The effect of scan interval and bolus length on the quantitative accuracy of cerebral computed tomography perfusion analysis using a hollow-fiber phantom.

The shuttle scan technique is expected to extend scan range in cerebral computed tomography (CT) perfusion by 16- or 64-row multidetector CT (MDCT), but it may affect quantitative accuracy. This study aims to evaluate the effect of long scan interval and bolus length on the quantitative accuracy of perfusion indices using an innovative hollow-fiber phantom.We used an originally developed hollow-fiber hemodialyzer covered with polyurethane resin as a perfusion phantom. We scanned the phantom during various scan intervals (1-13 s) and bolus injection lengths (5, 10, 15, and 20 s), and evaluated cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time-to-peak (TTP). We verified the influence on measured values using a two-way analysis of variance (ANOVA). All measured CBF values were smaller than the theoretical CBF values, and all the measured MTT values were larger that the theoretical MTT values (95% confidence interval). Extended scan intervals resulted in more overestimation of MTT and more underestimation of CBF (p < 0.001). CBV is not affected by the change in scan interval (p < 0.001), and a longer bolus length improved the underestimation of CBV (p < 0.001). Extended scan intervals resulted in the loss of quantitative accuracy in MTT, even with longer bolus injection length, while quantitative CBF values were underestimated and TTP values overestimated. The CBV measurement was not affected by the change in scan interval, and a longer bolus injection improved the accuracy of these measurements.

Quantitative accuracy of computed tomography perfusion under low-dose conditions, measured using a hollow-fiber phantom.

PURPOSE: The purpose of this study was to investigate the quantitative accuracy under low-dose conditions on computed tomography (CT) perfusion using a hollow-fiber phantom that had the theoretical absolute values of perfusion indices. MATERIALS AND METHODS: Our phantom comprised two components, i.e., a hollow-fiber hemodialyzer to pump the diluted contrast material and a surrounding syringe-shaped X-ray-absorbing body to simulate the absorption of X-rays by a brain and cranium. We performed CTP scans on the phantom under various dose conditions ranging from 20 to 140 mA using a 64-row CT scanner, measuring experimental cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time to peak (TTP) values using a deconvolution algorithm. RESULTS: The theoretical value of the CBV was within the 95% confidence interval of CBV values measured under 80 mA. The CBV measured under low-dose settings and all CBF values measured were smaller than the theoretically calculated ones, and all MTT values measured were larger. All measured values of the CBV, CBF, MTT, and TTP decreased with an increase in image noise under lower dose conditions. CONCLUSION: It is difficult to define a low-dose limit in clinical scan conditions because of the complex characteristics of perfusion indices.

Technique and Theory of Hollow-fiber Phantom for Cerebral CT Perfusion.

We developed a phantom using a hollow-fiber hemodialyzer to evaluate the quantitative reliability of cerebral computed tomography (CT) perfusion. Our phantom consisted of a hollow-fiber hemodialyzer and a syringe-shaped X-ray device made up of resin. The phantom can give theoretical true values for cerebral blood volume, cerebral blood flow, and mean transit time. We compared the values measured in the phantom with predicted theoretical values. The purpose of the current report is to describe the theory and experimental technique used to obtain an absolute value in a phantom.

Imaging of the superficial inferior epigastric vascular anatomy and preoperative planning for the SIEA flap using MDCTA.

UNLABELLED: The superficial inferior epigastric artery (SIEA) flap consists of skin and subcutaneous fat with limited donor-site morbidity and has the potential to be very versatile - either as a thin flap without excessive fat tissue or as a voluminous flap for breast reconstruction. However, anatomical inter-individual variability often makes the choice of a free SIEA flap difficult. Imaging of small-calibre vessels is possible with the multi-detector-row computed tomography angiography (MDCTA) and to obtain the characteristics of the superficial inferior epigastric vascular anatomy, we investigated the superficial inferior epigastric system using MDCTA. METHODS: We investigated 17 patients who had abdominal wall MDCTA in preparation for a free flap procedure using either the deep inferior epigastric perforator (DIEP), SIEA or the groin flap. The visibility and anatomical characteristics including the branching pattern, the diameter, course of travel and layers were noted. RESULTS: The SIEA was visible in 64.7% and, of these, 36.4% had a common trunk formation with the superficial circumflex iliac artery (SCIA), while 63.6% arose independently. The measured diameters were SIEA 1.6 ± 0.4mm, SCIA 1.4 ± 0.4mm, deep circumflex iliac artery (DCIA) 2.4 ± 0.4mm, DIEA 2.9 ± 0.4mm and superficial inferior epigastric vein (SIEV) 3.1 ± 0.5mm. The SIEA consistently coursed lateral to and deeper than the SIEV and also lateral to the DIEA. CONCLUSION: MDCTA provided detailed three-dimensional information of the superficial inferior epigastric vascular system including the course and size of the SIEA. The information on vascular anatomy obtained with the MDCTA is valuable in the preoperative planning of the free SIEA flap and should be performed routinely.