Intracranial Lesion Detection and Artifact Characterization: Comparative Study of Susceptibility and T2*-Weighted Imaging in Dogs and Cats

Susceptibility-weighted imaging (SWI), an MRI sequence for the detection of hemorrhage, allows differentiation of paramagnetic and diamagnetic substances based on tissue magnetic susceptibility differences. The three aims of this retrospective study included a comparison of the number of areas of signal void (ASV) between SWI and T2*-weighted imaging (T2*WI), differentiation of hemorrhage and calcification, and investigation of image deterioration by artifacts. Two hundred twelve brain MRIs, 160 dogs and 52 cats, were included. The sequences were randomized and evaluated for presence/absence and numbers of ASV and extent of artifacts causing image deterioration by a single, blinded observer. In cases with a CT scan differentiation of paramagnetic (hemorrhagic) and diamagnetic (calcification) lesions was made, SWI was performed to test correct assignment using the Hounsfield Units. Non-parametric tests were performed to compare both sequences regarding detection of ASV and the effect of artifacts on image quality. The presence of ASV was found in 37 SWI sequences and 34 T2*WI sequences with a significant increase in ASV only in dogs >5 and ≤ 15 kg in SWI. The remaining weight categories showed no significance. CT examination was available in 11 cases in which 81 ASV were found. With the use of phase images, 77 were classified as paramagnetic and none as diamagnetic. A classification was not possible in four cases. At the level of the frontal sinus, significantly more severe artifacts occurred in cats and dogs (dogs, p < 0.001; cats, p = 0.001) in SWI. The frontal sinus artifact was significantly less severe in brachycephalic than non-brachycephalic dogs in both sequences (SWI, p < 0.001; T2*WI, p < 0.001). In conclusion, with the advantages of better detection of ASV in SWI compared with T2*WI and the opportunity to differentiate between paramagnetic and diamagnetic origin in most cases, SWI is generally recommended for dogs. Frontal sinus conformation appears to be a limiting factor in image interpretation.

Dimensions and Forms of Artefacts in 1.5T and 3T MRI Caused by Cochlear Implants

Introduction:Cochlear implantation is a standard treatment option due to expanding indicationsCranial magnetic resonance imaging (cMRI) has become a widespread diagnostic tool. Therefore, an increased number of cochlear implant (CI) users are undergoing cMRI scans.This study aimed to investigate the issue of the CI magnet impacting MRI quality and artifacts.Material and Methods:1.5T and 3T MRI scans with 4 defined sequences (T2-TSE, T2-TIRM, T1-3D-MPRAGE, and TDI) were performed on a phantom with a CI (Synchrony® System by MEDEL Austria®) in place. The resulting MRI artifacts were retrospectively compared to MRI artifacts observed in patients with a CI. All images were transferred to Amira® and visualized by manual segmentation.Results:Usable image quality was achieved in three sequences(T2-TSE, T2-TIRM and T1-mprage). Observed artifacts differed in shape and size depending on the sequence. Maximum diameters of fully extinguished areas ranged from 58x108x98 mm to 127x123x153 mm. Image distortions were larger.Conclusion:MRI artifacts caused by the Synchrony® system are asymmetric with varying shape, depending on the sequence. The phantom artefacts are similar to those in CI users. Considering the observed asymmetry, the hypothesis of varying implantation locations resulting in varying positions of the signal void area needs to be further investigated.

The role of cochlear implant positioning on MR imaging quality: a preclinical in vivo study with a novel implant magnet system

Purposes To investigate the effects for Ultra 3D cochlear implant (CI) positioning on MR imaging quality, looking at a comprehensive description of intracranial structures in cases of unilateral and bilateral CI placement. Methods Four CI angular positions (90°, 120°, 135° and 160°) at 9 cm distance from the outer-ear canal were explored. The 1.5 T MRI assessment included our institutional protocol for the investigation of brain pathologies without gadolinium application. Three investigators (two experienced neuroradiologists and one experienced otoneurosurgeon) independently evaluated the MR findings. A 4-point scale was adopted to describe 14 intracranial structures and to determine which CI positioning allowed the best image quality score and how bilateral CI placement modified MRI scan visibility. Results A high positive correlation was found between the three blinded observers. Structures situated contralateral from the CI showed high-quality values in all four placements. Structures situated ipsilaterally provided results suitable for diagnostic purposes for at least one position. At 90°, artifacts mainly involved brain structures located cranially and anteriorly (e.g., temporal lobe); on the contrary, at 160°, artifacts mostly influenced the posterior fossa structures (e.g., occipital lobe). For the bilateral CI condition, MR imaging examination revealed additional artifacts involving all structures located close to either CI, where there was a signal void/distortion area. Conclusions Suitable unilateral CI positioning can allow the visualization of intracranial structures with sufficient visibility for diagnostic purposes. Bilateral CI positioning significantly deteriorates the anatomical visibility. CI positioning might play a crucial role for patients who need post-operative MRI surveillance.

Quantitative OCT angiography of the retinal microvasculature and choriocapillaris in highly myopic eyes with myopic macular degeneration

PurposeTo quantify retinal and choriocapillaris (CC) microvasculature in highly myopic (HM) eyes with myopic macular degeneration (MMD) using swept-source optical coherence tomography angiography (SS-OCTA).Methods162 HM eyes (spherical equivalent ≤ −6.0 dioptres or axial length (AL) ≥26.5 mm) from 98 participants were enrolled, including 60 eyes (37.0%) with tessellated fundus, 54 eyes (33.3%) with peripapillary diffuse chorioretinal atrophy (PDCA), 27 eyes (16.7%) with macular diffuse chorioretinal atrophy (MDCA) and 21 eyes (13.0%) with patchy or macular atrophy. PLEX Elite 9000 SS-OCTA was performed to obtain perfusion densities (PD) of the superficial and deep retinal capillary plexus, and CC signal voids (number, area and density).ResultsRetinal PD decreased with increasing severity of MMD. Multivariable analysis showed that after adjustment of age and other factors, retinal PD decreased significantly in eyes with longer AL (β≤−0.51, p<0.001) and with an MMD severity of MDCA or worse (β≤−1.63, p<0.001). Reduced retinal PD were significantly associated with worse vision (β≤−0.01, p≤0.04). In terms of CC signal voids, multivariable analysis showed that longer AL (p<0.001), but not MMD severity (p≥0.12) was significantly associated with CC signal void changes in the earliest stage of MMD.ConclusionWe demonstrate significant OCTA alterations in the retina and CC in HM eyes with varying severities of MMD. In eyes with early-stage PDCA, lower retinal PD and more extensive CC signal voids are predominantly associated with increasing AL. In contrast, in eyes with MDCA or worse, MMD itself was associated with sparser retinal and CC circulation.

Haematomyelia and myelomalacia following an inadvertent thoracic intraspinal injection in a cat

Case summary A 4-month-old cat was presented with acute paraplegia after the referring veterinarian performed a subcutaneous injection (cefovecin and dexamethasone) in the caudodorsal thoracic area, during which the cat suddenly became uncooperative. A complete neurological examination performed 1 day after the injection revealed paraplegia without deep pain perception and reduced segmental spinal reflexes in the pelvic limbs. Findings were consistent with either an L4–S3 myelopathy or a T3–L3 myelopathy with subsequent spinal shock. MRI showed swelling of the spinal cord from T1 to L1 with heterogeneous T2-weighted intramedullary hyperintensity and no contrast enhancement. A centrally located intraspinal signal void was visible in T2*-weighted images. These changes were compatible with a suspected traumatic intraspinal injection. Despite intensive supportive care over 4 days, neurological status did not improve and the cat was euthanased. Gross pathology findings revealed severe intramedullary haemorrhage and myelomalacia in the T10–L1 spinal cord segments. Histopathology of the spinal cord after haematoxylin and eosin staining revealed a severe intramedullary space-occupying haemorrhage with focal malacia. A trajectory-like, optically empty cavity containing some eosinophilic droplets at the edges was detected. Although no further evidence of trauma was noted in the surrounding structures, the spinal cord changes were compatible with a perforating trauma. Relevance and novel information To our knowledge, this is the first report of thoracic intraspinal injection causing myelomalacia defined by an ante-mortem MRI and confirmed post mortem by histopathology. The traumatic myelopathy appeared to be most compatible with an intraspinal injection causing vascular rupture.

A comparative study of Accuracy, Sensitivity, and Specificity of MR Cholangiopancreatography versus Ultrasonography for diagnosis of hepatobiliary and pancreatic pathologies

Background: The diagnosis of abdominal pathologies is a challenge and radiology is a very important tool in diagnosis. Various methods are often used for the diagnosis of such conditions. We in the present study tried to compare the efficacy of magnetic resonance cholangiopancreatography and ultrasonography in evaluating biliary duct diseases. Methods: The present study was conducted in the Department of Radiodiagnosis, Prathima Institute of Medical Sciences, Naganur, Karimnagar. All patients presenting with recurrent pancreatitis, hypochondriac pain, jaundice presenting to the radiology department are included in the present study. Patients with metallic implants, claustrophobia are excluded from the present study. Ultrasonography was performed using a Philips HD 15 and Philips affinity 70 machine. Both curvilinear and linear probes were used in the study. Images of the biliary tree were recorded for later review. MRI-MRCP was performed on Philips ACHIEVA 1.5 Tesla MRI Scanner. Results : In this study, n=13 subjects were clinically suspected to have cholelithiasis (n=7), choledocholithiasis (n=2), and both Cholelithiasis with choledocholithiasis (n=4). Ultrasonography was able to diagnose Cholelithiasis correctly in n=5 cases, choledocholithiasis in n=1 case, Cholelithiasis with choledocholithiasis in n=4 cases and rule out Cholelithiasis in n=2 cases, but failed to identify distal CBD calculus in n=1 case (choledocholithiasis) hence having a diagnostic accuracy of 92.31% for the cholelithiasis-choledocholithiasis group. Conclusion: MR Cholangiopancreatography is very accurate in demonstrating calculi at the distal end of CBD as an area of the signal void, also in demonstrating strictures as the cause of dilatation of biliary radicals. It showed the length of the stricture segment very well and differentiated stricture as malignant and benign.

Imaging of calcific tendinopathy around the shoulder: usual and unusual presentations and common pitfalls

Rotator cuff calcific tendinopathy (RCCT) is a very common condition, characterized by calcium deposition over fibrocartilaginous metaplasia of tenocytes, mainly occurring in the supraspinatus tendon. RCCT has a typical imaging presentation: in most cases, calcific deposits appear as a dense opacity around the humeral head on conventional radiography, as hyperechoic foci with or without acoustic shadow at ultrasound and as a signal void at magnetic resonance imaging. However, radiologists have to keep in mind the possible unusual presentations of RCCT and the key imaging features to correctly differentiate RCCT from other RC conditions, such as calcific enthesopathy or RC tears. Other presentations of RCCT to be considered are intrabursal, intraosseous, and intramuscular migration of calcific deposits that may mimic infectious processes or malignancies. While intrabursal and intraosseous migration are quite common, intramuscular migration is an unusual evolution of RCCT. It is important also to know atypical regions affected by calcific tendinopathy as biceps brachii, pectoralis major, and deltoid tendons. Unusual presentations of RCCT may lead to diagnostic challenge and mistakes. The aim of this review is to illustrate the usual and unusual imaging findings of RCCT that radiologists should know to reach the correct diagnosis and to exclude other entities with the purpose of preventing further unnecessary imaging examinations or interventional procedures.

Pituitary tumour apoplexy due to pituitary adenoma in a dog: clinical, 3T MRI and CT features

Pituitary apoplexy (PA) is a neurological syndrome resulting from sudden infarction/haemorrhage within a normal or tumoural pituitary gland. Prompt imaging is essential to correlate haemorrhagic/ischaemic changes with clinical signs. The purpose of this report is to describe the clinical, CT and 3T MRI findings of PA in a 13-year-old dog previously diagnosed with pituitary-dependent hyperadrenocorticism. Neurological examination revealed an anxious-compulsive behaviour, internal ophthalmoplegia and bilaterally reduced menace response. Brain MRI showed a pituitary mass with two focal well-defined areas. The first was T2 weighted (T2w) and T1 weighted (T1w) hyperintense, FLAIR hypointense to the grey matter, and mildly contrast-enhancing with signal void artefact in GE-T2*, compatible with late/subacute haemorrhage; the second was T2w hypointense, T1w, FLAIR and GE-T2* isointense/hypointense to the grey matter and moderately enhancing, compatible with acute haemorrhage. The dog recovered after 24 hours, but internal ophthalmoplegia remained. To the authors’ knowledge, this is the first report describing MRI findings in a dog with PA.

In Vivo Mapping of the Choriocapillaris in High myopia: a Widefield Swept Source Optical Coherence Tomography Angiography

To report variation of choriocapillaris (CC) flow in widefield in high in myopic subjects compared with an age-matched normal control group using ultra widefield optical coherence tomography angiography (UW-OCTA). This is a Prospective, cross-sectional study. Thirty high myopia subjects and fifty healthy subjects were enrolled. Healthy and high myopia subjects were imaged with the SS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc., Dublin, CA, USA). For each eye, five 12 × 12-mm OCTA volume scans were acquired. The en face CC images were then exported to imageJ and a semi-automated algorithm was used for subsequent quantitative analysis. The main outcome was a quantitative analysis of the CC. This analysis was performed in three different regions: (i) peripapillary, (ii) macular, and (iii) periphery. In addition, CC variables were further investigated in distinct fields within these three different regions. Thirty myopic eyes (32 subjects; myopic group) and fifty eyes (50 subjects; control group) without elevated myopia were included in the analysis. Mean ± SD age was 26.9 ± 2.9 years [median: 27 years; range: 20.0–40.0 years]. Mean ± SD axial length was 26.6 ± 0.6 mm [median: 26.2 mm; range: 26.1 to 28.0 mm]. Mean ± SD axial length was 26.6 ± 0.6 mm [median: 26.2 mm; range: 26.1 to 28.0 mm] in the myopic group and 23.9 ± 1.1 mm [median: 23.9 mm; range: 21.8 to 25.9 mm] in the control group. The total signal void area was significantly greater in myopic eyes compared with control group. The peripapillary region exhibited the greatest total signal void area (p < 0.0001 vs macular region, p < 0.0001 vs peripheral region). Within the macular region, the foveal area exhibited a greater total signal void area in comparison with both the parafoveal area (p < 0.0001) and the perifoveal area (p < 0.0001). In conclusion we report quantitative mapping of the choriocapillaris in myopic eyes compared with an age-matched normal control group. The CC perfusion appears to have a wide topographical variation.

Changes in Retinal and Choroidal Vascularity in Eyes with Acute Central Serous Chorioretinopathy Using Optical Coherence Tomography Angiography

Background To compare the vascular changes of superficial capillary layer (SCP) and deep capillary layer (DCP) in retina and choriocapillary layer in eyes with acute central serous chorioretinopathy (CSC) by optical coherence tomography angiography (OCTA) between at baseline and 3 months. Methods Prospective case series; Twelve patients (12 eyes) with acute CSC at the baseline and 3 months were included. All patients underwent comprehensive ophthalmic examinations. Subfoveal choroidal thickness (SFCT) and central macular thickness (CMT) were evaluated by spectral domain optical coherence tomography (SD-OCT). The foveal avascular zone (FAZ), the microvascular morphology and density of SCP and DCP, and the choroicapillary morphology were assessed by OCTA or Image J software. All data in this study were presented as mean and standard deviations (SD) Results The mean±SD CMT (p=0.018), the mean±SD SFCT (p=0.013), the mean±SD microvascular density of DCP (p＜0.001) and choroicapillary layer (p＜0.001) at baseline were different from the ones at 3 months. The density of DCP was increased and choriocapillaris flow signal void was recovered at 3months in the process of self-resolve. Two eyes exhibited vascularized flat pigment epithelial detachment (FIPED) by OCTA. The en-face OCT can illstrate the area of the elongation of ellipsoid zone (EZ). Conclusions OCTA enables the visualization of microvascular features of the DCP and choroidcapillary in eyes with acute CSC in the process of self-resovle to help elucidate the pathophysiology. Vascularized FIPED could be obtained in acute CSC eyes by OCTA. OCTA imaging seems to be a useful tool in the identification of acute CSC.