Radiation doses of cerebral blood volume measurements using C-arm CT: A phantom study

BACKGROUND AND PURPOSE

Parenchymal blood volume measurement by C-arm CT facilitates in-room peritherapeutic perfusion evaluation. However, the radiation dose remains a major concern. This study aimed to compare the radiation dose of parenchymal blood volume measurement using C-arm CT with that of conventional CTP using multidetector CT.

MATERIALS AND METHODS

A biplane DSA equipped with C-arm CT and a Rando-Alderson phantom were used. Slab parenchymal blood volume (8-cm scanning range in a craniocaudal direction) and whole-brain parenchymal blood volume with identical scanning parameters, except for scanning ranges, were undertaken on DSA. Eighty thermoluminescent dosimeters were embedded into 22 organ sites of the phantom. We followed the guidelines of the International Commission on Radiation Protection number 103 to calculate the effective doses. For comparison, 8-cm CTP with the same phantom and thermoluminescent dosimeter distribution was performed on a multidetector CT. Two repeat dose experiments with the same scanning parameters and phantom and thermoluminescent dosimeter settings were conducted.

RESULTS

Brain-equivalent dose in slab parenchymal blood volume, whole-brain parenchymal blood volume, and CTP were 52.29 ± 35.31, 107.51 ± 31.20, and 163.55 ± 89.45 mSv, respectively. Variations in the measurement of an equivalent dose for the lens were highest in slab parenchymal blood volume (64.5%), followed by CTP (54.6%) and whole-brain parenchymal blood volume (29.0%). The effective doses of slab parenchymal blood volume, whole-brain parenchymal blood volume, and CTP were 0.87 ± 0.55, 3.91 ± 0.78, and 2.77 ± 1.59 mSv, respectively.

CONCLUSIONS

The dose measurement conducted in the current study was reliable and reproducible. The effective dose of slab parenchymal blood volume is about one-third that of CTP. With the advantages of on-site and immediate imaging availability and saving procedural time and patient transportation, slab parenchymal blood volume measurement using C-arm CT can be recommended for clinical application.

Monitoring peri-therapeutic cerebral circulation time: a feasibility study using color-coded quantitative DSA in patients with steno-occlusive arterial disease

BACKGROUND AND PURPOSE

Intracranial hemodynamics are important for management of SOAD. This study aimed to monitor peri-stent placement intracranial CirT of patients with SOAD.

MATERIALS AND METHODS

Twenty-five patients received stent placement for extracranial ICA stenosis, and 34 patients with normal CirT were recruited as controls. Their color-coded DSAs were used to define the Tmax of selected intravascular ROI. A total of 20 ROIs of the ICA, OphA, ACA, MCA, FV, PV, OV, SSS, SS, IJV, and MCV were selected. rTmax was defined as the Tmax at the selected region of interest minus Tmax at the cervical segment of the ICA (I1 on AP view and IA on lateral view). rTmax of the PV was defined as intracranial CirT. Intergroup and intragroup longitudinal comparisons of rTmax were performed.

RESULTS

rTmax values of the normal cohorts were as follows: ICA-AP, 0.12; ICA-LAT, 0.10; A1, 0.28; A2, 0.53; A3, 0.81; M1, 0.40; M2, 0.80; M3, 0.95; OphA, 0.35; FV, 4.83; PV, 5.11; OV, 5.17; SSS, 6.16; SS, 6.51; IJV, 6.81; and MCV, 3.86 seconds. Before stent placement, the rTmax values of arterial ROIs, except A3 and M3, were prolonged compared with values from control subjects (P < .05). None of the rTmax of any venous ROIs in the stenotic group was prolonged with significance. After stent placement, the rTmax of all arterial ROIs shortened significantly, except A1and M3. Poststenting rTmax was not different from the control group.

CONCLUSIONS

Without extra contrast medium and radiation dosages, color-coded quantitative DSA enables real-time monitoring of peri-therapeutic intracranial CirT in patients with SOAD .

Evaluating geometric accuracy of multi-platform stereotactic neuroimaging in radiosurgery

We used a spherical phantom to evaluate geometric accuracy in multi-platform stereotactic neuroimaging for radiosurgery. The phantom consisted of two plastic 16-cm-diameter hemispheres in which an exchangeable 8-cm plastic functional cube was incorporated. The functional cube contained cylinder and point targets. The targets were filled with a mixed aqueous solution of 2-mM copper sulfate and 300-mg/ml iodinated contrast medium and were visible on both MR and X-ray images. Two MR scanners and a biplane X-ray angio-suite were used to scan the phantom stereotactically in two sessions of the experiment. The angio-suite was equipped with digital subtraction and distortion-correction software. The resulting stereotactic images were transferred to a dose-planning computer for length measurement and coordinate determination of the targets. The mean errors of the measured cylinder length on distortion non-corrected X-ray stereotactic images were 0.24 +/- 0.14 and 0.73 +/- 0.10 mm, respectively, in the experiments; on distortion-corrected images 0.22 +/- 0.10 and 0.35 +/- 0.39 mm. They were 0.50 +/- 0.24, 0.25 +/- 0.19 and 0.49 +/- 0.34, 0.23 +/- 0.25 mm, respectively, of the two MR scanners. The mean errors of coordinate determination of point targets between the stereotactic MR and the distortion-corrected X-ray images were 0.70 +/- 0.18, 0.52 +/- 0.22 and 0.76 +/- 0.25, 0.40 +/- 0.10 mm, respectively, in the experiments. We found that the overall geometric errors of target delineation between stereotactic MR and X-ray images were in the submillimeter range. The current study validates the multi-platform and multi-facility stereotactic neuroimaging practice and ensures imaging accuracy in radiosurgery.

Electron transfer between cytochrome c and metal hexacyanide complexes. Effect of thermodynamic driving force on the electron transfer rate

The electron transfer reactions between ferrocytochrome c and three isomorphic hexacyanide complexes, [Fe(CN)6]3-, [Os(CN)6]3- and [Ru(CN)6]3-, have been studied using the method of photoexcitation. The transfer rates for [Os(CN)6]3- and [Ru(CN)6]3- are, respectively, about 45- and 200-times higher than that of [Fe(CN)6]3-. A reorganization energy of approx. 0.8 eV was found for the cytochrome c-hexacyanide system when the data were analyzed according to the theory of Marcus.

Kinetics of electron transfer between cytochrome c and iron hexacyanides. Evidence for two electron-transfer sites

The electron-transfer reaction between ferrocytochrome c and ferricyanide has been studied by the method of photoexcitation. The observed transfer rate shows saturation behaviour at high ferricyanide concentration. Data analysis indicates that there are two binding sites of vastly different affinities at which electron transfer occurs. The binding constant for the strong binding site decreases from 1600 M-1 to 80 M-1 as the ionic strength increases from 15 mM to 140 mM. At 20 degrees C, the intramolecular electron-transfer rate for this site is 4.65 X 10(4) s-1, which gives an electron-transfer distance of approx. 9.7 A according to Hopfield's model.