Diffusion‐weighted imaging of the liver: Comparison of navigator triggered and breathhold acquisitions

Purpose

To compare a free breathing navigator triggered single shot echoplanar imaging (SS EPI) diffusion‐weighted imaging (DWI) sequence with prospective acquisition correction (PACE) with a breathhold (BH) DWI sequence for liver imaging.

Materials and Methods

Thirty‐four patients were evaluated with PACE‐DWI and BH DWI of the liver using b‐values of 0, 50, and 500 s/mm². There were 29 focal liver lesions in 18 patients. Qualitative evaluation was performed on a 3‐point scale ( 1 - 3 ) by two independent observers (maximum score 9). Quantitative evaluation included estimated SNR (signal to noise ratio), lesion‐to‐liver contrast ratio, liver and lesion apparent diffusion coefficients (ADCs), and coefficient of variation (CV) of ADC in liver parenchyma and focal liver lesions (estimate of noise contamination in ADC).

Results

PACE‐DWI showed significantly better image quality, higher SNR and lesion‐to‐liver contrast ratio when compared with BH DWI. ADCs of liver and focal lesions with both sequences were significantly correlated (r = 0.838 for liver parenchyma, and 0.904 for lesions, P < 0.0001), but lower with the BH sequence (P < 0.02). There was higher noise contamination in ADC measurement obtained with BH DWI (with a significantly higher SD and CV of ADC).

Conclusion

The use of a navigator echo to trigger SS EPI DWI improves image quality and liver to lesion contrast, and enables a more precise ADC quantification compared with BH DWI acquisition. J. Magn. Reson. Imaging 2009;30:561–568. © 2009 Wiley‐Liss, Inc.     

Dual‐source parallel RF transmission for diffusion‐weighted imaging of the abdomen using different b values: Image quality and apparent diffusion coefficient comparison with conventional single‐source transmission

Purpose:

To prospectively and intraindividually evaluate what effects dual‐source parallel radiofrequency (RF) transmission have on image quality and apparent diffusion coefficient (ADC) of abdomen diffusion‐weighted imaging (DWI) using different b values, compared with the single‐source RF transmission.

Materials and Methods:

Eighteen healthy male volunteers were enrolled in this Health Insurance Portability and Accountability Act (HIPAA)‐compliant Institutional Review Board (IRB)‐approved study. Abdominal DWI was performed with dual‐source and single‐source RF transmission at 3.0 T using a series of b‐value combinations: 0/100, 0/500, 0/800, and 0/100/800. RF field homogeneity, subjective image quality, and signal to noise ratio (SNR) of each abdominal organ were evaluated. ADC values were calculated for each abdominal organ. Wilcoxon test and repeated‐measures analysis of variance was used to calculate statistical significance.

Results:

The parallel RF transmission significantly improved homogeneity of the RF field (P = 0.0001–0.008) and subjective image quality (P < 0.0001) at each b value and also increased SNR. At lower and higher b value, the measured ADC of lateral left hepatic lobe and spleen between dual‐source and single‐source images were significantly different (P = 0.0001–0.047). At b = 0/500, there was no significant difference in ADC measurements between dual‐source and single‐source RF transmission for abdominal organs, except a slight statistically significant difference for spleen (P = 0.047).

Conclusion:

Parallel RF transmission significantly improved the image quality and homogeneity of the RF field. The RF transmission had a significant influence on measured ADC of lateral left hepatic lobe and spleen. At b = 0/500 the influence was minimum for all abdominal organs. J. Magn. Reson. Imaging 2013;37:875–885. © 2012 Wiley Periodicals, Inc.     

Reproducibility of measurement of apparent diffusion coefficients of malignant hepatic tumors: Effect of DWI techniques and calculation methods

Purpose:

To evaluate the effect of diffusion‐weighted imaging (DWI) methods, apparent diffusion coefficient (ADC) calculation methods, and selection of b‐values on the ADCs and the measurement reproducibility of malignant hepatic tumors.

Materials and Methods:

Nineteen patients with pathologically confirmed malignant hepatic tumors underwent breath‐hold DWI (b‐values = 0, 50, 500 s/mm²) and respiratory‐triggered DWI (0, 50, 300, 500, 1000 s/mm²) twice on a 1.5 T magnetic resonance imaging (MRI) scanner. ADCs were calculated using a two b‐value and/or a multiple b‐value method. The reproducibility of the ADC measurements was evaluated from the intraclass correlation coefficients (ICCs) and the 95% Bland–Altman limit‐of‐agreement (LOA).

Results:

The ADCs were different according to the DWI methods (P = 0.040–0.282), ADC calculation methods (P = 0.003–0.825), and the choice of b‐values (P < 0.001). The ADC tended to be more reproducible with use of breath‐hold DWI (ICC: 0.898–0.933; LOA, 18.8%–24.0%) than respiratory‐triggered DWI (ICC: 0.684–0.928; LOA, 15.0%–31.9%) (P = 0.008–0.122). For respiratory‐triggered DWI, the multiple b‐value method using five b‐values had better reproducibility than the two b‐value method for measurement of ADC (P = 0.009–0.221).

Conclusion:

The DWI method, ADC calculation method, and selection of b‐values potentially influence the ADCs and the reproducibility of malignant hepatic tumors. ADCs calculated from breath‐hold DWI are more reproducible than from respiratory‐triggered DWI. A multiple b‐value method may improve the reproducibility of respiratory‐triggered DWI. J. Magn. Reson. Imaging 2012;36:1131–1138. © 2012 Wiley Periodicals, Inc.     

Comparison and reproducibility of ADC measurements in breathhold, respiratory triggered, and free-breathing diffusion-weighted MR imaging of the liver

Purpose

To compare and determine the reproducibility of apparent diffusion coefficient (ADC) measurements of the normal liver parenchyma in breathhold, respiratory triggered, and free‐breathing diffusion‐weighted magnetic resonance imaging (DWI).

Materials and Methods

Eleven healthy volunteers underwent three series of DWI. Each DWI series consisted of one breathhold, one respiratory triggered, and two free‐breathing (thick and thin slice acquisition) scans of the liver, at b‐values of 0 and 500 s/mm². ADCs of the liver parenchyma were compared by using nonparametric tests. Reproducibility was assessed by the Bland–Altman method.

Results

Mean ADCs (in 10^?3 mm²/sec) in respiratory triggered DWI (2.07–2.27) were significantly higher than mean ADCs in breathhold DWI (1.57–1.62), thick slice free‐breathing DWI (1.62–1.65), and thin slice free‐breathing DWI (1.57–1.66) (P < 0.005). Ranges of mean difference in ADC measurement ± limits of agreement between two scans were ?0.02–0.05 ± 0.16–0.24 in breathhold DWI, ?0.14–0.20 ± 0.59–0.60 in respiratory triggered DWI, ?0.03–0.03 ± 0.20–0.29 in thick slice free‐breathing DWI, and ?0.01–0.09 ± 0.21–0.29 in thin slice free‐breathing DWI.

Conclusion

ADC measurements of the normal liver parenchyma in respiratory triggered DWI are significantly higher and less reproducible than in breathhold and free‐breathing DWI. J. Magn. Reson. Imaging 2008;28:1141–1148. © 2008 Wiley‐Liss, Inc.

     

Evaluation of therapeutic response to concurrent chemoradiotherapy in patients with cervical cancer using diffusion‐weighted MR imaging

Purpose:

To investigate the changes in apparent diffusion coefficients (ADCs) in cervical cancer patients receiving concurrent chemoradiotherapy (CCRT), and to assess the relationship between tumor ADCs or changes in tumor ADCs and final tumor responses to therapy.

Materials and Methods:

Twenty‐four patients with cervical cancer who received CCRT were examined with 3 Tesla (T) MRI including diffusion‐weighted imaging (DWI). All patients had three serial MR examinations: before therapy (pre‐Tx); at 4 weeks of therapy (mid‐Tx); and 1 month after completion of therapy (post‐Tx). At each examination, ADC was measured in tumors and normal gluteus muscles. Final tumor response as determined by change in tumor size or volume using MRI was correlated with tumor ADCs at each therapeutic time or changes in tumor ADCs at mid‐Tx.

Results:

From pre‐Tx to post‐Tx, mean tumor ADCs were 0.88, 1.30, and 1.47 × 10^?3 mm²/s in sequence (P < 0.001), while those of normal gluteus muscles were 1.24, 1.29, and 1.21 × 10^?3 mm²/s in sequence (P > 0.05). At mid‐Tx, tumor ADCs and changes in tumor ADCs had a significant correlation with final tumor size responses (P = 0.029 and 0.025, respectively). However, the tumor ADC values at pre‐Tx were not associated with the final tumor size response (P = 0.47). The final tumor volume response was not associated with tumor ADC at pre‐Tx or mid‐Tx (P > 0.05) or changes in tumor ADCs at mid‐Tx (P > 0.05).

Conclusion:

DWI may have potentials in evaluating the therapeutic response to CCRT in patients with cervical cancer. J. Magn. Reson. Imaging 2013;37:187–193. © 2012 Wiley Periodicals, Inc.

     

Combined T2‐weighted and diffusion‐weighted MRI for diagnosis of urinary bladder invasion in patients with prostate carcinoma

Purpose

To retrospectively determine the diffusion‐weighted imaging (DWI) characteristics and apparent diffusion coefficient (ADC) values of prostate carcinoma (PCa) with urinary bladder invasion, and to compare the accuracy of T2‐weighted MRI alone and T2 combined with DWI for predicting urinary bladder invasion.

Materials and Methods

Sixty‐eight patients with proven PCa were diagnosed with urinary bladder invasion after conventional magnetic resonance imaging (MRI) and DWI (b value = 750 sec/mm²) examinations. All the 68 cases underwent cystoscopy examination. DWI appearances of all urinary bladder invasion and a normal urinary bladder wall were analyzed, and their ADC values were measured. T2 images alone and then T2 images combined with DWI were scored for the likelihood of urinary bladder invasion on the basis of radiologists' written reports. The area under the receiver operating characteristic curve (AUC) was used to assess accuracy. Statistical significance was inferred at P < 0.05.

Results

After cystoscopy examination, 45 (66%) of 68 cases were pathologically proven urinary bladder invasion. The mean ADCs for urinary bladder invasion and normal urinary bladder wall were (0.963 ± 0.155) × 10^?3mm²/sec and (1.517 ± 0.103) × 10^?3mm²/sec, respectively. The ADC values of urinary bladder invasion were significantly lower than those of normal urinary bladder wall (P = 0.000). The AUC for T2‐weighted imaging plus DW imaging (0.861) was significantly larger than that for T2‐weighted imaging alone (0.734) or for DW imaging alone (0.703) (P < 0.001).

Conclusion

Urinary bladder invasion had lower ADC values compared with normal urinary bladder wall. T2 images plus DWI is significantly better than T2‐weighted imaging alone in the detection of urinary bladder invasion in patients with PCa. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.

     

Diffusion-weighted MRI in rectal cancer: apparent diffusion coefficient as a potential noninvasive marker of tumor aggressiveness

Purpose:

To assess the value of diffusion‐weighted MR imaging (DWI) as a potential noninvasive marker of tumor aggressiveness in rectal cancer, by analyzing the relationship between tumoral apparent diffusion coefficient (ADC) values and MRI and histological prognostic parameters.

Materials and Methods:

Fifty rectal cancer patients underwent primary staging MRI including DWI before surgery and neo‐adjuvant therapy. In 47, surgery was preceded by short‐course radiation therapy (n = 28) or long‐course chemoradiation therapy (n = 19). Mean tumor ADC was measured and compared between subgroups based on pretreatment CEA levels, MRI parameters (mesorectal fascia ‐ MRF ‐ status; T‐stage; N‐stage) and histological parameters (differentiation grade: poorly differentiated, poorly moderately differentiated, moderately differentiated, moderately well differentiated, well‐differentiated; lymphangiovascular invasion).

Results:

Mean tumor ADCs differ between MRF‐free versus MRF‐invaded tumors (P = 0.013), the groups of cN0 versus cN+ cancers (P = 0.011), and between the several groups of histological differentiation grades (P = 0.025). There was no significant difference in mean ADCs between the various groups of CEA levels, the T stage, and the presence of lymphangiovascular invasion.

Conclusion:

Lower ADC values were associated with a more aggressive tumor profile. Significant correlations were found between mean ADC values and radiological MRF status, N stage and differentiation grade. ADC has the potential to become an imaging biomarker of tumor aggressiveness profile. J. Magn. Reson. Imaging 2012;35:1365–1371. © 2012 Wiley Periodicals, Inc.     

Diffusion‐weighted MRI of hepatic tumor in rats: Comparison between in vivo and postmortem imaging acquisitions

Purpose

To determine the feasibility of in vivo diffusion‐weighted imaging (DWI) to distinguish between normal liver, viable tumor and necrosis compared to postmortem DWI in a rat model with vascular‐targeting treatment.

Materials and Methods

Fifteen rats with liver implantation of 30 rhabdomyosarcomas were treated with combretastatin A‐4‐phosphate (CA4P) at 10 mg/kg. Two days after treatment, T2‐weighted imaging, precontrast T1‐weighted imaging, postcontrast T1‐weighted imaging, and DWI were performed in vivo and postmortem with a 1.5T scanner. Apparent diffusion coefficients (ADCs) calculated from DWIs with b values of 0, 50, and 100 seconds/mm² (ADC_low), 500, 750, and 1000 seconds/mm² (ADC_high), 0, 500, and 1000 seconds/mm² (ADC_3b), and 0–1000 seconds/mm² (ADC_10b) for tumor, liver, therapeutic necrosis, and phantoms were compared and validated with ex vivo microangiographic and histopathologic findings.

Results

Except ADC_low between tumor and necrosis, in vivo ADCs successfully differentiated liver, viable tumor, and necrosis (P < 0.05). Compared to in vivo outcomes, postmortem ADCs significantly dropped in tumor and liver (P < 0.05) except ADC_high of tumor, but not in necrosis and phantoms. Compared to ADC_low, ADC_high was less affected by vital status.

Conclusion

Advantageous over postmortem DWI, in vivo DWI provides a noninvasive easy‐performing tool for distinguishing between liver, viable tumor, and necrosis. ADC_low and ADC_high better reflect tissue perfusion and water diffusion, respectively. J. Magn. Reson. Imaging 2009;29:621–628. © 2009 Wiley‐Liss, Inc.     

Navigator respiratory‐triggered diffusion‐weighted imaging in the follow‐up after hepatic radiofrequency ablation—initial results

Purpose

To evaluate diffusion alterations after hepatic radiofrequency (RF) ablation using a navigator respiratory‐triggered diffusion‐weighted imaging (NRT‐DWI) sequence with regard to potential diagnostic information for detection of local tumor progression (LTP).

Materials and Methods

One hundred forty‐eight consecutive follow‐up magnetic resonance (MR) examinations of 54 patients after hepatic RF ablation were reviewed. Apparent diffusion coefficient (ADC) values of ablation zones and liver parenchyma were assessed using a single‐shot echoplanar imaging sequence with the NRT technique. ADC values of ablation zones and adjacent signal alterations identified in NRT‐DWI were analyzed with regard to LTP.

Results

Mean ADC values of ablation zones (119.9 ± 30.5 × 10^?5 mm²/sec) and liver (106.3 ± 21.2 × 10^?5 mm²/sec) differed significantly (P = 0.0003). No evident changes in ablations' ADC values over time could be identified. ADC values obtained from the entire ablation zone did not significantly differ regarding the presence of LTP. In 58 examinations, hyperintense areas in the periphery of the ablation zone were detected on the NRT‐DWI. Corresponding ADC values were significantly lower in patients with LTP (102.1 ± 22.4 versus 130.8 ± 47.6 × 10^?5 mm²/sec; P = 0.0124).

Conclusion

NRT‐DWI is useful in the follow‐up imaging after RF ablation. ADC‐based evaluation of signal alterations adjacent to the ablation zone may contribute to the identification of LTP and nontumoral posttreatment tissue changes. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.

     

Effect of Gd‐EOB‐DTPA on T2‐weighted and diffusion‐weighted images for the diagnosis of hepatocellular carcinoma

Purpose:

To evaluate the effect of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd‐EOB‐DTPA) on T2‐weighted imaging (T2WI) and diffusion‐weighted imaging (DWI) for the diagnosis of hepatocellular carcinoma (HCC).

Materials and Methods:

The phantom signal intensity was measured. We also evaluated 72 patients including 30 patients with HCC. T2WI and DWI were obtained before and then 4 and 20 min after injecting the contrast medium. The signal to noise ratio (SNR), contrast to noise ratio (CNR), and apparent diffusion coefficient (ADC) were calculated in the tumor and liver parenchyma.

Results:

The phantom signal intensity increased on T2WI at a concentration of contrast medium less than 0.2 mmol/L but decreased when the concentration exceeded 0.4 mmol/L. SNR of the liver parenchyma on T2WI was significantly different between before and 4 min after injecting the contrast medium, while there were no significant differences between before and 4 and 20 min after injection. On T2WI, SNR, and CNR of HCC showed no significant differences at any time. SNR, CNR, and ADC of the liver parenchyma and tumor on DWI also showed no significant differences at any time.

Conclusion:

It is acceptable to perform T2WI and DWI after injection of Gd‐EOB‐DTPA for the diagnosis of HCC. J. Magn. Reson. Imaging 2010;32:229–234. © 2010 Wiley‐Liss, Inc.     

Comparison of apparent diffusion coefficients and distributed diffusion coefficients in high‐grade gliomas

Purpose:

To compare apparent diffusion coefficients (ADCs) with distributed diffusion coefficients (DDCs) in high‐grade gliomas.

Materials and Methods:

Twenty patients with high‐grade gliomas prospectively underwent diffusion‐weighted MRI. Traditional ADC maps were created using b‐values of 0 and 1000 s/mm². In addition, DDC maps were created by applying the stretched‐exponential model using b‐values of 0, 1000, 2000, and 4000 s/mm². Whole‐tumor ADCs and DDCs (in 10^?3 mm²/s) were measured and analyzed with a paired t‐test, Pearson's correlation coefficient, and the Bland‐Altman method.

Results:

Tumor ADCs (1.14 ± 0.26) were significantly lower (P = 0.0001) than DDCs (1.64 ± 0.71). Tumor ADCs and DDCs were strongly correlated (R = 0.9716; P < 0.0001), but mean bias ± limits of agreement between tumor ADCs and DDCs was ?0.50 ± 0.90. There was a clear trend toward greater discordance between ADC and DDC at high ADC values.

Conclusion:

Under the assumption that the stretched‐exponential model provides a more accurate estimate of the average diffusion rate than the mono‐exponential model, our results suggest that for a little diffusion attenuation the mono‐exponential fit works rather well for quantifying diffusion in high‐grade gliomas, whereas it works less well for a greater degree of diffusion attenuation. J. Magn. Reson. Imaging 2010;31:531–537. © 2010 Wiley‐Liss, Inc.

     

Diffusion‐weighted echo‐planar magnetic resonance imaging for the assessment of tumor cellularity in patients with soft‐tissue sarcomas

Purpose

To investigate the eligibility of diffusion‐weighted imaging (DWI) for the evaluation of tumor cellularity in patients with soft‐tissue sarcomas.

Materials and Methods

Thirty consecutive patients with a total of 31 histologically‐proven soft‐tissue sarcomas prospectively underwent magnetic resonance imaging (MRI) including DWI with echo‐planar imaging (EPI) technique immediately before open biopsy (N = 1) or tumor resection (N = 30). Fourteen patients had no previous anticancer treatment, 16 had received neoadjuvant therapy. Tumor cellularity as determined from histological sections was compared with minimum apparent diffusion coefficient (ADC).

Results

Tumor cellularity correlated well with minimum ADC in a linear fashion, with a Pearson correlation coefficient of –0.88 (95% confidence interval [CI]: –0.75 to –0.96). This relationship was not influenced by prior anticancer treatment. There was only a tendency toward lower ADC in tumor with higher grading but no significant dependency (P = 0.08).

Conclusion

DWI has proven useful for the assessment of tumor cellularity in soft‐tissue sarcomas. In result, DWI may be used as a powerful noninvasive tool to monitor responses of cytotoxic treatment as reflected by changes in tumor cellularity. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.     

Prediction of locally recurrent prostate cancer after radiation therapy: Incremental value of 3T diffusion‐weighted MRI

Purpose

To prospectively evaluate the incremental value of diffusion‐weighted imaging (DWI) with apparent diffusion coefficient (ADC) maps in addition to T2‐weighted imaging (T2WI) for predicting locally recurrent prostate cancer in patients with biochemical failure after radiation therapy.

Materials and Methods

Thirty‐six consecutive patients with an increased prostate‐specific antigen level after radiation therapy underwent 3T MRI followed by transrectal biopsy. The MRI findings and biopsy results were correlated in sextant prostate sectors of peripheral zones (PZs). Two radiologists in consensus reviewed T2WI and combined T2WI and DWI with ADC maps, and rated the likelihood of recurrent cancer on a five‐point scale. ADC values were calculated for recurrent cancer and benign tissue.

Results

Of 216 sectors, 65 prostate sectors (30%) were positive for cancer in 18 patients. For predicting recurrent cancer, combined T2WI and DWI showed a greater sensitivity compared to T2WI (P < 0.001). A significantly greater area under the receiver operating characteristics curve (Az) was determined for combined T2WI and DWI (Az = 0.879, P < 0.01) as compared to T2WI (Az = 0.612). Mean ADC values between recurrent cancer and benign tissue showed a statistically significant difference (P < 0.01).

Conclusion

For predicting locally recurrent prostate cancer after radiation therapy, the use of combined T2WI and DWI showed a better diagnostic performance compared to T2WI. J. Magn. Reson. Imaging 2009;29:391–397. © 2009 Wiley‐Liss, Inc.     

Diffusion‐weighted imaging of breast cancer: Correlation of the apparent diffusion coefficient value with prognostic factors

Purpose

To evaluate the role of diffusion‐weighted imaging (DWI) in the detection of breast cancers, and to correlate the apparent diffusion coefficient (ADC) value with prognostic factors.

Materials and Methods

Sixty‐seven women with invasive cancer underwent breast MRI. Histological specimens were analyzed for tumor size and grade, and expression of estrogen receptors (ER), progesterone receptors, c‐erbB‐2, p53, Ki‐67, and epidermal growth factor receptors. The computed mean ADC values of breast cancer and normal breast parenchyma were compared. Relationships between the ADC values and prognostic factors were determined using Wilcoxon signed rank test and Kruskal‐Wallis test.

Results

DWI detected breast cancer as a hyperintense area in 62 patients (92.5 %). A statistically significant difference in the mean ADC values of breast cancer (1.09 ± 0.27 × 10^?5 mm²/s) and normal parenchyma (1.59 ± 0.27 × 10^?5 mm²/s) was detected (P < 0.0001). There were no correlations between the ADC value and prognostic factors. However, the median ADC value was lower in the ER‐positive group than the ER negative group, and this difference was marginally significant (1.09 × 10^?5 mm²/s versus 1.15 × 10^?5 mm²/s, P = 0.053).

Conclusion

The ADC value was a helpful parameter in detecting malignant breast tumors, but ADC value could not predict patient prognosis. J. Magn. Reson. Imaging 2009;30:615–620. © 2009 Wiley‐Liss, Inc.

     

Microperfusion‐induced elevation of ADC is suppressed after contrast in breast carcinoma

Purpose

To investigate the effect of gadolinium (Gd)‐DTPA on the apparent diffusion coefficient (ADC) of breast carcinoma and to analyze the relationship between pre/postcontrast ADC and the degree of contrast enhancement.

Materials and Methods

Nineteen histopathologically confirmed breast carcinomas (mean size = 22 mm) were analyzed. Their ADCs before and after contrast administration were measured. The contrast‐to‐noise ratios (CNRs) of the tumors were measured on fat‐suppressed 3D T1‐weighted images in precontrast, early, and late postcontrast phases. These results were correlated with the measured ADC values.

Results

A significant decrease in the measured ADC was noted after contrast administration (?23%, P = 0.01). Lesions with relatively high ADC before contrast (>1.3 × 10^?3 mm²/sec; n = 12) demonstrated a larger degree of ADC reduction (mean 34%) than lesions with low ADC (≤1.3 × 10^?3 mm²/sec; n = 7) (mean 4.5%). When an early postcontrast image was used as a surrogate marker of malignant potential, we found a significant inverse correlation with postcontrast ADC (γ = ?0.57, P = 0.02).

Conclusion

Postcontrast ADC exhibited lower values than precontrast ADC, which is thought to reflect suppression of the microperfusion‐induced effect on diffusion‐weighted imaging. Postcontrast ADC may be a better indicator than precontrast ADC to reflect malignant potential of tumors. J. Magn. Reson. Imaging 2009;29:1080–1084. © 2009 Wiley‐Liss, Inc.

     

Differential diagnosis of mammographically and clinically occult breast lesions on diffusion‐weighted MRI

Purpose:

To investigate the diagnostic performance of diffusion‐weighted imaging (DWI) for mammographically and clinically occult breast lesions.

Materials and Methods:

The study included 91 women with 118 breast lesions (91 benign, 12 ductal carcinoma in situ [DCIS], 15 invasive carcinoma) initially detected on dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) and assigned BI‐RADS category 3, 4, or 5. DWI was acquired with b = 0 and 600 s/mm². Lesion visibility was assessed on DWI. Apparent diffusion coefficient (ADC) values were compared between malignancies, benign lesions, and normal (no abnormal enhancement on DCE‐MRI) breast tissue, and the diagnostic performance of DWI was assessed based on ADC thresholding.

Results:

Twenty‐four of 27 (89%) malignant and 74/91 (81%) benign lesions were hyperintense on the b = 600 s/mm² diffusion‐weighted images. Both DCIS (1.33 ± 0.19 × 10^?3 mm²/s) and invasive carcinomas (1.30 ± 0.27 × 10^?3mm²/s) were lower in ADC than benign lesions (1.71 ± 0.43 × 10^?3mm²/s; P < 0.001), and each lesion type was lower in ADC than normal tissue (1.90 ± 0.38 × 10^?3mm²/s, P ≤ 0.001). Receiver operating curve (ROC) analysis showed an area under the curve (AUC) of 0.77, and sensitivity = 96%, specificity = 55%, positive predictive value (PPV) = 39%, and negative predictive value (NPV) = 98% for an ADC threshold of 1.60 × 10^?3mm²/s.

Conclusion:

Many mammographically and clinically occult breast carcinomas were visibly hyperintense on diffusion‐weighted images, and ADC enabled differentiation from benign lesions. Further studies evaluating DWI while blinded to DCE‐MRI are necessary to assess the potential of DWI as a noncontrast breast screening technique. J. Magn. Reson. Imaging 2010;1:562–570. © 2010 Wiley‐Liss, Inc.

     

Discrimination of metastatic lymph nodes in patients with gastric carcinoma using diffusion‐weighted imaging

Purpose:

To determine the accuracy of diffusion‐weighted imaging (DWI) in discrimination of metastatic lymph nodes (LNs) in gastric carcinoma with rigorous histopathological correlation.

Materials and Methods:

With Institutional Review Board (IRB) approval, 28 patients with gastric carcinoma underwent magnetic resonance imaging (MRI) and DWI before surgery. LNs were resected at surgery and thereafter submitted for histopathological analyses. All histopathologically identified LNs (≥5 mm) that exactly matched the location and size of nodes on MRI/DWI were submitted to lesion‐by‐lesion analyses. Short‐axis diameter, border irregularity, enhanced patterns, and apparent diffusion coefficient (ADC) values of each LN were recorded. Each measurement was compared between metastatic and benign LNs, confirmed by nodal histopathology. A receiver operating characteristic (ROC) curve was generated to evaluate the capability of morphological and ADC measurements in distinguishing metastatic lymph nodes.

Results:

The median ADC value of metastatic nodes was significantly lower (1.28 × 10^?3 mm²/sec; interquartile range, 1.20–1.31) than that of benign (1.55; 1.47–1.73) nodes (P < 0.001). DWI showed greater diagnostic accuracy in determining metastatic nodes (AUC = 0.857) than the combined morphological measurements of short‐axis, border irregularity, and enhanced patterns (AUC = 0.746, P = 0.03). Adding ADC values to the combined morphologic criteria demonstrated the greatest predictive power (AUC = 0.889).

Conclusion:

DWI may provide great potential in effective discrimination of metastatic LNs in gastric carcinoma. J. Magn. Reson. Imaging 2013;37:1436–1444. © 2012 Wiley Periodicals, Inc.

     

Pancreatic diffusion‐weighted imaging (DWI): Comparison between mass‐forming focal pancreatitis (FP), pancreatic cancer (PC), and normal pancreas

Purpose

To compare diffusion‐weighted imaging (DWI) findings and the apparent diffusion coefficient (ADC) values of pancreatic cancer (PC), mass‐forming focal pancreatitis (FP), and the normal pancreas.

Materials and Methods

DWI (b = 0 and 600 seconds/mm²) findings of 14 patients with mass‐forming FP proven by histopathology and or clinical follow‐up, 10 patients with histopathologically‐proven PC, and 14 subjects with normal pancreatic exocrine function and normal imaging findings were retrospectively evaluated. ADC values of the masses, the remaining pancreas, and the normal pancreas were measured.

Results

On b = 600 seconds/mm² DWI, mass‐forming FP was visually indistinguishable from the remaining pancreas whereas PC was hyperintense relative to the remaining pancreas. The mean ADC value of PC (1.46 ± 0.18 mm²/second) was significantly lower than the remaining pancreas (2.11 ± 0.32 × 10^–3 mm²/second; P < 0.0001), mass‐forming FP (2.09 ± 0.18 × 10^–3 mm²/second; P < 0.0001), and pancreatic gland in the control group (1.78 ± 0.07 × 10^–3 mm²/second; P < 0.0005). There was no significant difference of ADC values between the mass‐forming focal pancreatitis and the remaining pancreas (2.03 ± 0.2 × 10^–3 mm²/second; P > 0.05).

Conclusion

Differences on DWI may help to differentiate PC, mass‐forming FP, and normal pancreas from each other. J. Magn. Reson. Imaging 2009;29:350–356. © 2009 Wiley‐Liss, Inc.     

Diffusion‐weighted imaging of the healthy pancreas: ADC values are age and gender dependent

Purpose:

To investigate the healthy pancreas with diffusion‐weighted imaging (DWI) for characterization of age and gender‐related differences in apparent diffusion coefficient (ADC) values.

Materials and Methods:

Sixty six volunteers were prospectively enrolled (33 male, 33 female; range 1.4 to 83.7 years of age) and echo‐planar DWI of the pancreas was performed. ADC values were measured in the pancreas head, body, and tail using a pixel‐by‐pixel approach. Effects of age and gender on ADC values were analyzed using a two‐factorial multivariate analysis of variance (MANOVA).

Results:

ADC values correlated inversely with the age of the volunteers. The mean global pancreatic ADC values (× 10^?3 mm²/s) in the age groups 0–20 years, 21–40 years, and > 40 years were 1.18 ± 0.19, 1.07 ± 0.13, and 0.99 ± 0.18, respectively. Female individuals had higher mean global ADC values than male (1.13 ± 0.14 versus 1.02 ± 0.18 × 10^?3 mm²/s). MANOVA showed significant effects of age (P value 0.022, eta² = 0.13) and gender (P value 0.001, eta² = 0.28) on ADC values.

Conclusion:

Pancreatic ADC values decline with ageing and show significant gender differences with higher mean values in females. The awareness of baseline values adjusted to age and gender will be important for correct interpretation of individual cases and design of future studies. J. Magn. Reson. Imaging 2013;37:886–891. © 2012 Wiley Periodicals, Inc.

     

Diffusion-weighted imaging of the abdomen at 3.0 Tesla: image quality and apparent diffusion coefficient reproducibility compared with 1.5 Tesla

Purpose

To compare single‐shot echo‐planar imaging (SS EPI) diffusion‐weighted MRI (DWI) of abdominal organs between 1.5 Tesla (T) and 3.0T in healthy volunteers in terms of image quality, apparent diffusion coefficient (ADC) values, and ADC reproducibility.

Materials and Methods

Eight healthy volunteers were prospectively imaged in this HIPAA‐compliant IRB‐approved study. Each subject underwent two consecutive scans at both 1.5 and 3.0T, which included breathhold and free‐breathing DWI using a wide range of b‐values (0 to 800 s/mm²). A blinded observer rated subjective image quality (maximum score= 8), and a separate observer placed regions of interest within the liver, renal cortices, pancreas, and spleen to measure ADC at each field strength. Paired Wilcoxon tests were used to compare abdominal DWI between 1.5T and 3.0T for specific combinations of organs, b‐values, and acquisition techniques.

Results

Subjective image quality was significantly lower at 3.0T for all comparisons (P = 0.0078– 0.0156). ADC values were similar at 1.5T and 3.0T for all assessed organs, except for lower liver ADC at 3.0T using b0‐500‐600 and breathhold technique. ADC reproducibility was moderate at both 1.5T and 3.0T, with no significant difference in coefficient of variation of ADC between field strengths.

Conclusion

Compared with 1.5T, SS EPI at 3.0T provided generally similar ADC values, however, with worse image quality. Further optimization of abdominal DWI at 3.0T is needed. J. Magn. Reson. Imaging 2011;33:128–135. © 2010 Wiley‐Liss, Inc.