Implementation of a high-sensitivity Micro-Angiographic Fluoroscope (HS-MAF) for in-vivo endovascular image guided interventions (EIGI) and region-of-interest computed tomography (ROI-CT)

Abstract

New advances in catheter technology and remote actuation for minimally invasive procedures are continuously increasing the demand for better x-ray imaging technology. The new x-ray high-sensitivity Micro-Angiographic Fluoroscope (HS-MAF) detector offers high resolution and real-time image-guided capabilities which are unique when compared with commercially available detectors. This detector consists of a 300 μm CsI input phosphor coupled to a dual stage GEN2 micro-channel plate light image intensifier (LII), followed by minifying fiber-optic taper coupled to a CCD chip. The HS-MAF detector image array is 1024×1024 pixels, with a 12 bit depth capable of imaging at 30 frames per second. The detector has a round field of view with 4 cm diameter and 35 microns pixels. The LII has a large variable gain which allows usage of the detector at very low exposures characteristic of fluoroscopic ranges while maintaining very good image quality. The custom acquisition program allows real-time image display and data storage. We designed a set of in-vivo experimental interventions in which placement of specially designed endovascular stents were evaluated with the new detector and with a standard x-ray image intensifier (XII). Capabilities such fluoroscopy, angiography and ROI-CT reconstruction using rotational angiography data were implemented and verified. The images obtained during interventions under radiographic control with the HS-MAF detector were superior to those with the XII. In general, the device feature markers, the device structures, and the vessel geometry were better identified with the new detector. High-resolution detectors such as HS-MAF can vastly improve the accuracy of localization and tracking of devices such stents or catheters.

Figure 1

HSMAF detector: (top) schematic drawing, (center) actual detector, and (bottom) plot showing the LII calibration curve relating the gain to the LII setting.

Figure 2

Micro-Angiographic detector mounted on a standard C-Arm with XII (left) and HSMAF mounted with FP (right). The images acquired with the HSMAF detector are automatically displayed on a monitor adjacent to the flat panel monitors. The automatic collimation button (white arrow in the right image) is attached onto the HSMAF holder

Figure 3

Asymmetric Vascular Stent (AVS), and schematics of aneurysm treatment with the AVS

Figure 4

Placement of a coronary stent using fluoroscopic roadmaping: left column HSMAF, right column XII. The first picture was acquired before stent deployment and the second picture was acquired after stent deployment

Figure 5

Alignment of the AVS with regard to the aneurysm neck. The white arrows indicate the four platinum markers. On left column we show the images acquired using the HS-MAF and on the right column those acquired with the standard II. In the top row the stent is undeployed, in the bottom row images the stent is deployed

Figure 6

Sequence of images showing stent navigation into the brain vasculature. Tone variations in the roadmap are used to orient the micro-wire tip to advance further in the brain

Figure 7

Images acquired with the HSMAF and FP of the brain vasculature in rabbits. Solid arrow indicates a small branch not visible in the FP DSA. Dotted arrow indicates real separation between the two arteries visible in the HSMAF DSA but not in the FP.

Figure 8

High-resolution region acquired with HSMAF fused into a low-resolution, low-dose FP projection.

Figure 9

ROI-CT slices at two different levels and a 3D rendering showing the full stent in the rabbit brain vasculature. The projection data was acquired using both the HSMAF and the FP as indicated in Figure 8