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

Abstract

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.

Fig 1.

A, Ten yellow dots simulating TLDs are placed on a lateral skull view of the Rando-Alderson phantom. The scanning ranges of s-PBV and CTP are both 8 cm at the isocenter in a craniocaudal direction (blue dashed lines), while that of w-PBV is 30 cm (green solid lines). B, Eight-centimeter CTP is performed with a 360° rotation of the x-ray source in CT, and both s-PBV and w-PBV (C and D) are obtained with a 200° rotation of the x-ray source in DSA from the dorsal side of the Rando-Alderson phantom. The red arrows indicate x-ray beams. The 5 yellow dots placed on transaxial sections of the phantom indicate the TLDs placed on a phantom section. The numbers indicate the equivalent dose of each TLD in millisieverts. The elliptic head configuration of the phantom makes the dose heterogeneous (ie, the attenuation distance of TLDs on the ventral side of the phantom is longer than that on the dorsal side and the attenuation distance of the center one is longer than that of the peripheral one). The geometry makes the overall variation of the dose in the brain area the largest in s-PBV (67.5%), followed by CTP (54.7%) and then w-PBV (31.8%).

Fig 2.

Equivalent dose (millisieverts) of the lens for CTP, s-PBV, and w-PBV. Variation in the measurement of the equivalent dose for the lens is larger in CTP (54.6%) and s-PBV (64.5%) and lower in w-PBV (29.0%). Two TLDs are within the primary beams, and the other 2 TLDs are within the secondary beams in CTP and s-PBV, while in w-PBV, all TLDs are within the primary beam.

Fig 3.

Anteroposterior views of the Rando-Alderson phantom for s-PBV and w-PBV. For the brain region, CTP received the largest equivalent dose followed by w-PBV and s-PBV. For the salivary and thyroid gland regions, the equivalent dose of w-PBV is higher than that of s-PBV and CTP due to larger x-ray beam z-axial coverage.