CT-Angiographie der Koronararterien mit einem 16-Mehrzeilen-Spiral-CT Einfluss der räumlichen Auflösung auf die Bildqualität

PURPOSE

To evaluate image quality of coronary CT angiography with retrospectively ECG-gated 16 multi-slice spiral CT (MSCT), reconstructed with 0.75 mm slice thickness for optimal spatial resolution and with 1.3 mm slice thickness, to produce spatial resolution comparable to a 4-MSCT.

MATERIALS AND METHODS

Ten patients underwent coronary CT angiography with a 16-MSCT (Siemens Sensation 16, Forchheim, Germany) with 0.75 mm detector collimation. Raw helical CT data were retrospectively reconstructed using two different settings. Setting A: B20f smooth kernel, axial MPR with 1.3 mm slice thickness and 0.7 mm increment. Setting B: B35f "HeartView" medium-smooth kernel, 0.75 mm slice thickness, 0.5 mm increment. In the axial slices two regions of interest (ROIs) were placed in the area of the aortic root (AR) and more caudal in the area of the left ventricle (LV). Image noise was determined by the standard deviation of the CT numbers.Two readers determined visibility of coronary arteries by standardized maximum intensity projections (MIP) post-processing in left, right anterior and left anterior oblique projection plane from setting A and B. Each projection was rated on a five point rating scale concerning plaque delineation. Points determined for each data set were summed up and used for comparison.

RESULTS

No significant difference between the CT-numbers was found for setting A and B (A: 283.0 in AR/295.9 in LV and B: 282,9 in AR/297.2 in LV; p >0.2). However, the image noise was significantly different for setting A and B (A: 4.46 in AR/1.67 in LV and B: 8.16 in AR/7.38 in LV; p <0.01). Better delineation of the coronary arteries and atherosclerotic lesions could be achieved from MIP projections in setting B compared to setting A.

CONCLUSION

Higher image noise is present in coronary 16-MSCT with thin-slice reconstruction compared to simulated 4-MSCT. However the MIP-reconstructions benefit most from the higher spatial resolution.

[Influence of atracurium on cardiovascular parameters in horses undergoing vitrectomy during general anaesthesia, and on recovery duration and quality]

OBJECTIVE

In most ocular procedures, a central position of the eye is necessary. This can be achieved using a deep plane of anaesthesia, locoregional blocks or with neuromuscular blocking agents. The aim of this study was to evaluate the influence of atracurium on cardiovascular parameters, and on recovery quality and duration in horses.

MATERIAL AND METHODS

Thirty-four warmblood horses undergoing in total 50 vitrectomies were divided into two groups. Premedication, induction and maintenance were identical in all patients. After 20 minutes, horses of group A received atracurium (0.1 mg/kg) while in the control group (group K) the depth of anaesthesia was adapted to keep the bulbus in a central position. Dobutamine and fluids were administered to maintain the mean arterial blood pressure (MAP) above 70 mmHg. Cardiac output (CO), heart rate (HR), MAP, respiratory rate, end-expiratory isoflurane concentration (ETIso) and dobutamine requirements were determined. Position and movement of the globe during the surgical procedure were scored. Time and quality of the recovery period was scored.

RESULTS

Horses of group K required significantly higher concentrations of isoflurane (group A: 1.08 ± 0.1%; group K: 1.34 ± 0.2%) and had an overall lower MAP (group A: 88.4 ± 10.3 mmHg; group K: 76.6 ± 11.6 mmHg) and CO (group A: 36.9 ± 11.7 l/min; group K: 28.5 ± 7.2 l/min) but needed significantly more dobutamine (group A: 0.37 ± 0.17 μg/kg/min; group K: 0.99 ± 0.46 μg/kg/min) compared to group A. Complete relaxation occurred 9.5 ± 2.5 minutes after atracurium bolus and lasted for 25 ± 7.1 minutes. The score of the bulbus position and movement was significantly lower in group A, resulting in a better quality for the surgical procedure. In group A, the recovery time to standing was significantly shorter (group A: 18.1 ± 5.4 min; group K: 31.5 ± 7.1 min), with no difference in quality.

CONCLUSION AND CLINICAL RELEVANCE

The use of atracurium resulted in a better cardiovascular condition, probably because of the isoflurane-sparing effect. The recovery time was shorter in these horses without negative effects on recovery quality. No signs of residual atracurium effects were detected.

Einsatz von Atracurium bei der Vitrektomie des Pferdes

Gegenstand und Ziel: Eingriffe am Auge erfordern einen zentral und ruhig liegenden Bulbus, der sich mittels sehr tiefer Narkose, regionalanästhetischer Techniken oder peripherer Muskelrelaxanzien erreichen lässt. Ziel der Studie war, den Einfluss des peripheren Muskelrelaxans Atracurium auf den Relaxationsgrad der okulären Muskulatur, intraoperative Kreislaufparameter sowie Qualität und Dauer der Aufstehphase zu evaluieren. Material und Methoden: Die Untersuchung erfolgte an 34 Pferden (insgesamt 50 Vitrektomien), die randomisiert zwei Gruppen (je n = 17) zugeteilt wurden. Narkoseprämedikation, -induktion und -erhaltung waren identisch. Nach 20 Minuten wurde Pferden der Gruppe A Atracurium appliziert (0,1 mg/kg i. v.) und die Dauer der neuromuskulären Blockade mittels Nervenstimulator überwacht. In der Kontrollgruppe (Gruppe K) wurde bei Bedarf zur Relaxation der okulären Muskeln die Isoflurankonzentration erhöht. Die Applikation von Dobutamin erfolgte nach Wirkung, um einen mittleren arteriellen Blutdruck (MAP) von mindestens 70 mmHg zu erhalten. Folgende Parameter wurden ausgewertet: Herz- und Atemfrequenz, endexspiratorische Isoflurankonzentration (ETIso), MAP, Herzminutenvolumen (HMV), arterielle Blutgase, Dobutaminverbrauch, Dauer und Qualität der Aufstehphase. Zur Erfassung von Bulbusposition und -bewegung diente ein Score. Ergebnisse: In Gruppe K war für einen MAP von 76,6 ± 11,6 mmHg eine Dobutamindosis von 0,99 ± 0,46 μg/kg/min notwendig, in Gruppe A für einen MAP von 88,4 ± 10,3 mmHg 0,37 ± 0,17 μg/kg/min. Das durchschnittliche HMV betrug in Gruppe K 28,5 ± 7,2 l/min, in Gruppe A 36,9 ± 11,7 l/min. Dobutaminverbrauch und HMV differierten signifikant. Der mittlere ETISO war in Gruppe K mit 1,34 ± 0,16 Vol% signifikant höher als in Gruppe A mit 1,08 ± 0,1 Vol%. Innerhalb von 9,5 ± 2,5 Minuten nach Atracuriumgabe waren alle Pferde für 25 ± 7,5 Minuten vollständig relaxiert. Der Bulbus lag bis Operationsende zentral. Die Aufstehphase dauerte in Gruppe K signifikant länger als in Gruppe A (31,5 ± 7,1 vs. 18,1 ± 5,4 Minuten). Schlussfolgerung und klinische Relevanz: Eine Muskelrelaxation mit Atracurium erlaubt eine Einsparung von Inhalationsanästhetikum mit deutlich verbesserten Kreislaufparametern während der Vitrektomie. Neuromuskuläre Restblockaden konnten nicht beobachtet werden.

Necrosis of the nasal conchae in 12 horses

Twelve horses with a history of a unilateral malodorous nasal discharge were examined clinically, endoscopically and radiographically. The head of one of the horses was examined by computed tomography. Tissue samples were taken for microbiology from four of the horses and for histology from three. The conchal necrosis was unilateral in 11 of the horses and bilateral in the other, and no particular concha was affected more than the others. The affected tissue was removed transendoscopically with a polypectomy snare while the horses were sedated and standing. Mild disinfectants were used locally in six of the horses. After the removal of all the necrotic tissue, the affected concha healed without any complications in all 12 horses.

Reactivity of equine airways--a study on precision-cut lung slices

A study was performed to evaluate the use of precision-cut lung slices (PCLS) for studies on the contraction of equine airways. Lungs of 10 horses were taken to prepare PCLS of approximately 250 microm from equine lung tissue using a special microtome. The lung slices were cultured and the enclosed small airways were monitored using a microscope with coupled digital camera, which was used to determine the airway luminal area and diameter from digital images. As indicated by the beating of the ciliated epithelium and reactivity of airways on methacholine challenge, the tissue slices were found to be viable for at least 24 h. The airways were not precontracted, as indicated by a missing dilatory effect of 1 mmol/L clenbuterol. Bronchoconstriction induced by both methacholine and histamine was found to be dose dependent. EC(50) values based on luminal area were 1.12 micromol/L x / / 3.82 for methacholine and 0.68 micromol/L x / / 6.99 for histamine. In conclusion, the PCLS technique is promising for studies on small airways in the equine lung. In the present study the basic principles of in vitro (ex vivo) examinations with equine PCLS on airway reactivity were developed.

Effects of Two Different Dosages of Dobutamine on Pulmonary Artery Wedge Pressure, Systemic Arterial Blood Pressure and Heart Rate in Anaesthetized Horses

The purpose of the present study was to investigate the effects of two different dobutamine concentrations on pulmonary artery wedge pressure (PAWP) and on mean systemic arterial blood pressure (MAP) in horses anaesthetized with isoflurane, after induction of general anaesthesia with xylazine, ketamine and diazepam. Eight healthy warm-blood horses were included in the study. Each horse was subjected to general anaesthesia twice with two different dosages of dobutamine, 3 and 5 microg/kg bw/min, being infused over 15 min, starting 50 min after induction of general anaesthesia (T(0)). The heart rate, the PAWP and the MAP were recorded after 10 min (T(1)) and then every 5 min until 15 min after cessation of intravenous dobutamine administration (T(3)-T(5)). The PAWP was measured by a right heart catheter, which was positioned in the pulmonary capillaries. Mean systemic arterial blood pressure was monitored at the facial artery for the duration of general anaesthesia. All parameters increased at both dosage rates of dobutamine and decreased significantly when dobutamine administration ceased. The increase in heart rate was significantly higher after administration of 3 microg/kg bw/min dobutamine compared with the dosage of 5 microg/kg bw/min dobutamine. The increase in MAP was also higher at this dosage, but not significantly different to the dosage of 5 microg/kg bw/min dobutamine. During both dosages the MAP was above a value considered to be compatible with good peripheral circulation. The greater increase in PAWP was observed during administration of 5 g/kg bw/min dobutamine, but PAWP was not significantly different with the dosage of 3 microg/kg bw/min dobutamine. In conclusion, the administration of dobutamine led to an increase in MAP and PAWP above a value considered to be compatible with a good peripheral circulation. The results of the present study indicate that dobutamine improves circulation, in addition to its well-known effect on the periphery.

An unusual mucinous osteoma with features of an ossifying fibroma in the nasal cavity of a horse

A 4-month-old Warm-blooded colt presented with facial distorsion and an abnormal respiratory noise of 2 weeks' duration. A proliferative mass was found endoscopically and by computer tomography. Clinical differential diagnosis included cyst formation of the concha, malformation and neoplasia. Euthanasia was followed by post-mortem examination, which revealed a well-circumscribed, semi-solid, jelly like structure, measuring 14.5 x 9.0 x 12.0 cm, in the left posterior nasal cavity extending into the left frontal and maxillary sinus. Histologically, the mass consisted of trabeculae of woven bone, focal lamellar bone and fibroblast proliferation within a moderate fibro-vascular stroma. Abundant mucin production was noted within areas of fibroblastic differentiation. Some areas contained irregularly shaped spicules of osteoid rimmed by osteoblasts, randomly distributed within a moderately vascularized, fibro-osseous stroma. On the basis of the histopathological features, a nasal mucinous osteoma with focal ossifying fibroma-like structures was diagnosed.

[On the way to isotopic spatial resolution: technical principles and applications of 16-slice CT]

The broad introduction of multi-slice CT by all major vendors in 1998 was a milestone with regard to extended volume coverage, improved axial resolution and better utilization of the tube output. New clinical applications such as CT-examinations of the heart and the coronary arteries became possible. Despite all promising advances, some limitations remain for 4-slice CT systems. They come close to isotropic resolution, but do not fully reach it in routine clinical applications. Cardiac CT-examinations require careful patient selection. The new generation of multi-slice CT-systems offer simultaneous acquisition of up to 16 sub-millimeter slices and improved temporal resolution for cardiac examinations by means of reduced gantry rotation time (0.4 s). In this overview article we present the basic technical principles and potential applications of 16-slice technology for the example of a 16-slice CT-system (SOMATOM Sensation 16, Siemens AG, Forchheim). We discuss detector design and dose efficiency as well as spiral scan- and reconstruction techniques. At comparable slice thickness, 16-slice CT-systems have a better dose efficiency than 4-slice CT-systems. The cone-beam geometry of the measurement rays requires new reconstruction approaches, an example is the adaptive multiple plane reconstruction, AMPR. First clinical experience indicates that sub-millimeter slice width in combination with reduced gantry rotation-time improves the clinical stability of cardiac examinations and expands the spectrum of patients accessible to cardiac CT. 16-slice CT-systems have the potential to cover even large scan ranges with sub-millimeter slices at considerably reduced examination times, thus approaching the goal of routine isotropic imaging.

[Verrucous pastern dermatitis syndrome in heavy draught horses. Part II: Clinical findings]

In the present field study the skin of the feet of 37 heavy draught horses of different breeds showing verrucous pastern dermatitis was examined clinically. Included were the degree of severity of the disease and the prevalence of anatomically normal structures associated with the skin: fetlock tufts of hair ("feathering"), ergots, chestnuts, bulges in the pastern region, cannon circumference. Each horse was examined for Chorioptes sp. skin mites. Information was also collected on the development of the skin alterations and housing conditions and feeding. These individual data were correlated with the clinical degree of severity of verrucous pastern dermatitis, which was evaluated using a numerical code (scoring system). In addition, punch biopsies were taken from the diseased skin of the feet and from healthy skin of the neck for comparative patho-histological examination (see Part III). Verrucous pastern dermatitis is a chronic disease which can be divided into four groups: scaling (group I), hyperkeratotic and hyperplastic plaque-like lesions (group II), tuberous skin masses (group III), and verrucous skin lesions with rugged surfaces (group IV). No correlation was found between the clinical degree of severity of the skin lesions and sex, breed, amount of work, use of stallions for breeding, grooming condition of the hair, white markings in the foot region, or Chorioptes sp. infestation. In regard to feeding it was found that the amount of maize and oats fed had some influence on the clinical degree of severity. Statistical analysis revealed a significant correlation between the clinical degree of severity and the age, the grooming condition of the hooves, and the mean cannon circumference. The prevalence of fetlock tufts of hair, chestnuts, ergots, and anatomically normal bulges in the pastern region also increased significantly with the clinical degree of severity. Furthermore the study revealed that the clinical degree of severity depended on the hygienic conditions of the stables and of the ground where the horses were kept outdoors.

[The development of verrucous pastern dermatitis syndrome in heavy draught horses. Part I: Review of the literature]

Verrucous pastern dermatitis is a chronic hyperplastic dermatopathy of the feet of horses which is characterized by a greasy, odorous coating of the skin and, in advanced stages, by clearly demarcated calluses and wart-like proliferations. The disease occurs almost exclusively in cold-blooded and other heavy horses, with certain breeds affected most frequently. It is considered a distinct disease entity within the framework of pastern dermatitis syndrome. There is no consensus in the literature about relationship of the disease to the sex and age of the horse. Horses with a high cannon circumference and pronounced fetlock tufts of hair seem to be affected most severely. In chiefly anecdotal reports the cause of the disease or its aggravation has been ascribed to housing conditions and environmental influences, chemicals, mechanical insults, feeding, or infections with Chorioptes skin mites. It thus seems likely that the disease is affected by a variety of factors. Although verrucous pastern dermatitis has been known for hundreds of years, its etiology and pathogenesis remain unclear.