Introdução: O uso da tomografia de múltiplos detectores para avaliar a doença arterial coronariana tem aumentado, fornecendo informações valiosas para rotina clínica. O risco potencial da exposição à radiação, por outro lado, exige manter a dose de radiação tão baixo quanto razoavelmente possível. Objetivo: testar e avaliar o ajuste de parâmetros de aquisição no bolus tracking (BT) para reduzir a dose de radiação nos exames de angiotomografias das artérias coronárias (ATCC), sem comprometer a qualidade da imagem. Métodos: Este é um estudo prospectivo de 289 pacientes que realizaram ATCC. Os pacientes foram distribuídos consecutivamente em 4 grupos: A (n = 70), B (n = 79), C (n = 68) e D (n = 72). O grupo A foi o protocolo de referência - recomendado pelo fabricante do tomógrafo. As imagens dos outros grupos foram adquiridas por parâmetros de configuração diferentes do BT, em tempo, para alcançar a redução da dose de radiação. As imagens da fase da angiografia, para todos os grupos, foram realizadas com configurações semelhantes. Foram avaliados parâmetros de qualidade de imagem qualitativa e quantitativamente e a exposição da radiação. Resultados: A dose de radiação do BT foi significativamente diferente entre os grupos, principalmente quando comparados os grupos D e A (p < 0,001), grupos C e A (p < 0,001) e grupos B e A (p < 0,001), com a maior redução no grupo D (redução de 50% em relação ao grupo A). Não houve nenhuma diferença significativa entre os grupos em relação à dose de radiação efetiva e à qualidade de imagem da fase angiográfica. No entanto, a dose de radiação efetiva total (BT + fase angiográfica) foi estatisticamente diferente entre os grupos A e D (p = 0,025). Conclusão: O ajuste do tempo para a aquisição do BT reduz significativamente a dose de radiação efetiva em até 50%, sem reduzir a qualidade da imagem, oferecendo uma nova perspectiva para a redução da radiação total durante a ATCC / Introduction: Modern multidetector computed tomography scanners for assessing coronary artery disease have been growing in use, providing valuable information in clinical routine. The potential risk of radiation exposure, on the other hand, requires keeping radiation dose as low as reasonably achievable. Objectives: Test and evaluate the bolus tracking (BT) acquisition parameters adjustment to reduce radiation dose in coronary computed tomography angiography (CCTA), without compromising image quality. Methods: This is a prospective study of 289 patients referred to CCTA. Patients were consecutively distributed into 4 groups: A (n=70), B (n=79), C (n=68) and D (n=72). Group A was the reference protocol - recommended by the scanner manufacturer. The images of other groups were acquired by setting different time BT parameters in order to achieve radiation dose reduction. The images of angiography phase for all groups were performed with similar settings. Qualitative and quantitative image quality parameters and radiation exposures were evaluated. BT radiation dose was significantly different among groups, mainly when comparing groups D and A (p < 0.001), groups C and A (p < 0.001) and groups B and A (p < 0.001), with the highest reduction in group D (50% reduction in relation to group A). There was no significant difference between groups regarding effective radiation dose for the angiographic phase or image quality. However, total effective radiation dose (BT + angiographic phase) was statistically different between groups A and D (p= 0.025). Conclusion: Time adjustment of BT acquisition significantly reduces effective radiation dose in up to 50%, without reducing image quality, offering a new perspective for total radiation reduction during CCTA

Introdução: O uso da tomografia de múltiplos detectores para avaliar a doença arterial coronariana tem aumentado, fornecendo informações valiosas para rotina clínica. O risco potencial da exposição à radiação, por outro lado, exige manter a dose de radiação tão baixo quanto razoavelmente possível. Objetivo: testar e avaliar o ajuste de parâmetros de aquisição no bolus tracking (BT) para reduzir a dose de radiação nos exames de angiotomografias das artérias coronárias (ATCC), sem comprometer a qualidade da imagem. Métodos: Este é um estudo prospectivo de 289 pacientes que realizaram ATCC. Os pacientes foram distribuídos consecutivamente em 4 grupos: A (n = 70), B (n = 79), C (n = 68) e D (n = 72). O grupo A foi o protocolo de referência - recomendado pelo fabricante do tomógrafo. As imagens dos outros grupos foram adquiridas por parâmetros de configuração diferentes do BT, em tempo, para alcançar a redução da dose de radiação. As imagens da fase da angiografia, para todos os grupos, foram realizadas com configurações semelhantes. Foram avaliados parâmetros de qualidade de imagem qualitativa e quantitativamente e a exposição da radiação. Resultados: A dose de radiação do BT foi significativamente diferente entre os grupos, principalmente quando comparados os grupos D e A (p < 0,001), grupos C e A (p < 0,001) e grupos B e A (p < 0,001), com a maior redução no grupo D (redução de 50% em relação ao grupo A). Não houve nenhuma diferença significativa entre os grupos em relação à dose de radiação efetiva e à qualidade de imagem da fase angiográfica. No entanto, a dose de radiação efetiva total (BT + fase angiográfica) foi estatisticamente diferente entre os grupos A e D (p = 0,025). Conclusão: O ajuste do tempo para a aquisição do BT reduz significativamente a dose de radiação efetiva em até 50%, sem reduzir a qualidade da imagem, oferecendo uma nova perspectiva para a redução da radiação total durante a ATCC / Introduction: Modern multidetector computed tomography scanners for assessing coronary artery disease have been growing in use, providing valuable information in clinical routine. The potential risk of radiation exposure, on the other hand, requires keeping radiation dose as low as reasonably achievable. Objectives: Test and evaluate the bolus tracking (BT) acquisition parameters adjustment to reduce radiation dose in coronary computed tomography angiography (CCTA), without compromising image quality. Methods: This is a prospective study of 289 patients referred to CCTA. Patients were consecutively distributed into 4 groups: A (n=70), B (n=79), C (n=68) and D (n=72). Group A was the reference protocol - recommended by the scanner manufacturer. The images of other groups were acquired by setting different time BT parameters in order to achieve radiation dose reduction. The images of angiography phase for all groups were performed with similar settings. Qualitative and quantitative image quality parameters and radiation exposures were evaluated. BT radiation dose was significantly different among groups, mainly when comparing groups D and A (p < 0.001), groups C and A (p < 0.001) and groups B and A (p < 0.001), with the highest reduction in group D (50% reduction in relation to group A). There was no significant difference between groups regarding effective radiation dose for the angiographic phase or image quality. However, total effective radiation dose (BT + angiographic phase) was statistically different between groups A and D (p= 0.025). Conclusion: Time adjustment of BT acquisition significantly reduces effective radiation dose in up to 50%, without reducing image quality, offering a new perspective for total radiation reduction during CCTA

Einleitung: Der portosystemische Shunt (PSS) stellt eine vaskuläre Anomalie dar, die eine direkte venöse Kommunikation des portalen mit dem systemischen Kreislauf ermöglicht. Für die Bestätigung oder den Ausschluss eines makroskopischen PSS ist bildgebende Diagnostik unerlässlich. In der vorliegenden Arbeit wurden computertomographische (CT)-Portographie und Splenoportographie als nicht- bzw. minimalinvasive Verfahren zur Diagnose von PSS beim Hund untersucht. Ziel der Studie war ein Vergleich von CT-Portographie mittels Bolus Tracking (BT) und jeju-naler Portographie im Hinblick auf die Genauigkeit der Shuntlokalisation (intra-, extrahepatisch) und des Shunttyps (Ursprungs- und Mündungsgefäß bei extrahepatischen PSS; rechts-, linksseitig oder zentral bei intrahepatischen PSS). Zudem sollte das BT zur Abschätzung des korrekten Scanzeitpunktes in der CT evaluiert werden (Gruppe 1). In Gruppe 2 sollte mit Hilfe der ultraschallgestützten Splenoportographie die Darstellbarkeit des Portalvenensystems zur Diagnose und Charakterisierung eines PSS sowie Komplikationen durch dieses Verfahren eva-luiert werden. Zudem wurde die Nutzung der ultraschallgestützten Splenoportographie zur Beurteilung eines Restshuntflusses nach chirurgischem Shuntverschluss untersucht. Tiere, Material und Methoden: In die retrospektive Studie wurden Hunde aus dem Patientengut der Klinik für Kleintiere von Februar 2000 bis Dezember 2017 eingeschlossen, bei denen der Verdacht auf einen PSS bestand. Bei Tieren der Gruppe 1 wurde zunächst eine CT-Kontrastmittelstudie durchgeführt, in der Shuntlokalisation und Shunttyp klassifiziert wurden. Diese wurden mit den Befunden der anschließenden jejunalen Porto¬graphie verglichen. Der korrekte Scanzeitpunkt in der CT wurde mit Hilfe des BT ermittelt. Zur Objektivierung des korrekten Scanstarts in der portalvenösen Phase und zur Abgrenzung des Portalvenensystems zum umliegenden Lebergewebe wurden die Schwächungsprofile in der V. portae vor und nach Kontrastmittelgabe sowie im Leberparenchym ermittelt. Eine Kontrastmitteldifferenz zwischen der Portalvene und der Leber von mehr als 50 HU wurde als ausreichend definiert. In der Gruppe 2 wurde mit Hilfe uniplanarer Durchleuchtungsgeräte eine ultraschallgestützte Splenoportographie durchgeführt. Auswertbarkeit des Splenoportogramms und mög-liche Komplikationen sowie Auftreten und Grad des intraabdominalen Kontrastmittelaustrittes wurden notiert. Quantitative Daten wurden auf Normalverteilung getestet (Shapiro-Wilk-Test). Vergleiche zwischen Variablen wurden mit dem Wilcoxon-Mann-Whitney-Test, dem Kruskal-Wallis-Test bzw. dem exakten Test nach Fisher durchgeführt. Ergebnisse: Bei 54 der 59 Patienten (91,5 %) der Gruppe 1 stimmte die Lokalisation und der Typ des PSS in CT-Portographie und jejunaler Portographie überein. Bei 5 Hunden erfolgte hingegen eine differierende Befundung hinsichtlich der Shuntlokalisation (n = 2) oder des Shunttyps (n = 3) in der CT-Portographie. Bei 13 Hunden (22,0 %) lag die Differenz zwischen dem Enhancement der Portalvene und des Leberparenchyms in der CT unter den geforderten 50 HU, bei 46 Hunden (77,9 %) lag sie darüber. Dennoch war bei allen Hunden eine sichere Identifikation der V. portae nach CT-Angiographie mittels Bolus Trackings möglich. Bei allen 42 Tieren der Gruppe 2 ermöglichte die ultraschallgestütze Splenoportographie eine adäquate Darstellung des Portalvenensystems. Bei 25 Hunden konnte ein PSS ausgeschlossen, bei 10 ein PSS diagnostiziert werden. Komplikationen oder Blutungen wurden nicht beobachtet. Bei 18 Hunden trat kein, bei 13 ein geringgradiger, bei 7 ein mittelgradiger und bei 4 ein hochgradiger Kontrastmittelaustritt auf. Es lag kein Zusammenhang zwischen dem Grad des intraperitonealen Kontrastmittelaustrittes und dem Gewicht und der Lagerung der Hunde oder der Induktion einer Apnoephase vor. Schlussfolgerungen: Die CT-Portographie lässt eine sichere Klassifizierung der Shuntform bei Hunden mit PSS zu. Die diagnostische Wertigkeit der nicht invasiven CT-Portographie mit Hilfe von BT ist vergleichbar mit der jejunalen Portographie. Durch das BT wurde eine gute Synchronisation des Kontrastmittelbolus mit dem Scanstart erreicht und eine adäquate Kontrastierung des Portalvenensystems ermöglicht. Die Splenoportographie unter sonographi-scher Kontrolle stellt ebenfalls ein sicheres minimalinvasives Diagnostikum zur Diagnose bzw. zum Ausschluss portalvenöser Anomalien dar.

Computed tomography (CT) is gaining popularity as a minimally invasive diagnostic modality in veterinary science. The use of contrast agents is well described and used with increasing frequency, having marked benefits over the invasive angiographic procedures used previously. Methods to perform CT angiographic (CTA) studies include bolus tracking, test bolus and empirical scan delay techniques. In human medicine, empirical scan delays have been extensively investigated but due to the marked patient variability encountered in veterinary medicine, this technique cannot, at this stage, be confidently used. This then poses the question that if both techniques can be used, is one significantly better than the other one when performing, in particular thoracic CTA? CTA studies were performed on 6 adult beagles, using the bolus tracking (BT) technique and the test bolus (TB) technique on two separate occasions, at least 2 weeks apart. Each beagle acted as its own control. The patients were placed under general anaesthesia. Two ml/kg of 300mgI/ml iodinated contrast agent was injected through a 20 gauge catheter place in the cephalic vein for the BT technique. Scans were initiated when the contrast in the aorta reached 150 Hounsfield units (HU). For the TB technique, the dogs received a test dose of 15% of 2ml/kg of 300mgI/ml iodinated contrast agent injected manually into the cephalic catheter, followed by a series of low dose sequential scans. Time attenuation curves were generated using dynamic evaluation software programs (DYNAEVA®). The full dose of 2ml/kg of the 300mgI/ml iodinated contrast agent was then administered and the scans were conducted at optimal times as identified from the time attenuation curves. The full dose of contrast administration was administered using a pressure injector operated at 3ml/sec and was followed by a manual saline flush for all studies. Mean attenuation in HU was taken at three consecutive levels in the aorta (Ao), caudal vena cava (CVC) and right caudal pulmonary artery (rCPA) by placing a region of interest (ROI) in the vessel of interest. These observations were done for both arterial and venous phases using the BT and TB studies in five of the six dogs. Additional observations included the visualisation of the smaller thoracic vessels, in particular the arteries, the study duration, milliampere (mA), computed tomography dose index volume (CTDI(vol)), dose length product (DLP) and the pressure and the duration of the contrast injection. These observations were done in all six dogs. Statistical analysis included the comparison of the attenuation achieved in the major vessels (Ao, CVC and rCPA) for the two techniques. The test bolus technique was deemed to be the gold standard, as this is adapted for each individual patient. In one beagle the study was considered non diagnostic with a later time to peak enhancement noted in the Ao than the CVC. No statistical analysis was done on the dynamic and attenuation data obtained in this dog. In all the other studies, the attenuation achieved in the vessels evaluated was deemed to be of diagnostic quality except for the attenuation achieved in the CVC during the arterial phase. The attenuation in the Ao during the arterial phase for the BT technique was not significantly different (660.52 HU ± 138.49) than the TB technique (469.82 HU ± 199.52)(p = 0.13). The attenuation in the Ao during the venous phase for the BT and TB techniques was also not significantly different (BT = 190.6 HU ± 28.29 and TB = 188.8 HU ± 21.9, p = 0.92). The attenuation in the CVC during the arterial phase and venous phases for the BT techniques were not significantly different (arterial phase BT = 37.84 HU ± 20.8, arterial phase TB = 91.48 HU ± 66.54, p = 0.069; venous phase BT = 171.3 HU ± 32.36, venous phase TB = 191.08 HU ± 19.59, p = 0.087). The attenuation in the rCPA during the arterial phase was not statistically different between the two techniques (BT= 606.34 HU ± 143.37 and TB = 413.72 HU ± 174.99, p = 0.28), nor was the attenuation in the rCPA during the venous phase (BT = 174.34 HU ± 27.25 and TB = 164.46 HU ± 18.51, p = 0.51). The mean mA for the BT technique (3538.5 ± 171.27) was significantly lower than the TB technique (3929.6 ± 312.3) with p = 0.024. The mean CTDI(vol) for the BT technique (24.42 ± 11.89) was significantly lower than the TB CTDI(vol) (45.32 ± 0.94) with a p-value of 0.013. The mean DLP did not differ significantly between the two techniques (BT = 139.1 ± 7.65, TB = 162.8 ± 33.1) (p = 0.12). The BT technique resulted in a significantly shorter procedural duration and utilised less contrast material than the TB technique. The injection duration and injection pressures did not differ significantly between the two techniques (p = 0.23 and p = 0.62 respectively). This study identifies that there is no preference for either technique when evaluating the Ao, CVC or rCPA, however, the BT technique is shown to be shorter in procedural duration, utilises less contrast material and results in less radiation dose to the patient when compared to the TB technique. Copyright / Dissertation (MMedVet)--University of Pretoria, 2011. / Companion Animal Clinical Studies / unrestricted

Hintergrund und Fragestellung Um den Zeitpunkt des Beginns der Datenakquisition bei der CT-Koronarangiographie festzulegen, bietet die Methode des Bolus-Trackings eine weit verbreitete Möglichkeit. Hierfür muss eine sogenannte Region of Interest (ROI) festgelegt werden, in der die Kontrastmittelanflutung gemessen wird. Bisher wurden die Auswirkungen unterschiedlicher Positionierungen dieser ROI auf die Bildqualität der Koronararterien (Hauptstamm der linken Koro-nararterie: LM; rechte Koronararterie: RCA) noch nicht systematisch untersucht. Zwei häufig verwendete Positionen sind der linke Herzvorhof (LV) und die Aorta ascendens (AA). Diese Positionierungen sollten in dieser Studie verglichen werden. Auch bei der Triple-Rule-Out-CT-Angiographie (TRO-CTA), in der zusätzlich zu den Koronararterien auch die Pulmonalarterien sowie die thorakale Aorta beurteilt werden sollen, kommt das Bolus-Tracking zur Anwendung. Die ROI wird hierbei meist im linken Herzvorhof positioniert. Da bisher nicht gezeigt wurde, ob die Pulmonalarterien (rechte Pulmonalarterie: RPA; linke Pulmonalarterie: LPA) dadurch tatsächlich in besserer Qualität dargestellt werden, sollte auch diese Frage in der Studie beantwortet werden. Methode Alle Patienten der vorliegenden monozentrischen, retrospektiven Studie erhielten eine CT-Koronarangiographie im Step-and-Shoot-Modus zum Ausschluss einer koronaren Herzkrankheit bei intermediärem Risiko. Mittels Propensity-Score-Matching wurden insgesamt 192 Patienten für die Studie ausgewählt: je 96 mit Positionierung der ROI im linken Vorhof bzw. in der Aorta ascendens (122 männliche und 70 weibliche Patienten, Alter 21 bis 87 Jahre, Durchschnittsalter 61 Jahre). Um möglichst ähnliche Patientencharakteristika in beiden Gruppen zu erreichen, wurden beim Propensity-Score-Matching folgende Faktoren berücksichtigt: Geschlecht, Körpergröße, Körpergewicht und Herzfrequenz. Für die Beurteilung der Bildqualität wurden sowohl ein quantitativer als auch ein qualitativer Score verwendet. Bei der quantitativen Analyse wurden die Signalintensitäten sowie deren Standardabweichungen in den zu beurteilenden Strukturen gemessen und daraus die Signal-Rausch-Verhältnisse (SNR) errechnet. Die qualitative Auswertung wurde von zwei Fachärzten für Radiologie mit 10 bzw. 6 Jahren Erfahrung in der CT-Koronarangiographie unabhängig voneinander mit Hilfe einer 5-Punkte-Likert-Skala durchgeführt. So wurde zum einen die Qualität der Darstellung der Koronararterien verglichen, zum anderen die der Pulmonalarterien. Für die statistische Auswertung wurde der Wilcoxon-Test verwendet, um die quantitativen sowie qualitativen Scores beider Patientengruppen miteinander zu vergleichen. Außerdem wurde bezüglich der qualitativen Analyse die Interrater-Reliabilität mittels gewichtetem Cohens Kappa (κ) bestimmt. Zusätzlich wurde die Strahlenbelastung beider Gruppen durch die Betrachtung der Dosis-Längen-Produkte sowie die Berechnung der effektiven Dosen verglichen. Ergebnisse Bezüglich der Koronararterien fanden sich sowohl beim Vergleich der quantitativen (SNR AA 14.92 vs. 15.46; p = 0.619 | SNR LM 19.80 vs. 20.30; p = 0.661 | SNR RCA 24.34 vs. 24.30; p = 0.767) als auch der qualitativen Scores (4.25 vs. 4.29; p = 0.672) keine signifikanten Unterschiede in beiden Gruppen. Für die Darstellung der Pulmonalarterien hat die Position der ROI allerdings eine entscheidende Bedeutung. Bei einer Positionierung im linken Vorhof ergeben sich signifikant höhere quantitative (SNR RPA 8.70 vs. 5.89; p < 0.001 | SNR LPA 9.06 vs. 6.25; p < 0.001) und auch qualitative Scores (3.97 vs. 2.24; p < 0.001) als bei einer Positionierung in der Aorta ascendens. Bezüglich der Interrater-Reliabilität konnte in dieser Studie eine beachtliche Konkordanz bei der Analyse der Koronararterien (κ = 0.654) bzw. eine nahezu vollkommene Konkordanz bei der Analyse der Pulmonalarterien (κ = 0.846) festgestellt werden. Die Strahlenbelastung war in beiden Gruppen nahezu identisch (4.13 mSv vs. 4.13 mSv; p = 0.501). Schlussfolgerung Für CT-Angiographien mit ausschließlich koronarer Indikation bedeutet dieses Ergebnis, dass die Positionierung der ROI für das Bolus-Tracking in der Aorta ascendens bzw. im linken Herzvorhof zu gleichwertigen Ergebnissen bezüglich der Bildqualität führen und somit die aktuell von vielen Untersuchern bevorzugte Positionierung der ROI in der Aorta ascendens weiterhin angewendet werden kann. Außerdem wurde in dieser Studie nachgewiesen, dass eine Positionierung der ROI im linken Herzvorhof zu einer besseren Beurteilbarkeit der Pulmonalarterien führt und deshalb bei der TRO-CTA angewendet werden sollte. Das Ergebnis zeigt aber auch, dass diese bei der TRO-CTA übliche Positionierung im linken Herzvorhof die Abbildung der Koronararterien nicht beeinträchtigt und der Einsatzbereich der TRO-CTA somit weiter ausgedehnt werden kann. / Background, aims and objectives The bolus tracking technique is widely used for choosing the optimal starting point of data acquisition in coronary computed tomography angiography (CCTA) scans. It utilizes repeated scans at a predefined position in order to determine the concentration of contrast media in a region of interest (ROI). The scan starts automatically when a trigger threshold is reached. The effect by different ROI positioning on image quality in CCTA has not been systematically evaluated yet. In CCTA, the ROI may be positioned in the left atrium (LV) or the ascending aorta (AA). In triple-rule-out-CTA (TRO-CTA), which allows for the evaluation of the pulmonary arteries and the thoracic aorta in addition to the coronary arteries, the ROI is mostly positioned in the left atrium. This choice of ROI positioning is empirical and its effect on the contrast filling of the pulmonary arteries has not been studied systematically. In the current study we evaluated the effect of ROI positioning on image quality of the coronary arteries (left main coronary artery: LM; right coronary artery: RCA) and the pulmonary arteries (right pulmonary artery: RPA; left pulmonary artery: LPA), respectively. Method In the current monocentric retrospective study all patients underwent CCTA by step-and-shoot mode to rule out coronary artery disease at intermediate risk. We compared two groups of patients with ROI in the left atrium or the ascending aorta. Each group contained 96 patients, so overall 192 patients were included (122 male, 70 female, age 21 to 87 years, 61 years on average). To select pairs of patients with similar characteristics, propensity score matching was used. Matching criteria were height, body weight, sex and heart rate. To evaluate the image quality, we used quantitative and qualitative scores. Signal-to-noise ratio (SNR), defined as the quotient of the mean signal intensity and the standard deviation of signal intensity, represented the quantitative score. For generating the qualitative score, overall image quality was assessed independently by two radiologists with ten and six years of experience with CCTA, respectively, using a five point Likert scale. This way, we compared the quality of the depiction of the coronary arteries on the one hand and of the pulmonary arteries on the other hand. For statistical evaluation the Wilcoxon test was used to compare the quantitative and qualitative scores of the two groups. Regarding the qualitative analysis, interrater agreement was evaluated using weighted Cohens kappa. Furthermore the radiation exposure was compared by viewing the dose-length products provided by the scanner and calculating the effective doses from these. Results In terms of the coronary arteries, there was no significant difference between both groups regarding quantitative (SNR AA 14.92 vs. 15.46; p = 0.619 | SNR LM 19.80 vs. 20.30; p = 0.661 | SNR RCA 24.34 vs. 24.30; p = 0.767) or qualitative scores (4.25 vs. 4.29; p = 0.672), respectively. In terms of the pulmonary arteries, we can see significant higher quantitative (SNR RPA 8.70 vs. 5.89; p < 0.001 | SNR LPA 9.06 vs. 6.25; p < 0.001) and qualitative scores (3.97 vs. 2.24; p < 0.001) for bolus tracking positioning in the left atrium than for bolus tracking positioning in the ascending aorta. The calculation of the interrater reliability showed substantial agreement for the analysis of the coronary arteries (κ = 0.654) and almost perfect agreement for the analysis of the pulmonary arteries (κ = 0.846). The radiation exposure was almost identical in both groups of patients (4.13 mSv vs. 4.13 mSv; p = 0.501). Conclusion Bolus tracking positioning in the left atrium or the ascending aorta causes equivalent image quality of the coronary arteries, so that the current mostly preferred position for the exclusively consideration of the coronary arteries in the ascending aorta can be maintained. Positioning in the left atrium causes a significant higher image quality of the pulmonary arteries, therefore it should be used for TRO-CTA. In addition, the study shows that this for TRO-CTA mostly used position in the left atrium does not adversely affect depiction of the coronary arteries, if compared to conventional bolus tracking positioning in the ascending aorta. This implies that despite the improved depiction of the pulmonary arteries and the aorta in TRO-CTA, the depiction of the coronary arteries is not restricted. Consequently these results are a further argument for an extension of the indication for TRO-CTA in place of conventional CCTA in patients with acute thoracic pain.

This thesis deals with the possibilities of determining perfusion parameters of vascular system, using contrast-enhanced ultrasound imaging, which is non-invasive method. Properties of ultrasonography and use of contrast agents are briefly summarized. The methods selected for perfusions analysis were Bolus-tracking¬¬, Burst-replenishment and both of them combined – Bolus&Burst. Parametric models based on these methods were created for modelling an approximation of set perfusion parameters with the use of blind deconvolution.

No description available.