the homogeneous defect and heterogeneous defect groups had a mean ADC value of 0.99 × 10⁻³ and 1.07 × 10⁻³ mm²/s, respectively, without statistically significant difference.

Conclusion

Hepatic metastasis from colorectal cancer usually showed as a heterogeneous defect on HBP and a heterogeneous high SI on T2WI. The generally accepted “true defect” was not a common finding in hepatic metastasis from colorectal cancer.     

Effect of gadolinium chelate contrast agents on diffusion weighted MR imaging of the liver, spleen, pancreas and kidney at 3 T

Purpose

To retrospectively test the null hypotheses that the qualitative appearance of DWI and the signal intensity values in DWI and corresponding ADC values of the liver, spleen, pancreas and kidneys are identical before and after the administration of gadolinium.

Materials and methods

Following IRB approval, DWI was acquired in 50 patients (25 male; mean age 54.9 years) prior to and after contrast administration, using single-shot echo planar imaging with b-values of 50 s/mm² and 800 s/mm² at 3 T. Binomial analysis was used to determine which image set was more significantly preferred in conveying the diffusion information. Pre- and post-gadolinium DWI and ADC values of corresponding regions of each organ were analyzed using standardized signal intensity measurements.

Results

Pre-contrast DWI images of the liver, spleen, and pancreas were preferred 52%, 49%, and 58%, respectively, with none of the differences being statistically significant. DWI of the kidneys was preferred on pre-contrast images in 83% (p < 0.001). In the liver and spleen, contrast caused a significant increase in the post-contrast DWI signal intensity values at b = 50 (p < 0.02) and b = 800 (p < 0.05) but had no statistically significant effect on the ADC value (p > 0.40). Pancreatic DWI signal intensity and ADC values pre- and post-contrast were also not significantly different (p = 0.489). In the renal parenchyma, significant decrease in the values of DWI at b = 50 (p < 0.01) and b = 800 (p < 0.01) as well as ADC (p < 0.02) was demonstrated following gadolinium administration.

Conclusion

Intravenous gadolinium administration does not make a statistically significant difference in the qualitative appearance or ADC measurements of the liver, spleen, or pancreas when comparing pre-contrast to post-contrast DWI. In the kidneys, however, ADC values are significantly lower post-contrast with the pre-contrast diffusion weighted images also being qualitatively preferred.     

Preoperative histological grading of meningiomas using apparent diffusion coefficient at 3T MRI

Purpose

We assessed whether a high b-value DWI at b = 4000 s/mm² would discriminate the histopathological differentiation of the tumor grade of meningiomas, and also focused on the relationship between radiologic features and the tumor grade.

Materials and methods

We acquired DWI at 3T with b = 1000 and b = 4000 s/mm² in 77 patients (42, 31 and 4 patients were WHO grades I (G1), II (G2), and III (G3), respectively). The apparent diffusion coefficient (ADC) was measured by placing multiple regions of interest (ROIs) on ADC maps. The ADC values of each tumor were determined preoperatively from several ROIs, and expressed as the minimum (ADC_MIN), mean (ADC_MEAN), and maximum absolute values (ADC_MAX). We evaluated the relationship between ADCs and histological findings, and assessed the radiologic features such as tumor location, tumor size, presence/absence of peritumoral edema, shape of the tumor, presence/absence of bone destruction or hyperplasia, status of contrast enhancement, presence/absence of calcification and cyst.

Results

ADCs of the meningiomas were inversely correlated with the histological grade of meningiomas. According to results of the discriminant analysis, the apparent log likelihood value was greatest for ADC_MIN at b = 4000. Furthermore, only the ADC_MIN value at b = 4000 was significantly correlated with the histological grade of meningiomas when we performed a multiple logistic regression analysis to identify the significant independent factors such as shape of tumor, presence/absence of bone destruction, status of contrast enhancement, presence/absence of cyst and ADC_MIN at b = 4000.

Conclusion

A meningioma with a low ADC_MIN at a high b-value might imply a high-grade meningioma.     

Diagnosis and quantification of hepatic fibrosis in children with diffusion weighted MR imaging

Purpose

To evaluate the accuracy of diffusion weighted MR imaging in diagnosis and quantification of hepatic fibrosis in children with chronic hepatitis.

Materials and methods

Sixty-three consecutive children (40 boys, 23 girls, median age 9.3 years), with chronic hepatitis and thirty age matched volunteers underwent diffusion weighted MR imaging of the liver using a single shot echoplanar imaging with b-value = 0, 250, and 500 s/mm². Liver biopsy was obtained with calculation of METAVIR score. The ADC value of the liver was correlated with METAVIR score. Receiver operating characteristic curve was done for diagnosis and grading of hepatic fibrosis.

Results

There was statistical difference in the mean ADC value between volunteers and patients with hepatic fibrosis (P = 0.001) and in patients with different grades of METAVIR scores (P = 0.002). There was correlation between the mean ADC value and METAVIR score (r = 0.807, P = 0.001). The cut off point to predict fibrosis (1.7 × 10⁻³ mm²/s) revealed 83% accuracy, 85% sensitivity, 82% specificity, 83% PPV, and 85% NPV. The area under the curve was 0.91 for F1, 0.85 for F2, 0.86 for F3 and 0.90 for F4.

Conclusion

The apparent diffusion coefficient value is a promising quantitative parameter used for diagnosis and quantification of hepatic fibrosis in children with chronic hepatitis.     

Diagnostic performance of breast MRI with and without the addition of quantitative diffusion weighted imaging

Objective

The purpose of our study was to investigate whether adding diffusion weighted imaging to dynamic contrast-enhanced MRI could improve the diagnostic performance of breast MRI.

Materials and methods

This retrospective study included 86 women with 93 primary and postoperative breast lesions detected on DCE-MRI who underwent subsequent biopsy. The diagnostic performance was calculated for DCE-MRI alone, combined DCE-MRI and quantitative DWI, and for quantitative DWI alone.

Results

Of the 93 lesions, 42 were benign and 51 malignant (5 DCIS, 41 IDC, 2 ILC, 3 NOS). Both DCIS (mean ADC = 1.17 ± 0.12 × 10⁻³ mm²/s) and IDC (mean ADC, 0.98 ± 0.14) exhibited lower mean ADC values than benign lesions (ADC value = 1.72 ± 0.36). Applying an ADC cutoff value of 1.33 increased the specificity and PPV of DCE-breast MRI from 59.5% and 75% to 78.5% and 83.3%, respectively. The specificity and PPV for quantitative DW-MRI alone (73.5% and 83.3%) were close to those broken out from the combined use of DCE and quantitative DW-MRI. However, the sensitivity and NPV of DWI remains lower than that of DCE-MRI.

Conclusion

DWI shows potential for improving the diagnostic performance of breast MRI and may reduce the number of unnecessary biopsies.     

Rectal tumour volume (GTV) delineation using T2-weighted and diffusion-weighted MRI: Implications for radiotherapy planning

Purpose

To compare the rectal tumour gross target volume (GTV) delineated on T2 weighted (T2W MRI) and diffusion weighted MRI (DWI) images by two different observers and to assess if agreement is improved by DWI.

Material and methods

27 consecutive patients (15 male, range 27.1–88.8 years, mean 66.9 years) underwent 1.5 T MRI prior to chemoradiation (45 Gy in 25 fractions; oral capecitabine 850 mg/m²), including axial T2W MRI (TR = 6600 ms, TE = 90 ms) and DWI (TR = 3000 ms, TE = 77 ms, b = 0, 100, 800 s/mm²). 3D tumour volume (cm³) was measured by volume of interest (VOI) analysis by two independent readers for the T2W MRI and b800 DWI axial images, and the T2W MRI and DWI volumes compared using Mann–Whitney test. Observer agreement was assessed using Bland–Altman statistics. Significance was at 5%.

Results

Artefacts precluded DWI analysis in 1 patient. In the remaining 26 patients evaluated, median (range) T2W MRI MRI and DWI (b = 800 s/mm²) 3D GTVin cm³ were 33.97 (4.44–199.8) and 31.38 (2.43–228), respectively, for Reader One and 43.78 (7.57–267.7) and 42.45 (3.68–251) for Reader Two. T2W MRI GTVs were slightly larger but not statistically different from DWI volumes: p = 0.52 Reader One; p = 0.92 Reader Two. Interobserver mean difference (95% limits of agreement) for T2W MRI and DWI GTVs were −9.84 (−54.96 to +35.28) cm³ and −14.79 (−54.01 to +24.43) cm³ respectively.

Conclusion

Smaller DWI volumes may result from better tumour conspicuity but overall observer agreement is not improved by DWI.     

Diffusion-weighted magnetic resonance imaging of head and neck squamous cell carcinomas

Objective

To evaluate whether diffusion-weighted imaging (DWI) is a reliable technique to quantify microstructural differences between head and neck squamous cell carcinomas (SCC) and tumour-free soft tissue.

Materials and methods

DWI was obtained from 20 patients with histologically proven, untreated head and neck SCC. DWI was acquired using a diffusion-weighted, navigated echo-planar imaging sequence with a maximum b-value of 800 s/mm². For an objective assessment of image quality, the signal-to-noise ratio (SNR) was calculated. Microstructural differences between vital tumour tissue and tumour-free soft tissue were quantified by calculating the apparent-diffusion-coefficients (ADC) on a pixel by pixel method.

Results

Echo-planar DWI provided good image quality in all patients (mean SNR 18.4). The mean ADC of SCC, (0.64 ± 0.28 × 10⁻³ mm²/s), was significantly (P < 0.0001) lower than that of the tumour-free soft tissue, (2.51 ± 0.82 × 10⁻³ mm²/s).

Conclusion

DWI is a reliable diagnostic tool to quantify the microstructural differences between vital tumour tissue and tumour-free soft tissue in patients with head and neck SCC.