Retrobulbar Fat Research Articles

MR Imaging Characteristics of Solitary Fibrous Tumors of the Orbit

PurposeSolitary 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 MethodsMagnetic 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.ResultsOf 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.ConclusionThe 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 evaluation of retrobulbar fat tissue in Graves' orbitopathy with shear-wave ultrasound elastography.

To evaluate retrobulbar adipose tissue of patients with active and inactive Graves' orbitopathy (GO) by shear-wave ultrasound elastography (SWE). Followed-up in our ophthalmology clinic due to GO, 72 eyes of 36 patients and 38 eyes of 19 healthy controls were included in this cross-sectional case-control study. Graves' patients were divided into two subgroups under clinical activity score (CAS): active Graves' orbitopathy (AGO) (CAS ≥ 3) and inactive Graves' orbitopathy (IGO) (CAS < 3). SWE measurement values of retrobulbar adipose tissue of all participants were recorded in meters/second, and the intergroup comparisons were performed. Thirty-four eyes of 17 patients in AGO, 38 eyes of 19 patients in IGO, and 38 eyes of 19 participants in the control group were included in the study. Mean values measured from retrobulbar adipose tissue through SWE were 1.00 ± 0.01m/sec in AGO, 1.16 ± 0.01m/sec in IGO, and 0.94 ± 0.01m/sec in the control groups. Even so, the mean SWE value was significantly higher in the IGO group than in the other groups (p < 0.001). Mean SWE values were significantly higher in the AGO group than in the controls (p = 0.008). In the correlation analysis performed, a significant positive correlation was found between SWE and Hertel exophthalmometer measurement values (p = 0.026, r = 0.212), and thyroid-stimulating hormone receptor antibody (TSHR-Ab) levels (p = 0.018, r = 0.224). We detected SWE values of retrobulbar adipose tissue high in GO, especially in the IGO group. Such a situation, which we associated with the development of fibrosis, may be an indicator of unresponsiveness to immunomodulatory treatments.

Where Should We Focus in Emergency Orbital Trauma?

Aim: To describe the most common findings in orbital trauma and to support radiologic decision making by comparing them in 7 pathology regions.&#x0D; Material and Methods: A total of 190 patients (119 males and 71 females) participated in the study. Orbital injury pathologies were documented and compared in seven regions. The most typical results of orbital tomography were determined. Binominal regression analysis was also performed for each trauma region.&#x0D; Results: 190 orbital CT scans showed 13.7% orbital bone fractures (n=26), 7.9% bulbus pathology (n=15), 2.6% vitreous pathology (n=5), 2.1% extraocular muscle pathology (n=4), and 6.3% (n=13) retrobulbar pathology. The most common globe pathologies were lens displacement and globe rupture. Retrobulbar fat plane changes (4.2% n=8) were the most common pathology in the region. Periorbital edema was the most common periorbital disease in 86.3% of cases (n=164). When evaluated using cross-tabulations between the seven pathologic regions, the relationship between bone pathology and retrobulbar area and between globe and vitreous was statistically significant (p

A clinical study of the effect of 3D reconstruction on exophthalmos after an operation on an old orbital wall fracture.

Orbital blowout fracture is common in ocular trauma. Accurate measurement of orbital volume after fracture is key in improving intraocular correction. This study aims to explore the impact of 3D reconstruction technology in restoring normal exophthalmos in patients with old orbital wall fractures. A total of 31 patients were randomly divided into an experimental group (n= 15) and a control group (n= 16). For orbital wall repair and reconstruction, the conventional group used the conventional surgical scheme, and the 3D group used 3D printing technology. There was no statistical difference between the preoperative mean extraocular muscle volume of the healthy eye and the affected eye. However, the mean orbital volume (24.76 vs 27.11, P= 0.005) and mean retrobulbar fat volume (17.53 vs 16.42, P= 0.006) were significantly different between the healthy eye and the affected eye. After an average follow-up of 16 weeks, the differences in pre- and post-surgery exophthalmos in the two groups were 0.42 ± 0.08 mm and 1.63 ± 0.51 mm, respectively. The difference between the two groups was statistically significant (t= 4.42, P= 0.003). The complications were not statistically different. Using 3D reconstruction technology preoperatively can significantly improve exophthalmos in patients with old orbital wall fractures.

A quantitative sonoelastography evaluation of ocular and periocular elasticity after intravitreal ranibizumab injection

We evaluated changes in ocular and periocular elasticity by ultrasound (US) elastography in intravitreal ranibizumab-treated eyes and the healthy fellow eyes of patients with neovascular AMD. The study was performed on 52 eyes of 26 volunteers who ranged in age from 59 to 89 (mean 72±7.78) years old. The study group consisted of the patients with neovascular AMD treated with intravitreal ranibizumab. The fellow eyes (without choroidal neovascularization) of the study group were selected as the control group. All patients were examined with sonoelastography before intravitreal injection and at 1day, 1week, and 1month after intravitreal injection. All images were acquired with a Toshiba Aplio 500 ultrasound system (Tokyo, Japan) including software with a combined autocorrelation method and a multifrequency linear probe. The elastography values of the anterior vitreous (AV), posterior vitreous (PV), retina-choroid-sclera complex (RCS), retrobulbar fat tissue (RF), optic nerve head (ONH) and retrobulbar optic nerve (RON) were measured in each eye. There were 13 male (50%) and 13 female (50%) participants in our study. Anterior vitreous, posterior vitreous, RCS, retrobulbar fat tissue, ONH, and RON US elastography values were similar in both groups (P˃0.05 for all). On the other hand, there was a positive correlation between the difference between baseline and 1-month PV sonoelastography values and age (r=0.47, P=0.035). A single dose intravitreal Ranibizumab (Lucentis®, Genentech, USA) injection does not alter the elasticity of ocular and periocular structures.

Osteopathic manipulative treatment in improving symptoms and quality of life in patients with Graves’ ophthalmopathy: A case report

BackgroundGraves' Disease (GD) is an autoimmune disorder, with ∼50% of GD patients developing Graves’ Ophthalmopathy (GO). Common presentations include lid retraction, exophthalmos, disfigurement, ocular pain, and pressure. Treatment of GD depends on disease severity, ranging from artificial tears to ocular surgeries. Patients with GO symptoms experience a decreased quality of life (QoL) and could benefit from additional treatment options. ObjectiveThis case report describes the use of osteopathic manipulative treatment (OMT) as an adjunct to standard care for a patient with symptomatic GO, and measurement of treatment response with a standardized QoL assessment tool. Clinical featuresClinical evaluation of a patient with GO showed clinical activity score to be 4 with oppressive feeling behind globes, hyperemia, and eyelid edema. Corneal displacement measured by Hertel exophthalmometer indicated increased proptosis. CT scan showed enlarged extraocular muscles bilaterally, with signs of edema in retrobulbar fat. Visual acuity and optic nerves were within normal limits. Intervention and outcomesThis case report demonstrates the use of OMT in long-term reduction of ocular pain and pressure by relieving orbital myofascial tension along with improving ocular circulation, in a patient with GO. Using the European Group On Graves’ Orbitopathy QoL questionnaire, the patient noted better quality of life (93, 81.3 for pretreatment visual and appearance scores, respectively, and 100, 87.5 for post-treatment visual and appearance scores, respectively) and perceived reduced exophthalmos. ConclusionsProviding OMT as a cost effective, non-invasive treatment option for GO symptoms could meet a significant need for GO patients and warrants further study.

Isolation and cultivation as well as in situ identification of MSCs from equine dental pulp and periodontal ligament.

The lifelong eruption places a great demand on the dental pulp and periodontal ligament (PDL) of horse teeth. Cells within the pulp and PDL seem to play a key role during this remodeling. In this study, we isolated and cultivated MSCs (medicinal signaling cells) from dental pulp, PDL and retrobulbar fat of four horses. Subsequently, we analyzed them by flow cytometry and immunohistochemistry to determine and compare their characteristics. In addition, we localized these cells within the tissue structure via immunohistochemistry of histological sections. For these analyses, several surface markers were applied. The described method illustrates a feasible approach to isolate and cultivate MSCs from equine dental pulp and PDL. In the flow cytometry a vast majority of cultivated cells were positive for CD90 and CD40 and negative for CD11a/18, CD45, CD105 and MHCII suggesting that these cells feature characteristics of MSCs. Immunohistochemistry of histological pulp and PDL sections showed the localization of CD90 positive cells especially in the perivascular region and the subodontoblastic layer. Our findings indicate that the isolation and cultivation of MSCs from equine dental pulp and PDL is feasible although an elaborate and complicated harvesting protocol is required. MSCs isolated from dental pulp and PDL are regarded as candidates for new therapeutical approaches in equine dental medicine like regeneration of periodontal lesions, enhancement of periodontal re-attachment after dental replantation and stimulation of pulp-obliteration and apexification in combination with endodontic therapies.

Application of Multiparameter Quantitative Magnetic Resonance Imaging in the Evaluation of Graves' Ophthalmopathy.

Assessment of the activity of Graves' ophthalmopathy (GO) is difficult. Existing methods need improvement. Investigate the application of multiparametric magnetic resonance imaging (MRI) in GO. Retrospective. A total of 235 GO patients (age: 38.8± 13.4 years; 90 male; 96 active patients). Short-tau inversion recovery (STIR) fast spin echo, multiecho spin echo T2 mapping and 3D T1-weighted fast field echo sequences at 3.0 T. Two physicians assessed the mean and maximum signal intensity ratio of extraocular muscles to white matter (SIR), T2 relaxation time (T2RT), extraocular muscle area (EMA), fat fraction (FF), retrobulbar fat volume (RFV), and extraocular muscle volume (EMV). Clinical activity score (CAS)≧3 was in active stage. The optimal cut-off point of diagnostic efficacy was selected using receiver operating characteristic (ROC) curve analysis and evaluated using area under the curve (AUC), compared using Student's t test, analysis of variance or Kruskal-Wallis H test. The correlation used Pearson correlation analysis. The discriminant equation used a binary logistic regression analysis. P < 0.05 was considered statistically significant. The SIRmean, SIRmax, T2RTmean, T2RTmax, EMA, and EMV in active GO patients were significantly higher than those in inactive and were positively correlated with CAS (r=0.276, 0.228, 0.438, 0.388, 0.502, and 0333, respectively). The FFmax of active patients was significantly lower than that of inactive patients and was negatively correlated with CAS (r=-0.44). Logistic regression analysis indicated that T2RTmean was independently associated with GO active periods and had good diagnostic performance (area under ROC curve=0.736, sensitivity 70.7%, specificity 69.3%). T2RTmean≧74.295 could be a diagnostic cut-off for judging GO activity (sensitivity 55.3%). SIR, T2RT, EMV, and FF can quantitatively assess the activity and severity of GO and can potentially provide a basis for clinical judgment and selection of treatment options. 4. Stage 2.

Orbital Lipolysis.

HomeRadiologyVol. 307, No. 2 PreviousNext Reviews and CommentaryFree AccessImages in RadiologyOrbital LipolysisTuba Kalelioglu , Sohil H. PatelTuba Kalelioglu , Sohil H. PatelAuthor AffiliationsFrom the Department of Radiology and Medical Imaging, University of Virginia Health System, 1215 Lee St, 1st Floor, Charlottesville, VA 22903.Address correspondence to T.K. (email: [email protected]).Tuba Kalelioglu Sohil H. PatelPublished Online:Jan 24 2023https://doi.org/10.1148/radiol.221947MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In A 47-year-old man with a history of squamous cell carcinoma of the oral tongue, alcohol-induced chronic pancreatitis with gastrostomy tube dependence, and chronic diarrhea presented to the emergency department with altered mental status. The patient was cachectic, with a body mass index of 14.3 kg/m2.MRI of the brain demonstrated diffuse loss of expected fat signal intensity with T1-weighted imaging, including within the orbits, bone marrow, and subcutaneous scalp (Figure). This appearance is similar to a fat-saturated T1-weighted image; hence, it is called “pseudo fat-saturated” (1). It is due to excessive lipolysis and lipid peroxidation induced by cachexia from chronic malnutrition in the setting of anorexia nervosa or systemic cancer. Furthermore, endothelial injury results in edema and contrast enhancement in the involved areas, conspicuous in the postseptal orbit (2).Images in a 47-year-old man with cachectic state. (A) T1-weighted image before cachectic state for comparison shows expected normal high signal intensity of the orbital, scalp, and bone marrow fat. (B) Axial T1-weighted image without fat suppression shows lack of expected hyperintense fat in the orbits, subcutaneous scalp, and bone marrow. The imaging appearance mimics a fat-saturated T1-weighted image. The volume of subcutaneous fat in temporal regions is decreased. (C) Postcontrast T1-weighted image shows diffuse contrast enhancement of the affected areas secondary to increased vessel wall permeability. (D) Noncontrast CT scan shows increased attenuation in the retrobulbar fat, consistent with edema.Download as PowerPointOpen in Image Viewer Disclosures of conflicts of interest: T.K. No relevant relationships. S.H.P. No relevant relationships.

Effects of Androgen Deprivation Therapy on Extraocular Muscles, Retrobulbar Orbital Fat, and the Optic Nerve in Patients with Prostate Cancer

Introduction: The aim of this study was to evaluate radiologically the effects of long-term luteinizing hormone-releasing hormone (LHRH) agonist therapy on extraocular muscle thickness, retrobulbar orbital fat (ROF), and the optic nerve (ON) in prostate cancer (PCa) patients. Methods: The retrospective study included patients with primary or recurrent PCa who received androgen deprivation therapy (ADT) for at least 12 months. Each patient underwent gallium-68 prostate-specific membrane antigen positron emission tomography-computed tomography both before and at the end of the 12-month treatment. Thickness of the ON, lateral rectus muscle, medial rectus muscle, superior rectus muscle, and inferior rectus muscle were measured by using the coronal CT sections in soft tissue window. ROF, ocular protrusion, and ON length were measured in sagittal and coronal planes. Changes in these anatomical structures induced by LHRH analogs were investigated by comparing pre- and post-treatment measurements. Results: A total of 57 patients were included in the study. Median PSA and TT values ​​of the patients before treatment were 36.5 (range, 19.6–51.2) ng/mL and 614.0 (range, 472.0–743.0) ng/dL, respectively, and these values ​​decreased significantly after the treatment (10.6 [range, 5.2–14.2] ng/mL and 36.5 [range, 19.6–51.2] ng/dL, respectively, p < 0.001 for both). After the treatment, there was a statistically significant decrease in the areas of inferior rectus muscle, superior rectus muscle, lateral rectus muscle, and medial rectus muscle (p < 0.001 for all), while significant increases were observed in ROF (11.9%, p < 0.001) and ON thickness (14.3%, p = 0.004). The amount of ocular protrusion also showed a significant increase of approximately 14% after the treatment (14.0 [range, 12.0–16.0] mm vs. 16.0 [range, 14.0–17.2] mm, p < 0.001). Discussion/Conclusion: Our findings, for the first time in the literature, indicated that ADT causes a decrease in extraocular muscle mass and an increase in ROF with ocular protrusion. It can be asserted that these changes are similar to the changes in skeletal muscle and fat mass in other body parts. Further studies with a higher level of evidence are needed to clinically evaluate the increase in ocular protrusion and ON enlargement, which are likely to be caused by the increase in ROF.

Optic nerve sheath diameter assessment by neurosonology: A review of methodologic discrepancies.

Reported cutoff values of the optic nerve sheath diameter (ONSD) for the diagnosis of elevated intracranial pressure (ICP) are inconsistent. This hampers ONSD as a possible noninvasive bedside monitoring tool for ICP. Because the influence of methodological differences on variations in cutoff values is unknown, we performed a narrative review to identify discrepancies in ONSD assessment methodologies and to investigate their effect on reported ONSD values. We used a structured and quantitative approach in which each ONSD methodology found in the reviewed articles was categorized based on the characteristic appearance of the ultrasound images and ultrasound marker placement. Subsequently, we investigated the influence of the different methodologies on ONSD values by organizing the ONSDs with respect to these categories. In a total of 63 eligible articles, we could determine the applied ONSD assessment methodology. Reported ultrasound images either showed the optic nerve and its sheath as a dark region with hyperechoic striped band at its edges or as a single dark region surrounded by lighter retrobulbar fat. Four different ultrasound marker positions were used to delineate the optic nerve sheath, which resulted in different ONSD values and more importantly, different sensitivities to changes in ICP. Based on our observations, we recommend to place ultrasound markers at the outer edges of the hyperechoic striped bands or at the transitions from the single dark region to the hyperechoic retrobulbar fat because these locations yielded the highest sensitivity of ONSD measurements for increased ICP.

Temperature and species-dependent regulation of browning in retrobulbar fat

Retrobulbar fat deposits surround the posterior retina and optic nerve head, but their function and origin are obscure. We report that mouse retrobulbar fat is a neural crest-derived tissue histologically and transcriptionally resembles interscapular brown fat. In contrast, human retrobulbar fat closely resembles white adipose tissue. Retrobulbar fat is also brown in other rodents, which are typically housed at temperatures below thermoneutrality, but is white in larger animals. We show that retrobulbar fat in mice housed at thermoneutral temperature show reduced expression of the brown fat marker Ucp1, and histological properties intermediate between white and brown fat. We conclude that retrobulbar fat can potentially serve as a site of active thermogenesis, that this capability is both temperature and species-dependent, and that this may facilitate regulation of intraocular temperature.

Eye Injury- Baseball

HISTORY: A 12 year-old male sustained an injury to left eye during a baseball game. While playing first base, the outfielder threw a ball to him so patient could tag the runner out. When catching the ball, he missed, and instead the ball struck him in the face in the area of the left eye. There was no loss of consciousness, vomiting, hematoma or altered mental status. He initially had difficulty seeing out of the eye, but vision returned soon after and appeared blurry. PHYSICAL EXAMINATION: Normocephalic. With the exception of limitation in upward gaze of left eye, the remaining extraocular movements were intact. Hyphema of left eye noted. Pupils equal, round and reactive to light bilaterally. Moderate left periorbital edema and ecchymosis. Vision intact to left eye. Sensation intact in V1-V3 distribution, facial nerve function intact bilaterally. Normal occlusion, midface stable. Hearing to spoken voice intact and TM’s clear with no evidence of hemotympanum. Remainder of examination was normal. DIFFERENTIAL DIAGNOSIS: 1. Orbital Ridge Fracture 2. Orbital Blowout Fracture 3. Hyphema 4. Retinal detachment 5. Commotio Retinae 6. Globe Rupture TEST AND RESULTS: CT facial bones: -Blowout fracture of left inferior and medial wall of left orbit -Left orbital emphysema with small contusion vs hematoma within the retrobulbar fat -Minimal blood within the left ethmoid and maxillary sinus Ophthalmology Consult: -Visual Acuity 20/30 Right, 20/200 Left -3 mm Hyphema of left eye -Commotio Retinae of left macula -Normal intraocular pressure FINAL/WORKING DIAGNOSIS: Left orbital floor fracture, Traumatic Hyphema, Commotio Retinae involving the macula TREATMENT AND OUTCOMES: 1. CT scan without significant displacement and no ocular muscle entrapment on repeat exam, no operative repair needed; follow-up with plastic surgery 1-2 weeks 2.Per ophthalmology recommendations: a. Ongoing observation for cataract, retinal detachment, and glaucoma due to increased risk from blunt ocular trauma b. Bed rest with bathroom privileges 3-4 days c. Ophthalmic prednisolone and ophthalmic atropine for hyphema with monitoring for absorption and rebleed d. Monitor for macular hole as increased risk secondary to commotio retinae e. Follow-up in 1-2 days

Primer Açık Açılı Glokomlu Hastalarda Göz Elastisitesi

Purpose: The present study was performed to assess elasticity changes in the ocular and periocular structures of patients with primary open angle glaucoma POAG via sonoelastography. Patients and Methods: Forty-three patients 19 male, 24 female; ranging from 45 to 80, mean age, 63.20 ± 2.31 years diagnosed with POAG were prospectively analyzed. This patient group was compared with a control group of 28 individuals 17 male, 11 female; ranging from 40 to 85, mean age, 63.50 ± 1.89 years who had no eye diseases apart from refractive errors. Following an ophthalmologic assessment and B-mode sonography, all participants underwent semiquantitative sonoelastographic analysis. The elasticity of the retrobulbar fat tissue, optic nerve, lens, and retina–choroid–sclera complex RCSC was compared between the two groups via sonoelastography. Student’s t test and the Mann–Whitney U test were used for statistical assessment. Results: There was no significant differences in the degree of elasticity of the ocular and periocular structures between patients with and without POAG. Conclusion: No difference was detected between elasticity levels of ocular and periocular structures in between patients with and without POAG.

Demystifying Role of Ultrasound Elastography in the Evaluation of Primary Open Angle Glaucoma

For this cross-sectional comparative study, 20 patients with primary open-angle glaucoma (POAG) and 20 healthy volunteers were recruited. Ultrasound elastography measurements were taken with a sonographic scanner of the RCS complex, anterior vitreous (AV), posterior vitreous (PV), retrobulbar fat tissue (RFT), optic disc, and optic nerve in each eye.

Feasibility of a low-dose orbital CT protocol with a knowledge-based iterative model reconstruction algorithm for evaluating Graves' orbitopathy

PurposeTo evaluate the clinical feasibility of low-dose orbital CT with a knowledge-based iterative model reconstruction (IMR) algorithm for evaluating Graves' orbitopathy. MethodsLow-dose orbital CT was performed with a CTDIvol of 4.4 mGy. In 12 patients for whom prior or subsequent non-low-dose orbital CT data obtained within 12 months were available, background noise, SNR, and CNR were compared for images generated using filtered back projection (FBP), hybrid iterative reconstruction (iDose4), and IMR and non-low-dose CT images. Comparison of clinically relevant measurements for Graves' orbitopathy, such as rectus muscle thickness and retrobulbar fat area, was performed in a subset of 6 patients who underwent CT for causes other than Graves' orbitopathy, by using the Wilcoxon signed-rank test. ResultsThe lens dose estimated from skin dosimetry on a phantom was 4.13 mGy, which was on average 59.34% lower than that of the non-low-dose protocols. Image quality in terms of background noise, SNR, and CNR was the best for IMR, followed by non-low-dose CT, iDose4, and FBP, in descending order. A comparison of clinically relevant measurements revealed no significant difference in the retrobulbar fat area and the inferior and medial rectus muscle thicknesses between the low-dose and non-low-dose CT images. ConclusionsLow-dose CT with IMR may be performed without significantly affecting the measurement of prognostic parameters for Graves' orbitopathy while lowering the lens dose and image noise.

Retinal Stem Cells Reprogramming Using Omotoxicological Pharmaceuticals Blend Therapy Through Retrobulbar Injections

The author reports his experience derived from his first Autologous Stem Cells transplant from Bone Marrow (from the hip) and reimplantation into the retrobulbar fat of the Eye. To define a new concept of Informational Therapy for Regenerative Medicine using a system of Reformatting the pathological retina through the therapeutic Regulation of affected Tissues of the inner Eye no more capable to regulate normal biological functions.

Multimodal assessment of orbital immune cell infiltration and tissue remodeling during development of graves disease by 1 H19 F MRI.

To evaluate key molecular and cellular features of Graves orbitopathy (GO) by simultaneous monitoring of alterations in morphology, inflammatory patterns, and tissue remodeling. To this end, we utilized a murine model of GO induced by immunization with a human thyroid-stimulating hormone receptor A-subunit plasmid. Altogether, 52 mice were used: 27 GOs and 25 controls (Ctrl) immunized with β-galactasidose plasmid. From these, 17 GO and 12 Ctrl mice were subjected to multimodal MRI at 9.4T, whereas 23 mice only underwent histology. Beyond anatomical hydrogen-1 (1 H) MRI, we employed transverse relaxation time (T2 ) mapping for visualization of edema, chemical exchange saturation transfer (CEST) for detection of hyaluronan, and fluorine-19 (19 F) MRI for tracking of in situ-labeled immune cells after intravenous injection of perfluorcarbons (PFCs). 1 H/19 F MRI demonstrated substantial infiltration of PFC-loaded immune cells in peri and retro-orbital regions of GO mice, whereas healthy Ctrls showed only minor 19 F signals. In parallel, T2 mapping indicated onset of edema in periorbital tissue and adjacent ocular glands (P = 0.038/0.017), which were associated with enhanced orbital CEST signals in GO mice (P = 0.031). Concomitantly, a moderate expansion of retrobulbar fat (P = 0.029) was apparent; however, no signs for extraocular myopathy were detectable. 19 F MRI-based visualization of orbital inflammation exhibited the highest significance level to discriminate between GO and Ctrl mice (P = 0.006) and showed the best correlation with the clinical score (P = 0.0007). The present approach permits the comprehensive characterization of orbital tissue and holds the potential for accurate GO diagnosis in the clinical setting. Magn Reson Med 80:711-718, 2018. © 2018 International Society for Magnetic Resonance in Medicine.

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

ABSTRACTThe 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.

Radiation dose reduction in parasinus CT by spectral shaping.

Spectral shaping aims to narrow the X-ray spectrum of clinical CT. The aim of this study was to determine the image quality and the extent of radiation dose reduction that can be achieved by tin prefiltration for parasinus CT. All scans were performed with a third generation dual-source CT scanner. A study protocol was designed using 100kV tube voltage with tin prefiltration (200mAs) that provides image noise levels comparable to a low-dose reference protocol using 100kV without spectral shaping (25mAs). One hundred consecutive patients were prospectively enrolled and randomly assigned to the study or control group. All patients signed written informed consent. The study protocol was approved by the local Institutional Review Board and applies to the HIPAA. Subjective and objective image quality (attenuation values, image noise, and contrast-to-noise ratio (CNR)) were assessed. Radiation exposure was assessed as volumetric CT dose index, and effective dose was estimated. Mann-Whitney U test was performed for radiation exposure and for image noise comparison. All scans were of diagnostic image quality. Image noise in air, in the retrobulbar fat, and in the eye globe was comparable between both groups (all p>0.05). CNReye globe/air did not differ significantly between both groups (p=0.7). Radiation exposure (1.7 vs. 2.1mGy, p<0.01) and effective dose (0.055 vs. 0.066mSv, p<0.01) were significantly reduced in the study group. Radiation dose can be further reduced by 17% for low-dose parasinus CT by tin prefiltration maintaining diagnostic image quality.