Sooyoung Choi

Jerky hemi-seesaw nystagmus and head tilt reaction combined with internuclear ophthalmoplegia from a pontine infarction

Internuclear ophthalmoplegia (INO) is a complex ocular motility disorder caused by damage to the medial longitudinal fasciculus. The occurrence of hemi-seesaw nystagmus in an INO patient has been reported rarely. This nystagmus may be caused by damage to the pathway from the contralateral vertical semicircular canal. The ocular tilt reaction is characterized by ipsilateral head and neck tilt, skew deviation, and ocular torsion. We report a patient who presented with hemi-seesaw nystagmus, ocular tilt reaction, and limb ataxia combined with an INO from a right focal pontine infarction. INO may be accompanied by a variety of ocular findings associated with the disruption of the medial longitudinal fasciculus.

Establishment of optimal scan delay for multi-phase computed tomography using bolus-tracking technique in canine pancreas

To establish a protocol for a multi-phase computed tomography (CT) of the canine pancreas using the bolus-tracking technique, dynamic scan and multi-phase CT were performed in six normal beagle dogs. The dynamic scan was performed for 60 sec at 1-sec intervals after the injection (4 ml/sec) of a contrast medium, and intervals from aortic enhancement appearance to aortic, pancreatic parenchymal and portal vein peaks were measured. The multi-phase CT with 3 phases was performed three times using a bolus-tracking technique. Scan delays were 0, 15 and 30 in first multi-phase scan; 5, 20 and 35 in second multi-phase scan; and 10, 25 and 40 sec in third multi-phase scan, respectively. Attenuation values and contrast enhancement pattern were analyzed from the aorta, pancreas and portal vein. The intervals from aortic enhancement appearance to aortic, pancreatic parenchymal and portal vein peaks were 3.8 ± 0.7, 8.7 ± 0.9 and 13.3 ± 1.5 sec, respectively. The maximum attenuation values of the aorta, pancreatic parenchyma and portal vein were present at scan sections with no scan delay, a 5-sec delay and a 10-sec delay, respectively. When a multi-phase CT of the canine pancreas is triggered at aortic enhancement appearance using a bolus-tracking technique, the recommended optimal delay times of the arterial and pancreatic parenchymal phases are no scan delay and 5 sec, respectively.

Evaluation of glomerular filtration rate by use of dynamic computed tomography and Patlak analysis in clinically normal cats

OBJECTIVE To obtain quantitative variables of the abdominal aorta and both kidneys on the basis of time-attenuation curves (TACs) and to measure glomerular filtration rate (GFR) for each kidney and the global GFR in clinically normal cats by use of dynamic computed tomography (CT) and Patlak analysis. ANIMALS 9 healthy cats. PROCEDURES All the cats were anesthetized with propofol. Anesthesia was maintained by administration of isoflurane, and CT examination was performed in the anesthetized cats. The TACs and renal volume were measured by use of the baseline precontrast and single-slice dynamic scans. The CT-GFR of each kidney and the global CT-GFRs were calculated via Patlak plot analysis. RESULTS CT-GFR results from 7 cats were valid. Peak aortic enhancement was detected between 9.0 and 14.0 seconds after iohexol injection, and the initial peak time of renal parenchymal enhancement was 15 to 24 seconds after iohexol injection. Mean ± SD global GFR was 2.06 ± 0.62 mL/min/kg. Mean ± SD CT-GFR of the right and left kidneys was 0.97 ± 0.32 mL/min/kg and 1.05 ± 0.31 mL/min/kg, respectively. CONCLUSIONS AND CLINICAL RELEVANCE The CT-GFR method can be rapidly and conveniently performed in clinically normal cats. This combined structural-functional approach provided physiologic and morphological information on the kidneys of cats.

Classification and Serial Evolution of PLEDs

Background and Purpose Periodic lateralized epileptiform discharges (PLEDs) are defined as spikes or sharp waves occurring at an approximately regular interval. PLEDs are subdivided into PLEDs proper and PLEDs plus in Reihers classification, but since this does not sufficiently reflect the pleomorphism of PLEDs, we propose a new subclassification scheme of PLEDs, and discuss the relationship between them and clinical prognoses. Methods Thirty-seven patients who had at least two available EEGs were included in this study. Each patient had structural brain lesions identified in brain CT/MRI: 237 EEGs from 37 patients were reviewed and the patterns of PLEDs were classified by electroencephalographic characteristics based on Reihers classification. PLEDs proper of class 3 were subclassified into four categories: (1) simple, (2) benign, (3) vigorous, and (4) suppressed. Results Most of the PLEDs that started with the vigorous or suppressed pattern of class 3 evolved into the simple or benign pattern of class 3 and subsequently changed into class 1 or class 2, finally intermingling with the neighboring background waves. PLEDs that started with the benign or simple pattern of class 3 rapidly changed into class 1 or 2. Patients showing the benign or simple pattern of class 3 exhibited a better clinical prognosis. Conclusions PLEDs have five distinctive classes, and over time they evolve from malignant PLEDs plus to benign PLEDs proper before finally disappearing. It appears that those of class 3 have more diverse patterns, with the vigorous and suppressed patterns being the more malignant forms of PLEDs in this class.

Optimal scan delay depending on contrast material injection duration in abdominal multi-phase computed tomography of pancreas and liver in normal Beagle dogs

This study was conducted to establish the values for optimal fixed scan delays and diagnostic scan delays associated with the bolus-tracking technique using various contrast material injection durations in canine abdominal multi-phase computed tomography (CT). This study consisted of two experiments employing the crossover method. In experiment 1, three dynamic scans at the porta hepatis were performed using 5, 10 and 15 sec injection durations. In experiment 2, two CT scans consisting of five multi-phase series with different scan delays of 5 sec intervals for bolus-tracking were performed using 5, 10 and 15 sec injection duration. Mean arrival times to aortic enhancement peak (12.0, 15.6, and 18.6 sec for 5, 10, and 15 sec, respectively) and pancreatic parenchymal peak (17.8, 25.1, and 29.5 sec) differed among injection durations. The maximum mean attenuation values of aortas and pancreases were shown at the scan section with 0 and 5, 0 and 10 and 5 and 10 sec diagnostic scan delays during each injection duration, respectively. The optimal scan delays of the arterial and pancreatic parenchymal phase in multi-phase CT scan using fixed scan delay or bolus-tracking should be determined with consideration of the injection duration.

Imaging characteristics of persistent left cranial vena cava incidentally diagnosed with computed tomography in dogs

Persistent left cranial vena cava (PLCVC) is an uncommon congenital thoracic venous anomaly in dogs. This study examines the clinical and CT findings of dogs diagnosed with PLCVC incidentally. In this study, complete type of PLCVC was diagnosed in 26 dogs with CT angiography. Shih tzu (17 cases) and Pekingese dogs (3 cases) were overrepresented. There was no gender predisposition, and the average age at presentation was 10.3 years. Of 26 dogs, one dog had a bridging vein connecting right and left cranial vena cavae, and another dog showed azygos vein terminating PLCVC. On the thoracic CT images in the third dog, the right cranial vena cava was absent so that right brachiocephalic vein ended to PLCVC. However, the right costocervical vein drained another vein coursing caudally to the right atrium with azygos vein. In conclusion, CT angiography is a very useful method to diagnose PLCVC and variations of related thoracic vein anomalies in dogs.

Contrast enhanced ultrasonography of kidney in conscious and anesthetized beagle dogs

Contrast enhanced ultrasound (CEUS) is useful to evaluate tissue perfusion in the kidney. In veterinary medicine, sedation or anesthesia may be required in uncooperative or panting patients. The aim of this study was to evaluate and compare the normal kidney perfusion patterns in conscious and anesthetized dogs using CEUS. Eight healthy beagles were used in this study. Scanning was performed in conscious dogs using manual restraint (conscious group), or under general anesthesia using tiletamine-zolazepam and medetomidine (TZM group) or medetomidine (M group). The contrast agent (Sonovue®) was administered as an IV bolus. The peak intensity (PI), time to peak enhancement from injection (TTP0) and the time to peak enhancement from the initial rise (TTPup), upslope, downslope and area under the curve (AUC) were analyzed. Compared to the cortical values in the conscious group, TTP0 was significantly delayed in the TZM group, and upslope, TTP0 and TTPup were significantly different in the M group. The AUCs in the TZM and M groups were not different from those in the conscious group. The upslope of renal medullary perfusion was significantly decreased in the TZM and M groups. TTP0 and TTPup were also significantly delayed in these groups. The AUC of the medulla was significantly decreased in the M group. Therefore, TZM is useful as an anesthetic protocol when performing CEUS, and the obtained data may serve as reference values in the evaluation of renal perfusion using CEUS in dogs under anesthesia.

Multi-voxel magnetic resonance spectroscopy of cerebral metabolites in healthy dogs at 1.5 Tesla

This study was conducted to measure the difference in levels of cerebral metabolites in the right and left hemispheres, gray (GM) and white matter (WM), imaging planes, and anatomical regions of healthy dogs to establish normal variations. Eight male Beagle dogs (1 to 4 years of age; mean age, 2 years) with no evidence of neurologic disease were studied. Using the multi-voxel technique on a 1.5 Tesla magnetic resonance imaging scanner, metabolite values (N-acetyl aspartate [NAA], choline [Cho], creatine [Cr]) were obtained from the frontoparietal WM, parietal GM, temporal GM, occipital GM, thalamus, cerebellum, mid-brain, and pons. There was no significant difference in levels of these metabolites between the right and left in any locations or between the GM and WM in the cerebral hemispheres. However, there were significant differences in metabolite ratios within imaging planes. The NAA/Cr was lower in the cerebellum than other regions and the thalamus had a higher Cho/Cr and lower NAA/Cho ratio than in other regions. The spectral and metabolic values will provide a useful internal reference for clinical practice and research involving multi-voxel magnetic resonance spectroscopy. Measurement of metabolite values in the transverse plane is recommended for comparing levels of regional metabolites.

Clinical experience of MRI in two dogs with muscle-invasive transitional cell carcinoma of the urinary bladder.

This study described high-field magnetic resonance imaging (MRI) and computed tomography (CT) characteristics of muscle-invasive bladder transitional cell carcinoma (TCC) in two dogs. Ultrasonography revealed a urinary bladder mass with ambiguous result about invasion to the muscular layer. Contrast-enhanced CT showed that the bladder wall in which the mass was attached was more intensely enhanced than the normal bladder walls, supporting invasion to the muscular layer. The mass revealed an intermediate signal intensity with interruption of the hypointense muscular layer on T2-weighted MRI and showed greater enhancement compared with the normal bladder wall on postcontrast T1-weighted images. T2-weighted MRI, postcontrast T1-weighted MRI and contrast-enhanced dual-phasic CT were useful for evaluating muscle-invasive bladder TCC in dogs.

Diagnosis of a large splenic tumor in a dog: computed tomography versus magnetic resonance imaging

This study demonstrated magnetic resonance imaging (MRI) and computed tomography for large-sized splenic hemangiosarcoma. Radiography and ultrasonography revealed the presence of a large-sized soft-tissue mass in the cranial abdomen. Computed tomography showed hypoattenuating mass. The mass was located in contact with liver, spleen and stomach, and the origin of the mass remained ambiguous. The mass was T2-hyperintense and T1-hypointense with mild contrast enhancement. MRI allowed a differentiation between large-sized tumor and neighboring normal structure, and the mass was consequently identified as arising from spleen. These results suggested that MRI might be a useful tool to visualize large-sized splenic tumors and improve the accuracy of diagnosis.