Quantitative diffusion-weighted MR imaging in the differential diagnosis of breast lesion

The role of diffusion-weighted magnetic resonance imaging (DWI) to differentiate breast lesions in vivo was evaluated. Sixty women (mean age, 53 years) with 81 breast lesions were enrolled. A coronal echo planar imaging (EPI) sequence sensitised to diffusion (b value=1,000 s/mm²) was added to standard MR. The mean diffusivity (MD) was calculated. Differences in MD among cysts, benign lesions and malignant lesions were evaluated, and the sensitivity and specificity of DWI to diagnose malignant and benign lesions were calculated. The diagnosis was 18 cysts, 21 benign and 42 malignant nodules. MD values (mean±SD ×10⁻³ mm²/s) were (1.48±0.37) for benign lesions, (0.95±0.18) for malignant lesions and (2.25±0.26) for cysts. Different MD values characterized different malignant breast lesion types. A MD threshold value of 1.1×10⁻³ mm²/s discriminated malignant breast lesions from benign lesions with a specificity of 81% and sensitivity of 80%. Choosing a cut-off of 1.31×10⁻³ mm²/s (MD of malignant lesions -2 SD), the specificity would be 67% with a sensitivity of 100%. Thus, MD values, related to tumor cellularity, provide reliable information to differentiate malignant breast lesions from benign ones. Quantitative DWI is not time-consuming and can be easily inserted into standard clinical breast MR imaging protocols.     

SSH-EPI diffusion-weighted MR imaging of the spine with low b values: is it useful in differentiating malignant metastatic tumor infiltration from benign fracture edema?

Objective  Conventional MR sequences are sometimes not helpful in differentiating benign from pathologic fractures. Our aim was to evaluate the usefulness of single-shot echo-planar imaging sequences (diffusion-weighted imaging (DWI)/SSH-EPI) with low b value in differentiating malignant metastatic tumor infiltration of vertebral bone marrow from benign vertebral fracture edema. Materials and methods  A total of 47 patients, 20 with benign fractures and 27 with tumor infiltration, were included in this prospective study. Diffusion-weighted MR images were obtained by single-shot echo-planar imaging technique with diffusion gradient (b = 300 s/mm²; TR/TE, 1,400/100), using a 1.5 T MR scanner. T1- and T2-weighted images and short inversion time inversion-recovery images were available for all 64 lesions. The lesions on DWI/SSH-EPI were categorized as having hypo-, iso-, or hyperintense signal intensity relative to normal vertebrae by two experienced radiologists. Results  We evaluated signal intensity patterns on DWI/SSH-EPI in 64 lesions, which showed low signal intensity on T1-weighted images in both benign fractures and metastasis. With the exception of sclerotic metastases in two patients, malignant metastatic tumor infiltration was hyperintense with respect to normal bone marrow on diffusion-weighted images; all but four benign vertebral fractures were isointense with respect to normal bone marrow. Conclusion  Single-shot echo-planar imaging sequences (DWI/SSH-EPI) with low b value provided excellent distinction between metastatic tumor infiltration and benign vertebral fracture edema. Hyperintense signal intensity on DWI/SSH-EPI was highly specific for the diagnosis of metastatic tumor infiltration of the spine.     

Respiratory gated diffusion-weighted imaging of the liver: value of apparent diffusion coefficient measurements in the differentiation between most commonly encountered benign and malignant focal liver lesions

The purpose of this study was to measure apparent diffusion coefficient values of normal liver parenchyma and focal liver lesions utilizing a respiratory gated diffusion sequence with multiple b-values and to investigate whether apparent diffusion coefficient (ADC) measurements may be utilized to characterize and differentiate between malignant and benign focal hepatic lesions. Thirty-eight consecutive patients underwent MRI of the liver including diffusion-weighted imaging (DWI). A single-shot echo planar imaging sequence was applied in coronal orientation with multiple b-values (0, 50, 500, 1,000 s/mm²) and respiratory gating. ADC values were recorded on corresponding maps utilizing region of interest measurements in patients with benign (group A), malignant (group B) focal lesions and liver parenchyma (group C). Statistical analysis was applied to check whether differences in mean ADC values were significant (p<0.05). No focal lesions were detected in 11 patients, with a mean ADC value (CI 95%) of liver parenchyma 1.25×10⁻³ mm²/s (1.21×10⁻³ mm²/s−1.29×10⁻³ mm²/s). Differences in mean ADC of liver parenchyma between group A and B were not significant (p=0.054, 1.30×10⁻³ mm²/s and 1.31×10⁻³ mm²/s, respectively). Mean ADC value (95% CI) of 22 benign lesions found in 18 patients was 2.55×10⁻³ mm²/s (2.35×10⁻³ mm²/s−2.74×10⁻³ mm²/s), while the mean ADC value (95% CI) of 16 malignant lesions recorded in 9 patients was 1.04×10⁻³ mm²/s (0.9×10⁻³ mm²/s−1.17×10⁻³ mm²/s). The difference between mean ADC values of benign and malignant focal lesions was statistically significant (p<0.0001). Respiratory gated diffusion-weighted imaging in the liver is technically feasible. Apparent diffusion coefficient measurements can be useful in differentiating malignant from benign focal liver lesions.     

Diagnostic accuracy of the apparent diffusion coefficient in differentiating benign from malignant uterine endometrial cavity lesions: initial results

Our purpose is to evaluate the diagnostic accuracy of apparent diffusion coefficient (ADC) measurement in differentiating malignant from benign uterine endometrial cavity lesions. We retrospectively evaluated 25 uterine endometrial cavity lesions in 25 female patients: endometrial carcinoma (n = 11), carcinosarcoma (n = 2), submucosal leiomyoma (n = 8), and endometrial polyp (n = 4). Diffusion-weighted images were performed at 1.5 T with b factors of 0–1,000/mm². The region of interest was defined within the tumor on T2-weighted EPI image and then manually copied to an ADC map. Thereby, the ADC value was obtained. We compared ADC values between malignant and benign lesions using Student’s t-test. The mean and standard deviation of ADC values (×10⁻³ mm²/s) were as follows: endometrial carcinoma, 0.98±0.21; carcinosarcoma, 0.97±0.02; submucosal leiomyoma, 1.37±0.28; and endometrial polyp, 1.58±0.45. The ADC values differed significantly between malignant (0.98±0.19) and benign lesions (1.44±0.34) (P < 0.01). We defined malignant tumors as cases with an ADC value less than 1.15 × 10⁻³ mm²/s for obtaining the highest accuracy. Sensitivity, specificity, and accuracy were 84.6%, 100%, and 92%, respectively. ADC measurement can provide useful information in differentiating malignant from benign uterine endometrial cavity lesions.     

Diagnostic accuracy and additional value of diffusion-weighted imaging for discrimination of malignant cervical lymph nodes in head and neck squamous cell carcinoma

Introduction  The aim was to determine the diagnostic accuracy and additional value of diffusion-weighted imaging for detection of malignant lymph nodes in head and neck squamous cell carcinoma. Methods  Two hundred nineteen lymph nodes, predominantly smaller than 10 mm (95.4%), in 16 consecutive patients were evaluated at 1.5 T. Lymph nodes were evaluated for maximum short axial diameter, morphological criteria, and apparent diffusion coefficient (ADC) values (b = 0 and b = 1,000 s/mm²). Sensitivity, specificity, positive and negative predictive values as well as diagnostic odds ratios (DORs) and areas under the curves (AUCs) of ROC curves were calculated for the various magnetic resonance imaging (MRI) criteria individually and in combination. Histological examination of lymph nodes in the neck dissection specimen was the gold standard to determine malignant involvement. Results  The optimal ADC threshold was 1.0 × 10⁻³ mm²/s. Using this cutoff point, sensitivity and specificity were 92.3% and 83.9%, respectively. When used in combination with size and morphological criteria, ADC value <1.0 × 10⁻³ mm²/s was the strongest predictor of presence of metastasis (DOR = 97.6). A model which added ADC values to the other MRI criteria performed significantly better than a model without ADC values: AUC = 0.98 versus AUC = 0.91 (p = 0.036). Conclusion  In this study, with predominantly small lymph nodes, the ADC criterion is the strongest independent predictor of presence of metastasis. The use of ADC values in combination with the other MRI criteria significantly improves the discrimination between malignant and benign lymph nodes.     

Diffusion MRI of acute pancreatitis and comparison with normal individuals using ADC values

The aim of this study was to retrospectively measure and compare pancreatic apparent diffusion coefficient (ADC) in patients with acute pancreatitis (AP) with aged matched controls who underwent diffusion weighted imaging (DWI). The institutional review board approved this retrospective Health Insurance Portability and Accountability Act compliant study with a waiver for informed consent. Pancreatic ADC values from 27 patients with a clinical diagnosis of AP and 38 normal age-matched controls evaluated with DWI (b = 0 and 800 mm²/s) were retrospectively and independently measured by two radiologists. The ADCs were compared between the groups and between each of the pancreatic segments in the normal group. Inter-observer reliability was calculated and receiver operating characteristic analysis was used to determine the sensitivity and specificity of DW imaging in the diagnosis of acute pancreatitis. P < 0.05 was considered statistically significant. The ICC for inter-observer reliability was 0.98 in the control and 0.97 in the AP group. The mean pancreatic ADC in the AP group (1.32 × 10⁻³ mm²/s ± 0.13) was significantly lower than in the normal group (1.77 × 10⁻³ mm²/s ± 0.32). There was no significant difference in mean ADCs between each of the pancreatic segments in the controls. A threshold ADC value of 1.62 × 10–3 mm²/s yielded a sensitivity of 93% and specificity of 87% for detecting acute pancreatitis for b values of 0 and 800 s/mm². Pancreatic ADCs are significantly lower in patients with AP than normal controls.     

Diagnostic performance of diffusion-weighted magnetic resonance imaging in esophageal cancer

The purpose of this study was to assess the value of diffusion-weighted magnetic resonance imaging (DWI) in detecting esophageal cancer and assessing lymph-node status, compared with histopathological results. DWI was prospectively performed in 24 consecutive patients with esophageal cancer, using the diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) sequence. DWIBS images were fused with T2-weighted images, and independently and blindly evaluated by three board-certified radiologists, regarding primary tumor detectability and lymph-node status. Apparent diffusion coefficients (ADCs) of the primary tumor and lymph nodes were also measured. Average primary tumor detection rate was 49.4%, average patient-based sensitivity and specificity for the detection of lymph-node metastasis were 77.8 and 55.6%, and average lymph-node group-based sensitivity and specificity were 39.4 and 92.6%. There were no interobserver differences among the three readers (P < 0.0001). Mean ADC of detected primary tumors was 1.26 ± 0.29×10⁻³ mm²/s. Mean ADC of metastatic lymph nodes (1.46 ± 0.35×10⁻³ mm²/s) was significantly higher (P < 0.0001) than that of nonmetastatic lymph nodes (1.15 ± 0.24 mm²/s), but ADCs of both groups overlapped. In conclusion, this study suggests that DWI only has a limited role in detecting esophageal cancer and nodal staging.     

Diffusion-weighted MR imaging (DWI) in the evaluation of epidural spinal lesions

Introduction Epidural spinal cord compression is one of the most critical emergency conditions requiring medical attention and requires prompt and adequate treatment. The aim of our study was to assess the role of diffusion-weighted magnetic resonance (MR) imaging (DWI) in the diagnosis and differentiation of epidural spinal lesions. Methods Three patients with epidural lymphoma, two with sarcoma and three with epidural metastatic disease were imaged on a 1.5T MRI unit. DWI was performed using navigated, interleaved, multi-shot echo planar imaging (IEPI). Three region of interest (ROI)-measurements were obtained on corresponding apparent diffusion coefficient (ADC) maps, and the mean ADC value was used for further analysis. The cellularity of tumors was determined as the N/C ratio (nucleus/cytoplasma ratio) from histological samples. The ADC values and N/C ratios of lesions were compared using a Kruskal-Wallis test. Results The mean ADC of the lymphomas was 0.66 × 10⁻³ mm²/s, that of the sarcomas was 0.85 × 10⁻³ mm²/s and the ADC of the metastatic lesions was 1.05 × 10⁻³ mm²/s; however, the differences were not statistically significant. Mean N/C ratios in the lymphoma, sarcomas and metastases were 4:1, 2:1, and 2.6:1, respectively, with a statistically significant difference between the groups (p < 0.025). Conclusion Although not statistically significant due to the small patient sample, our results clearly show a tendency toward decreased diffusivity in neoplastic lesions with higher cellularity. The data from our study suggest that DWI is a feasible and potentially useful technique for the evaluation of epidural lesions that cause spinal cord compression on a per-patient basis.     

Diffusion tensor imaging and fiber tractography of the median nerve at 1.5T: optimization of <Emphasis Type="Italic">b</Emphasis> value

Objective  The objective of this study was to systematically assess the optimal b value for diffusion tensor imaging and fiber tractography of the median nerve at 1.5 T. Materials and methods  This is a prospective study which was carried out with institutional review board approval and written informed consent from the study subjects. Fifteen healthy volunteers (seven men, eight women; mean age, 31.2 years) underwent diffusion tensor imaging of the wrist. A single-shot spin-echo-based echo-planar imaging sequence (TR/TE, 7000/103 ms) was performed in each subject at eight different b values ranging from 325 to 1,550 s/mm². Number and length of reconstructed fiber tracts, fiber density index (FDi), fractional anisotropy (FA), and apparent diffusion coefficient (ADC) were calculated for the median nerve. Signal-to-noise ratio (SNR) was also calculated for each acquisition. The overall image quality was assessed by two readers in consensus by ranking representative fiber tract images for each subject using a scale range from 1 to 8 (1 = best to 8 = worst image quality). Results  Longest fibers were observed for b values between 675 and 1,025 s/mm². Maximum FDi was found at b values of 1,025 s/mm². FA was between 0.5 and 0.6 for all b values. ADC gradually decreased from 1.44 × 10⁻³ to 0.92 × 10⁻³ mm²/s with increasing b values. Maximum SNR ± standard deviation (175.4 ± 72.6) was observed at the lowest b value and decreased with increasing b values. SNR at b values of 1,025 s/mm² was 48.5% of the maximum SNR. Optimal fiber tract image quality was found for b values of 1,025 s/mm². Conclusions  The optimal b value for diffusion tensor imaging and fiber tractography of the median nerve at 1.5 T was 1,025 s/mm².     

Diffusion-weighted imaging of the brain: comparison of stimulated- and spin-echo echo-planar sequences

We used a rat model of focal cerebral ischaemia to compare stimulated-echo (STE) and spin-echo (SE) echo planar (EPI) diffusion-weighted sequences as regards image quality and accuracy of calculation of apparent diffusion coefficients (ADC). Focal cerebral ischaemia was induced by endovascular occlusion of the middle cerebral artery in five rats. MRI was performed on a 2.35 tesla imager. For diffusion-weighted imaging (DWI) we used STE-EPI and SE-EPI with different diffusion times (Δ) of 15, 30, 45, 60, 75 and 90 ms using values of b of 200, 300, 400, 500, 600 and 700 s/mm². We assessed image quality, the signal-to-noise-ratio (SNR) and the accuracy of the ADC calculated from both sequences. Infarcts were delineated in all cases, independent of sequence type and Δ. The image quality and SNR of the SE-EPI images were significantly better, with a higher SNR than STE-EPI images for short and intermediate values of Δ. However, when Δ reached 75 ms STE-EPI became superior to SE-EPI. ADC calculated from STE-EPI images were smaller than those from SE-EPI images for short and intermediate diffusion times, possibly because of the lower SNR of the former. We suggest that SE-EPI sequences be used for DWI of the brain, particularly on experimental systems and whole-body imagers with enhanced gradient hardware, where it is possible to run highly diffusion-weighted sequences (b > 500 s/mm²) with Δ less than 50 ms. However, when using very long values of Δ because of hardware restrictions or for measurement of restricted diffusion, STE sequences give better results. Received: 17 August 2000 Accepted: 5 December 2000     

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.     

Role of diffusion-weighted imaging with ADC mapping and in vivo H-MR spectroscopy in thyroid nodules

Purpose

To evaluate the role of the combined techniques of apparent diffusion coefficient (ADC) generated from diffusion-weighted magnetic resonance (MR) imaging (DWI) and metabolite spectrum acquired by magnetic resonance spectroscopy (MRS) in differentiating benign from malignant thyroid nodules.

Materials and methods

Thirty-seven patients with 56 thyroid nodules were evaluated with conventional MRI (T1- & T2-WI), DWI (b value 0.500 s/mm²; ADC values were calculated for the thyroid nodules), and MRS (for the presence or absence of choline peak). The ADC values and MRS findings were correlated with the histopathological results.

Results

The mean ADC of the malignant thyroid nodules (0.89 ± 0.27 × 10⁻³ mm²/s) was significantly lower than that of the mean ADC of the benign thyroid nodules (1.85 ± 0.24 × 10⁻³ mm²/s) (p value <0.0001). ADC value of 1.5 × 10⁻³ mm²/s was used as a cut-off value for differentiation benign from malignant thyroid nodules. The sensitivity, specificity, PPV&NPV of DWI in differentiating benign from malignant thyroid nodules were 94%, 95%, 94% & 95%, respectively (Kappa test 0.84, p value <0.0001), whereas they were 94.7%, 89.2%, 81.8% & 97.1% (Kappa test 0.8, p value <0.0001) with MRS, and 96%, 100%, 100% & 97% (Kappa test 0.96, p value <0.0001) with both DWI and MRS.

Conclusion

Both DWI and MRS are useful diagnostic modalities for characterization and differentiation between benign and malignant thyroid nodules. Our preliminary results showed that combination of DWI with calculated ADC values and metabolite spectrum acquired by MRS add more information to MRI and should be considered as an additional and complementary tool to conventional MRI for differentiating benign from malignant thyroid nodules.     

Role of diffusion-weighted MR imaging in cervical lymphadenopathy

The role of diffusion-weighted magnetic resonance imaging (MRI) for differentiation between various causes of cervical lymphadenopathy was evaluated. In a prospective study, 31 untreated patients (22 males and nine females, aged 5–70 years) with 87 cervical lymph nodes underwent diffusion-weighted MRI before performance of neck dissection (n=14), surgical biopsy (n=9) or core biopsy (n=8). Diffusion-weighted MR images were acquired with a b factor of 0 and 1,000 s/mm² using single-shot echo-planar sequence. Apparent diffusion coefficient (ADC) maps were reconstructed for all patients. The signal intensity of the lymph nodes was assessed on images obtained at b=0 or 1,000 s/mm² and from the ADC maps. The ADC value of lymph nodes was also calculated. On the ADC map, malignant nodes showed either low (n=52) or mixed (n=20) signal intensity and benign nodes revealed high (n=13) or low (n=2) signal intensity. The mean ADC value of metastatic (1.09±0.11×10⁻³ mm²/s) and lymphomatous (0.97±0.27×10⁻³ mm²/s) lymph nodes was significantly lower than that of benign (1.64±0.16×10⁻³ mm²/s) cervical lymph nodes (P<0.04). When an ADC value of 1.38×10⁻³ mm²/s was used as a threshold value for differentiating malignant from benign lymph nodes, the best results were obtained with an accuracy of 96%, sensitivity of 98%, specificity of 88%, positive predictive value of 98.5% and negative predictive value of 83.7%. The smallest detected lymph node was 0.9 cm. In conclusion, diffusion-weighted MRI with ADC mapping is a new promising technique that can differentiate malignant from benign lymph nodes and delineate the solid viable part of the lymph node for biopsy. This technique provides additional useful physiological and functional information regarding characterization of cervical lymph nodes.     

Feasibility of a RARE-based sequence for quantitative diffusion-weighted MRI of the spine

The feasibility of a diffusion-weighted single-shot fast-spin-echo sequence for the diagnostic work-up of bone marrow diseases was assessed. Twenty healthy controls and 16 patients with various bone marrow pathologies of the spine (bone marrow edema, tumor and inflammation) were examined with a diffusion-weighted single-shot sequence based on a modified rapid acquisition with relaxation enhancement (mRARE) technique; four diffusion weightings (b-values: 50, 250, 500 and 750 s/mm²) in three orthogonal orientations were applied. Apparent diffusion coefficients (ADCs) were determined in the bone marrow and in the intervertebral discs of healthy volunteers and in diseased bone marrow. Ten of the 20 volunteers were repeatedly scanned within 30 min to examine short-time reproducibility. Spatial reproducibility was assessed by measuring ADCs in two different slices including the same lesion in 12 patients. The ADCs of the lesions exhibited significantly higher values, (1.27 ± 0.32)×10⁻³ mm²/s, compared with healthy bone marrow, (0.21 ± 0.10)×10⁻³ mm²/s. Short-time and spatial reproducibility had a mean coefficient of variation of 2.1% and 6.4%, respectively. The diffusion-weighted mRARE sequence provides a reliable tool for determining quantitative ADCs in vertebral bone marrow with adequate image quality.     

Characterization of pediatric head and neck masses with diffusion-weighted MR imaging

We aimed to assess the clinical usefulness of the ADCs calculated from diffusion-weighted echo-planar MR images in the characterization of pediatric head and neck masses. This study included 78 pediatric patients (46 boys and 32 girls aged 3 months–15 years, mean 6 years) with head and neck mass. Routine MR imaging and diffusion-weighted MR imaging were done on a 1.5-T MR unit using a single-shot echo-planar imaging (EPI) with a b factor of 0.500 and 1,000 s mm⁻². The ADC value was calculated. The mean ADC values of the malignant tumours, benign solid masses and cystic lesions were (0.93 ± 0.18) × 10⁻³, (1.57 ± 0.26) × 10^–3 and (2.01 ± 0.21 )× 10^–3 mm² s⁻¹, respectively. The difference in ADC value between the malignant tumours and benign lesions was statistically significant (p < 0.001). When an apparent diffusion coefficient value of 1.25 × 10^–3 mm² s⁻¹ was used as a threshold value for differentiating malignant from benign head and neck mass, the best results were obtained with an accuracy of 92.8%, sensitivity of 94.4%, specificity of 91.2%, positive predictive value of 91% and negative predictive value of 94.2%. Diffusion-weighted MR imaging is a new promising imaging approach that can be used for characterization of pediatric head and neck mass.     

Diagnostic ability of apparent diffusion coefficients for lymphomas and carcinomas in the pharynx

We evaluated the diagnostic ability of diffusion-weighted imaging for the differentiation between lymphomas and carcinomas in the pharynx and between carcinomas with different histological types in the pharynx. T1-weighted, fat-suppressed T2-weighted, and diffusion-weighted MR imaging was performed on 14 patients with pharyngeal lymphomas, 26 patients with carcinomas of the pharynx, 5 patients with adenoidal hypertrophy, and 22 patients with normal tonsils. Apparent diffusion coefficients (ADCs) were determined by using two b factors (500 and 1,000 s/mm²). The ADCs of lymphomas were significantly smaller (0.454 ± 0.075 × 10⁻³ mm²/s) than those of carcinomas (0.863 ± 0.238 × 10⁻³ mm²/s). The ADCs of poorly differentiated and undifferentiated carcinomas (0.691 ± 0.149 × 10⁻³ mm²/s) were significantly smaller than those of moderately differentiated and well-differentiated carcinomas (0.971 ± 0.221 × 10⁻³ mm²/s), but were significantly larger than those of lymphomas. When an ADC smaller than 0.560 × 10⁻³ mm²/s was used for predicting lymphomas, we obtained the highest accuracy of 96%, with 100% sensitivity and 94% specificity, 86% positive predictive value, and 100% negative predictive value. Therefore, ADC measurements effectively differentiate lymphomas from carcinomas in the pharynx and could be a useful adjunct to biopsy-based development of treatment planning.     

Diagnostic value of apparent diffusion coefficients to differentiate benign from malignant vertebral bone marrow lesions

Aim

The aim of this study is to evaluate the value of the apparent diffusion coefficient (ADC) obtained in diffusion-weighted (DW) MR sequences for the differentiation between malignant and benign bone marrow lesions.

Method

Forty-five patients with altered signal intensity vertebral bodies on conventional MR sequences were included. The cause of altered signal intensity was benign osteoporotic collapse in 16, acute neoplastic infiltration in 15, and infectious processes in 14; based on plain-film, CT, bone scintigraphy, conventional MR studies, biopsy or follow-up. All patients underwent isotropic DW MR images (multi-shot EPI, b values of 0 and 500 s/mm²). Signal intensity at DW MR images was evaluated and ADC values were calculated and compared between malignancy, benign edema and infectious spondylitis.

Results

Acute malignant fractures were hyperintense compared to normal vertebral bodies on the diffusion-weighted sequence, except in one patient with sclerotic metastases. Mean ADC value from benign edema (1.9 ± 0.39 × 10⁻³ mm²/s) was significantly (p < 0.0001) higher than untreated metastasic lesions (0.9 ± 1.3 × 10⁻³ mm²/s). Mean ADC value of infectious spondilytis (0.96 ± 0.49 × 10⁻³ mm²/s) was not statistically (p > 0.05) different from untreated metastasic lesions. ADC value was low (0.75 × 10⁻³ mm²/s) in one case of subacute benign fracture.

Conclusions

ADC values are a useful complementary tool to characterize bone marrow lesions, in order to distinguish acute benign fractures from malignant or infectious bone lesions. However, ADC values are not valuable in order to differentiate malignancy from infection.     

Optimization of b value in diffusion-weighted MRI for characterization of benign and malignant gynecological lesions

Purpose:

To explore the optimal b value in diffusion‐weighted (DW)‐MRI for differentiation of benign and malignant gynecological lesions.

Materials and Methods:

Consecutive 58 patients (66 lesions) with pathologically confirmed diagnosis of gynecological disease were included in the study. Routine pelvic MRI sequences were used for defining the lesions and reviewed independently for benignity/ malignity. Single‐shot echoplanar imaging (SH‐EPI) DW‐MRI with eight b values and nine apparent diffusion coefficient (ADC) maps were obtained. The lesions were analyzed qualitatively on DW‐MRI for benignity/malignity on a five‐point‐scale and quantitatively by measurement of apparent diffusion coefficient (ADC) values. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic accuracy of ADC values for differentiating between benign and malignant lesions. Pathology results were the reference standard.

Results:

Differentiation between benign and malignant gynecological lesions using visual scoring was found to be successful with b values of 600, 800, or 1000 s/mm². The mean ADC values of malignant lesions were significantly lower than those of benign lesions for all b value (P < 0.005). The ADCs with b = 0 and 600, 0 and 1000 s/mm², 0, 600, 800 and 1000 s/mm², and all b values were more effective for distinguishing malignant from benign gynecological lesions (Az = 0.851, 0.847, 0.848, 0.849, respectively). Using ADC with b = 0, 600, 800, and 1000 s/mm², a threshold value of 1.20 × 10^?3 mm²/s permitted this distinction with a sensitivity of 83%, a specificity of 81%.

Conclusion:

DW‐MRI is an important method, and the optimal b values are between 600 and 1000 s/mm² for differentiation between benign and malignant gynecological lesions. J. Magn. Reson. Imaging 2012;35:650‐659. © 2011 Wiley Periodicals, Inc.

     

Use of FDG-PET in differentiating benign from malignant compression fractures

Objective The objective was to evaluate the use of fluorodeoxyglucose positron emission tomography (FDG-PET) in differentiating benign from malignant compression fractures. Patients and methods In a retrospective analysis, we identified 33 patients with 43 compression fractures who underwent FDG-PET. On FDG-PET the uptake pattern was recorded qualitatively and semiquantitatively and fractures were categorized as benign or malignant. Standardized uptake values (SUV) were obtained. MRI, CT, and biopsy results as well as clinical follow-up for 1–3 years served as standards of reference. The Student’s t test was used to determine whether there was a statistically significant difference between the SUV for benign and malignant compression fractures. Results There were 14 malignant and 29 benign compression fractures, including 5 acute benign fractures. On FDG-PET, 5 benign fractures were falsely classified as malignant (false-positive). Three of these patients underwent prior treatment with bone marrow-stimulating agents. There were two false-negative results. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FDG-PET in differentiating benign from malignant compression fractures were 86%, 83%, 84%, 71%, and 92% respectively. The difference between SUV values of benign and malignant fractures was statistically significant (1.9 ± 0.97 for benign and 3.9 ± 1.52 for malignant fractures, p < 0.001). SUV of benign acute and chronic fractures were not statistically significant. Conclusion Fluorodeoxyglucose positron emission tomography is useful in differentiating benign from malignant compression fractures. Therapy with bone marrow-stimulating agents can mimic malignant involvement.     

The effect of intravenous gadolinium-DTPA on diffusion-weighted imaging

Introduction Diffusion-weighted imaging (DWI) is usually performed before injection of intravenous paramagnetic contrast medium. Occasionally, it may be necessary to perform or to repeat DWI after such administration. Our purpose was to evaluate the effect of intravenous gadodiamide (Gd [DTPA-BMA]) on DWI.Methods DWI was performed on 88 brain lesions immediately before, immediately after, and 5–10 min following the end of 0.1 mmol/kg Gd [DTPA-BMA] administration. Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of the lesions, and the SNRs of normal brain tissue were calculated on b=0 s/mm² and b=1,000 s/mm² DW images. Apparent diffusion coefficient (ADC) values of the lesions were measured on ADC maps. A paired t-test was used to determine the significance of differences between the values before and after administration of contrast medium.Results The lesions consisted of 23 intraaxial and 11 extraaxial masses, 19 ischemic strokes, 15 intracranial hemorrhages and 20 demyelinating lesions. Images before and after contrast administration were not significantly different regarding SNRs and CNRs on DWI. This statement was also true for strongly enhanced lesions. However, ADC values significantly decreased after contrast medium injection on early post-contrast DWI in normal brain tissue (1%, P<0.049) and (3%, P<0.008) in lesions. By contrast, on late images, ADC values were normalized.Conclusion Contrast medium injection had significant and time-dependent effects on ADC values. Therefore, only pre-contrast and late DW images should be used in quantitative ADC studies.