Diffusion-weighted echoplanar MR imaging of the salivary glands

Diffusion-weighted magnetic resonance imaging for the diagnosis of giant cell arteritis: a comparison with T1-weighted black-blood imaging

OBJECTIVES

To investigate the diagnostic performance of diffusion-weighted imaging (DWI) of the superficial cranial arteries in the diagnosis of GCA.

METHODS

Retrospectively, 156 patients with clinically suspected GCA were included. A new 4-point ordinal DWI rating scale was developed. A post-contrast, fat-suppressed, T1-weighted 'black-blood' sequence (T1-BB) was rated for comparison. Ten arterial segments were assessed: common superficial temporal arteries, temporal and parietal branches, occipital and posterior auricular arteries bilaterally. The expert clinical diagnosis after ≥6 months of follow-up was the diagnostic reference standard. Diagnostic accuracy was evaluated for different rating methods.

RESULTS

The study cohort consisted of 87 patients with and 69 without GCA. For DWI, the area under the curve was 0.90. For a cut-off of ≥2 consecutive pathological slices, DWI showed a sensitivity of 75.9%, a specificity of 94.2% and a positive likelihood ratio of 13.09. With a cut-off of ≥3 consecutive pathological slices, sensitivity was 70.1%, specificity was 98.6% and the positive likelihood ratio was 48.38. For the T1-BB, values were 88.5%, 88.4% and 7.63, respectively. The inter-rater analysis for DWI with a cut-off of ≥2 pathological slices showed a kappa of 1.00 on the patient level and 0.85 on the arterial segment level. For the T1-BB the kappa was 0.78 and 0.79, respectively.

CONCLUSION

DWI of the superficial cranial arteries demonstrates a good diagnostic accuracy and reliability for the diagnosis of GCA. DWI is widely available and can be used immediately in clinical practice for patients with suspected GCA.

Advances in imaging of the lacrimal gland in Sjögren's syndrome: A narrative review

Due to lymphocytic infiltration of the salivary and lacrimal glands, Sjogren's syndrome (SS), a systemic autoimmune illness that mostly affects the exocrine glands, causes dry mouth (xerostomia) and dry eyes (xerophthalmia). Additionally, SS is associated with various comorbidities such as cardiovascular diseases, infections, musculoskeletal diseases, and cancers. Among patients with SS, xerophthalmia frequently arises as a complication, leading to insufficient tear production or rapid tear evaporation, thereby causing discomfort, irritation, and a gritty sensation in the eyes. This article aims to examine recent advancements in the imaging of the lacrimal gland in Sjögren's syndrome and briefly discusses the utilization of various imaging examinations for the lacrimal gland in this particular disease.

The Efficiency of Diffusion-weighted Magnetic Resonance Imaging in the Differentiation of Malign and Benign Cavitary Lung Lesions

PURPOSE

The present study investigates the diagnostic efficiency of apparent diffusion coefficient (ADC) values in differentiating between malignant and benign cavitary lesions on diffusion-weighted magnetic resonance imaging (DWI).

MATERIALS AND METHODS

This prospective study included 45 consecutive patients identified with a cavitary lung lesion with a wall thickness of ≥5 mm on thoracic computed tomography in our clinic between 2020 and 2022, and who underwent thoracic DWI within 1 week of their original computed tomography. ADC measurements were made on DWI by drawing a region of interest manually from the cavity wall, away from the lung parenchyma in the axial section where the lesion was best demonstrated. The patients were then classified into benign and malignant groups based on the pathology or clinico-radiologic follow-up.

RESULTS

The sample included 29 (64.4%) male and 16 (35.6%) female patients, with a mean age of 59.06±17.3 years. Included in the study were 1 patient with 3 and 3 patients with 2 cavitary lesions each, with a total for the sample of 50 cavitary lesions. There were 23 (46%) malignant and 27 (54%) benign cavitary lung lesions. The mean ADC value (×10 -3  mm 2 /s) of the malignant and benign cavitary lesions was 0.977±0.522 (0.511 to 2.872) and 1.383±0.370 (0.930 to 2.213), respectively. The findings were statistically significant using an independent samples t test ( P =0.002). The mean wall thickness of the malignant and benign lesions was 12.47±5.51 mm (5 to 25 mm) and 10.11±4.65 mm (5 to 22 mm), respectively. Although malignant cavities had a higher mean wall thickness than benign cavities, the difference was statistically insignificant ( P =0.104).

CONCLUSION

A significant difference was identified between the ADC values measured in DWI of the malignant and benign cavitary lung lesions. DWI, a noninvasive and rapid imaging method, can provide useful information for the differential diagnosis of cavitary lesions and can minimize unnecessary biopsies.

A review of diffusion-weighted magnetic resonance imaging in head and neck cancer patients for treatment evaluation and prediction of radiation-induced xerostomia

The incidence of head and neck cancers (HNC) is rising worldwide especially with HPV-related oropharynx squamous cell carcinoma. The standard of care for the majority of patients with locally advanced pharyngeal disease is curative-intent radiotherapy (RT) with or without concurrent chemotherapy. RT-related toxicities remain a concern due to the close proximity of critical structures to the tumour, with xerostomia inflicting the most quality-of-life burden. Thus, there is a paradigm shift towards research exploring the use of imaging biomarkers in predicting treatment outcomes. Diffusion-weighted imaging (DWI) is a functional MRI feature of interest, as it quantifies cellular changes through computation of apparent diffusion coefficient (ADC) values. DWI has been used in differentiating HNC lesions from benign tissues, and ADC analyses can be done to evaluate tumour responses to RT. It is also useful in healthy tissues to identify the heterogeneity and physiological changes of salivary glands to better understand the inter-individual differences in xerostomia severity. Additionally, DWI is utilised in irradiated salivary glands to produce ADC changes that correlate to clinical xerostomia. The implementation of DWI into multi-modal imaging can help form prognostic models that identify patients at risk of severe xerostomia, and thus guide timely interventions to mitigate these toxicities.

Impact of physiological parameters on the parotid gland fat fraction in a normal population

Quantifying physiological fat tissue in the organs is important to further assess the organ's pathologic status. This study aimed to investigate the impact of body mass index (BMI), age, and sex on the fat fraction of normal parotid glands. Patients undergoing magnetic resonance imaging (MRI) of iterative decomposition of water and fat with echo asymmetry and least squares estimation (IDEAL-IQ) due to non-salivary gland-related disease were reviewed. Clinical information of individual patients was categorized into groups based on BMI (under/normal/overweight), age (age I/age II/age III), and sex (female/male) and an inter-group comparison of the fat fraction values of both parotid glands was conducted. Overall, in the 626 parotid glands analyzed, the fat fraction of the gland was 35.80%. The mean fat fraction value increased with BMI (30.23%, 35.74%, and 46.61% in the underweight, normal and overweight groups, respectively [p < 0.01]) and age (32.42%, 36.20%, and 41.94% in the age I, II, and III groups, respectively [p < 0.01]). The fat content of normal parotid glands varies significantly depending on the body mass and age regardless of sex. Therefore, the patient's age and body mass should be considered when evaluating fatty change in the parotid glands in imaging results.

Does Diffusion Magnetic Resonance Imaging (DWI) has Role in Irradiated Laryngeal Carcinoma?

DWI involves acquisition of signal of movement of water proton in cellular spaces of body (Brownian motion). It includes qualitative method either restricted or facilitated and quantitive method which is apparent diffusion coefficient value(ADC) which is related to proportion of extracellular and intracellular components of the tissue., ADC is calculated with use of at least two b value more accurate using more DWI with different b value,ADC levels is low in increased tissue cellularity, as malignancy., ADC levels is high in non-tumoral tissue alterations such as direct endoscopy oedema, radiotherapy necrosis are expected to have minimal cellularity. ADC is most accurate in the detection of malignancy versus tissue edema or radionecrosis the aim of study to assess value of ADC as regarding measuring sensitivity and specificity and accuracy to differentiate tumor recurrence from radionecrosis. This study includes 36 patients who were suspected patients of tumor recurrence after radiotherapy; it is a prospective randomized comparative clinical trial. The patients were assessed using direct laryngoscopic examination under general anaesthesia and biopsy, and diffusion weighted image on the neck (b0 and b1000), ADC map and ADC value measured al lesion and normal tissues and compared with pathology results. ADC value (mean 0.93 ± 0.30 X 10-3 mm2/s) in patients had recurrent carcinoma was significantly lower (P < .0001) than the mean ADC of normal tissue in the same patients (1.26 ± 0.134) while mean ADC of tumour recurrence (P < .0001) was lower than mean ADC value of radio necrosis (1.63 ± 0.21 × 10-3 mm2/s). MRI ADC value is a sensitive and non-invasive method in detection of a recurrent laryngeal lesion from radionecrosis.

Apparent diffusion coefficient measurement of the parotid gland parenchyma

The measurements of apparent diffusion coefficient (ADC) with diffusion weighted magnetic resonance imaging (DW-MRI) is becoming a popular diagnostic and research tool for examination of parotid glands. However, there is little agreement between the reported ADC values of the parotid gland in published literature. In this review 43 studies on ADC measurement of the parotid glands were included. The analyses indicated several possible culprits of the observed ADC discrepancies. For example, DW-MRI examinations under gustatory stimulation gives higher ADC values compared to the unstimulated parotid gland (P=0.003). The diffusion weighting factors (b-values) can either increase (b-value <200 s/mm²) or decrease ADC values (b-values >1,000 s/mm²). The timing of follow-up DW-MRI after radiotherapy (RT) indicates correlation to the found ADC values (R² =0.39). Interestingly, the choice of regions of interest (ROI) appears not to affect the measurements of ADC (P=0.75). It can be concluded that there is a critical need for standardization of ADC measurement of the parotid glands to allow valid inter-study comparisons and eventually to reach consensus on the use of ADC as biomarker.

Dynamic Three-Dimensional ADC Changes of Parotid Glands During Radiotherapy Predict the Salivary Secretary Function in Patients With Head and Neck Squamous Carcinoma

Objective

To investigate the changes of three-dimensional apparent diffusion coefficient (3D-ADC) of bilateral parotid glands during radiotherapy for head and neck squamous cell carcinoma (HNSCC) patients and explore the correlations with the radiation dose, volume reduction of parotid gland and the salivary secretary function.

Materials and Methods

60 HNSCC were retrospectively collected in Sichuan cancer hospital. The patients were all received diffusion-weighted imaging (DWI) scan at pre-radiation, the 15^th radiation, the 25^th radiation and completion of radiation. Dynamic 3D-ADC were measured in different lobes of parotid glands (P1: deep lobe of ipsilateral; P2: superficial lobe of ipsilateral; P3: deep lobe of contralateral; P4: superficial lobe of contralateral), and the 3D-ADC of spinal cord were also recorded. Chewing stimulates test, radionuclide scan and RTOG criteria were recorded to evaluate the salivary secretary function. Pearson analysis was used to assess the correlation between 3D-ADC value, radiation dose, volume change, and salivary secretary function.

Results

The mean 3D-ADC of parotid glands increased. It began to change at the 15^th radiation and the mostly increased in P1. However, there was no change for the maximum and minimum 3D-ADC. The 3D-ADC values of spinal cord changes were almost invisible (ratio ≤ 0.03 ± 0.01). The mean 3D-ADC was negatively correlated with the salivary secretary function (r=-0.72) and volume reduction of different lobes of parotid glands (r1=-0.64; r2=-0.61; r3=-0.57; r4=-0.49), but it was positively correlated with the delivered dose (r1 = 0.73; r2 = 0.69; r3 = 0.65; r4 = 0.78).

Conclusion

Dynamic 3D-ADC changes might be a new and early indicator to predict and evaluate the secretary function of parotid glands during radiotherapy.

Radiological imaging features of the salivary glands in xerostomia induced by an immune checkpoint inhibitor

The clinical features of xerostomia induced by immune checkpoint inhibitors (ICI) are similar to those of Sjögren’s syndrome (SS), whereas the immunohistological and serological features are known to differ from those of SS. However, the radiologic imaging features of salivary glands are not yet well known. We report a case of a 56-year-old male patient diagnosed with ICI-induced xerostomia. The patient underwent various imaging examinations to investigate the condition of the salivary glands, which indicated the following: (1) less specific findings on contrast-enhanced computed tomography, (2) mixed with intermediate and low signal intensity on both T₁-weighted and fat-suppressed T₂-weighted magnetic resonance imaging and poor “salt and pepper” appearance on magnetic resonance sialography, and (3) multiple ovoid hypoechoic areas with hyperechoic bands without acute sialadenitis on ultrasound. These radiologic imaging findings suggested remarkable lymphocyte infiltration, which could be a characteristic of ICI-induced xerostomia.

Imaging quality of PROPELLER diffusion-weighted MR imaging and its diagnostic performance in distinguishing pleomorphic adenomas from Warthin tumors of the parotid gland

The aim of this study was to evaluate the imaging quality and diagnostic performance of fast spin echo diffusion-weighted imaging with periodically rotated overlapping parallel lines with enhanced reconstruction (FSE-PROP-DWI) in distinguishing parotid pleomorphic adenoma (PMA) from Warthin tumor (WT). This retrospective study enrolled 44 parotid gland tumors from 34 patients, including 15 PMAs and 29 WTs with waived written informed consent. All participants underwent 1.5 T diffusion-weighted imaging including FSE-PROP-DWI and single-shot echo-planar diffusion-weighted imaging (SS-EP-DWI). After imaging resizing and registration among T2WI, FSE-PROP-DWI and SS-EP-DWI, imaging distortion was quantitatively analyzed by using the Dice coefficient. Signal-to-noise ratio and contrast-to-noise ratio were qualitatively evaluated. The mean apparent diffusion coefficient (ADC) of parotid gland tumors was calculated. Wilcoxon signed-rank test was used for paired comparison between FSE-PROP-DWI versus SS-EP-DWI. Mann-Whitney U test was used for independent group comparison between PMAs versus WTs. Diagnostic performance was evaluated by receiver operating characteristics curve analysis. P < 0.05 was considered statistically significant. The Dice coefficient was statistically significantly higher on FSE-PROP-DWI than SS-EP-DWI for both tumors (P < 0.005). Mean ADC was statistically significantly higher in PMAs than WTs on both FSE-PROP-DWI and SS-EP-DWI (P < 0.005). FSE-PROP-DWI and SS-EP-DWI successfully distinguished PMAs from WTs with an AUC of 0.880 and 0.945, respectively (P < 0.05). Sensitivity, specificity, positive predictive value, negative predictive value and accuracy in diagnosing PMAs were 100%, 69.0%, 62.5%, 100% and 79.5% for FSE-PROP-DWI, and 100%, 82.8%, 75%, 100% and 88.6% for SS-EP-DWI, respectively. FSE-PROP-DWI is useful to distinguish parotid PMAs from WTs with less distortion of tumors but lower AUC than SS-EP-DWI.

Stafne bone defects radiographic features in panoramic radiographs: Assessment of 91 cases

Background

To evaluate 91 cases of Stafne bone defect (SBD) in panoramic radiographs (PR) to determine the prevalence of different SBD variants, considering age, gender, and side. Additionally, to assess the most frequent imaging features of SBD.

Material and Methods

Participant data were collected from 91 SBD cases with PR imaging. First, SBDs were classified according to their location, as anterior, posterior, or ramus variant. SBD imaging features were classified according to radiographic imaging findings, assessing margins, degree of internal radiolucency, shape, topographic relationship between the defect and mandibular border, location of the defect according to mandibular teeth, and locularity. The topographic relationship between the SBD and the mandibular canal was described for the inferior variant only. Mean sizes were also described.

Results

A total of 92 SBD cases were evaluated from 91 radiographs. One case presented multiple defects. Mean patient age was 60.80 years. Men were more affected than women. The most frequent SBD variant was the posterior variant, and the least frequent was the ramus variant. The most observed radiographic features were thick sclerotic bone margin in the entire contour of the defect, partially radiolucent internal content, oval shape, continuity with mandible base without discontinuity of mandible border, third molar region location, and unilocular shape. With the posterior variant only, the most common topographic relationship between the defect and the upper wall of the mandibular canal was the defect located below the upper wall and continuous with the inferior wall of the mandibular canal.

Conclusions

The knowledge of common SBD radiographic imaging features in PR can help dental practitioners with the differential diagnosis of SBD.

Key words:Panoramic radiograph, mandible, bone cysts, salivary glands, Stafne bone defect.

Diagnostic work-up in obstructive and inflammatory salivary gland disorders

Inflammatory and obstructive disorders of the salivary glands are caused by very different pathological conditions affecting the gland tissue and/or the excretory system. The clinical setting is essential to address the appropriate diagnostic imaging work-up. According to history and physical examination, four main clinical scenarios can be recognised: (1) acute generalised swelling of major salivary glands; (2) acute swelling of a single major salivary gland; (3) chronic generalised swelling of major salivary glands, associated or not with "dry mouth"; (4) chronic or prolonged swelling of a single major salivary gland. The algorithm for imaging salivary glands depends on the scenario with which the patient presents to the clinician. Imaging is essential to confirm clinical diagnosis, define the extent of the disease and identify complications. Imaging techniques include ultrasound (US), computed tomography (CT) and magnetic resonance (MR) with MR sialography.

JOURNAL CLUB: The Warthin Tumor Score: A Simple and Reliable Method to Distinguish Warthin Tumors From Pleomorphic Adenomas and Carcinomas

OBJECTIVE

The objective of this article is to propose a Warthin tumor (WT) score to distinguish WTs from other parotid tumors.

MATERIALS AND METHODS

The study included 78 patients with 92 histologically proven parotid tumors, including 42 WTs, 30 pleomorphic adenomas (PMAs), and 20 carcinomas. Echo-planar DW images were acquired. The WT score, which comprised the mean apparent diffusion coefficient (ADC_M) and the SD of the ADC (ADC_SD) of tumors, patient age, and patient sex, was used to predict WTs. The diagnostic performance of the WT score was evaluated using ROC analyses. Statistical significance was denoted by p < 0.05.

RESULTS

With the use of optimized criteria, including an ADC_M less than or equal to 1.016 × 10^-3 mm²/s (WT score, 1), an ADC_SD less than or equal to 0.1171 × 10^-3 mm²/s (WT score, 1), patient age older than 49 years (WT score, 1), and male sex (WT score, 1), a WT score greater than 2 had a sensitivity, specificity, positive negative value, negative predictive value, and accuracy of 85.7%, 100.0%, 100.0%, 89.3%, and 93.4%, respectively.

CONCLUSION

The WT score allows parotid WTs to be distinguished from PMAs and carcinomas with high accuracy.

Early Changes in Apparent Diffusion Coefficient for Salivary Glands during Radiotherapy for Nasopharyngeal Carcinoma Associated with Xerostomia

Objective

To evaluate the early changes in the apparent diffusion coefficient (ADC) of the salivary glands during radiotherapy (RT) and their association with the degree of xerostomia at 6 months after RT in patients with nasopharyngeal carcinoma (NPC).

Materials and Methods

We enrolled 26 patients with NPC who underwent RT. Each patient underwent diffusion-weighted MRI of the salivary glands at rest and with gustatory stimulation within 1 week before RT and 2 weeks after the beginning of RT. The ADC at rest (ADC_R) and increase and increase rate with stimulation (ADC_I, ADC_IR) of the submandibular and parotid glands were calculated. The differences in the variables' values between 2 weeks after the beginning of RT and baseline (ΔADC_R, ΔADC_I, and ΔADC_IR) were compared to the degree of xerostomia at 6 months after RT.

Results

The ADC_R of the submandibular and parotid glands were both significantly higher at 2 weeks after the beginning of RT than found at baseline (both p < 0.01). The ADC_I and ADC_IR for the parotid glands were both significantly lower at 2 weeks after the beginning of RT than found at baseline (both p < 0.01). ΔADC_I and ΔADC_IR of the parotid glands were associated with the degree of xerostomia at 6 months after RT (r = −0.61 and −0.72, both p < 0.01).

Conclusion

The ADCs of the salivary glands change early during RT. The differences in the ADC increase and increase rate of the parotid glands between 2 weeks after the beginning of RT and baseline were associated with the degree of xerostomia at 6 months after RT.

Diffusion weighted magnetic resonance imaging in the diagnosis of parotid masses. Preliminary results

Objective

To demonstrate the diagnostic potentials of MRI, diffusion weighted imaging (DWI), and apparent diffusion coefficient (ADC) mapping in the detection of parotid masses correlated to the histopathological results.

Methods

Study design was retrospective. Fifteen patients with parotid gland masses were included as the study group and contralateral normal parotis glands of same patients were taken as the control group. Patients with bilateral parotid gland tumors were excluded, 7 right-sided and 8 left-sided parotid masses were included in the research. The study took place at the Department of Radiology, Ankara, Turkey, between May 2012 and September 2014.

Results

Apparent diffusion coefficient measurements of 15 parotis tumors in 1000 and 750 sec/mm²b-values with comparison to the contralateral normal gland parenchyma were demonstrated. Neurofibromas was predicted as the highest, and lipomas as the lowest ADC values. Pleomorphic adenomas, Warthin’s tumor, and normal parotid parenchyma indicate significant statistical differences from each other on the basis of mean ADC values (p<0.05).

Conclusion

The DWI and ADC mapping of parotis gland could aid in the differential diagnosis of benign and malignant masses.

Quantitative MR imaging of intra-orbital structures: Tissue-specific measurements and age dependency compared to extra-orbital structures using multispectral quantitative MR imaging

The orbit can be affected by unique pathologic conditions and often requires MRI evaluation. The purpose of this study was to investigate the age-related changes in multiple intra-orbital structures using quantitative MRI (qMRI). Thirty-eight subjects (20 males, 18 females; ages 0.5-87 years) underwent MRI with a mixed turbo spin echo sequence. T1 and T2 measurements were obtained within ROI in 6 intra-orbital structures (medial and lateral rectus muscles, medial and lateral retrobulbar fat, lacrimal gland, and optic nerve), and compared with those of corresponding extra-orbital structures (masseter muscle, subcutaneous cheek fat, buccal fat, parotid gland, and frontal white matter). Statistical analyses were performed using Pearson's correlation coefficients. T1 and T2 values of the extra-ocular muscles increased with age, with higher T1 and T2 values compared to the masseter muscles. Retrobulbar fat showed significant age-associated increases in T1 values in the lateral side and in T2 values in both sides. T1 and T2 values in the lacrimal gland increased with age, while the parotid gland showed an age-associated increase in T2 values and decrease in T1 values. Optic nerves demonstrated age-related changes, similar to that of frontal white matter; rapid decreases with age in T1 and T2 times in early stages of life, and slight increases in T1 and T2 times later in life. Intra-orbital structures demonstrated specific qMRI measurements and aging patterns, which were different from extra-orbital structures. Location-specific age-related changes of intra-orbital structures should be considered in the qMRI assessment of the orbital pathology.

Diffusional kurtosis imaging of parotid glands in Sjögren's syndrome: Initial findings

PURPOSE

To explore the role of diffusion kurtosis imaging (DKI) of parotid glands in diagnosing Sjögren's syndrome (SS).

MATERIALS AND METHODS

A total of 40 patients with SS and 40 healthy volunteers underwent 3.0T magnetic resonance imaging (MRI) including DKI, which generated the apparent diffusion coefficient (ADC), corrected diffusion (D), and diffusional kurtosis (K) values. The MR nodular grade was determined on the basis of MR morphological findings.

RESULTS

The parotid ADC, D, and K values in patients with SS were significantly higher than those of healthy volunteers (P = 0.011, < 0.001, 0.022, respectively). The parotid ADC and D values in patients with SS of MR nodular grade 0 were significantly higher than those of healthy volunteers (all P < 0.001). The parotid D value showed an accuracy of 75.0% and 87.9% in diagnosing patients with SS and MR nodular grade 0, respectively. The parotid ADC and D values correlated negatively, while the K values correlated positively with the MR nodular grade significantly in patients with SS (r = -0.741, -0.605, 0.424, all P < 0.001). All parotid DKI parameters differed significantly among patients with SS at different MR nodular grades (all P < 0.001).

CONCLUSION

Parotid DKI parameters hold great potential in diagnosing SS, especially in early-stage SS without MR morphological changes.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1409-1417.

Effects of regions of interest methods on apparent coefficient measurement of the parotid gland in early Sjögren's syndrome at 3T MRI

BACKGROUND

The apparent diffusion coefficient (ADC) has been used to assess parotid gland abnormalities in Sjögren's syndrome (SS) patients; however, few data exist on the influence of region of interest (ROI) methods on ADC measurements.

PURPOSE

To assess the influence of ROI methods on ADC measurement, and their diagnostic ability in detecting parotid gland abnormalities in early SS patients.

MATERIAL AND METHODS

Thirteen early SS patients underwent parotid gland diffusion-weighted imaging scans at a 3.0 T MR unit. Two readers independently measured the parotid gland ADC value using three different ROIs (whole-gland [WG], single-slice [SS], and reader-based circular [RBC]). The ADC value based on three different ROIs (ADC-ROI_WG, ADC-ROI_SS, ADC-ROI_RBC) were compared between the SS group and a matched healthy control (HC) group (n = 19). Receiver operating characteristic (ROC) curves and intra-class correlation coefficients (ICC) were used to determine the diagnostic ability and reproducibility of the parameters.

RESULTS

The ADC-ROI_WG, ADC-ROI_SS, and ADC-ROI_RBC in the SS group were all significantly higher than those in HC group (all P < 0.05). The ADC-ROI_WG showed better diagnostic ability than did ADC-ROI_RBC (P = 0.0200), while no significant difference was found between ADC-ROI_WG and ADC-ROI_SS (P = 0.4636). The ROI_WG method showed the best inter- and intra-reader agreement (ICC, 0.902 and 0.928, respectively), followed by ROI_SS and ROI_RBC.

CONCLUSION

The ROI methods can influence the parotid gland ADC measurements and their diagnostic ability. Considering our results, we suggest using in clinical practice single-slice ROIs to measure the ADC of the parotid gland.

Evaluating Instantaneous Perfusion Responses of Parotid Glands to Gustatory Stimulation Using High-Temporal-Resolution Echo-Planar Diffusion-Weighted Imaging

BACKGROUND AND PURPOSE

Parotid glands secrete and empty saliva into the oral cavity rapidly after gustatory stimulation. However, the role of the temporal resolution of DWI in investigating parotid gland function remains uncertain. Our aim was to design a high-temporal-resolution echo-planar DWI pulse sequence and to evaluate the instantaneous MR perfusion responses of the parotid glands to gustatory stimulation.

MATERIALS AND METHODS

This prospective study enrolled 21 healthy volunteers (M/F = 2:1; mean age, 45.2 ± 12.9 years). All participants underwent echo-planar DWI (total scan time, 304 seconds; temporal resolution, 4 s/scan) on a 1.5T MR imaging scanner. T2WI (b = 0 s/mm²) and DWI (b = 200 s/mm²) were qualitatively assessed. Signal intensity of the parotid glands on T2WI, DWI, and ADC was quantitatively analyzed. One-way ANOVA with post hoc group comparisons with Bonferroni correction was used for statistical analysis. P < .05 was statistically significant.

RESULTS

Almost perfect interobserver agreement was achieved (κ ≥ 0.656). The parotid glands had magnetic susceptibility artifacts in 14.3% (3 of 21) of volunteers during swallowing on DWI but were free from perceptible artifacts at the baseline and at the end of scans on all images. Increased ADC and reduced signal intensity of the parotid glands on T2WI and DWI occurred immediately after oral administration of lemon juice. Maximal signal change of ADC (24.8% ± 10.8%) was significantly higher than that of T2WI (-10.1% ± 5.2%, P < .001). The recovery ratio of ADC (100.71% ± 42.34%) was also significantly higher than that of T2WI (22.36% ± 15.54%, P < .001).

CONCLUSIONS

Instantaneous parotid perfusion responses to gustatory stimulation can be quantified by ADC by using high-temporal-resolution echo-planar DWI.

Diffusion-weighted MRI findings in Sjögren's syndrome: a preliminary study

BACKGROUND

Parotid glands diffusion-weighted imaging (DWI) in Sjögren's syndrome patients have provided conflicting results currently.

PURPOSE

To determine if parotid gland DWI using a small region of interest (ROI) can provide diagnosis and assess therapeutic efficacy in Sjögren's syndrome.

MATERIAL AND METHODS

Twenty-three women with Sjögren's syndrome, five with dry mouth who did not meet diagnostic criteria for Sjögren's syndrome, and 11 healthy volunteers (controls) were evaluated with DWI. All participants received routine T1-weighted (T1W) imaging and T2-weighted (T2W) fat-suppressed imaging, and DWI. The SI ratios (SIRs) and ADC ratios (ADCRs) for parotid gland/spinal cord were then calculated. Approximately 8-10 round ROIs measuring approximately 5 mm(2) were placed on each lobe of the parotid gland, and the signal intensity (SI) was measured while avoiding fat, ducts, and blood vessels. A ROI encompassing the entire lobe of the parotid gland was also used to measure SI.

RESULTS

Using 5 mm(2) ROIs significantly higher DWI SIRs were noted in participants with Sjögren's syndrome compared with either participants with dry mouth without Sjögren's syndrome or healthy volunteers (all, P <0.001). The difference was not related to the presence of fat. No differences were noted when the larger ROI was used. In addition, parotid gland from untreated Sjögren's participants showed significantly higher SIRs compared with those from treated participants (P = 0.015).

CONCLUSION

A small ROI DWI can provide morphological and functional information on the parotid gland in Sjögren's syndrome patients, and can aid in the diagnosis and evaluation of therapeutic efficacy.

Intravoxel incoherent motion MR imaging measurements of the bilateral parotid glands at 3.0-T MR: effect of age, gender and laterality in healthy adults

OBJECTIVE

To investigate the effect of age, gender and laterality on the intravoxel incoherent motion (IVIM) MR imaging measurements of parotid glands in healthy participants at 3.0-T MRI.

METHODS

A total of 108 healthy participants were prospectively recruited. IVIM MRI scan was performed using a 3.0-T MR scanner, and corresponding parameters (perfusion fraction, f; pseudodiffusion coefficient, D*; tissue diffusivity, D) were derived from biexponential fitting of IVIM data. Pearson correlation analysis was performed to determine the association between the IVIM MRI parameters and age. The parameter difference between male and female participants or between left and right parotid glands was compared using unpaired or paired t test, respectively.

RESULTS

Excellent interreader and intrareader agreements on the measurements of IVIM MRI parameters were achieved. Both D and f values correlated inversely with the age in both left and right parotid glands (p < 0.05) while D* value did not (p > 0.05). Male participants had higher IVIM MRI parameters than the female participants in both left and right glands (p < 0.05). No significant differences were found in the IVIM MRI parameters between left and right glands in both male and female participants (p > 0.05).

CONCLUSION

The IVIM MRI parameters are age and gender dependent, but not laterality dependent. Age- and gender-related effect should be taken into consideration in future IVIM MRI studies for parotid glands.

ADVANCES IN KNOWLEDGE

(1) Both D and f values correlated inversely with the age in healthy parotid glands, while D* value did not. (2) The parotid glands of males showed higher IVIM MRI parameters than that of females. (3) There were no significant differences on the IVIM MRI parameters between the left and right glands. (4) Age- and gender-related effect should be taken into consideration in future IVIM MRI studies for parotid glands.

Temporal Evolution of Parotid Volume and Parotid Apparent Diffusion Coefficient in Nasopharyngeal Carcinoma Patients Treated by Intensity-Modulated Radiotherapy Investigated by Magnetic Resonance Imaging: A Pilot Study

Purpose

To concurrently quantify the radiation-induced changes and temporal evolutions of parotid volume and parotid apparent diffusion coefficient (ADC) in nasopharyngeal carcinoma (NPC) patients treated by intensity-modulated radiotherapy by using magnetic resonance imaging (MRI).

Materials and Methods

A total of 11 NPC patients (9 men and 2 women; 48.7 ± 11.7 years, 22 parotid glands) were enrolled. Radiation dose, parotid sparing volume, severity of xerostomia, and radiation-to-MR interval (RMI) was recorded. MRI studies were acquired four times, including one before and three after radiotherapy. The parotid volume and the parotid ADC were measured. Statistical analysis was performed using SPSS and MedCalc. Bonferroni correction was applied for multiple comparisons. A P value less than 0.05 was considered as statistically significant.

Results

The parotid volume was 26.2 ± 8.0 cm³ before radiotherapy. The parotid ADC was 0.8 ± 0.15 × 10⁻³ mm²/sec before radiotherapy. The parotid glands received a radiation dose of 28.7 ± 4.1 Gy and a PSV of 44.1 ± 12.6%. The parotid volume was significantly smaller at MR stage 1 and stage 2 as compared to pre-RT stage (P < .005). The volume reduction ratio was 31.2 ± 13.0%, 26.1 ± 13.5%, and 17.1 ± 16.6% at stage 1, 2, and 3, respectively. The parotid ADC was significantly higher at all post-RT stages as compared to pre-RT stage reciprocally (P < .005 at stage 1 and 2, P < .05 at stage 3). The ADC increase ratio was 35.7 ± 17.4%, 27.0 ± 12.8%, and 20.2 ± 16.6% at stage 1, 2, and 3, respectively. The parotid ADC was negatively correlated to the parotid volume (R = -0.509; P < .001). The parotid ADC was positively associated with the radiation dose significantly (R² = 0.212; P = .0001) and was negatively associated with RMI significantly (R² = 0.203; P = .00096) significantly. Multiple regression analysis further showed that the post-RT parotid ADC was related to the radiation dose and RMI significantly (R² = 0.3580; P < .0001). At MR stage 3, the parotid volume was negatively associated with the dry mouth grade significantly (R² = 0.473; P < .0001), while the parotid ADC was positively associated with the dry mouth grade significantly (R² = 0.288; P = .015).

Conclusion

Our pilot study successfully demonstrates the concurrent changes and temporal evolution of parotid volume and parotid ADC quantitatively in NPC patients treated by IMRT. Our results suggest that the reduction of parotid volume and increase of parotid ADC are dominated by the effect of acinar loss rather than edema at early to intermediate phases and the following recovery of parotid volume and ADC toward the baseline values might reflect the acinar regeneration of parotid glands.

A potential risk of overestimating apparent diffusion coefficient in parotid glands

Objectives

To investigate transient signal loss on diffusion weighted images (DWI) and overestimation of apparent diffusion coefficient (ADC) in parotid glands using single shot echoplanar DWI (EPDWI).

Materials and Methods

This study enrolled 6 healthy subjects and 7 patients receiving radiotherapy. All participants received dynamic EPDWI with a total of 8 repetitions. Imaging quality of DWI was evaluated. Probability of severe overestimation of ADC (soADC), defined by an ADC ratio more than 1.2, was calculated. Error on T2WI, DWI, and ADC was computed. Statistical analysis included paired Student t testing and Mann-Whitney U test. A P value less than 0.05 was considered statistically significant.

Results

Transient signal loss was visually detected on some excitations of DWI but not on T2WI or mean DWI. soADC occurred randomly among 8 excitations and 3 directions of diffusion encoding gradients. Probability of soADC was significantly higher in radiotherapy group (42.86%) than in healthy group (24.39%). The mean error percentage decreased as the number of excitations increased on all images, and, it was smallest on T2WI, followed by DWI and ADC in an increasing order.

Conclusions

Transient signal loss on DWI was successfully detected by dynamic EPDWI. The signal loss on DWI and overestimation of ADC could be partially remedied by increasing the number of excitations.

Diffusion-weighted magnetic resonance imaging in preoperative assessment of non-small cell lung cancer

BACKGROUND

Diffusion-weighted magnetic resonance imaging (DWI) frequently shows heterogeneity of signal intensity (SI) in non-small cell lung cancer (NSCLC). The purpose of our study was to examine the association of SI and DWI patterns with histology, tumor invasiveness, lymph node metastasis, and (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) uptake in NSCLC.

METHODS

One hundred forty-five patients with NSCLC underwent preoperative DWI and FDG-PET. DWI patterns were visually classified as homogenous (HOM) (n = 81) or heterogeneous (HET) (n = 64). The former was further classified as faint (faint-HOM) (n = 27) or dark (dark-HOM) (n = 54) according to a cutoff value of SI. Associations of SI and DWI patterns with tumor histology, lymphatic or vascular invasion, pleural invasion, lymph node metastasis, and FDG uptake were evaluated.

RESULTS

All faint-HOM tumors were well-differentiated adenocarcinoma, whereas dark-HOM and HET tumors were less-differentiated adenocarcinoma or non adenocarcinoma. Although the dark areas in HET tumors showed a dense aggregation of tumor cells, their faint areas showed abundant fibrovascular stroma or necrosis, or a well-differentiated part of adenocarcinoma. Tumor size and the frequencies of lymphatic or vascular invasion, pleural invasion, and nodal metastasis were highest in HET tumors, followed by dark-HOM and faint-HOM (P = .1-P < .001) tumors. Sixty-five tumors having at least 1 of the invasions or metastasis showed significantly higher SI than the 81 tumors without (P < .001). HET tumors had the highest FDG uptake, followed by dark-HOM and faint-HOM tumors; differences between the groups were significant (P < .01 to P < .001).

CONCLUSIONS

The SI and heterogeneity of DWI reflect the histologic heterogeneity, tumor aggressiveness, and FDG-PET uptake in NSCLC.

Diffusion-weighted MR imaging of salivary glands with gustatory stimulation: comparison before and after radiotherapy

BACKGROUND

Xerostomia is the most prominent complication in patients with head and neck carcinoma after radiotherapy (RT). Diffusion-weighted magnetic resonance imaging (DWI) with gustatory stimulation may contribute to the evaluation of salivary gland function.

PURPOSE

To investigate the value of DWI for quantifying physiological changes of the parotid gland during gustatory stimulation in patients before and after RT.

MATERIAL AND METHODS

Magnetic resonance imaging (MRI) was performed in 28 consecutive patients with nasopharyngeal carcinoma before and after RT and clinical xerostomia was also assessed. A DWI sequence was performed once at rest and continually repeated seven times during stimulation with ascorbic acid. Apparent diffusion coefficient (ADC) maps for parotid glands at different time points and the range of increase with stimulation were calculated. Paired two-tailed Student t tests were used to compare the ADC values before and after stimulation, and before and after RT.

RESULTS

Before RT, the ADC showed an initial increase (P < 0.001) and then fluctuated during stimulation. After RT, as the clinical xerostomia changed from Grade 0 to Grade 2, the mean ADC at rest increased compared with the pre-RT value (P < 0.001). A similar response to stimulation was observed, but the range of increase between the maximum ADC during stimulation and the baseline value at rest was higher post-RT than pre-RT (P = 0.022). The minimum ADC during stimulation was higher than the baseline value post-RT (P = 0.028), but there was no difference pre-RT (P = 0.603).

CONCLUSION

DWI combined with gustatory stimulation seems to display the physiological changes of the parotid gland following RT and may be a potential tool for non-invasively assessing salivary gland function.

Age-related relaxo-volumetric quantitative magnetic resonance imaging of the major salivary glands

OBJECTIVE

To study age-related characteristics of T1 and T2 relaxation times and volume of the major salivary glands.

METHODS

Thirty-five subjects (0.5-87 years old) with normal salivary glands were imaged with mixed turbo spin-echo pulse sequences at 1.5-T magnetic resonance units. Bilateral parotid, submandibular, and sublingual glands were segmented manually. Histograms for each salivary gland were generated and modeled with Gaussian functions for every parameter.

RESULTS

Seventy parotid glands, 52 submandibular glands, and 50 sublingual glands were segmented and the histograms were analyzed. The parotid gland exhibited shorter-peak T1s and longer-peak T2s relative to the submandibular and sublingual glands. The peak T2s for all glands showed a minimum value between 2 and 4 years of age and increased monotonically thereafter. From birth to early adulthood, all glands increased in size logarithmically.

CONCLUSION

Age-related relaxo-volumetric changes of the major salivary glands show clear T2 and volumetric age-related patterns for all glands.

Prediction of nodal metastasis in head and neck cancer using a 3T MRI ADC map

BACKGROUND AND PURPOSE

The detection of cervical nodal metastases is important for the prognosis and treatment of head and neck tumors. The purpose of this study was to assess the ability of ADC values at 3T to distinguish malignant from benign lymph nodes.

MATERIALS AND METHODS

From July 2009 to June 2010, twenty-two patients (21 men and 1 woman; mean age, 49.8±9.5 years; age range, 28-66 years) scheduled for surgical treatment of biopsy-proved head and neck cancer were prospectively and consecutively enrolled in this study. All patients were scanned on a 3T imaging unit (Verio) by using a 12-channel head coil combined with a 4-channel neck coil. Histologic findings were the reference standard for the diagnosis of lymph node metastasis.

RESULTS

The ADC values derived from the signal intensity averaged across images obtained with b-values of 0 and 800 s/mm2 were 1.086±0.222×10(-3) mm2/s for benign lymph nodes and 0.705±0.118×10(-3) mm2/s for malignant lymph nodes (P<.0001). When an ADC value of 0.851×10(-3) mm2/s was used as a threshold value for differentiating benign from malignant lymph nodes, the best results were obtained with an accuracy of 91.0%, sensitivity of 91.3%, and specificity of 91.1%.

CONCLUSIONS

The ADC value is a sensitive and specific parameter that can help to differentiate malignant from benign lymph nodes.

Ultrasound GLCM texture analysis of radiation-induced parotid-gland injury in head-and-neck cancer radiotherapy: an in vivo study of late toxicity

PURPOSE

Xerostomia (dry mouth), secondary to irradiation of the parotid glands, is one of the most common side effects of head-and-neck cancer radiotherapy. Diagnostic tools able to accurately and efficiently measure parotid gland injury have yet to be introduced into the clinic. This study's purpose is to investigate sonographic textural features as potential imaging signatures for quantitative assessment of parotid-gland injury after head-and-neck radiotherapy.

METHODS

The authors have investigated a series of sonographic features obtained from the gray level co-occurrence matrix (GLCM) - a second order statistical method of texture analysis. These GLCM textural features were selected based on empirical observations that the normal parotid gland exhibits homogeneous echotexture, whereas the postradiotherapy parotid gland often exhibits heterogeneous echotexture. We employed eight sonographic features: (1) angular second moment (ASM), (2) inverse differential moment (IDM), (3) contrast, (4) variance, (5) correlation, (6) entropy, (7) cluster shade, and (8) cluster prominence. Altogether, sonographic properties of the parotid glands were quantified by their degrees of homogeneity (ASM and IDM), heterogeneity (contrast and variance), smoothness (correlation), randomness (entropy), and symmetry (cluster shade and prominence). The sonographic features were tested in a pilot study of 12 postradiotherapy patients and 7 healthy volunteers. The mean follow-up time for the postradiotherapy patients was 17.2 months (range: 12.1-23.9 months) and the mean radiation dose to the parotid glands was 32.3 Gy (range: 11.0-63.4 Gy). Each participant underwent one ultrasound study in which longitudinal (vertical) ultrasound scans were performed on the bilateral parotids - a total of 24 postirradiation and 14 normal parotid glands were examined. The 14 normal parotid glands served as the control group. A radiologist contoured the parotid glands on the B-mode images and the sonographic features were computed from the contoured region-of-interest.

RESULTS

The authors observed significant differences (p < 0.05) in all sonographic features between the normal and postradiotherapy parotid glands. The sonographic findings were consistent with the clinical observations of the ultrasound images: normal parotid glands exhibited homogeneous texture, while the postradiotherapy parotid glands exhibited heterogeneous echotexture (e.g., hyperechoic lines and spots), which likely represents fibrosis.

CONCLUSIONS

The authors have demonstrated the feasibility of ultrasonic texture evaluation of parotid glands; and the sonographic features may serve as imaging signatures to assess radiation-induced parotid injury.

Diffusion-weighted MR imaging in the head and neck

Extracranial applications of diffusion-weighted (DW) magnetic resonance (MR) imaging are gaining increasing importance, including in head and neck radiology. The main indications for performing DW imaging in this relatively small but challenging region of the body are tissue characterization, nodal staging, therapy monitoring, and early detection of treatment failure by differentiating recurrence from posttherapeutic changes. Lower apparent diffusion coefficients (ADCs) have been reported in the head and neck region of adults and children for most malignant lesions, as compared with ADCs of benign lesions. For nodal staging, DW imaging has shown promise in helping detect lymph node metastases, even in small (subcentimeter) nodes with lower ADCs, as compared with normal or reactive nodes. Follow-up of early response to treatment is reflected in an ADC increase in the primary tumor and nodal metastases; whereas nonresponding lesions tend to reveal only a slight increase or even a decrease in ADC during follow-up. Optimization and standardization of DW imaging technical parameters, comparison of DW images with morphologic images, and increasing experience, however, are prerequisites for successful application of this challenging technique in the evaluation of various head and neck pathologic conditions.

DWI of the brain: postmortal DWI of the brain in comparison with in vivo data

PURPOSE

Changes in water diffusion can be quantified by diffusion-weighted MR imaging. However, there are only few reports about changes in post mortem brain. The aim of this study was to investigate the temporal pattern of the apparent diffusion coefficient (ADC) in the brain after death, to compare the values to in vivo brain and to assess the value of ex vivo DWI as a forensic tool.

MATERIAL AND METHODS

The study was approved by the local Ethics Committee, and informed consent was obtained from all relatives and the control subjects. Twenty-one corpses, died of natural cause, were examined (13 males, 8 females; age: 70.5±8.7 y, weight 74±18 kg). Diffusion-Weighted Imaging (DWI) was performed with b-values of 0 and 1000 s/mm(2) at 1.5 T. Scans were repeated in intervals of 1 h. ADC-maps were calculated in thalamus, cerebrum and cerebellum. The obtained values were statistically compared to healthy volunteers (n=3) and to literature data.

RESULTS

The ADC in the three regions decreased characteristically during the examination time. In the cerebrum there was a significant difference between ex vivo and in vivo ADC (p<0.001) as well as in the other regions (thalamus: p<0.001, cerebellum: p=0.045).

CONCLUSION

DWI of the postmortal brain can be added to the MRI methods for a post mortem imaging.

Diffusion-weighted magnetic resonance for pulmonary nodules: 1.5 vs. 3 Tesla

The usefulness of diffusion-weighted magnetic resonance for assessing malignant pulmonary nodules was examined in 58 patients with 76 (58 malignant, 18 benign) pulmonary nodules (1.0-5.6 cm) who underwent 1.5-T and 3-Tesla imaging and (18)F-fluorodeoxyglucose positron-emission tomography prior to surgery. The sensitivities and specificities of these techniques for discriminating benign and malignant nodules were compared. The apparent diffusion coefficients of the pulmonary nodules on 1.5-T and 3-T imaging correlated significantly. The sensitivities and specificities for discriminating benign and malignant lesions were similar among the 3 imaging techniques: 1.5-T imaging, 0.91 and 0.90; 3-T imaging, 0.88 and 0.94; positron-emission tomography, 0.94 and 0.94. The apparent diffusion coefficient on 1.5-T imaging showed a significant reverse correlation with positron-emission tomography, and the correlation between 3-T imaging and positron-emission tomography was marginally significant. Both 1.5-T and 3-T diffusion-weighted magnetic resonance imaging modalities are equally useful for assessing malignant pulmonary nodules.

Diagnosing common parotid tumours with magnetic resonance imaging including diffusion-weighted imaging vs fine-needle aspiration cytology: a comparative study

OBJECTIVES

the purpose of this study was to evaluate the accuracy of MRI combined with diffusion-weighted imaging (DWI) vs fine-needle aspiration cytology (FNAC) in diagnosing common parotid masses.

METHODS

25 consecutive patients (mean age 61 years) with parotid masses were included in this study. Informed consent and ethical approval was obtained. 22 patients underwent both MRI combined with DWI and FNAC. From DWI data, apparent diffusion coefficient maps were generated. The MRI study protocol consisted of T(1) weighted spin echo; T(2) weighted and T(2) weighted fat-suppressed turbo spin echo; DWI; and T(1) weighted fat-suppressed post-contrast images. MRI and FNAC diagnoses were compared with histopathology. Youden's index was used to compare the two methods.

RESULTS

masses comprised eight Warthin tumours, eight adenomas (six pleomorphic adenomas, two basal cell adenomas), five carcinomas, two lipomas, one haemagioma and one benign lymphadenopathy. Technically, MRI was successful in 24 of the 25 patients (96%), FNAC was successful in 20 of the 23 patients (87.0%). The accuracy, sensitivity and specificity of MRI without DWI were 96%, 80% and 100%, respectively. Diagnostic accuracy did not increase by adding DWI to conventional MRI; however, DWI was helpful for diagnosing benign tumour histology. MRI combined with DWI was successful for determining accurate tumour typing in all benign masses except one lymphadenopathy. When FNAC had adequate material the accuracy, sensitivity and specificity were 95%, 75% and 100%, respectively. Youden's index was 0.80 for MRI and 0.75 for FNAC.

CONCLUSIONS

MRI combined with DWI seems to have similar diagnostic potential as FNAC in differentiation of benign vs malignant parotid masses.