Dual-phase helical CT of the liver: Effects of bolus tracking and different volumes of contrast material

Department of Radiology, University Hospital of Goettingen, Germany.
Radiology (Impact Factor: 6.87). 12/1996; 201(2):321-6. DOI: 10.1148/radiology.201.2.8888218
Source: PubMed


To evaluate the effects of tracking and volume of contrast material on dual-phase helical computed tomography (CT) of the liver.
CT was performed in 120 consecutive patients. Either 100 mL (groups 1 and 2) or 120 mL (groups 3 and 4) of contrast material was injected at a rate of 4 mL/sec. In groups 1 and 3, the scanning delay was fixed, whereas in groups 2 and 4, scanning delays were determined individually by means of a semiautomatic bolus tracking device. The arterial phase began when splenic enhancement was greater than 10 HU and ended when hepatic enhancement was greater than 20 HU, which characterized the start of the portal venous phase.
The mean duration of the arterial phase was 11.6 (100 mL) and 12.2 seconds (120 mL). The arterial phase of the liver within the defined limits was sufficiently timed in only 16 (54%) patients in group 1, 25 (83%) in group 2, and 20 (67%) in groups 3, whereas it was significantly (P < .05) better in 28 (93%) patients in group 4. A significantly (P < .05) higher mean parenchymal enhancement in the portal venous phase (63.6 HU +/- 8.5) was obtained in group 4.
Bolus tracking of a volume of 120 mL provided the most accurate results in dual-phase liver CT.

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    • "One method used to increase the CNR in the medical image is to modify the bolus injection as to make the resulting bolus profile more conducive to the pre-set constant-speed tracking method. This method is called bolus geometry optimization [1], [3], [4], [13], [19] and requires a priori knowledge of the patient's vascular system to achieve the desirable results, which cannot be known before a preliminary injection. Therefore, the geometry optimization method potentially increases the overall contrast dose. "
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    ABSTRACT: To improve imaging quality and to reduce contrast dose and radiation exposure, an optimal adaptive bolus chasing controller is proposed and tested based on actual patient data. The controller estimates and predicts the unknown 2D bolus density online and then determines the optimal control actions. Tracking errors are mathematically quantified in terms of estimation errors. The test results not only support the analytical analysis and exhibit its superior performance over the current constant-speed controller, but also demonstrate the clinical feasibility.
    IEEE Transactions on Control Systems Technology 02/2008; 16(1-16):60 - 69. DOI:10.1109/TCST.2007.903082 · 2.47 Impact Factor
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    • "However, the table control strategy has not evolved beyond the simple constant speed scheme. In a typical CT scan, the arrival of the bolus triggers a constant movement of the patient table [1] [2]. The problem with this method is that the contrast bolus does not travel at a constant speed. "
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    ABSTRACT: In order to reduce contrast dose and radiation exposure involved in CT angiography, an automatic adaptive control scheme was proposed for bolus chasing, which offers substantial improvements over the conventional constant speed control scheme. In this paper, a manual control scheme is proposed to utilize the expert's knowledge optimally based on real-time imaging feedback. The technical objective is to synchronize the bolus dynamics and the imaging aperture. To test the proposed technique, a realistic simulator is designed, developed and evaluated. It is shown statistically that the manual control outperforms the traditional constant speed control.
    Journal of X-Ray Science and Technology 01/2007; 15(1):1-9. · 1.40 Impact Factor
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    • "One determinant of image quality is the accurate spatial and temporal synchronization of the peak bolus density with the imaging acquisition window. For CT, this involves translating the scanner table appropriately after intravascular injection [6,7]. MRA and Digital Subtraction Angiography (DSA) have a relatively large FOV, which makes the synchronization easier. "
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    ABSTRACT: A detailed contrast bolus propagation model is essential for optimizing bolus-chasing Computed Tomography Angiography (CTA). Bolus characteristics were studied using bolus-timing datasets from Magnetic Resonance Angiography (MRA) for adaptive controller design and validation. MRA bolus-timing datasets of the aorta in thirty patients were analyzed by a program developed with MATLAB. Bolus characteristics, such as peak position, dispersion and bolus velocity, were studied. The bolus profile was fit to a convolution function, which would serve as a mathematical model of bolus propagation in future controller design. The maximum speed of the bolus in the aorta ranged from 5-13 cm/s and the dwell time ranged from 7-13 seconds. Bolus characteristics were well described by the proposed propagation model, which included the exact functional relationships between the parameters and aortic location. The convolution function describes bolus dynamics reasonably well and could be used to implement the adaptive controller design.
    BioMedical Engineering OnLine 02/2006; 5(1):53. DOI:10.1186/1475-925X-5-53 · 1.43 Impact Factor
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