Why Is a b-value Range of 1500–2000 s/mm2 Optimal for Evaluating Prostatic Index Lesions on Synthetic Diffusion-Weighted Imaging?

ObjectiveIt is uncertain why a b-value range of 1500–2000 s/mm² is optimal. This study was aimed at qualitatively and quantitatively analyzing the optimal b-value range of synthetic diffusion-weighted imaging (sDWI) for evaluating prostatic index lesions.Materials and MethodsThis retrospective study included 92 patients who underwent DWI and targeted biopsy for magnetic resonance imaging (MRI)-suggested index lesions. We generated sDWI at a b-value range of 1000–3000 s/mm² using dedicated software and true DWI data at b-values of 0, 100, and 1000 s/mm². We hypothesized that lesion conspicuity would be best when the background (i.e., MRI-suggested benign prostatic [bP] and periprostatic [pP] regions) signal intensity (SI) is suppressed and becomes homogeneous. To prove this hypothesis, we performed both qualitative and quantitative analyses. For qualitative analysis, two independent readers analyzed the b-value showing the best visual conspicuity of an MRI-suggested index lesion. For quantitative analysis, the readers assessed the b-value showing the same bP and pP region SI. The 95% confidence interval (CI) or interquartile range of qualitatively and quantitatively selected optimal b-values was assessed, and the mean difference between qualitatively and quantitatively selected b-values was investigated.ResultsThe 95% CIs of optimal b-values from qualitative and quantitative analyses were 1761–1805 s/mm² and 1640–1771 s/mm² (median, 1790 s/mm² vs. 1705 s/mm²; p = 0.003) for reader 1, and 1835–1895 s/mm² and 1705–1841 s/mm² (median, 1872 s/mm² vs. 1763 s/mm²; p = 0.022) for reader 2, respectively. Interquartile ranges of qualitatively and quantitatively selected optimal b-values were 1735–1873 s/mm² and 1573–1867 s/mm² for reader 1, and 1775–1945 s/mm² and 1591–1955 s/mm² for reader 2, respectively. Bland–Altman plots consistently demonstrated a mean difference of less than 100 s/mm² between qualitatively and quantitatively selected optimal b-values.Conclusionb-value range showing a homogeneous background signal may be optimal for evaluating prostatic index lesions on sDWI. Our qualitative and quantitative data consistently recommend b-values of 1500–2000 s/mm².     

Apparent diffusion coefficient mapping of experimental focal cerebral ischemia using diffusion-weighted echo-planar imaging

Diffusion-weighted, echo-planar imaging (EPI) was used to map regional changes In the apparent diffusion coefficient (ADC) during experimental focal ischemia in the rat brain following permanent middle cerebral arterial occlusion (MCAO). Sixteen 64 × 64 diffusion-weighted EPIs were acquired in 32 s with successively increasing amplitudes of the diffusion-sensitive gradient pulses. A linear least-squares regression algorithm was used to fit 15 of the 16 two-dimensional matrices, on a pixel-by-pixel basis, to solve for the slope from which the ADC value was calculated. The correlation coefficient of the fit, R² was used to filter the final ADC maps, and the ADCs were then scaled appropriately to be displayed in a 256 gray level format. Ranges (bins) of 0.05 × 10⁻³ mm²/s were then grouped and color coded to qualify and quantify the evolution of ischemia in the MCA territory. The percentage of area in the ischemic and contralateral hemispheres in seven ADC bins were calculated at 30, 60, and 120 min after MCAO for 10 animals and demonstrated a significant increase in ADC bins below 0.45 × 10⁻³ mm²/s and a decrease in bins above 0.50 × 10⁻³ mm²/s over the. The postmortem infarct area, as measured by TTC staining, was highly correlated with the portion of the ischemic hemisphere falling below ADC values of 0.55 × 10⁻³ mm²/s at 2 h after stroke onset. These studies suggest that focally ischemic brain tissue can be quantitatively subdivided according to ADC values and that ADC values below 0.55 × 10⁻³ mm²/s 2 h following ischemia highly predict infarction in a rat permanent occlusion stroke model.     

The value of b required to avoid T2 shine-through from old lucunar infarcts in diffusion-weighted imaging

Multiple small infarcts of different ages are common in small-vessel disease. Diffusion-weighted imaging (DWI) is a powerful method for discriminating new from chronic lesions. This can be done on the diffusion-weighted images provided that b is sufficiently high. Our purpose was to determine that critical value of b. We reviewed DWI from a previous study of acute, mainly lacunar strokes, and selected 18 old lacunar infarcts, well defined on uncoded images with b 0 s/m² (i. e., T2-weighted images) but invisible on DWI with b 1200 × 10⁶ s/m². We used a 1.5 tesla imager and single-shot echo-planar technique. We had seven separate acquisitions with echo time 123 ms and b in steps between 0 and 1200 × 10⁶ s/m². Two neuroradiologists blinded to the selection of lesions carried out two different lesion-detection procedures, thereby testing each lesion four times, giving a total of 72 tests of b values. The results were consistent, indicating a level for detection of 800 × 10⁶ s/m² in two tests, 400–600 × 10⁶ s/m² in 65 tests and at lower values in the remainder. For imagers up to 1.5 tesla, at long repetition times and an echo time up to 120 ms T2-shine through of old lacunar infarcts can be avoided using b of 1000 × 10⁶ s/m². Received: 5 July 2000 Accepted: 6 December 2000     

Diffusion-weighted magnetic resonance imaging for diagnosis of liver fibrosis and inflammation in chronic viral hepatitis: the performance of low or high B values and small or large regions of interest

Objective

To investigate the performance of different b values and regions of interest (ROI) for diagnosing liver fibrosis in patients with chronic viral hepatitis by using diffusion-weighted (DW) magnetic resonance imaging (MRI).

Methods

Eleven healthy participants and 33 patients with viral hepatitis B or C were enrolled. The stage of liver fibrosis and the grade of necroinflammation were determined by using a histologic activity index. Single-shot spin-echo echo-planar DW-MRI was performed in all participants at b values of 0-500, 0-700, and 0-1000 s/mm² by using 2 circular small and large ROIs of 100 and 200 mm². To evaluate the performance of different b values for determining cirrhosis, the receiver-operating characteristic curves were depicted, and the areas under the curves were compared.

Results

The average values of apparent diffusion coefficients significantly decreased with increasing stage or grade categories at all the 3 b values and for both small and large ROIs. The performance at b = 500 s/mm² was significantly better than b = 1000 s/mm² for determining cirrhosis or bridging fibrosis. The cut point of 153.4 for apparent diffusion coefficient (×10⁻⁵ mm²/s) at b = 500 s/mm² could determine cirrhosis or bridging fibrosis with a sensitivity of 96% and specificity of 82%. No difference was found between the average apparent diffusion coefficient values of large or small ROIs. Also, there was no difference in performance of large or small ROIs in the diagnosis of liver fibrosis.

Conclusions

This study provided beneficial data for clinical utilisation of DW-MRI in diagnosing liver fibrosis: b = 500 s/mm² is better in performance than b = 1000 s/mm², and a small ROI of 100 mm² is sufficient for determining cirrhosis or bridging fibrosis.     

The use of dietary loading of 133Cs as a potassium substitute in NMR studies of tissues

¹³³Cs NMR chemical shifts and relaxation times have been measured for tissue samples in vitro and in vivo from rats which have been fed on a high cesium, low potassium diet, which leads to a predominantly intracellular distribution of this ion, similar to that of K ⁺. The high sensitivity, large chemical shift range, and narrow linewidths of ¹³³Cs, compared with ³⁹K, allow chemical shift differences to be observed between tissues, and in subcellular organelles such as mitochondria. For example, in vitro tissue chemical shifts, relative to 150 mM CsCl, are 1.06 ± 0.11 ppm for liver, 0.02 ± 0.05 ppm for brain, 1.76 ± 0.20 ppm for erythrocytes, and ?0.13 ± 0.02 ppm for plasma. T₁ and spin-echo T₂ values range from 1.26 ± 0.05 s (T₂), and 0.028 ± 0.006 s (T₂) for liver, to 6.49 ± 0.19 s and 1.12 ± 0.03 s for plasma. ¹³³Cs relaxation times show the same relative trends between tissues as are observed in ³⁹K tissue Studies.     

Assessment of vasogenic edema in eclampsia using diffusion imaging

We qualitatively assessed the regional distribution of vasogenic edema in a case of postpartum eclampsia. Although diffusion-weighted imaging showed no abnormalities, bilateral high signal was seen on T2-weighted images and apparent diffusion coefficient (ADC) maps. ADC of 1.45 ± 0.10 mm²/s × 10^–3 for the posterior cerebral artery (PCA) territory and 1.22 ± 0.12 mm²/s × 10^–3 for the watershed areas were significantly higher than those in the territories of the anterior (0.85 ± 0.07 mm²/s × 10^–3) and middle cerebral (0.79 ± 0.06 mm²/s × 10^–3)arteries (P < 0.05). The predilection of ADC changes within the PCA territory and in a previously undescribed watershed distribution supports the hypothesis that vasogenic edema in eclampsia is due to hypertension-induced failure of vascular autoregulation. Received: 8 July 1999 Accepted: 25 April 2000     

Validation of functional diffusion maps (fDMs) as a biomarker for human glioma cellularity

Purpose:

To present comprehensive examinations of the assumptions made in functional diffusion map (fDM) analyses and provide a biological basis for fDM classification.

Materials and Methods:

Sixty‐nine patients with gliomas were enrolled in this study. To determine the sensitivity of apparent diffusion coefficients (ADCs) to cellularity, cell density from stereotactic biopsy specimens was correlated with preoperative ADC maps. For definition of ADC thresholds used for fDMs, the 95% confidence intervals (CI) for changes in voxel‐wise ADC measurements in normal appearing tissue was analyzed. The sensitivity and specificity to progressing disease was examined using both radiographic and neurological criteria.

Results:

Results support the hypothesis that ADC is inversely proportional to cell density with a sensitivity of 1.01 × 10^?7 [mm²/s]/[nuclei/mm²]. The 95% CI for white matter = 0.25 × 10^?3 mm²/s, gray matter = 0.31 × 10^?3 mm²/s, a mixture of white and gray matter = 0.40 × 10^?3 mm²/s, and a mixture of white matter, gray matter, and cerebrospinal fluid = 0.75 × 10^?3 mm²/s. Application of these measurements as ADC thresholds produce varying levels of sensitivity and specificity to disease progression, which were all significantly better than chance.

Conclusion:

This study suggests fDMs are valid biomarkers for brain tumor cellularity. J. Magn. Reson. Imaging 2010;31:538–548. ©2010 Wiley‐Liss, Inc.

     

Diffusion-weighted MRI in cystic or necrotic intracranial lesions

Our purpose was to investigate the signal intensities of cystic or necrotic intracranial lesions on diffusion-weighted MRI (DWI) and measure their apparent diffusion coefficients (ADC). We examined 39 cystic or necrotic intracranial lesions in 33 consecutive patients: five malignant gliomas, seven metastases, two other necrotic tumours, a haemangioblastoma, three epidermoids, an arachnoid cyst, seven pyogenic abscesses, 12 cases of cysticercosis and one of radiation necrosis. DWI was performed on a 1.5 T unit using a single-shot echo-planar spin-echo pulse sequence with b 1000 s/mm². The signal intensity of the cystic or necrotic portion on DWI was classified by visual assessment as markedly low (as low as cerebrospinal fluid), slightly lower than, isointense with, and slightly or markedly higher than normal brain parenchyma. ADC were calculated in 31 lesions using a linear estimation method with measurements from b of 0 and 1000 s/mm². The cystic or necrotic portions of all neoplasms (other than two metastases) gave slightly or markedly low signal, with ADC of more than 2.60 × 10⁻³ mm²/s. Two metastases in two patients showed marked high signal, with ADC of 0.50 × 10⁻³ mm²/s and 1.23 × 10⁻³ mm²/s, respectively. Epidermoids showed slight or marked high signal, with ADC of less than 1.03 × 10⁻³ mm²/s. The arachnoid cyst gave markedly low signal, with ADC of 3.00 × 10⁻³ mm²/s. All abscesses showed marked high signal, with ADC below 0.95 × 10⁻³ mm²/s. The cases of cysticercosis showed variable signal intensity; markedly low in five, slightly low in three and markedly high in four. Received: 17 November 1999/Accepted: 3 February 2000     

Treatment of Bowen’s disease with a specially designed radioactive skin patch

Bowen’s disease can be treated by various methods, including surgical excision, cryosurgery, laser ablation, curettage, Mohs’ microsurgery and ionizing radiation. Radiotherapy has been a useful therapeutic modality in the treatment of Bowen’s disease and other skin cancers in areas which are difficult to excise, especially the central areas of the face, including eyelids, nose and lips. To overcome some of the disadvantages of external radiotherapy, a specially designed skin patch coated with high-energy beta-emitter holmium-166 was made for topical application at our institute. Twenty-nine sites of Bowen’s disease in eight patients, confirmed by skin biopsy, were treated with ¹⁶⁶Ho patches. The patches were applied to the surface of skin cancers for 30–60 min for a total radiation dose of 35 Gy (3500 rads). One to two weeks after application of the ¹⁶⁶Ho patch, desquamation, erythema or erosion developed in treated sites, but these acute radiation reactions healed gradually with epithelial regeneration, and they showed good functional and cosmetic results without any complications. Follow-up biopsies were performed 1–5 months after ¹⁶⁶Ho patch therapy, and they did not show any signs of Bowen’s disease. One to two years after treatment with ¹⁶⁶Ho skin patches, there were no recurrences of Bowen’s diseases and no late complications. The ¹⁶⁶Ho patch is an effective and convenient alternative method for the treatment of Bowen’s disease that yields good cosmetic and functional results. Received 14 December 1999 and in revised form 7 March 2000     

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.     

Role of diffusion-weighted imaging in prediction of nipple-areolar complex invasion by breast cancer

The aim of this workThe aim of this work was to estimate the role of diffusion-weighted imaging (DWI) in predicting malignant invasion of the nipple-areolar complex (NAC) by underlying breast cancer.Material and methodsThis prospective study included 70 female patients with breast cancer with a mean age of 45.8 years (range: 28–68). DWI of the breast was done for all patients. Apparent diffusion coefficient (ADC) maps were automatically constructed. The mean ADC values of NAC were independently measured by two observers who are experts in breast imaging and correlated with the results of histopathological examinations.ResultsBoth observers found a significantly lower ADC value of malignant NAC invasion (n = 18) when compared with free NAC (n = 52), with mean ADC value for malignant NAC invasion was 0.86 ± 0.35 × 10⁻³ mm²/s and 0.84 ± 0.08 × 10⁻³ mm²/s for observer one and two respectively versus mean ADC value of 1.34 ± 0.25 × 10⁻³ mm²/s and 1.4 ± 0.26 × 10⁻³ mm²/s for free NAC by observer one and two respectively (P-value =0.001). Observer one found that a cutoff ADC value of 1.05 × 0⁻³ mm²/s can predict malignant NAC invasion with 0.975 AUC, 92.8% accuracy, 94.4% sensitivity, and 92.3% specificity. Observer two found that a cutoff ADC value of 0.95 × 10⁻³ mm²/s can predict malignant NAC invasion with 0.992 AUC, 95.7% accuracy, 88.9% sensitivity, and 98.1% specificity.ConclusionDWI can predict malignant NAC invasion in patients with breast cancer.     

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.     

High b-value diffusion (b = 3000 s/mm2) MR imaging in cerebral gliomas at 3T: visual and quantitative comparisons with b = 1000 s/mm2

BACKGROUND AND PURPOSE: High b-value diffusion-weighted imaging (DWI) provides different features not appreciated at lower b-value and have been recently studied in several clinical issues. The purpose of this study was to assess whether DWI at b = 3000 s/mm² is more useful in discriminating high-grade and low-grade gliomas than DWI at b = 1000 s/mm² at 3T.MATERIALS AND METHODS: DWIs at both b = 1000 and 3000 s/mm² were performed at 3T in 62 patients, 49 high-grade gliomas (20 World Health Organization [WHO] grade III and 29 grade IV) and 13 low-grade gliomas (13 grade II). Visual assessments based on 5-point scaled evaluations, receiver operating characteristic (ROC) curve analysis, and quantitative assessment based on DWI signal intensity (SI) ratio (tumor SI/normal SI) and apparent diffusion coefficient (ADC) values were compared between DWIs at b = 1000 and 3000 s/mm².RESULTS: By visual assessment, DWI at b = 3000 s/mm² showed more conspicuous hyperintensity in high-grade gliomas and hypointensity in low-grade gliomas than DWI at b = 1000 s/mm². Sensitivity and specificity at b = 3000 s/mm² were higher than at b = 1000 s/mm² (83.7%, 84.6% vs 69.4%, 76.9%, respectively). Quantitative assessments showed that mean SI ratio of high-grade gliomas was significantly higher than that of low-grade gliomas at both b-values. The mean ADC value of high-grade gliomas was significantly lower than that of low-grade gliomas at both b-values. The difference between the SI ratios of high-grade and low-grade gliomas was significantly larger at b = 3000 s/mm² than at b = 1000 s/mm².CONCLUSION: DWI at b = 3000 s/mm² is more useful than DWI at b = 1000 s/mm² in terms of discriminating high-grade and low-grade gliomas at 3T.

Diffusion-weighted imaging (DWI) is a sensitive technique that reflects microscopic water diffusion with the use of a pair of strong diffusion gradients¹ and has been used routinely for the early detection of cerebral ischemia with diffusion restriction.² DWI and apparent diffusion coefficient (ADC) value have been studied in other clinical situations, including the differential diagnosis and grading of brain tumors.^3–15Although it is known that higher cellularity in high-grade glioma results in greater diffusion restriction and a reduction in ADC values, whereas lower cellularity in low-grade glioma increases ADC values,^8–14 DWI at a standard b-value (b = 1000 s/mm²) at 1.5T barely differentiates high-grade and low-grade gliomas in many cases because of overlapping signal intensities (SI) on DWI and ADC maps.Theoretically, a higher b-value DWI provides better contrast with its reflection of more tissue diffusivity and less T2 shinethrough effect.^{16, 17} However, at 1.5 or lower field strength, higher b-values are not usually used in clinical practice because of poor image quality secondary to an inferior signal-to-noise ratio (SNR).^18–21 Recently, stronger gradients and faster slew rates have permitted high b-value DWI, particularly in 3T units, because higher SNRs at 3T compensate for the inferior SNRs of high b-value DWI without increasing data acquisition time.The purpose of our investigation was to assess whether DWI at high b-value (b = 3000 s/mm²), is better than DWI at a standard b-value (b = 1000 s/mm²) for the differential diagnosis of high-grade and low-grade cerebral gliomas in clinical practice at 3T.     

Apparent Diffusion Coefficient of Uterine Leiomyoma as a Predictor of the Potential Response to Uterine Artery Embolization

PurposeTo determine the utility of the apparent diffusion coefficient (ADC) of uterine leiomyoma for prediction of the potential response to uterine artery embolization (UAE).Materials and MethodsThis prospective study included 49 patients with uterine leiomyomas who underwent diffusion-weighted magnetic resonance (MR) imaging before UAE between May 2011 and January 2012. All patients also underwent 3-month follow-up MR imaging after UAE. Using conventional and diffusion-weighted MR imaging sequences, 72 uterine leiomyomas ≥ 3 cm were prospectively evaluated. The volume of each leiomyoma was calculated, and quantitative measurement of ADC was performed. Regression analysis was used to evaluate the relationship between ADC and volumetric response after UAE. Receiver operating characteristic curve analysis was performed to determine the sensitivity and specificity of ADC for prediction of the potential response to UAE. Interclass correlation coefficient analysis was used to assess interobserver variability between two radiologists.ResultsVolume reduction rates of leiomyomas after UAE ranged from 0.2%–89.1% (mean, 44.1%). ADC ranged from 0.559 × 10^?3 mm²/s to 1.814 × 10^?3 mm²/s (mean, 1.170 × 10^?3 mm²/s). ADC was statistically significantly related to volumetric response of leiomyomas (P = .014). Using a threshold of 1.092 × 10^?3 mm²/s, the sensitivity and specificity of ADC for prediction of > 50% volume reduction of the leiomyoma after UAE were 82.6% and 52.3%, respectively. Using a threshold of 1.023 × 10^?3 mm²/s, the sensitivity and specificity of ADC for prediction of < 30% volume reduction were 80.8% and 33.3%, respectively. The interclass correlation coefficient for measuring ADC of uterine leiomyomas between two radiologists was 0.98.ConclusionsADC of uterine leiomyomas was significantly related to the volume reduction after UAE. ADC may be useful in predicting the potential response to UAE. A high ADC of the uterine leiomyoma may be associated with a greater volume reduction after UAE.     

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.     

The efficacy of apparent diffusion coefficient value calculation in differentiation between malignant and benign thyroid nodules

PurposeTo evaluate the efficacy of apparent diffusion coefficient (ADC) calculation in differentiation between malignant and benign thyroid nodules.Methods and materialsA prospective study was conducted in 52 patients. Diffusion-weighted echoplanar imaging was performed and b factors were taken as 0 and 400 s/mm².ResultsThe mean ADC value for malignant thyroid nodules was 0.829±0.179×10^?3 mm²/s and that for benign thyroid nodules was 1.984±0.482×10^?3 mm²/s. The mean ADC value for malignant nodules was significantly lower than that for benign nodules (P=.0001).ConclusionADC value calculation is an effective method in differentiation of malignant thyroid nodules from benign ones.     

Diffusion tensor imaging in polymicrogyria: a report of three cases

Introduction Polymicrogyria (PMG), a neuronal migration disorder, commonly manifests as a seizure disorder. The aim of this study was to look for the abnormalities in the underlying white matter using diffusion tensor imaging (DTI) that appeared normal on conventional magnetic resonance imaging (MRI) in patients with PMG.Methods DTI was performed in three patients with PMG and eight age- and sex-matched healthy controls. Fractional anisotropy (FA) and mean diffusivity (MD) values were calculated for the cortex and adjoining subcortical white matter in both controls and patients.Results We observed a significantly decreased mean FA value with no significant change in the MD value in subcortical white matter underlying polymicrogyric cortex (FA=0.23±0.04, MD=1.0±0.05×10⁻³ mm²/s) as compared to both contralateral (FA=0.32±0.04, MD=1.0±0.05×10⁻³ mm²/s) and normal control (FA=0.32±0.04, MD=1.0±0.06×10⁻³ mm²/s) white matter. Significantly increased MD and decreased FA values were also observed in the polymicrogyric cortex (FA=0.08±0.01, MD=1.2±0.10×10⁻³ mm²/s) as compared to normal contralateral (FA=0.12±0.04, MD=1.1±0.09×10⁻³ mm²/s) and normal control (FA=0.12±0.01, MD=1.1±0.09×10⁻³ mm²/s) cortex.Conclusion Significantly decreased FA values with no change in MD values in the subcortical white matter subjacent to polymicrogyric cortex reflect microstructural changes in the white matter probably due to the presence of ectopic neurons.     

Role of diffusion-weighted MR imaging in chest wall masses

Purpose

To determine the role of diffusion weighted MR imaging and apparent diffusion coefficient (ADC) in chest wall masses.

Materials and methods

This study included 62 patients with chest wall masses. They underwent routine MR imaging and diffusion MR weighted imaging on a 1.5 T MR unit (Symphony-Siemens). Diffusion MR imaging was done with diffusion factor b value of 0, 500, and 1000 s/mm². The apparent diffusion coefficient (ADC) map was reconstructed. The signal intensity was visually assessed on ADC maps and ADC value was measured in chest wall lesions. The mean ADC values correlated with histo-pathological results.

Results

Adequate ADC maps were obtained in 62 patients. The mean ADC values of chest wall lesions were 1.76 ± 0.08 × 10⁻³ mm²/s in inflammatory lesion, 3.21 ± 0.05 × 10⁻³ mm²/s in the cystic lesions, 1.67 ± 0.03 × 10⁻³ mm²/s in neurofibroma, 2.12 ± 0.07 × 10⁻³ in haemangioma, and 0.89 ± 0.06 × 10⁻³ mm²/s in malignant tumors. The mean ADC value of the malignant tumor was significantly different from that of benign chest wall tumors (P < 0.001).

Conclusion

Diffusion weighted MR imaging is a new imaging modality for differentiation malignant from benign chest wall masses. In addition, it has a role in characterization of different malignant and benign tumors.     

Apparent diffusion coefficient values of cryptorchid testes and malignant transformation of cryptorchidism (MTC) (seminoma) in postpubertal patients

Objectives:Diffusion-weighted imaging signal contrast can be quantified by apparent diffusion coefficient (ADC) maps, which reflect the diffusion properties of the examined tissue and are helpful for identifying pathology. To determine ADC values of cryptorchid testes in post-pubertal patients and assess performance for characterizing cryptorchid testes.Methods:The medical records from 35 patients with unilateral scrotal vacuity were retrospectively reviewed. Data were analyzed in three groups: Group A, normal testes (i.e. the contralateral testes of the patients with cryptorchidism or MTC); Group B, cryptorchid testes; and Group C, malignant transformation of cryptorchidism (MTC) (seminoma). DWI used b-values of 0 and 800 s/mm². Mean ADC values were compared using the independent samples t-test. The ability of ADC values was assessed using receiver operating characteristic curve analysis. The sensitivity, specificity, and accuracy were calculated.Results:Mean ADC values for normal testes, cryptorchid testes, and MTC were 1.18 ± 0.18×10⁻³ mm²/s, 1.82 ± 0.40×10⁻³ mm²/s, and 0.80 ± 0.06×10⁻³ mm²/s, respectively. There were statistically significant differences in mean ADC values between normal testes and cryptorchid testes or MTC (p < 0.001). The cut-off ADC value for differentiating normal testes from cryptorchid testes was 1.47 × 10⁻³ mm²/s. The sensitivity, specificity, and accuracy were 88%, 91%, and 90%, respectively. The cut-off ADC value for differentiating normal testes from MTC was 1.22 × 10⁻³ mm²/s. The sensitivity, specificity, and accuracy were 100%, 31%, and 43%, respectively.Conclusion:ADC values of cryptorchid testes may be used to inform clinical decision-making and also monitor testicular function in patients who retain undescended testicles or post-operatively.Advances in knowledge:Mean ADC values of cryptorchidism and MTC (seminoma) were used to reflect their pathological features.     

Diffusion-weighted MR imaging of pleural fluid: differentiation of transudative vs exudative pleural effusions

The aim of this study was to evaluate the ability of diffusion-weighted MRI in differentiating transudative from exudative pleural effusions. Fifty-seven patients with pleural effusion were studied. Diffusion-weighted imaging (DWI) was performed with an echo-planar imaging (EPI) sequence (b values 0, 1000 s/mm²) in 52 patients. The apparent diffusion coefficient (ADC) values were reconstructed from three different regions. Subsequently, thoracentesis was performed and the pleural fluid was analyzed. Laboratory results revealed 20 transudative and 32 exudative effusions. Transudates had a mean ADC value of 3.42±0.76×10^–3 mm²/s. Exudates had a mean ADC value of 3.18±1.82×10^–3 mm²/s. The optimum cutoff point for ADC values was 3.38×10^–3 mm²/s with a sensitivity of 90.6% and specificity of 85%. A significant negative correlation was seen between ADC values and pleural fluid protein, albumin concentrations and lactate dehydrogenase (LDH) measurements (r=–0.69, –0.66, and –0.46, respectively; p<0.01). The positive predictive value, negative predictive value, and diagnostic accuracy of ADC values were determined to be 90.6, 85, and 88.5%, respectively. The application of diffusion gradients to analyze pleural fluid may be an alternative to the thoracentesis. Non-invasive characterization of a pleural effusion by means of DWI with single-shot EPI technique may obviate the need for thoracentesis with its associated patient morbidity.