Micro-angiography for neuro-vascular imaging. I. Experimental evaluation and feasibility.
Minimally invasive image-guided neuro-vascular interventions require very high image-resolution and quality, specifically over regions-of-interest (ROI) crucial to the procedure. ROI imaging or micro-angiography, allows limited patient integral radiation dose while permitting rapid frame transfer of high-resolution images. The design and performance of a charge coupled device (CCD) based x-ray detector or micro-angiographic camera was assessed for neuro-vascular procedures. The detector consists of a 250-microm-thick CsI(Tl) phosphor fiber-optically coupled through a 1.8:1 taper to a CCD chip, with an effective image pixel size of 50 microm and a frame rate of 5 fps in the 2:1 pixel-binned mode. The characteristics of the camera including the modulation transfer function (MTF), the noise equivalent quanta, the detective quantum efficiency, observer studies, and the effect of geometric magnification were evaluated. The MTF was found to have nonzero (1.7%) value at the Nyquist frequency of 10 cycles/mm, while the DQE(0) had a value of approximately 55%. All values were measured using head equivalent attenuating material in the beam at 80 kVp. Human observer studies performed using the 2 Alternative Forced Choice method revealed that iodinated vessels with inner diameter of 100 microm and 2 cm in length can be seen with a confidence level greater than 75%. The observer studies included a comparison with ideal observer performance calculations based on the integral signal to noise ratio in the image. Probabilities of visualization of various objects of interest in a neuro-intervention, such as stents, were assessed. A geometric magnification of 1 was found to be best for imaging under neuro-angiographic conditions. The detector appeared to satisfy all the demands of neuro-angiography and showed promise as an improvement over existing angiographic detectors.
Ganguly
Arundhuti
A
Toshiba Stroke Research Center, Department of Physics, State University of New York at Buffalo, Buffalo, New York 14214, USA. aganguly@stanford.edu
Rudin
Stephen
S
Bednarek
Daniel R
DR
Hoffmann
Kenneth R
KR
Kyprianou
Iacovos S
IS
D000792:Angiography / Q000295:instrumentation* / Q000379:methods; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging*; D002560:Cerebrovascular Circulation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005240:Feasibility Studies; D006801:Humans; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers; D014741:Video Recording / Q000295:instrumentation* / Q000379:methods