Parotid gland tumors: comparison of conventional and diffusion-weighted MRI findings with histopathological results

Objectives:The aim of this study was to investigate the relationship between pathological classification of parotid gland tumors and conventional MRI – diffusion-weighted imaging findings and also contribute the possible effect of apparent diffusion coefficient (ADC) to diagnosis.Methods:60 patients with parotid masses diagnosed using histopathology and/or cytology were enrolled in this retrospective study. All patients were evaluated using a 1.5 T MRI. Demographic features, conventional MRI findings, and ADC values (mean, minimum, maximum, and relative) were recorded. MRI findings and ADC values were compared between benign–malignant groups and pleomorphic adenoma vs Warthin’s tumor groups.Results:60 tumors (48 benign, 12 malignant) were evaluated in a total of 60 patients (39 males, 21 females). The mean age was 59 (±14, 18–86) years old; the mean lesion size was 26 (±10, 11–61) mm. On the texture of conventional MRI, T2 dominantly hyperintense/with hypointensity signal was seen in 87% of pleomorphic adenomas and T2 dominantly hypointense/with hyperintesity signal was encountered in 64% of all Warthin’s tumors. Seven (28%) Warthin’s tumors were misdiagnosed as pleomorphic adenomas and two others (8%) as malignant tumors. The commonly used mean ADC value was 1.6 ± 0.6 × 10^–3 mm² s⁻¹ for benign tumors, 0.8 ± 0.3 × 10^–3 mm² s⁻¹ for malign tumors, 1 (0.9–1.8) × 10^–3 mm² s⁻¹ for Warthin’s tumors, and 1.9 ± 0.3 × 10^–3 mm² s⁻¹ for pleomorphic adenomas. There was a statistically significant difference in ADC values between benign-malignant tumors and pleomorphic adenomas-Warthin’s tumors.Conclusions:Warthin’s tumor may occasionally be misdiagnosed as pleomorphic adenoma and malignant tumor because of variable morphologic features. In addition to benign–malignant differentiation, the added ADC measurement may also be useful for differentiating Warthin’s tumors from pleomorphic adenomas.     

Changes in apparent diffusion coefficients in the normal uterus during different phases of the menstrual cycle

This study investigated the apparent diffusion coefficients (ADCs) of the uterine zonal structures (myometrium, endometrium and junctional zone) among reproductive women, and their changes during the menstrual cycle. Magnetic resonance (MR) images of seven healthy females (aged 24–31 years) were obtained during the periovulatory, luteal and menstrual phases. Diffusion-weighted imaging (DWI) was performed with a single-shot echo-planar imaging (EPI) sequence in the midsagittal plane of the uterus using three b-values (b = 0, 500 or 1000 s mm⁻²). The ADC values of the three uterine zonal structures were measured on an ADC map by placing two regions of interest (ROI) on the corresponding zonal structures. The average changes of ADC values (intra-individual ADC value variation) over three menstrual phases were 0.41 × 10⁻³ mm² s⁻¹ (range, 0.08–0.91) for myometrium, 0.55 × 10⁻³ mm² s⁻¹ (0.35–0.84) for endometrium, and 0.40 × 10⁻³ mm² s⁻¹ (0.18–0.59) for the junctional zone. The ADC values for myometrium and endometrium were lower in the menstrual phase, although there was some overlap of individual values. Interindividual variation in ADC value for a given zone or phase ranged from 0.48 × 10⁻³ mm² s⁻¹ to 0.85 × 10⁻³ mm² s⁻¹. Intermeasurement variation between the two ROIs ranged from 0 to 0.48 × 10⁻³ mm² s⁻¹ per measurement. The magnitude of these variations was comparable to reported differences between malignant and non-malignant tissues. These preliminary results, from a small number of subjects, suggest that the menstrual cycle and individual variation in pre-menopausal women should be considered when interpreting the ADC values of uterine structures.Diffusion-weighted imaging (DW) is an emerging functional imaging technique that is based on the diffusion of water molecules [1]. DWI can measure the apparent diffusion coefficient (ADC) of the water in tissue, which reflects its cell density, cellular oedema and microcirculation [1, 2]. Malignant tissue tends to have low ADC values, and so ADCs are increasingly used as a quantitative parameter to distinguish malignant tissue from non-malignant tissue [3–5]. Recent studies in gynaecological imaging have reported ADC values that were lower than normal in uterine cervical cancer, endometrial cancer and leiomyosarcoma [6–8].In pre-menopausal women, T₂ weighted images of the uterus, a three-layer zonal structure, change during the menstrual cycle [9–11]. When the variation in the appearance of the uterus on T₂ weighted images and the underlying physiological changes are considered, it seems possible that there might be variation of ADCs in the normal uterus during the menstrual cycle, which could affect the baseline ADC values used in the assessment of uterine abnormalities. Thus, the purpose of this study was to investigate the ADC values of each zonal structure in the uterus among reproductive women, and their variation in three different phases of the menstrual cycle.     

Diffusion-weighted imaging in the head and neck region: usefulness of apparent diffusion coefficient values for characterization of lesions

PURPOSE

We aimed to evaluate the role of apparent diffusion coefficient (ADC) values calculated from diffusion-weighted imaging for head and neck lesion characterization in daily routine, in comparison with histopathological results.

METHODS

Ninety consecutive patients who underwent magnetic resonance imaging (MRI) at a university hospital for diagnosis of neck lesions were included in this prospective study. Diffusion-weighted echo-planar MRI was performed on a 1.5 T unit with b factor of 0 and 1000 s/mm² and ADC maps were generated. ADC values were measured for benign and malignant whole lesions seen in daily practice.

RESULTS

The median ADC value of the malignant tumors and benign lesions were 0.72×10⁻³ mm²/s, (range, 0.39–1.51×10⁻³ mm²/s) and 1.17×10⁻³ mm²/s, (range, 0.52–2.38×10⁻³ mm²/s), respectively, with a significant difference between them (P < 0.001). A cutoff ADC value of 0.98×10⁻³ mm²/s was used to distinguish between benign and malignant lesions, yielding 85.3% sensitivity and 78.6% specificity. The median ADC value of lymphomas (0.44×10⁻³ mm²/s; range, 0.39–0.58×10⁻³ mm²/s) was significantly smaller (P < 0.001) than that of squamous cell carcinomas (median ADC value 0.72×10⁻³ mm²/s; range, 0.65–1.06×10⁻³ mm²/s). There was no significant difference between median ADC values of inflammatory (1.13×10⁻³ mm²/s; range, 0.85–2.38×10⁻³ mm²/s) and noninflammatory benign lesions (1.26×10⁻³ mm²/s; range, 0.52–2.33×10⁻³ mm²/s).

CONCLUSION

Diffusion-weighted imaging and the ADC values can be used to differentiate and characterize benign and malignant head and neck lesions.Diagnosis of head and neck lesions is difficult due to the complicated anatomic structure and different histological components of the many tissues that the neck contains. Imaging of head and neck lesions is not only important for diagnosis of lesions, but also for differentiation of benign lesions from malignant lesions and staging of tumors. While conventional imaging methods mainly evaluate morphological properties, their value is limited in recognizing prognostic characteristics such as benign-malignant differentiation of lesions (1). Routine magnetic resonance imaging (MRI) is a time-consuming method, which is sensitive to differences between examiners and may require the use of contrast material. With development of rapid MRI sequences (such as echo-planar [EPI], fast advanced spin echo [FASE], split echo acquisition of fast spin echo [SPLICE]), the sensitivity to susceptibility artifacts limiting the use of MRI for the head and neck region and limitations linked to duration have been significantly reduced (2, 3).Diffusion-weighted magnetic resonance imaging (DW-MRI) is a short sequence produced from EPI, FASE, SPLICE sequences. DW-MRI is sensitive to the randomized (Brownian) motion of water molecules at a microscopic level, which provides functional information about tissues. DW-MRI was initially used to diagnose early stroke in the brain and to evaluate brain masses (4–6). Previous studies have shown that rapid growth of high-grade tumors like astrocytoma and lymphoma causes hypercellularity, which leads to limitation of the diffusion of water molecules. Nowadays, apparent diffusion coefficient (ADC) maps calculated from DW-MRI sequences are being increasingly used to provide quantitative data for head and neck lesion diagnosis. In malignant lesions, the DW-MRI signal increases and signal loss is observed on ADC maps (5, 7, 8). Many researchers benefited from this feature of DW-MRI and evaluated the effectiveness of DW-MRI for head and neck lesion identification, benign-malignant differentiation, and characterization of malignant lesions (9–11).In this prospective study, head and neck lesions that are seen in daily routine were evaluated using DW-MRI, and the role of ADC values in lesion characterization was investigated with the guidance of histopathological results.     

Differentiation of benign and malignant lesions of the tongue by using diffusion-weighted MRI at 3.0?T

Objectives:

Diffusion-weighted MRI (DWI) has been introduced in head and neck lesions and adds important information to the findings obtained through conventional MRI. The purpose of this study was to assess the role of DWI in differentiating benign and malignant lesions of the tongue at 3.0-T field strength imaging.

Methods:

78 patients with 78 lingual lesions underwent conventional MRI and DWI with b-values of 0 and 1000 s mm⁻² before therapy. The apparent diffusion coefficient (ADC) maps were reconstructed, and the ADC values of the lingual lesions were calculated and compared between benign and malignant lesions of the tongue.

Results:

The mean ADC values of the malignant tumours, benign solid lesions and cystic lesions were (1.08 ± 0.16) × 10⁻³, (1.68 ± 0.33) × 10⁻³ and (2.21 ± 0.35) × 10⁻³ mm² s⁻¹, respectively. The mean ADC values of malignant tumours were significantly lower (p < 0.001) than those of benign solid lesions, and the mean ADC values of benign solid lesions were significantly lower (p < 0.001) than those of cystic lesions. Receiver operating characteristic analysis showed that when an ADC value <1.31 × 10⁻³ mm² s⁻¹ was used for predicting malignancy, the highest accuracy of 95.3%, sensitivity of 92.6% and specificity of 97.3% were obtained.

Conclusions:

ADC values of benign and malignant lesions are significantly different at 3.0-T imaging. DWI can be applied as a complementary tool in the differentiation of benign and malignant lesions of the tongue.     

Chordoid Meningioma: Differentiating a Rare World Health Organization Grade II Tumor from Other Meningioma Histologic Subtypes Using MRI

BACKGROUND AND PURPOSE:Meningiomas are very commonly diagnosed intracranial primary neoplasms, of which the chordoid subtype is seldom encountered. Our aim was to retrospectively review preoperative MR imaging of intracranial chordoid meningiomas, a rare WHO grade II variant, in an effort to determine if there exist distinguishing MR imaging characteristics that can aid in differentiating this atypical variety from other meningioma subtypes.MATERIALS AND METHODS:Ten cases of WHO grade II chordoid meningioma were diagnosed at our institution over an 11-year span, 8 of which had preoperative MR imaging available for review and were included in our analysis. Chordoid meningioma MR imaging characteristics, including ADC values and normalized ADC ratios, were compared with those of 80 consecutive cases of WHO grade I meningioma, 21 consecutive cases of nonchordoid WHO grade II meningioma, and 1 case of WHO grade III meningioma.RESULTS:Preoperative MR imaging revealed no significant differences in size, location, signal characteristics, or contrast enhancement between chordoid meningiomas and other meningiomas. There were, however, clear differences in the ADC values and normalized ADC ratios, with a mean absolute ADC value of 1.62 ± 0.33 × 10⁻³ mm²/s and a mean normalized ADC ratio of 2.22 ± 0.47 × 10⁻³ mm²/s in chordoid meningiomas compared with mean ADC and normalized ADC values, respectively, of 0.88 ± 0.13 × 10⁻³ mm²/s and 1.17 ± 0.16 × 10⁻³ mm²/s in benign WHO grade I meningiomas, 0.84 ± 0.11 × 10⁻³ mm²/s and 1.11 ± 0.15 × 10⁻³ mm²/s in nonchordoid WHO grade II meningiomas, and 0.57 × 10⁻³ mm²/s and 0.75 × 10⁻³ mm²/s in the 1 WHO grade III meningioma.CONCLUSIONS:Chordoid meningiomas have statistically significant elevations of ADC and normalized ADC values when compared with all other WHO grade I, II, and III subtypes, which enables reliable preoperative prediction of this atypical histopathologic diagnosis.

Meningiomas are the second most common primary intracranial neoplasm, constituting approximately 13%–25% of such tumors.¹ There are 15 variants of meningioma according the 2007 World Health Organization (WHO) classification of tumors of the central nervous system.² Although 80%–90% of meningiomas are classified as benign WHO grade I tumors, WHO grade II and III varieties demonstrate a more aggressive clinical course and have a greater propensity for recurrence, and the grade and extent of original resection accounts for these differences.³ Ideally, preoperative imaging to identify the potentially more aggressive grade II and III varieties would be helpful for presurgical planning and subsequent imaging follow-up. One such rare variant is the WHO grade II chordoid meningioma. A little more than 100 cases of chordoid meningioma have been described in the English-language literature, the majority of which are in the pathology and neurosurgery literature.^4–9Attempts to distinguish benign from atypical and malignant meningiomas have been undertaken with variable results, and DWI and ADC values have provided the most reliable means of differentiation,^10,11 though no data analysis specifically examining the chordoid morphologic variant has been performed. To the best of our knowledge, only 3 case reports in which the MR imaging characteristics of chordoid meningiomas were described have been published in the radiology literature.^12–14We compared 8 cases of intracranial chordoid meningioma to 80 consecutive cases of WHO grade I meningioma, 21 consecutive cases of nonchordoid WHO grade II meningioma, and 1 WHO grade III meningioma in an effort to determine if there exist distinguishing MR imaging characteristics that can aid in differentiating this particular subtype.     

Apparent diffusion coefficient for discriminating metastatic lymph nodes in patients with squamous cell carcinoma of the head and neck

PURPOSE

We aimed to evaluate the apparent diffusion coefficient (ADC) values of metastatic lymph nodes in patients with squamous cell carcinoma (SCC) of the head and neck.

METHODS

Patients with metastatic lymph nodes underwent 1.5 Tesla diffusion-weighted magnetic resonance imaging (MRI). The ADC values of the histologically proven metastases were evaluated retrospectively and mean ADC values were compared using one-way analysis of variance test. Receiver operating characteristic analysis was performed to identify ADC threshold values.

RESULTS

We included 33 patients (27 males, 6 females; mean age, 60.7 years) with 53 metastatic lymph nodes in the study. Mean ADC values for nodal metastases of nasopharyngeal carcinoma (NPC) (n=7), oropharyngeal (n=12), laryngeal (n=27), and hypopharyngeal (n=7) carcinoma were (0.810±0.158)×10⁻³ mm²/s, (0.985±0.099)×10⁻³ mm²/s, (1.037±0.150)×10⁻³ mm²/s, and (0.948±0.081)×10⁻³ mm²/s, respectively. The mean ADC values of nodal metastases of NPC were significantly lower than ADC values of laryngeal carcinoma (LSCC) (P = 0.002). An ADC value less than 0.890×10⁻³ mm²/s was found to facilitate differentiation of NPC from LSCC with a sensitivity of 71% and specificity of 85% (area under the curve, 0.852).

CONCLUSION

The mean ADC values showed significant differences between nodal metastases of NPC and LSCC. Considering SCCs as a single group may affect the accuracy of ADC-based differentiation. Location of the primary tumor should be taken into account and cutoff values should be determined separately for each anatomical location.Diffusion-weighted imaging (DWI) has the potential to characterize and differentiate various head and neck carcinomas (1–4). Differentiating nodal metastases of SCC from other less common tumors of the head and neck is important for treatment planning. Previous studies have shown that apparent diffusion coefficient (ADC) values may be used to differentiate metastatic lymph nodes due to SCC from lymphoma (5). However, the results of some studies indicated that ADC values of SCCs and their nodal metastases (e.g., poorly differentiated SCC and nasopharyngeal carcinoma) may sometimes overlap with the ADC values of lymphoma (5–7). Thus, the efficacy of using DWI for differentiation depends largely on the histologic characteristics of the lymph node.Approaching all pharyngeal space SCCs as a single homogeneous group may affect the accuracy of ADC-based discrimination of metastatic lymph nodes due to SCC from other tumors. Therefore, we aimed to retrospectively evaluate and compare the ADC values of metastatic lymph nodes from carcinoma of the nasopharynx, oropharynx, larynx, and hypopharynx.     

Diffusion-Weighted Imaging for Differentiation of Biliary Atresia and Grading of Hepatic Fibrosis in Infants with Cholestasis

ObjectiveTo determine whether the values of hepatic apparent diffusion coefficient (ADC) can differentiate biliary atresia (BA) from non-BA or be correlated with the grade of hepatic fibrosis in infants with cholestasis.Materials and MethodsThis retrospective cohort study included infants who received liver MRI examinations to evaluate cholestasis from July 2009 to October 2017. Liver ADC, ADC ratio of liver/spleen, aspartate aminotransferase to platelet ratio index (APRI), and spleen size were compared between the BA and non-BA groups. The diagnostic performances of all parameters for significant fibrosis (F3–4) were obtained by receiver-operating characteristics (ROCs) curve analysis.ResultsAltogether, 227 infants (98 males and 129 females, mean age = 57.2 ± 36.3 days) including 125 BA patients were analyzed. The absolute ADC difference between two reviewers was 0.10 mm²/s for both liver and spleen. Liver ADC value was specific (80.4%) and ADC ratio was sensitive (88.0%) for the diagnosis of BA with comparable performance. There were 33 patients with F0, 15 with F1, 71 with F2, 35 with F3, and 11 with F4. All four parameters of APRI (τ = 0.296), spleen size (τ = 0.312), liver ADC (τ = −0.206), and ADC ratio (τ = −0.288) showed significant correlation with fibrosis grade (all, p < 0.001). The cutoff values for significant fibrosis (F3–4) were 0.783 for APRI (area under the ROC curve [AUC], 0.721), 5.9 cm for spleen size (AUC, 0.719), 1.044 × 10⁻³ mm²/s for liver ADC (AUC, 0.673), and 1.22 for ADC ratio (AUC, 0.651).ConclusionLiver ADC values and ADC ratio of liver/spleen showed limited additional diagnostic performance for differentiating BA from non-BA and predicting significant hepatic fibrosis in infants with cholestasis.     

MR-enterography in Crohn’s disease: what MRE mural parameters are associated to one-year therapeutic management outcome?

Objective:To investigate the association of mural parameters of MR-enterography (MRE) with one-year therapeutic management of Crohn’s disease (CD) patients.Methods:CD patients, undergone MRE with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) maps between January 2017 and June 2018, were retrospectively enrolled. Extramural complications represented an exclusion criterion because of their potential influence on the intrinsic characteristic of the bowel wall. Two groups of patients were defined on the base of the therapeutic management adopted at 1-year follow-up: Medical-group and surgical-group. The following MRE parameters were evaluated: wall-thickening, longitudinal-extension, T2-fat-suppression-mural-signal, ulcers, mural-oedema, wall-enhancement-rate/pattern, DWI-scores, ADC-values, strictures.Results:70 CD patients were enrolled. 57/70 (81.4%) were included in Medical-group and 13/70 (18.6%) in Surgical-group. ADCmean and strictures resulted to be significantly (p < 0.01) different between the two groups. The ADCmean showed to be significantly associated to conservative management [p < 0.01; OR: 0.0003; 95% CI (0.00–0.13)], while the strictures to surgical management [p < 0.01; OR: 29.7; 95% CI (4.9–179.7)]. ROC curves for ADCmean showed that AUC was 0.717 [95% CI (0.607–0.810), p < 0.01] with an optimal cut-off value of 1.081 × 10⁻³ mm² s⁻¹. A negative predictive value of 90.2% was observed associating ADCmean values > 1.081 × 10⁻³ mm² s⁻¹ to conservative therapy. 13/17 (76%) strictures with an ADCmean > 1.081 × 10⁻³ mm² s⁻¹ benefited of conservative therapy.Conclusion:ADCmean values calculated on DWI-MRE may be associated to 1-year conservative medical therapy in patients with CD without extramural complications.Advances in knowledge:ADC maps may be proposed to select CD patients with a lower burden of mural active inflammatory cells and/or fibrosis benefiting of 1-year conservative treatment.     

Usefulness of 3T diffusion-weighted MRI for discrimination of reactive and metastatic cervical lymph nodes in patients with oral squamous cell carcinoma: a pilot study

Objectives:

To study the diagnostic accuracy of 3T diffusion-weighted MRI (DW-MRI) for the discrimination of reactive and metastatic cervical lymph nodes in patients with oral squamous cell carcinoma.

Methods:

DW T₁ and T₂ weighted MRI was performed in 25 patients with biopsy-proved primary oral squamous cell carcinoma. The mean apparent diffusion coefficient (ADC) values of 30 histopathologically proved reactive lymph nodes and 21 histopathologically proved metastatic lymph nodes were compared using an unpaired t-test. A cut-off ADC value with optimal diagnostic sensitivity, specificity and area under the curve in discrimination of the two groups was determined using a receiver operating characteristic curve analysis.

Results:

The mean ADC values of reactive lymph node and metastatic lymph node groups were (1.037 ± 0.149) × 10⁻³ and (0.702 ± 0.197) × 10⁻³ mm² s⁻¹, respectively. A statistically significant difference in ADC values of the two groups was certified (p < 0.0001). An optimal ADC threshold value of 0.887 × 10⁻³ mm² s⁻¹ was suggested as the cut-off point, which resulted in 93.33% sensitivity, 80.95% specificity, 88.20% accuracy and area under curve of 0.887.

Conclusions:

Our preliminary study indicates that the addition of 3T DW-MRI may be useful for discriminating between reactive lymph nodes and metastatic lymph nodes in patients with oral squamous cell carcinoma. However, larger studies are still required to validate our results and to standardize this imaging technique for daily clinical practice.     

Is Diffusion-Weighted MRI Useful for Differentiation of Small Non-Necrotic Cervical Lymph Nodes in Patients with Head and Neck Malignancies?

Objective

To evaluate the usefulness of measuring the apparent diffusion coefficient (ADC) in diffusion-weighted magnetic resonance imaging to distinguish benign from small, non-necrotic metastatic cervical lymph nodes in patients with head and neck cancers.

Materials and Methods

Twenty-six consecutive patients with head and neck cancer underwent diffusion-weighted imaging (b value, 0 and 800 s/mm²) preoperatively between January 2009 and December 2010. Two readers independently measured the ADC values of each cervical lymph node with a minimum-axial diameter of ≥ 5 mm but < 11 mm using manually drawn regions of interest. Necrotic lymph nodes were excluded. Mean ADC values were compared between benign and metastatic lymph nodes after correlating the pathology.

Results

A total of 116 lymph nodes (91 benign and 25 metastatic) from 25 patients were included. Metastatic lymph nodes (mean ± standard deviation [SD], 7.4 ± 1.6 mm) were larger than benign lymph nodes (mean ± SD, 6.6 ± 1.4 mm) (p = 0.018). Mean ADC values for reader 1 were 1.17 ± 0.31 × 10^-3 mm²/s for benign and 1.25 ± 0.76 × 10^-3 mm²/s for metastatic lymph nodes. Mean ADC values for reader 2 were 1.21 ± 0.46 × 10^-3 mm²/s for benign and 1.14 ± 0.34 × 10^-3 mm²/s for metastatic lymph nodes. Mean ADC values between benign and metastatic lymph nodes were not significantly different (p = 0.594 for reader 1, 0.463 for reader 2).

Conclusion

Measuring mean ADC does not allow differentiating benign from metastatic cervical lymph nodes in patients with head and neck cancer and non-necrotic, small lymph nodes.     

Diffusion-Weighted MRI of Malignant versus Benign Portal Vein Thrombosis

ObjectiveTo validate the diffusion-weighted MRI (DWI) for differentiation of benign from malignant portal vein thrombosis.ResultsThe mean ADC ± standard deviation of bland and malignant PVT were 1.00 ± 0.39 × 10^-3 mm²/sec and 0.92 ± 0.25 × 10^-3 mm²/sec, respectively; without significant difference (p = 0.799). The area under ROC curve for ADC was 0.520. An ADC value of > 1.35 × 10^-3 mm²/sec predicted bland PVT with a specificity of 94.6% (95% confidence interval [CI]: 84.9–98.9%) and a sensitivity of 22.2% (95% CI: 6.4–47.6%), respectively.ConclusionDue to the wide range and considerable overlap of the ADCs, DWI cannot differentiate the benign from malignant thrombi efficiently.     

Diffusion-weighted MRI in early assessment of tumour response to radiotherapy in high-risk prostate cancer

Objective:

The objective of this study was to assess the efficacy of diffusion-weighted MRI (DWI) in monitoring response to radiotherapy in high-risk prostate cancer (PC).

Methods:

This retrospective study included 78 patients with high-risk PC undergoing 3.0-T MRI (supplemented by DWI) before and after intensity-modulated radiotherapy (IMRT). Based on follow-up clinical examinations, patients were divided into two groups: the recurrence group (patients who suffered biochemical/clinical recurrence within 3 years, n = 13) and the non-recurrence group (patients who were recurrence free for over 3 years, n = 65). The apparent diffusion coefficient (ADC) values before and after IMRT were compared between these two groups. The receiver-operating characteristics (ROC) analysis was carried out to investigate the discriminatory capability for pre- and post-IMRT ADC values.

Results:

The overall ADC values were 1.04 ± 0.18 × 10⁻³ mm² s⁻¹ for PCs before IMRT and 1.45 ± 0.15 × 10⁻³ mm² s⁻¹ after IMRT (p < 0.001). A statistically significant difference in post-IMRT ADC values was noted between patients with and without recurrence (1.27 ± 0.14 × 10⁻³ mm² s⁻¹ vs 1.49 ± 0.12 × 10⁻³mm² s⁻¹; p < 0.001), although there was no statistical difference between them in pre-IMRT ADC values (1.00 ± 0.17 × 10⁻³ mm² s⁻¹ vs 1.05 ± 0.18 × 10⁻³ mm² s⁻¹; p = 0.31). The ROC curve analysis revealed that the post-IMRT ADC values could help identify patients suffering recurrences (area under the curve, 0.88; p < 0.001).

Conclusion:

Marked increase in ADC values was observed in PC after radiotherapy, especially in good responders. DWI is a valuable tool for monitoring the response to radiotherapy.

Advances in knowledge:

This study examined the relationship between ADC changes and tumour response to treatment of PC.Prostate cancer (PC) is the most common cancer in elderly males in Western Europe and North America.¹ Although China is considered to have low incidence, the trend appears to be on the rise. According to the 2002 database of the International Agency for Research on Cancer, the mortality-to-incidence rate ratio (MR/IR) of PC in China is 0.63, which was found to be higher than the average in Asia (MR/IR = 0.57) and much higher than that in North America (MR/IR = 0.13).^2,3 These data indicated that, in China, most PCs were at the advanced stage at the time of diagnosis, and patients had a short survival time thereafter. As such, it will be prudent to address this rising challenge by developing a method for an early detection of PC and for a reliable measure of tumour response to therapy, thereby improving the MR/IR of PC in China.Currently, clinical research in diffusion-weighted MRI (DWI) is undergoing rapid expansion to depict biological changes in humans, and it has been shown that early changes in apparent diffusion coefficient (ADC) values following anti-cancer treatment may hold promise to serve as an early surrogate for long-term response in various diseases such as metastatic liver tumours, breast cancers and bone sarcomas.^4–7 However, there are relatively few reports systematically examining the relationship between ADC changes and tumour response to treatment of PC.As such, the objective of the present study was to investigate the changes in ADC values after radiotherapy, in patients with high-risk PC who showed various degrees of response. It is hoped that this investigation can contribute to better evaluation of DWI in monitoring the response to radiotherapy in PC.     

Evaluation of Diffusivity in the Anterior Lobe of the Pituitary Gland: 3D Turbo Field Echo with Diffusion-Sensitized Driven-Equilibrium Preparation

BACKGROUND AND PURPOSE:3D turbo field echo with diffusion-sensitized driven-equilibrium preparation is a non–echo-planar technique for DWI, which enables high-resolution DWI without field inhomogeneity–related image distortion. The purpose of this study was to evaluate the feasibility of diffusion-sensitized driven-equilibrium turbo field echo in evaluating diffusivity in the normal pituitary gland.MATERIALS AND METHODS:First, validation of diffusion-sensitized driven-equilibrium turbo field echo was attempted by comparing it with echo-planar DWI. Five healthy volunteers were imaged by using diffusion-sensitized driven-equilibrium turbo field echo and echo-planar DWI. The imaging voxel size was 1.5 × 1.5 × 1.5 mm³ for diffusion-sensitized driven-equilibrium turbo field echo and 1.5 × 1.9 × 3.0 mm³ for echo-planar DWI. ADCs measured by the 2 methods in 15 regions of interests (6 in gray matter and 9 in white matter) were compared by using the Pearson correlation coefficient. The ADC in the pituitary anterior lobe was then measured in 10 volunteers by using diffusion-sensitized driven-equilibrium turbo field echo, and the results were compared with those in the pons and vermis by using a paired t test.RESULTS:The ADCs from the 2 methods showed a strong correlation (r = 0.79; P < .0001), confirming the accuracy of the ADC measurement with the diffusion-sensitized driven-equilibrium sequence. The ADCs in the normal pituitary gland were 1.37 ± 0.13 × 10⁻³ mm²/s, which were significantly higher than those in the pons (1.01 ± 0.24 × 10⁻³ mm²/s) and the vermis (0.89 ± 0.25 × 10⁻³ mm²/s, P < .01).CONCLUSIONS:We demonstrated that diffusion-sensitized driven-equilibrium turbo field echo is feasible in assessing ADC in the pituitary gland.

DWI is widely used to diagnose cerebrovascular diseases, intracranial tumors, and inflammation.^1–10 However, it is difficult to evaluate skull base structures by the most common imaging technique used with echo-planar (EP)-DWI. Previous studies have revealed the efficacy of DWI for skull base tumors such as pituitary adenoma; however, they are mostly limited to macroadenomas large enough to calculate the ADC by using EP sequences.^3–7 Compared with EP-DWI, 3D diffusion-sensitized driven-equilibrium turbo field echo (DSDE-TFE) obtained DWI has higher spatial resolution and fewer susceptibility artifacts.¹¹ To our knowledge, to date, the diffusivity of the normal pituitary gland has not been fully evaluated, especially in those glands surrounded by aerated sphenoid sinuses. Therefore, the purpose of this study was to evaluate the feasibility of DSDE-TFE in evaluating diffusivity in the normal pituitary gland.     

Reduced Field-of-View Diffusion-Weighted Magnetic Resonance Imaging of the Pancreas: Comparison with Conventional Single-Shot Echo-Planar Imaging

ObjectiveTo investigate the image quality (IQ) and apparent diffusion coefficient (ADC) of reduced field-of-view (FOV) di-ffusion-weighted imaging (DWI) of pancreas in comparison with full FOV DWI.ResultsOn qualitative analysis, reduced FOV DWI showed better anatomic structure visualization (2.76 ± 0.79 at b = 0 s/mm² and 2.81 ± 0.64 at b = 400 s/mm²), lesion conspicuity (3.11 ± 0.99 at b = 0 s/mm² and 3.15 ± 0.79 at b = 400 s/mm²), IQ score (8.51 ± 2.05 at b = 0 s/mm² and 8.79 ± 1.60 at b = 400 s/mm²), and higher clinical utility (3.41 ± 0.64), as compared to full FOV DWI (anatomic structure, 2.18 ± 0.59 at b = 0 s/mm² and 2.56 ± 0.47 at b = 500 s/mm²; lesion conspicuity, 2.55 ± 1.07 at b = 0 s/mm² and 2.89 ± 0.86 at b = 500 s/mm²; IQ score, 7.13 ± 1.83 at b = 0 s/mm² and 8.17 ± 1.31 at b = 500 s/mm²; clinical utility, 3.14 ± 0.70) (p < 0.05). Artifacts were significantly improved on reduced FOV DWI (2.65 ± 0.68) at b = 0 s/mm² (full FOV DWI, 2.41 ± 0.63) (p < 0.001). On quantitative analysis, there were no significant differences between the 2 DWI sequences in ADCs of various pancreatic lesions and parenchyma (p > 0.05). ADCs of adenocarcinomas (1.061 × 10^-3 mm²/s ± 0.133 at reduced FOV and 1.079 × 10^-3 mm²/s ± 0.135 at full FOV) and neuroendocrine tumors (0.983 × 10^-3 mm²/s ± 0.152 at reduced FOV and 1.004 × 10^-3 mm²/s ± 0.153 at full FOV) were significantly lower than those of parenchyma (1.191 × 10^-3 mm²/s ± 0.125 at reduced FOV and 1.218 × 10^-3 mm²/s ± 0.103 at full FOV) (p < 0.05).ConclusionReduced FOV DWI of the pancreas provides better overall IQ including better anatomic detail, lesion conspicuity and subjective clinical utility.     

Acute Cytotoxic and Vasogenic Edema after Subarachnoid Hemorrhage: A Quantitative MRI Study

BACKGROUND AND PURPOSE:The mechanism of early brain injury following subarachnoid hemorrhage is not well understood. We aimed to evaluate if cytotoxic and vasogenic edema are contributing factors.MATERIALS AND METHODS:A retrospective analysis was conducted in patients with SAH undergoing diffusion-weighted MR imaging within 72 hours of onset. Apparent diffusion coefficient values derived from DWI were evaluated by using whole-brain histograms and 19 prespecified ROIs in patients with SAH and controls with normal findings on MRI. Cytotoxic edema observed outside the ROIs was assessed in patients with SAH. The average median ADC values were compared between patients with SAH and controls and patients with SAH with mild (Hunt and Hess 1–3) versus severe early brain injury (Hunt and Hess 4–5).RESULTS:We enrolled 33 patients with SAH and 66 controls. The overall average median whole-brain ADC was greater for patients with SAH (808 × 10⁻⁶ mm²/s) compared with controls (788 × 10⁻⁶ mm²/s, P < .001) and was higher in patients with SAH across ROIs after adjusting for age: cerebral gray matter (826 versus 803 × 10⁻⁶ mm²/s, P = .059), cerebral white matter (793 versus 758 × 10⁻⁶ mm²/s, P = .023), white matter tracts (797 versus 739 × 10⁻⁶ mm²/s, P < .001), and deep gray matter (754 versus 713 × 10⁻⁶ mm²/s, P = .016). ADC values trended higher in patients with Hunt and Hess 4–5 versus those with Hunt and Hess 1–3. Early cytotoxic edema was observed in 13 (39%) patients with SAH and was more prevalent in those with severe early brain injury (87.5% of patients with Hunt and Hess 4–5 versus 24.0% of those with Hunt and Hess 1–3, P = .001).CONCLUSIONS:Age-adjusted ADC values were globally increased in patients with SAH compared with controls, even in normal-appearing brain regions, suggesting diffuse vasogenic edema. Cytotoxic edema was also present in patients with SAH and correlated with more severe early brain injury.

Early brain injury (EBI) incurred during aneurysm rupture in spontaneous subarachnoid hemorrhage is a major predictor of poor functional outcome,^1,2 yet the mechanism for EBI is not well-understood. In both animal and human models, SAH leads to transiently elevated intracranial pressure with concomitant inadequate cerebral blood flow and, in severe cases, intracranial circulatory arrest.^3,4 This transient global hypoperfusion is associated with endothelial activation, microthrombosis, ischemia, and vasogenic edema in animal models.^5–7 As a part of routine clinical MR imaging at many institutions, diffusion-weighted imaging presents a unique opportunity for the study of patients with SAH in the acute period. Apparent diffusion coefficient values may serve as a practical and useful biomarker for the severity of EBI following SAH. In humans, we and others have demonstrated that MR imaging–detected infarctions on DWI occur acutely after SAH and before the onset of delayed cerebral ischemia/vasospasm.^8–11These infarctions are more common in patients with more severe EBI (Hunt and Hess [HH] 4–5); occur in unusual, nonvascular patterns (eg, corpus callosum, bilateral medial frontal lobes); and are associated with an increased risk of delayed cerebral ischemia and worse 3-month functional outcomes.^8–10 The volume of infarction associated with worse functional outcomes is small, however.⁸ Thus, this finding led us to hypothesize that conventional, nonquantitative MR imaging techniques are not sensitive enough to detect the full extent of brain injury.We hypothesized that patients with SAH (compared with controls) would demonstrate global reductions in apparent diffusion coefficient values, indicating diffuse cytotoxic edema presumably due to ischemia/hypoperfusion, when whole-brain ADC mapping and ROI quantitative analyses were applied. We further hypothesized that patients with SAH with evidence of severe EBI would have a greater burden of cytotoxic edema than those with mild EBI.     

Can diffusion-weighted imaging distinguish between normal and squamous cell carcinoma of the palatine tonsil?

The utility of diffusion-weighted imaging (DWI) in the detection of squamous cell carcinoma (SCC) of the tonsils has not been previously investigated. This preliminary study compared DWI of apparent SCC tonsillar tumours with normal tonsils. DWI of the tonsils was performed in 10 patients with newly diagnosed tonsil SCC that was evident on conventional MRI and in 17 patients undergoing cranial MRI for other indications. Regions of interest (ROI) were drawn around each identifiable tonsil on the apparent diffusion coefficient (ADC) map and the mean ADC value for each tonsil was calculated. ADC values for normal and SCC tonsils were compared using the Mann–Whitney U-test. The median ADC and range (×10⁻³ mm² s^–1) were found to be 0.814 and 0.548–1.312, respectively, for normal tonsils compared with 0.933 and 0.789–1.175, respectively, for SCC tonsils. ADC values were significantly higher for SCC tonsils than for normal tonsils (p = 0.009). No SCC tonsil had an ADC less than 0.82×10⁻³ mm² s^–1 compared with 58% of normal tonsils. We conclude that there is a difference in the ADC between normal tonsils and SCC tonsils where the cancer is apparent on conventional MRI. These results are promising, although further studies are now required to determine whether DWI can be used to identify or exclude smaller foci of SCC within tonsils where the cancer is not evident on conventional MRI.Cancers in the palatine tonsil can be difficult to identify on conventional imaging using CT or MRI because they can have the same appearance as normal lymphoid tissue at this site. This leads to problems when imaging is used to search for the site of an “unknown primary” in head and neck squamous cell carcinoma (SCC) or to assess the extent of spread of SCC from adjacent sites in the oropharynx. Diffusion-weighted imaging (DWI) is an MR technique that shows potential for improving the detection of cancer. Early studies suggest that there are differences in the apparent diffusion coefficient (ADC) of metastatic nodes involved in SCC and normal nodes [1–3]. The aim of this preliminary study was to compare the ADC of normal tonsils with imaging-apparent SCC tonsils; to our knowledge, this has not been previously investigated. If it can be shown that there are differences in the ADC values of grossly infiltrated SCC tonsils and benign tonsils, this could provide justification for performing larger prospective studies to determine whether DWI can detect small occult cancers within the tonsil.     

Imaging diagnosis of basal ganglia germ cell tumors: subtype features subtype imaging features of GCTs

Objectives:To evaluate the subtype imaging features of basal ganglia germ cell tumors (GCTs).Methods:Clinical and imaging data of 33 basal ganglia GCTs were retrospectively analyzed, including 17 germinomas and 16 mixed germ cell tumors (MGCTs).Results:The cyst/mass ratio of germinomas (0.53 ± 0.32) was higher than that of MGCTs (0.28 ± 0.19, p = 0.030). CT density of the solid part of germinomas (41.47 ± 5.22 Hu) was significantly higher than that of MGCTs (33.64 ± 3.75 Hu, p < 0.001), while apparent diffusion coefficients (ADC, ×^10-3 mm²/s) value of the solid part was significantly lower in geminomas (0.86 ± 0.27 ×^10-3 mm²/s) than in MGCTs (1.42 ± 0.39 ×^10-3 mm²/s, p < 0.001). MGCTs were more common with intratumoral hemorrhage (68.75% vs 11.76%, p = 0.01), T1 hyperintense foci (68.75% vs 5.88%, p < 0.001) and calcification (64.29% vs 20.00%, p = 0.025) than germinomas. There was no significant difference in internal capsule involvement between the two subtypes (p = 0.303), but Wallerian degeneration was more common in germinomas than in MGCTs (70.59% vs 25.00%, p = 0.015).Conclusion:The subtypes of GCT have different imaging features. Tumoral cystic-solidity, heterogeneity, ADC value, CT density, and Wallerian degeneration are helpful to differentiate germinomas and MGCTs in basal ganglia.Advances in knowledge:The subtypes of GCT have different histological characteristics, leading to various imaging findings. The imaging features of GCT subtypes in basal ganglia may aid clinical diagnosis and treatment.     

Evaluation of foot hypoperfusion and estimation of percutaneous transluminal angioplasty outcome in patients with critical limb ischemia using intravoxel incoherent motion microperfusion MRI

Objectives:To emerge hypoperfusion of lower limbs in patients with critical limb ischemia (CLI) using Intravoxel Incoherent Motion microperfusion magnetic resonance imaging (IVIM-MRI). Moreover to examine the ability of IVIM-MRI to differentiate patients with severe peripheral arterial disease (PAD) from normal subjects and evaluate the percutaneous transluminal angioplasty (PTA) results in patients with CLI.Methods:Eight patients who presented with CLI and six healthy volunteers were examined. The patients underwent IVIM-MRI of lower extremity before and following PTA. The imaging protocol included sagittal diffusion-weighted (DW) sequences. DW images were analyzed and color parametric maps of the micro-circulation of blood inside the capillary network (D*) were constructed. The studies were evaluated by two observers to define interobserver reproducibility.Results:Technical success was achieved in all patients (8/8). The mean ankle-brachial index increased from 0.35 ± 0.2 to 0.76 ± 0.25 (p < 0.05). Successful revascularization improved IVIM microperfusion. Mean D* increased from 279.88 ± 13.47 10⁻⁵ mm²/s to 331.51 ± 31 10⁻⁵ mm²/s, following PTA, p < 0.05. Moreover, PAD patients presented lower D* values as compared to healthy individuals (279.88 ± 13.47 10⁻⁵ mm²/s vs 332.47 ± 22.95 10⁻⁵ mm²/s, p < 0.05, respectively). Good interobserver agreement was obtained with an ICC = 0.84 (95% CI 0.64–0.93).Conclusions:IVIM-MRI can detect differences in microperfusion between patients with PAD and healthy individuals. Moreover, significant restitution of IVIM microperfusion is found following successful PTA.Advances in knowledge:IVIM-MRI is a safe, reproducible and effective modality for evaluation of lower limb hypoperfusion in patients with PAD. It seems also to be a helpful tool to detect changes of tissue perfusion in patients with CLI following revascularization.     

The role of the ADC value in the characterisation of renal carcinoma by diffusion-weighted MRI

The purpose of this study is to evaluate the role of diffusion-weighted imaging (DWI) in combination with T₁ and T₂ weighted MRI for the characterisation of renal carcinoma. The institutional review board approved the study protocols and waived informed consent from all of the patients. 47 patients (32 male and 15 female; age range, 21–85 years; median age, 65 years) who had suspected renal lesions on abdominal CT underwent MRI for further evaluation and characterisation of the lesions from April 2005 to August 2007 in our university hospital. A region of interest was drawn around the tumour area on apparent diffusion coefficient (ADC) maps. Final diagnosis was confirmed by histological examination of surgical specimens from all patients. The ADC value was significantly higher in renal cell carcinoma (RCC) than in transitional cell carcinoma (2.71±2.35 × 10⁻³ mm² s⁻¹ vs 1.61±0.80 × 10⁻³ mm² s⁻¹; p = 0.022). While analysing the histological subtypes of RCC, a significant difference in ADC values between clear cell carcinoma and non-clear cell carcinoma was found (1.59±0.55 × 10⁻³ mm² s⁻¹ vs 6.72±1.85 × 10⁻³ mm² s⁻¹; p = 0.0004). Similarly, ADC values of RCC revealed a significant difference between positive and negative metastatic lesions (1.06±0.38 × 10⁻³ mm² s⁻¹ vs 3.02±2.44 × 10⁻³ mm² s⁻¹; p = 0.0004), whereas intensity on T₁ and T₂ weighted imaging did not reach statistical significance. In conclusion, DWI has clinical value in the characterisation of renal carcinomas and could be applied in clinical practice for their management.Renal cell carcinoma (RCC) is the most common primary malignant tumour of the kidney; it accounts for 2–3% of all adult cancers and is the sixth cause of death by tumour throughout the world. More than 80% of renal cancers that arise in the renal parenchyma are RCC, whereas the majority of renal pelvis cancers are transitional cell carcinomas (TCCs) [1–3]. The three most common subtypes of RCC are (i) clear cell carcinoma, one of the most common types, accounting for 70–80% of cases; (ii) papillary renal cell carcinoma, accounting for about 10–15% of cases; and (iii) chromophobe renal carcinoma, which is the least common, accounting for 5% of all RCCs. The annual rate of RCC diagnosis is increasing as a result of incidental detection by cross-sectional abdominal imaging of patients with suspected abdominal disorders. Increased detection rates carry a favourable prognosis; however, mortality from RCC has not decreased [2–4].Diffusion-weighted imaging (DWI) is frequently used in cranial MRI studies and has shown potential for the characterisation of lesions such as acute cerebral infarctions, intracranial tumours, various infectious diseases and metabolic disorders [5–8]. The role of DWI is limited outside the central nervous system, owing to its inherent extreme sensitivity to motion, such as that related to respiration, peristalsis and artefacts, thus resulting in a high signal to noise ratio. With the development of advanced MR technology and the use of faster robust sequences, better quality has been obtained in abdominal imaging [9]. DWI with high b-values has been reported to have a high sensitivity for depicting malignant disease. Apparent diffusion coefficient (ADC) values of malignant hepatic, ovarian, breast, prostatic, colonic and uterine cervical tumours were lower than those of benign lesions or normal tissue [10–18].Previous studies have suggested that patients with chromophobe and papillary RCC have a better prognosis than patients with clear cell RCC [19]. Accurate characterisation of patients with renal masses is essential to ensure appropriate clinical management, staging and prognosis. The clinical utility of ADC values in kidney disease has been reported: a higher value of ADC was noted in simple renal cysts and renal pelvis of hydronephrotic kidney, whereas a lower value was noted in solid renal tumours and kidneys with chronic and acute renal failure [9, 20–22]. The role of the ADC value in characterising the histological subtypes of renal carcinoma is limited [3, 9]. Therefore, the present study aimed to evaluate the role of DWI in combination with T₁ and T₂ weighted MRI for the differential diagnosis and characterisation of renal carcinoma.