Differentiation of orbital lymphoma and idiopathic orbital inflammatory pseudotumor: combined diagnostic value of conventional MRI and histogram analysis of ADC maps

[Thrombosis of the superior ophthalmic vein-A case series and review of the literature]

BACKGROUND

Thrombosis of the superior ophthalmic vein (SOV) is rare. It can present with heterogeneous symptoms and requires a careful diagnostic work-up.

METHODS

This article reports on a case series of three female patients with thrombosis of the SOV and performed an extensive review of the existing literature in PubMed.

RESULTS

All three patients showed different leading symptoms but all had a triad of restricted eye motility, exophthalmos and a difference in intraocular pressure with the higher pressure on the side of the protruded eyeball. The pathophysiological background differed in all cases: in the two first cases a pre-existing anticoagulation treatment had been paused shortly before the event. Cofactors were an intraorbital venous outflow obstruction due to an unclear mass in the orbital apex in one case and hypercoagulability due to a malignant disease in the other case. In the third case, there was a cavernous sinus fistula.

CONCLUSION

The diagnosis should be considered not only in patients with dilated vessels of the anterior segment but also in unclear cases of exophthalmos or unilateral elevated intraocular pressure (IOP).

MR Imaging Characteristics of Solitary Fibrous Tumors of the Orbit : Case Series of 18 Patients

PURPOSE

Solitary fibrous tumor (SFT) of the orbit is a rare tumor that was first described in 1994. We aimed to investigate its imaging characteristics that may facilitate the differential diagnosis between SFT and other types of orbital tumors.

MATERIAL AND METHODS

Magnetic resonance imaging (MRI) data of patients with immunohistochemically confirmed orbital SFT from 2002 to 2022 at a tertiary care center were retrospectively analyzed. Tumor location, size, morphological characteristics, and contrast enhancement features were evaluated.

RESULTS

Of the 18 eligible patients 10 were female (56%) with a mean age of 52 years. Most of the SFTs were oval-shaped (67%) with a sharp margin (83%). The most frequent locations were the laterocranial quadrant (44%), the extraconal space (67%) and the dorsal half of the orbit (67%). A flow void phenomenon was observed in nearly all cases (94%). On the T1-weighted imaging, tumor signal intensity (SI) was significantly lower than that of the retrobulbar fat and appeared predominantly equivalent (82%) to the temporomesial brain cortex, while on T2-weighted imaging its SI remained equivalent (50%) or slightly hyperintense to that of brain cortex. More than half of the lesions showed a homogeneous contrast enhancement pattern with a median SI increase of 2.2-fold compared to baseline precontrast imaging.

CONCLUSION

The SFT represents a rare orbital tumor with several characteristic imaging features. It was mostly oval-shaped with a sharp margin and frequently localized in the extraconal space and dorsal half of the orbit. Flow voids indicating hypervascularization were the most common findings.

The volumetric ADC histogram analysis in differentiating stage IA endometrial carcinoma from endometrial polyp

OBJECTIVE

This study aimed to explore the value of apparent diffusion coefficient (ADC) histogram based on whole lesion volume in distinguishing stage IA endometrial carcinoma from the endometrial polyp.

METHODS

MRI of 108 patients with endometrial lesions confirmed by pathology were retrospectively analysed, including 65 cases of stage IA endometrial carcinoma and 43 cases of endometrial polyp. The volumetric ADC histogram metrics and general imaging features were evaluated and measured simultaneously. All the features were compared between the 2 groups. The receiver operating characteristic curve was utilized to evaluate the diagnostic performance.

RESULTS

The mean, max, min, and percentiles (10th, 25th, 50th, 75th, 95th) ADC values of endometrial carcinoma were significantly lower than that of polyp (all P < .05). The skewness and kurtosis of ADC values in the endometrial carcinoma group were significantly higher than those in the endometrial polyp group, and the variance of ADC values in the endometrial carcinoma group was lower than those in the endometrial polyp group (all P < .05). Endometrial carcinoma demonstrated more obvious myometrial invasion combined with intralesion haemorrhage than polyp (all P < .05). The 25th percentile of ADC values achieved the largest areas under the curve (0.861) among all the ADC histogram metrics and general imaging features, and the sensitivity and specificity were 83.08% and 76.74%, with the cut-off value of 1.01 × 10-3 mm2/s.

CONCLUSION

The volumetric ADC histogram analysis was an effective method in differentiating endometrial carcinoma from an endometrial polyp. The 25th percentile of ADC values has satisfactory performance for detecting malignancy in the endometrium.

ADVANCES IN KNOWLEDGE

The ADC histogram metric based on whole lesion is a promising imaging-maker in differentiating endometrial benign and malignant lesions.

Nonspecific Orbital Inflammation (NSOI): Unraveling the Molecular Pathogenesis, Diagnostic Modalities, and Therapeutic Interventions

Nonspecific orbital inflammation (NSOI), colloquially known as orbital pseudotumor, sometimes presents a diagnostic and therapeutic challenge in ophthalmology. This review aims to dissect NSOI through a molecular lens, offering a comprehensive overview of its pathogenesis, clinical presentation, diagnostic methods, and management strategies. The article delves into the underpinnings of NSOI, examining immunological and environmental factors alongside intricate molecular mechanisms involving signaling pathways, cytokines, and mediators. Special emphasis is placed on emerging molecular discoveries and approaches, highlighting the significance of understanding molecular mechanisms in NSOI for the development of novel diagnostic and therapeutic tools. Various diagnostic modalities are scrutinized for their utility and limitations. Therapeutic interventions encompass medical treatments with corticosteroids and immunomodulatory agents, all discussed in light of current molecular understanding. More importantly, this review offers a novel molecular perspective on NSOI, dissecting its pathogenesis and management with an emphasis on the latest molecular discoveries. It introduces an integrated approach combining advanced molecular diagnostics with current clinical assessments and explores emerging targeted therapies. By synthesizing these facets, the review aims to inform clinicians and researchers alike, paving the way for molecularly informed, precision-based strategies for managing NSOI.

MRI-based radiomics nomogram for distinguishing solitary fibrous tumor from schwannoma in the orbit: a two-center study

OBJECTIVES

To investigate the value of magnetic resonance imaging (MRI) radiomics for distinguishing solitary fibrous tumor (SFT) from schwannoma in the orbit.

MATERIALS AND METHODS

A total of 140 patients from two institutions were retrospectively included. All patients from institution 1 were randomized into a training cohort (n = 69) and a validation cohort (n = 35), and patients from institution 2 were used as an external testing cohort (n = 36). One hundred and six features were extracted from T2-weighted imaging (T2WI) and contrast-enhanced T1-weighted imaging (CET1WI). A radiomics model was built for each sequence using least absolute shrinkage and selection operator logistic regression, and radiomics scores were calculated. A combined model was constructed and displayed as a radiomics nomogram. Two radiologists jointly assessed tumor category based on MRI findings. The performances of the radiomics models and visual assessment were compared via area under the curve (AUC).

RESULTS

The performances of the radiomics nomogram combining T2WI and CET1WI radiomics scores were superior to those of the pooled readers in the training (AUC 0.986 vs. 0.807, p < 0.001), validation (AUC 0.989 vs. 0.788, p = 0.009), and the testing (AUC 0.903 vs. 0.792, p = 0.093), although significant difference was not found in the testing cohort. Decision curve analysis demonstrated that the radiomics nomogram had better clinical utility than visual assessment.

CONCLUSION

MRI radiomics nomogram can be used for distinguishing between orbital SFT and schwannoma, which may help tumor management by clinicians.

CLINICAL RELEVANCE STATEMENT

It is of great importance and challenging for distinguishing solitary fibrous tumor from schwannoma in the orbit. In the present study, an MRI-based radiomics nomogram were developed and independently validated, which could help the discrimination of the two entities.

KEY POINTS

• It is challenging to differentiate solitary fibrous tumor from schwannoma in the orbit due to similar clinical and image features. • A radiomics nomogram based on T2-weighted imaging and contrast-enhanced T1-weighted imaging has advantages over radiologists. • Radiomics can provide a non-invasive diagnostic tool for differentiating between the two entities.

The value of an apparent diffusion coefficient histogram model in predicting meningioma recurrence

OBJECTIVE

To investigate the predictive value of a model combining conventional MRI features and apparent diffusion coefficient (ADC) histogram parameters for meningioma recurrence.

MATERIALS AND METHODS

Seventy-two meningioma patients confirmed by surgical and pathological findings in our hospital (January 2017-June 2020) were retrospectively and divided into the recurrence and non-recurrence group. MaZda software was used to delineate the region of interest at the largest tumor level and generate histogram parameters. Univariate and multivariate logistic regression analysis were used to construct the nomogram for predicting recurrence. The predictive efficacy and diagnostic of this model were assessed by calibration and decision curve analysis, and receiver operating characteristic curve, respectively.

RESULTS

Maximum diameter, necrosis, enhancement uniformity, age, Simpson, tumor shape, and ADC first percentile (ADCp1) were significantly different between the two groups (p < 0.05), with the latter four being independent risk factors for recurrence. The model constructed combining the four factors had the best predictive efficacy, and the area under the curve, accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 0.965(0.892-0.994), 90.3%, 92.6%, 88.9%, 83.3%, and 95.2%, respectively. The calibration curve showed good agreement between the model-predicted and actual probabilities of recurrence. The decision curve analysis indicated good clinical availability of the model.

CONCLUSION

This model based on conventional MRI features and ADC histogram parameters can directly and reliably predict meningioma recurrence, providing a guiding basis for selecting treatment options and individualized treatment.

Utility of diffusion-weighted imaging to differentiate benign and malignant solid orbital tumours

OBJECTIVE

We assessed the utility of apparent diffusion coefficients (ADCs) derived from diffusion-weighted imaging to differentiate benign and malignant orbital tumours by oculoplastic surgeons in the clinical setting and sought to validate observed ADC cut-off values.

DESIGN AND PARTICIPANTS

Retrospective review of patients with benign or malignant biopsy-confirmed orbital tumours.

METHODS

Blinded graders including 2 oculoplastic surgeons, 1 neuroradiologist, and 1 medical student located and measured orbital tumour ADCs (10-6 mm2/s) using the Region of Interest tool.

OUTCOME MEASURES

Nonradiologist measurements were compared with each other to assess reliability and with an expert neuroradiologist measurement and final pathology to assess accuracy.

RESULTS

Twenty-nine orbital tumours met inclusion criteria, consisting of 6 benign tumours and 23 malignant tumours. Mean ADC values for benign orbital tumours were 1430.59 ± 254.81 and 798.68 ± 309.12 mm2/s for malignant tumours. Our calculated optimized ADC cut-off to differentiate benign from malignant orbital tumours was 1120.84 × 10-6 mm2/s (sensitivity 1, specificity 0.9). Inter-rater reliability was excellent (intraclass correlation coefficient = 0.92; 95% CI, 0.86-0.96). Our 3 graders had a combined accuracy of 84.5% (92.3%, 92.3%, and 65.4%).

CONCLUSIONS

Our ADC cut-off of 1120.84 × 10-6 mm2/s for benign and malignant orbital tumours agrees with previously established values in literature. Without priming with instructions, training, or access to patient characteristics, most tumours were correctly classified using rapid ADC measurements. Surgeons without radiologic expertise can use the ADC tool to quickly risk stratify orbital tumours during clinic visits to guide patient expectations and further work-up.

Development and validation of apparent diffusion coefficient histogram-based nomogram for predicting malignant transformation of sinonasal inverted papilloma

OBJECTIVES

To develop and validate a nomogram based on whole-tumour histograms of apparent diffusion coefficient (ADC) maps for predicting malignant transformation (MT) in sinonasal inverted papilloma (IP).

METHODS

This retrospective study included 209 sinonasal IPs with and without MT, which were assigned into a primary cohort (n = 140) and a validation cohort (n = 69). Eight ADC histogram features were extracted from the whole-tumour region of interest. Morphological MRI features and ADC histogram parameters were compared between the two groups (with and without MT). Stepwise logistic regression was used to identify independent predictors and to construct models. The predictive performances of variables and models were assessed using the area under the curve (AUC). The optimal model was presented as a nomogram, and its calibration was assessed.

RESULTS

Four morphological features and seven ADC histogram parameters showed significant differences between the two groups in both cohorts (all p < 0.05). Maximum diameter, loss of convoluted cerebriform pattern, ADC10th and ADCSkewness were identified as independent predictors to construct the nomogram. The nomogram showed significantly better performance than the morphological model in both the primary (AUC, 0.96 vs 0.88; p = 0.006) and validation (AUC, 0.96 vs 0.88; p = 0.015) cohorts. The nomogram showed good calibration in both cohorts. Decision curve analysis demonstrated that the nomogram is clinically useful.

CONCLUSIONS

The developed nomogram, which incorporates morphological MRI features and ADC histogram parameters, can be conveniently used to facilitate the pre-operative prediction of MT in IPs.

Diffusion-Weighted Imaging of the Orbit: A Case Series and Systematic Review

PURPOSE

To describe the findings of diffusion-weighted imaging (DWI) for a series of orbital lesions and provide a systematic review of relevant literature.

METHODS

A retrospective review of 20 patients with orbital lesions who underwent MRI with DWI at two academic institutions between 2015 and 2020 was performed. Lesion diagnosis was histopathologically confirmed except a presumed cavernous hemangioma. Echoplanar diffusion-weighted images had been acquired using 2 or 3 b values (b=0 and 1000 or b=0, 500, and 1000) at 1.5T or 3T. Lesions with significant artifacts were excluded. DWI sequences were analyzed by neuro-radiologists blinded to the diagnosis. Mean ADC values of lesions were calculated from a single region of interest. An independent two-tailed t test was used to compare categories of lesions with p < 0.05 considered significant. A systematic review of the literature was performed.

RESULTS

Our study included 21 lesions. ADC values were significantly lower for malignant lesions (0.628 ± 0.125 × 10 -3 mm 2 /s) than inflammatory lesions (1.167 ± 0.381 × 10 -3 mm 2 /s) ( p < 0.001). ADC values were significantly lower for orbital lymphoma (mean 0.621 ± 0.147 × 10 -3 mm 2 /s) than idiopathic orbital inflammation (mean 1.188 ± 0.269 × 10 -3 mm 2 /s) with no overlap ( p < 0.001).

CONCLUSIONS

Orbital malignancies demonstrated lower ADC values, while inflammatory processes demonstrated higher ADC values, except IgG4-related disease. DWI and ADC values differentiated idiopathic orbital inflammation from orbital lymphoma. This study highlights the role of DWI in evaluating orbital pathology.

Radiomics analysis of T1WI and T2WI magnetic resonance images to differentiate between IgG4-related ophthalmic disease and orbital MALT lymphoma

BACKGROUND

Preoperative differentiation between IgG4-related orbital disease (IgG4-ROD) and orbital mucosa-associated lymphoid tissue (MALT) lymphoma has a significant impact on clinical decision-making. Our research aims to construct and evaluate a magnetic resonance imaging (MRI)-based radiomics model to assist clinicians to better identify IgG4-ROD and orbital MALT lymphoma and make better preoperative medical decisions.

METHODS

MR images and clinical data from 20 IgG4-ROD patients and 30 orbital MALT lymphoma patients were classified into a training (21 MALT; 14 IgG4-ROD) or validation set (nine MALT; six IgG4-ROD). Radiomics features were collected from T1-weighted (T1WI) and T2-weighted images (T2WI). Student's t-test, the least absolute shrinkage and selection operator (LASSO) and principal component analysis (PCA) were conducted to screen and select the radiomics features. Support vector machine (SVM) classifiers developed from the selected radiomic features for T1WI, T2WI and combined T1WI and T2WI were trained and tested on the training and validation set via five-fold cross-validation, respectively. Diagnostic performance of the classifiers were evaluated with area under the curve (AUC) readings of the receiver operating characteristic (ROC) curve, and readouts for precision, accuracy, recall and F1 score.

RESULTS

Among 12 statistically significant features from T1WI, four were selected for SVM modelling after LASSO analysis. For T2WI, eight of 51 statistically significant features were analyzed by LASSO followed by PCA, with five features finally used for SVM. Combined analysis of T1WI and T2WI features selected two and four, respectively, for SVM. The AUC values for T1WI and T2WI classifiers separately were 0.722 ± 0.037 and 0.744 ± 0.027, respectively, while combined analysis of T1WI and T2WI classifiers further enhanced the classification performances with AUC values ranging from 0.727 to 0.821.

CONCLUSION

The radiomics model based on features from both T1WI and T2WI images is effective and promising for the differential diagnosis of IgG4-ROD and MALT lymphoma. More detailed radiomics features and advanced techniques should be considered to further explore the differences between these diseases.

A signature of structural MRI features at 3 Tesla allows an accurate characterization of orbital cavernous venous malformation

OBJECTIVES

To differentiate OCVM from other orbital lesions using structural MRI.

METHODS

This IRB-approved a historical-prospective cohort single-center analysis of a prospective cohort that included consecutive adult patients presenting with an orbital lesion undergoing a 3T MRI before surgery from December 2015 to May 2021. Two readers blinded to all data read all MRIs assessing structural MRI characteristics. A univariate analysis followed by a stepwise multivariate analysis identified structural MRI features showing the highest sensitivity and specificity when diagnosing OCVM.

RESULTS

One hundred ninety-one patients with 30/191 (16%) OCVM and 161/191 (84%) other orbital lesions were included. OCVM were significantly more likely to present with a higher signal intensity than that of the cortex on T2WI: 26/29 (89.7%) versus 28/160 (17.5%), p < 0.001, or with a chemical shift artifact (CSA): 26/29 (89.7%) versus 16/155 (10.3%), p < 0.001, or to present with a single starting point of enhancement, as compared to other orbital lesions: 18/29 (62.1%) versus 4/159 (2.5%), p = 0.001. The step-wise analysis identified 2 signatures increasing performances. Signature 1 combined a higher signal intensity than that of the cortex on T2WI and a CSA. Signature 2 included these two features and the presence of a single starting point of enhancement. Sensitivity, specificity, and accuracy were 0.83, 0.94, and 0.92 for signature 1 and 0.97, 0.93, and 0.93 for signature 2, respectively.

CONCLUSION

Structural MRI yields high sensitivity and specificity when diagnosing OCVM.

KEY POINTS

• Structural MRI shows high sensitivity and specificity when diagnosing orbital cavernous venous malformation. • We identified two signatures combining structural MRI features which might be used easily in routine clinical practice. • The combination of higher signal intensity of the lesion as compared to the cortex on T2WI and of a chemical shift artifact yields a sensitivity and specificity of 0.83 and 0.94 for the diagnosis of orbital cavernous venous malformation, respectively.

Cross-sectional imaging evaluation of atypical and uncommon extra-nodal head and neck Non-Hodgkin lymphoma: Case series

Extra-nodal Non-Hodgkin lymphoma (ENHL) of the head and neck is not uncommon and has variable clinical and imaging presentations. It represents about 25% of extra-nodal lymphomas. In addition, lymphoma is the third most common malignancy of the head and neck just after squamous cell carcinoma (SCC) and salivary gland neoplasms. Unlike SCC, ENHL usually presents as a well-defined mass in the oral cavity, along the pharyngeal mucosa, sinonasal cavity, orbit, and other different neck spaces. One of the common presentations of ENHL is the glandular type which can arise within the salivary or thyroid glands as marginal zone non-Hodgkin lymphoma. ENHL can infiltrate the bone resembling high grade osseous malignancies. Rarely, ENHL can present as perineural spread without definitive mass and manifest clinically with several neuropathies. In this case series, we presented different imaging features and presentation of ENHL of the head and neck. The knowledge of various presentations of ENHL of the head and neck can help early diagnosis and prompt management of these patients' population.

Clinical Evaluation of High-Resolution MRI Combined With DWI in Identifying Vulnerable Carotid Plaque

BACKGROUND

High-resolution magnetic resonance imaging combined with diffusion weighted imaging is used to identify vulnerable plaques (VP) and their characteristic components, and apparent diffusion coefficient (ADC) correlation analysis with serum inflammatory markers to assess plaque vulnerability.

METHODS

In this study, 60 eligible patients were included, including 29 patients in VP group and 31 patients in non-VP group (N group). The average ADC value, serum inflammatory marker levels (high-sensitivity C-reactive protein, myeloperoxidase, and erythrocyte sedimentation rate) of the 2 groups were measured, and the characteristics of different plaque components and ADC levels of vascular wall in VP group were compared, to evaluate the correlation between serum inflammatory markers and the mean value of plaque ADC.

RESULTS

The results showed that the ADC mean value of the plaques in the VP group was significantly lower than that in the N group, and the levels of hypersensitive C-reactive protein and myeloperoxidase were correlated with the ADC mean value of the plaques.

CONCLUSION

The ADC value of plaque measured by high-resolution magnetic resonance imaging combined with diffusion weighted imaging sequence can quantify the identification of VP and its characteristic components, reflect the inflammation of plaque to a certain extent, and thus prevent and treat stroke and other adverse outcomes more effectively.

Diagnostic Utility of Diffusion-Weighted Imaging and Apparent Diffusion Coefficient for Common Orbital Lesions: A Review

PURPOSE

To review and summarize the existing literature surrounding the clinical use of diffusion-weighted imaging and apparent diffusion coefficient (ADC) as diagnostic tools in differentiating common orbital lesions.

METHODS

A systematic literature review on the use of ADC and diffusion-weighted imaging sequences for orbital imaging was performed. Only original research articles that reported ADC values for benign or malignant lesions were included.

RESULTS

Malignant orbital tumors have an overall lower mean ADC value than benign masses. Orbital lymphoma is characterized by consistently lower ADC values compared with other malignant orbital masses; a threshold value less than 0.775 × 10 -3 mm 2 /s has been proposed to distinguish orbital lymphoma from other neoplastic and non-neoplastic orbital masses. To differentiate orbital inflammatory disease from lymphoma, an ADC threshold greater than 0.92 × 10 -3 mm 2 /s has been proposed.

CONCLUSIONS

Orbital masses encompass a host of benign and malignant etiologies and can present a diagnostic challenge on both clinical and radiological assessment. Recent advanced MRI techniques such as diffusion-weighted imaging and ADC can improve the diagnostic specificity for orbital disease, particularly in differentiating benign from malignant lesions and lymphoma from orbital inflammatory disease.

Whole-lesion apparent diffusion coefficient (ADC) histogram as a quantitative biomarker to preoperatively differentiate stage IA endometrial carcinoma from benign endometrial lesions

BACKGROUND

To assess the value of whole-lesion apparent diffusion coefficient (ADC) histogram analysis in differentiating stage IA endometrial carcinoma (EC) from benign endometrial lesions (BELs) and characterizing histopathologic features of stage IA EC preoperatively.

METHODS

One hundred and six BEL and 126 stage IA EC patients were retrospectively enrolled. Eighteen volumetric histogram parameters were extracted from the ADC map of each lesion. The Mann-Whitney U or Student's t-test was used to compare the differences between the two groups. Models based on clinical parameters and histogram features were established using multivariate logistic regression. Receiver operating characteristic (ROC) analysis and calibration curves were used to assess the models.

RESULTS

Stage IA EC showed lower ADC_10th, ADC_90th, ADC_min, ADC_max, ADC_mean, ADC_median, interquartile range, mean absolute deviation, robust mean absolute deviation (rMAD), root mean squared, energy, total energy, entropy, variance, and higher skewness, kurtosis and uniformity than BELs (all p < 0.05). ADC_median yielded the highest area under the ROC curve (AUC) of 0.928 (95% confidence interval [CI] 0.895-0.960; cut-off value = 1.161 × 10^-3 mm²/s) for differentiating stage IA EC from BELs. Moreover, multivariate analysis demonstrated that ADC-score (ADC_10th + skewness + rMAD + total energy) was the only significant independent predictor (OR = 2.641, 95% CI 2.045-3.411; p < 0.001) for stage IA EC when considering clinical parameters. This ADC histogram model (ADC-score) achieved an AUC of 0.941 and a bias-corrected AUC of 0.937 after bootstrap resampling. The model performed well for both premenopausal (accuracy = 0.871) and postmenopausal (accuracy = 0.905) patients. Besides, ADC_min and ADC_10th were significantly lower in Grade 3 than in Grade 1/2 stage IA EC (p = 0.022 and 0.047). At the same time, no correlation was found between ADC histogram parameters and the expression of Ki-67 in stage IA EC (all p > 0.05).

CONCLUSIONS

Whole-lesion ADC histogram analysis could serve as an imaging biomarker for differentiating stage IA EC from BELs and assisting in tumor grading of stage IA EC, thus facilitating personalized clinical management for premenopausal and postmenopausal patients.

Imaging Findings of Pediatric Orbital Masses and Tumor Mimics

Pediatric orbital masses are not common but encompass a wide spectrum of benign and malignant entities that range from developmental anomalies to primary and secondary orbital malignancies and metastatic disease. Certain orbital tumors are unique to pediatric patients, such as retinoblastoma and neuroblastoma. Clinical symptoms and signs are often insufficient to differentiate between orbital lesions, and imaging is essential for narrowing the diagnostic considerations and determining the most appropriate management strategy. MRI is the primary imaging modality for evaluating orbital masses in children, with US and CT playing complementary roles. The authors review a spectrum of masses and tumor mimics that affect the pediatric globe and orbit. The shared and differentiating characteristics of pediatric orbital lesions are reviewed. Emphasis is placed on utilizing an orbital compartment-based approach to narrow the differential diagnosis. By using this organizational scheme, the authors describe intraocular processes (retinoblastoma, persistent fetal vasculature, and Coats disease), intraconal lesions (lymphatic malformation, schwannoma, optic nerve sheath meningioma, and optic pathway glioma), extraconal lesions (infantile hemangioma, rhabdomyosarcoma, idiopathic orbital inflammation, lymphoma, venous varix, plexiform neurofibroma, and pleomorphic adenoma of the lacrimal gland), and lesions involving the bony orbit (dermoid cyst, metastatic neuroblastoma, and Langerhans cell histiocytosis). The authors describe the basic management of each entity. Orbital infections and traumatic lesions are beyond the scope of this article. ^©RSNA, 2022.

Joint Deformable Image Registration and ADC Map Regularization: Application to DWI-based Lymphoma Classification

The Apparent Diffusion Coefficient (ADC) is considered an important imaging biomarker contributing to the assessment of tissue microstructure and pathophysiology. It is calculated from Diffusion-Weighted Magnetic Resonance Imaging (DWI) by means of a diffusion model, usually without considering any motion during image acquisition. We propose a method to improve the computation of the ADC by coping jointly with both motion artifacts in whole-body DWI (through group-wise registration) and possible instrumental noise in the diffusion model. The proposed deformable registration method yielded on average the lowest ADC reconstruction error on data with simulated motion and diffusion. Moreover, our approach was applied on whole-body diffusion weighted images obtained with five different b-values from a cohort of 38 patients with histologically confirmed lymphomas of three different types (Hodgkin, diffuse large B-cell lymphoma and follicular lymphoma). Evaluation on the real data showed that ADC-based features, extracted using our joint optimization approach classified lymphomas with an accuracy of approximately 78.6\% (yielding a 11\% increase in respect to the standard features extracted from unregistered diffusion-weighted images). Furthermore, the correlation between diffusion characteristics and histopathological findings was higher than any other previous approach of ADC computation.

Orbital Muscle Enlargement: What if It’s Not Graves’ Disease?

Purpose of Review

To provide the radiologist with tools to recognize findings atypical for Graves’ ophthalmopathy and differentiate between the most important and common alternative causes of extraocular muscle enlargement on CT and MR imaging.

Recent findings

We introduce five ‘red flags’ representing features that are atypical for Graves’ ophthalmopathy: unilateral disease, atypical pattern of muscle involvement, adjacent structure involvement, restricted diffusion, and absence of pain.

Summary

About 95% of the cases with extraocular enlargement are due to Graves’ ophthalmopathy, other causes are less well known and recognized. The ‘red flags’ may aid in recognizing and suggesting alternative diagnoses.

CT and MRI features of extraocular muscle granular cell tumour: preliminary experience in eight cases

AIM

To characterise the computed tomography (CT) and magnetic resonance imaging (MRI) features, in particular the functional MRI characteristics, of extraocular muscle granular cell tumours (GCTs).

MATERIALS AND METHODS

The CT (n=6) and MRI (n=8) features of eight extraocular muscle GCTs cofirmed at histopathology were analysed retrospectively. The imaging findings were evaluated with emphasis on the location, size, margin, shape, extent, bony change, internal architecture, enhancement pattern, and extent of lesions. Based on diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) MRI, the apparent diffusion coefficient (ADC) value of six lesions and time-intensity curve (TIC) of one lesion were reviewed.

RESULTS

Immunohistochemistry revealed strong positivity for S-100 protein and a low Ki-67 index (2-5%) in all cases. Most of the lesions (7/8) were confined to the muscle belly with an ovoid shape. All of the tumours were isodense to cerebral grey matter and showed homogeneously mild enhancement on CT images. All lesions were hypointense to cerebral grey matter on T2-weighted imaging (T2WI) and showed homogeneously marked enhancement on contrast-enhanced T1-weighted imaging (T1WI). All lesions showed a hypo- or isointense signal on DWI images with a high b-value. The mean ADC of six lesions was (0.72 ± 0.14) × 10^-3 mm²/s. The TIC of the case examined using DCE-MRI showed a plateau pattern (type II).

CONCLUSION

A well-defined oval mass confined to the muscle belly with a hypointense signal on T2WI, homogeneously marked enhancement on contrast-enhanced T1WI, hypo- or isointense signal on DWI, and low ADC value is highly suggestive of a GCT.

Artificial Intelligence and Deep Learning of Head and Neck Cancer

Artificial intelligence (AI) algorithms, particularly deep learning, have developed to the point that they can be applied in image recognition tasks. The use of AI in medical imaging can guide radiologists to more accurate image interpretation and diagnosis in radiology. The software will provide data that we cannot extract from the images. The rapid development in computational capabilities supports the wide applications of AI in a range of cancers. Among those are its widespread applications in head and neck cancer.

Histogram analysis of diffusion-weighted imaging and dynamic contrast-enhanced MRI for predicting occult lymph node metastasis in early-stage oral tongue squamous cell carcinoma

OBJECTIVES

To investigate the feasibility of whole-tumor histogram analysis of diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) MRI for predicting occult lymph node metastasis (LNM) in early-stage oral tongue squamous cell cancer (OTSCC).

MATERIALS AND METHODS

This retrospective study included 55 early-stage OTSCC (cT1-2N0M0) patients; 34 with pathological LNM and 21 without. Eight whole-tumor histogram features were extracted from quantitative apparent diffusion coefficient (ADC) maps and two semi-quantitative DCE parametric maps (wash-in and wash-out). The clinicopathological factors and histogram features were compared between the two groups. Stepwise logistic regression was used to identify independent predictors. Receiver operating characteristic curves were generated to assess the performances of significant variables and a combined model for predicting occult LNM.

RESULTS

MRI-determined depth of invasion and ADC_entropy was significantly higher in the LNM group, with respective areas under the curve (AUCs) of 0.67 and 0.69, and accuracies of 0.73 and 0.73. ADC_10th. ADC_uniformity and wash-in_skewness were significantly lower in the LNM group, with respective AUCs of 0.68, 0.71, and 0.69, and accuracies of 0.65, 0.71, and 0.64. Histogram features from wash-out maps were not significantly associated with cervical node status. In the logistic regression analysis, ADC_10th, ADC_uniformity, and wash-in_skewness were independent predictors. The combined model yielded the best predictive performance, with an AUC of 0.87 and an accuracy of 0.82.

CONCLUSIONS

Whole-tumor histogram analysis of ADC and wash-in maps is a feasible tool for preoperative evaluation of cervical node status in early-stage OTSCC.

KEY POINTS

• Histogram analysis of parametric maps from DWI and DCE-MRI may assist the prediction of occult LNM in early-stage OTSCC. • ADC_10th, ADC_uniformity, and wash-in_skewness were independent predictors. • The combined model exhibited good predictive performance, with an accuracy of 0.82.

Discriminating between IgG4-related orbital disease and other causes of orbital inflammation with intra voxel incoherent motion (IVIM) MR imaging at 3T

PURPOSE

The purpose of this prospective study was to determine the capabilities of intravoxel incoherent motion (IVIM) MRI at 3 Tesla in discriminating between IgG4-related orbital disease (IgG4-ROD) and other causes of orbital inflammation.

MATERIALS AND METHODS

Main selection criteria for the patients enrolled in this prospective study were age over 18 years and histopathologicaly proven orbital inflammatory lesion. MRI examinations were performed prior to surgery and treatment in all patients with suspected orbital inflammation. Two neuroradiologists, blinded to clinical data, independently analyzed structural MRI examinations and IVIM sequences obtained with 15 b values ranging from 0 to 2000 s/mm². Apparent diffusion coefficient (ADC), "true" diffusion coefficient (D), perfusion fraction (f) and pseudodiffusion coefficient (D*) values were calculated from all orbital lesions. Diagnostic capabilities of IVIM parameters were assessed using receiver operating-characteristic (ROC) curves and area under the curve (AUC). Sensitivity, specificity, and accuracy of IVIM parameters were calculated for the best threshold values and reported with their corresponding 95% confidence intervals (CI).

RESULTS

Thirty-five patients (21 women and 14 men; mean age, 49.2 ± 13.75 [SD] years; age range: 23-77 years) with 48 orbital lesions were enrolled in the study. Fifteen patients (15/35; 43%) had IgG4-ROD and 20 (20/35; 57%) had other causes of orbital inflammation. Median D value was significantly greater in patients with IgG4-ROD (1 × 10^-3 mm²/s; interquartile range [IQR]: 0.9 × 10^-3; 1.2 × 10^-3) as compared to patients with non IgG4-ROD (0.80 × 10^-3 mm²/s; IQR: 0.7 × 10^-3; 1 × 10^-3) (P = 0.04). There was no significant difference for ADC, f or D*. Area under the curve were of 0.54, 0.73, 0.63 and 0.56 for ADC, D, f and D*, respectively. Optimal threshold derived from ROC curves for D was 0.87 × 10^-3 mm²/s, yielding 92% sensitivity (95% CI: 62-100%) and 71% specificity (95% CI: 44-90%) for the diagnosis of IgG4-ROD. No differences in standard morphological MRI criteria were found between IgG4-ROD and non IgG4-ROD.

CONCLUSION

Our study shows that IVIM MRI is a useful imaging technique to distinguish IgG4-ROD from other causes of orbital inflammation.

Advances in magnetic resonance imaging of orbital disease

Magnetic resonance imaging (MRI) is increasingly used by the orbital surgeon to aid in the diagnosis, surgical planning, and monitoring of orbital disease. MRI provides superior soft tissue detail compared with computed tomography or ultrasound, and advancing techniques enhance its ability to highlight abnormal orbital pathology. Diffusion-weighted imaging is a specialized technique that uses water molecule diffusion patterns in tissue to generate contrast signals and can help distinguish malignant from benign lesions. Steady-state free precession sequences such as Constructive Interference in Steady-State (CISS) and Fast Imaging Employing Steady-state Acquisition (FIESTA) generate highly detailed, 3-dimensional reconstructed images and are particularly useful in distinguishing structures adjacent to cerebral spinal fluid. Magnetic resonance angiography can be used to characterize vascular lesions within the orbit. New developments in magnetic field strength as well as the use of orbital surface coils achieve increasingly improved imaging resolution.

Diffusion-Weighted Imaging of the Head and Neck (Including Temporal Bone)

Diffusion techniques provide valuable information when performing head and neck imaging. This information can be used to detect the presence or absence of pathology, refine differential diagnosis, determine the location for biopsy, assess response to treatment, and prognosticate outcomes. For example, when certain technical factors are taken into consideration, diffusion techniques prove indispensable in assessing for residual cholesteatoma following middle ear surgery. In other scenarios, pretreatment apparent diffusion coefficient values may assist in prognosticating outcomes in laryngeal cancer and likelihood of response to radiation therapy. As diffusion techniques continue to advance, so too will its clinical utility.

To Explore MR Imaging Radiomics for the Differentiation of Orbital Lymphoma and IgG4-Related Ophthalmic Disease

Among orbital lymphoproliferative disorders, about 55% of diagnosed cancerous tumors are orbital lymphomas, and nearly 50% of benign cases are immunoglobulin G4-related ophthalmic disease (IgG4-ROD). However, due to nonspecific characteristics, the differentiation of the two diseases is challenging. In this study, conventional magnetic resonance imaging-based radiomics approaches were explored for clinical recognition of orbital lymphomas and IgG4-ROD. We investigated the value of radiomics features of axial T1- (T1WI-) and T2-weighted (T2WI), contrast-enhanced T1WI in axial (CE-T1WI) and coronal (CE-T1WI-cor) planes, and 78 patients (orbital lymphoma, 36; IgG4-ROD, 42) were retrospectively reviewed. The mass lesions were manually annotated and represented with 99 features. The performance of elastic net-based radiomics models using single or multiple modalities with or without feature selection was compared. The demographic features showed orbital lymphoma patients were significantly older than IgG4-ROD patients (p < 0.01), and most of the patients were male (72% in the orbital lymphoma group vs. 23% in the IgG4-ROD group; p = 0.03). The MR imaging findings revealed orbital lymphomas were mostly unilateral (81%, p = 0.02) and wrapped eyeballs or optic nerves frequently (78%, p = 0.02). In addition, orbital lymphomas showed isointense in T1WI (100%, p < 0.01), and IgG4-ROD was isointense (60%, p < 0.01) or hyperintense (40%, p < 0.01) in T1WI with well-defined shape (64%, p < 0.01). The experimental comparison indicated that using CE-T1WI radiomics features achieved superior results, and the features in combination with CE-T1WI-cor features and the feature preselection method could further improve the classification performance. In conclusion, this study comparatively analyzed orbital lymphoma and IgG4-ROD from demographic features, MR imaging findings, and radiomics features. It might deepen our understanding and benefit disease management.

Ophthalmic Magnetic Resonance Imaging: Where Are We (Heading To)?

Magnetic resonance imaging of the eye and orbit (MReye) is a cross-domain research field, combining (bio)physics, (bio)engineering, physiology, data sciences and ophthalmology. A growing number of reports document technical innovations of MReye and promote their application in preclinical research and clinical science. Realizing the progress and promises, this review outlines current trends in MReye. Examples of MReye strategies and their clinical relevance are demonstrated. Frontier applications in ocular oncology, refractive surgery, ocular muscle disorders and orbital inflammation are presented and their implications for explorations into ophthalmic diseases are provided. Substantial progress in anatomically detailed, high-spatial resolution MReye of the eye, orbit and optic nerve is demonstrated. Recent developments in MReye of ocular tumors are explored, and its value for personalized eye models derived from machine learning in the treatment planning of uveal melanoma and evaluation of retinoblastoma is highlighted. The potential of MReye for monitoring drug distribution and for improving treatment management and the assessment of individual responses is discussed. To open a window into the eye and into (patho)physiological processes that in the past have been largely inaccessible, advances in MReye at ultrahigh magnetic field strengths are discussed. A concluding section ventures a glance beyond the horizon and explores future directions of MReye across multiple scales, including in vivo electrolyte mapping of sodium and other nuclei. This review underscores the need for the (bio)medical imaging and ophthalmic communities to expand efforts to find solutions to the remaining unsolved problems and technical obstacles of MReye, with the objective to transfer methodological advancements driven by MR physics into genuine clinical value.

Arterial spin labeling and diffusion-weighted MR imaging: Utility in differentiating idiopathic orbital inflammatory pseudotumor from orbital lymphoma

PURPOSE

To assess arterial spin-labeling (ASL) and diffusion-weighted imaging (DWI) and in combination for differentiating between idiopathic orbital inflammatory pseudotumor (IOIP) and orbital lymphoma.

MATERIAL AND METHODS

A retrospective study was done on 37 untreated patients with orbital masses, suspected to be IOIP or orbital lymphoma that underwent ASL and DWI of the orbit. Quantitative measurement of tumor blood flow (TBF) and apparent diffusion coefficient (ADC) of the orbital lesion was done.

RESULTS

There was a significant difference (P = 0.001) in TBF between patients with IOIP (n = 21) (38.1 ± 6.2, 40.3 ± 7.1 ml/100 g/min) and orbital lymphoma (n = 16) (55.5 ± 7.1, 56.8 ± 7.9 ml/100 g/min) for both observers respectively. Thresholds of TBF used for differentiating IOIP from orbital lymphoma were 48, 46 ml/100 g/min revealed area under the curve (AUC) of (0.958 and 0.921), and accuracy of (86% and 83%) for both observers respectively. There was a significant difference (P = 0.001) in ADC between patients with IOIP (1.04 ± 0.19, 1.12 ± 0.23 × 10^-3 mm²/s) and orbital lymphoma (0.69 ± 0.10, 0.72 ± 0.11 × 10^-3 mm²/s) for both observers respectively. Thresholds of ADC used for differentiating IOIP from orbital lymphoma were 0.84 and 0.86 × 10^-3 mm²/s with AUC of (0.933 and 0.920), and accuracy of 89% and 90% for both observers respectively. The combined TBF and ADC used for differentiating IOIP from orbital lymphoma had AUC of (0.973 and 0.970) and accuracy of (91% and 89%) for both observers respectively.

CONCLUSION

TBF and ADC alone and in combination are useful for differentiating IOIP from orbital lymphoma.

Role of Quantitative Spectral CT Analysis for Differentiation of Orbital Lymphoma and Other Orbital Lymphoproliferative Disease

PURPOSE

To investigate the value of quantitative parameters from spectral computed tomography for the differentiation of orbital lymphoma from other lymphoproliferative disease, including idiopathic orbital inflammatory disease (IOID) and IgG4-related disease (IgG4-RD).

METHODS

Patients with orbital masses who underwent pre-treatment contrast-enhanced spectral CT were enrolled in this retrospective study. The subjects were divided into lymphoma and other orbital lymphoproliferative disease groups. Qualitative imaging features (margin, location, enhancement pattern, cranial nerves, soft tissue, and bone involvement) were reviewed. Quantitative parameters (iodine density and spectral attenuation curve slope) derived from spectral CT were measured.

RESULTS

Eleven patients had orbital lymphoma and 11 had other orbital lymphoproliferative diseases (idiopathic orbital inflammatory disease (IOID), n = 5; IgG4-related disease (IgG4-RD), n = 6). Qualitative analysis showed no significant difference between the two groups. There was significantly higher iodine density in orbital lymphoma (1.24 ± 0.24 mg/ml) than in IOID/IgG4-RD (0.83 ± 0.23 mg/ml; P = 0.001). An iodine density threshold of 1.0 mg/ml gave sensitivity, specificity, and accuracy of 81.8%, with an area under the curve of 0.876 (P = 0.0003). Orbital lymphoma had a significantly higher iodine spectral attenuation curve slope (2.44 ± 0.51 HU/keV) than IOID/IgG4-RD (1.66 ± 0.47 HU/keV; P = 0.001). A threshold of 1.99 HU/keV for the spectral attenuation curve slope of 40-70 keV gave sensitivity, specificity, and accuracy of 81.8%, with an area under the curve of 0.884 (P = 0.0002).

CONCLUSIONS

Quantitative spectral CT parameters can help differentiate orbital lymphoma from other orbital lymphoproliferative disease, with lymphoma having a significantly higher iodine density value and spectral attenuation curve slope than IOID/IgG4-RD.

Improving diagnostic performance of differentiating ocular adnexal lymphoma and idiopathic orbital inflammation using intravoxel incoherent motion diffusion-weighted MRI

PURPOSE

To investigate the utility of intravoxel incoherent motion diffusion-weighted MRI (IVIM-DWI) derived diffusion and perfusion parameters in differentiating ocular adnexal lymphoma (OAL) from idiopathic orbital inflammation (IOI), and to assess whether IVIM-DWI provides improved diagnostic performance for the distinction.

METHOD

Twenty-one patients with OAL and 24 patients with IOI underwent IVIM-DWI. Apparent diffusion coefficient (ADC) and IVIM-DWI parameters including true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f) were measured in lesions by two independent radiologists. The MRI parameter differences between OAL and IOI were tested using two-sample t-test. The receiver operating characteristic (ROC) analysis curves were used to determine the diagnostic performance of significant parameters for differentiation between OAL and IOI.

RESULTS

The ADC, D, and f were lower in OAL than those in IOI (ADC = 0.78 ± 0.12 vs. 0.99 ± 0.16 × 10^-3 mm²/s, P < 0.001; D = 0.34 ± 0.15 vs. 0.76 ± 0.25 × 10^-3 mm²/s, P < 0.001; f = 0.31 ± 0.06 vs. 0.41 ± 0.08 × 100 %, P < 0.001). There was no significant difference in D* between OAL and IOI (P = 0.235). The optimal cut-off values of ADC, D, and f in differentiating OAL from IOI were 0.83 × 10^-3 mm²/s, 0.56 × 10^-3 mm²/s, and 0.36 × 100 %, respectively. No significant differences were found in areas under the curve (AUCs) among ADC, D and f (all P > 0.05). The combination of D and f provided significantly higher AUC than ADC (AUC = 0.984 vs. 0.838, Z = 2.128, P = 0.033), and had higher sensitivity of 95.24 %, specificity of 95.83 %, and accuracy of 95.56 %.

CONCLUSIONS

IVIM-DWI is valuable in differentiating OAL from IOI, and D combined f can improve the performance of differential diagnosis.

Bag-of-features-based radiomics for differentiation of ocular adnexal lymphoma and idiopathic orbital inflammation from contrast-enhanced MRI

OBJECTIVES

To evaluate the effectiveness of bag-of-features (BOF)-based radiomics for differentiating ocular adnexal lymphoma (OAL) and idiopathic orbital inflammation (IOI) from contrast-enhanced MRI (CE-MRI).

METHODS

Fifty-six patients with pathologically confirmed IOI (28 patients) and OAL (28 patients) were randomly divided into training (n = 42) and testing (n = 14) groups. One hundred sixty texture features extracted from the CE-MR image were encoded into the BOF representation with fewer features. The support vector machine (SVM) with a linear kernel was used as the classifier. Data augmented was performed by cropping orbital lesions in different directions to alleviate the over-fitting problem. Student's t test and the Holm-Bonferroni method were employed to compare the performance of different analysis methods. The chi-square test was used to compare the analysis with MRI and human radiological diagnosis.

RESULTS

In the independent testing group, the differentiation by the BOF features with augmentation achieved an area under the curve (AUC) of 0.803 (95% CI: 0.725-0.880), which was significantly higher than that of the BOF features without augmentation and that of the texture features (p < 0.05). In addition, the same radiomic analysis with pre-contrast MRI obtained an AUC of 0.618 (95% CI: 0.560-0.677), which was significantly lower than that with CE-MRI. The diagnostic performance of the analysis with CE-MRI was significantly better than the radiology resident (p < 0.05) but had no significant difference with the experienced radiologist, even though there was less consistency between the radiomic analysis and the human visual diagnosis.

CONCLUSIONS

The BOF-based radiomics may be helpful for the differentiation between OAL and IOI.

KEY POINTS

• It is challenging to differentiate OAL from IOI due to the similar clinical and image features. • Radiomics has great potential for the noninvasive diagnosis of orbital diseases. • The BOF representation from patch to image may help the differentiation of OAL and IOI.

Intravoxel incoherent motion (IVIM) 3 T MRI for orbital lesion characterization

OBJECTIVES

To determine the diagnostic accuracy of MRI intravoxel incoherent motion (IVIM) when characterizing orbital lesions, which is challenging due to a wide range of locations and histologic types.

METHODS

This IRB-approved prospective single-center study enrolled participants presenting with an orbital lesion undergoing a 3-T MRI prior to surgery from December 2015 to July 2019. An IVIM sequence with 15 b values ranging from 0 to 2000 s/mm² was performed. Two neuroradiologists, blinded to clinical data, individually analyzed morphological MRIs. They drew one region of interest inside each orbital lesion, providing apparent diffusion coefficient (ADC), true diffusion coefficient (D), perfusion fraction (f), and pseudodiffusion coefficient (D*) values. T test, Mann-Whitney U test, and receiver operating characteristic curve analyses were performed to discriminate between orbital lesions and to determine the diagnostic accuracy of the IVIM parameters.

RESULTS

One hundred fifty-six participants (84 women and 72 men, mean age 54.4 ± 17.5 years) with 167 orbital lesions (98/167 [59%] benign lesions including 54 orbital inflammations and 69/167 [41%] malignant lesions including 32 lymphomas) were included in the study. ADC and D were significantly lower in malignant than in benign lesions: 0.8 × 10^-3 mm²/s [0.45] versus 1.04 × 10^-3 mm²/s [0.33], p < 0.001, and 0.75 × 10^-3 mm²/s [0.40] versus 0.98 × 10^-3 mm²/s [0.42], p < 0.001, respectively. D* was significantly higher in malignant lesions than in benign ones: 12.8 × 10^-3 mm²/s [20.17] versus 7.52 × 10^-3 mm²/s [7.57], p = 0.005. Area under curve was of 0.73, 0.74, 0.72, and 0.81 for ADC, D, D*, and a combination of D, f, and D*, respectively.

CONCLUSIONS

Our study showed that IVIM might help better characterize orbital lesions.

KEY POINTS

• Intravoxel incoherent motion (IVIM) helps clinicians to assess patients with orbital lesions. • Intravoxel incoherent motion (IVIM) helps clinicians to characterize orbital lymphoma versus orbital inflammation. • Management of patients becomes more appropriate.

Non-specific orbital inflammation: Current understanding and unmet needs

Non-specific orbital inflammation (NSOI) is a noninfectious inflammatory condition of the orbit. Although it is generally considered the most common diagnosis derived from an orbital biopsy, it is a diagnosis of exclusion, meaning that the diagnosis requires exclusion of a systemic process or another identifiable etiology of orbital inflammation. The clinical diagnosis of NSOI is ill-defined, but it is typically characterized by acute orbital signs and symptoms, including pain, proptosis, periorbital edema, chemosis, diplopia, and less commonly visual disturbance. NSOI poses a diagnostic and therapeutic challenge: The clinical presentations and histological findings are heterogeneous, and there are no specific diagnostic criteria or treatment guidelines. The etiology and pathogenesis of NSOI are poorly understood. Here we recapitulate our current clinical understanding of NSOI, with an emphasis on the most recent findings on clinical characteristics, imaging findings, and treatment outcomes. Furthermore, gene expression profiling of NSOI and its implications are presented and discussed.

Beyond the brain: Extra-axial pathology on diffusion weighted imaging in neuroimaging

Diffusion-weighted imaging (DWI) has a central role in the assessment of the brain parenchyma, particularly in the context of acute stroke. However, the applications of DWI extend far beyond the brain parenchyma and include the assessment of the extra-axial structures of the head and neck that are included in routine brain imaging. In this pictorial review, the added-value of DWI over other conventional sequences is illustrated through discussion of a broad range of disorders affecting the vasculature, skull, orbits, nasal cavity and salivary glands. This article highlights the requirement for all structures, both intra- and extra-axial, to be carefully reviewed on DWI.

The histogram analysis of apparent diffusion coefficient in differential diagnosis of parotid tumor

OBJECTIVES

Use apparent diffusion coefficient (ADC) histogram to investigate whether the parameters of ADC histogram can distinguish between benign and malignant tumors and further differentiate the tumor subgroups.

METHODS AND MATERIALS

This study retrospectively enrolls 161 patients with parotid gland tumors. Histogram parameters including mean, inhomogeneity, skewness, kurtosis and 10th, 25th, 50th, 75th, 90th percentiles are derived from ADC mono-exponential model. Mann-Whitney U test is used to compare the differences between benign and malignant groups. Kruskal-Wallis test with post-hoc Dunn-Bonferroni method is used for subgroup classification, then receiver operating characteristic curve analysis is performed in mean ADC value to obtain the appropriate cutoff values.

RESULTS

Except for kurtosis and 90th percentile, there are significant differences in all other ADC parameters between benign and malignant groups. In subgroup classification of benign tumors, there are significant differences in all ADC parameters between pleomorphic adenoma and Warthin's tumor (area under curve 0.988; sensitivity 93.8%; specificity 94.7%; all ps < 0.05). Pleomorphic adenoma has high value in mean than basal cell adenoma (area under curve 0.819; sensitivity 76.9%; specificity 76.9%; p < 0.05). Basal cell adenoma has high values in mean (area under curve 0.897; sensitivity 92.3%; specificity 78.9%; all ps < 0.05) and 10th, 25th, 50th percentiles than Warthin's tumor. In subgroup classification of malignant tumors, low-risk parotid carcinomas have higher values than hematolymphoid tumors in mean (area under curve 0.912; sensitivity 84.6%; specificity 100%, all ps < 0.05) and 10th, 25th percentiles.

CONCLUSION

ADC histogram parameters, especially mean and 10th, 25th percentiles, can potentially be an effective indicator for identifying and classifying parotid tumors.

[Clinical features of malignant orbital lymphoma]

INTRODUCTION

The occurrence of malignant lymphoma (ML) among patients with malignant orbital tumors ranges between 10 and 37.3% making early diagnosis clarification crucial for timely treatment.

PURPOSE

To study clinical features of ML with consideration of its morphological type and localization in the orbit.

MATERIAL AND METHODS

Clinical picture of primary malignant orbital lymphoma of 34 patients (36 orbits) was examined retrospectively with consideration of the tumor's morphotype. Median observation time was 6 years. Patients aged between 34 and 84 years, female to male ratio was 1.27:1.

RESULTS

The final diagnoses were: small cell MALT-type ML (23 patients), large cell B-lymphoma (5 patients), diffuse malignant lymphoma (5 patients), T-cell lymphoma (1 female patient). Systemic changes developed in 29.41% of cases after 6.7 years on average. 23.53% of patients has died. Clinical signs of MALT-type ML were described with consideration of tumor's localization in the orbit, and clinical features of B-cell, large cell, diffuse and T-cell lymphoma were shown. Signs helping differentiate ML from false tumor, composite tear gland tumor and malignant orbital tumor were established.

CONCLUSION

Despite the higher prevalence of malignant MALT-type lymphoma, primary malignant orbital lymphoma is characterized by unfavorable vital prognosis: in a third of all cases, signs of systemic lesion develop in 6.7 years on average. Clinical picture of MALT-type ML is defined by tumor's localization in the orbit. Recurrence of MALT-type ML after combined treatment (surgical, radiotherapy, polychemotherapy) happens in every fourth case among patients with tumor primarily localized in the orbital cellular tissues or in the tear gland. Describing clinical features of primary malignant orbital lymphoma allows faster diagnosis clarification reducing the number of orbital diseases that require differential diagnositcs.

CT and MR imaging of orbital inflammation

PURPOSE

Orbital inflammation can be idiopathic or in the context of a specific disease and it can involve different anatomical orbital structures. On imaging, inflammatory disease is frequently mistaken for infection and malignant tumors, and its underlying cause is often not determined. Through this article we aim to improve orbital inflammation diagnosis and underlying inflammatory diseases recognition.

METHODS

The imaging protocols and characteristics of orbital inflammation were reviewed.

RESULTS

A decision tree for the evaluation of these patients is provided. First, a combination of clinical and radiological clues is used to recognize inflammation, in particular to differentiate it both from orbital infection and tumor. Subsequently, different radiological patterns are recognized, often allowing the differentiation of the several orbital inflammatory diseases.

CONCLUSION

The use of adequate imaging protocols and subsequent evaluation allow the recognition of an orbital lesion as inflammatory and the diagnosis of the underlying inflammatory disease. All in all, a proper treatment can be established, and at times, a biopsy can be avoided.