A new cone-beam computed tomography dosimetry method providing optimal measurement positions: A Monte Carlo study

Assessment of fetal radiation exposure in pregnant women undergoing computed tomography and rotational angiography examinations for pelvic trauma

This study aimed to assess fetal radiation exposure in pregnant women undergoing computed tomography (CT) and rotational angiography (RA) examinations for the diagnosis of pelvic trauma. In addition, this study aimed to compare the dose distributions between the two examinations. Surface and average fetal doses were estimated during CT and RA examinations using a pregnant phantom model and real-time dosemeters. The pregnant model phantom was constructed using an anthropomorphic phantom, and a custom-made abdominal phantom was used to simulate pregnancy. The total average fetal dose received by pregnant women from both CT scans (plain, arterial and equilibrium phases) and a single RA examination was ~60 mGy. Because unnecessary repetition of radiographic examinations, such as CT or conventional 2D angiography can increase the radiation risk, the irradiation range should be limited, if necessary, to reduce overall radiation exposure.

Assessment of abdominal organ dose and image quality in varying arc trajectory interventional C-arm cone beam CT

PURPOSE

The aim of this study was to investigate the effect of varying arc exposure trajectory on radiation dose to radiosensitive organs and to assess image quality in abdominal C-arm cone beam computed tomography (CBCT) interventional procedures using a latest generation system.

METHODS

An anthropomorphic phantom that simulates the average adult individual was used. Individual-specific Monte Carlo (MC) simulation dosimetry was performed to estimate organ doses (OD) in abdominal C-arm CBCT. Seven examination protocols prescribed by the system for vascular and soft tissue CBCT, were simulated. These protocols are differentiated in the range of the arc exposure trajectory and the level of radiation dose delivered to the patient. OD was estimated for liver, adrenals, kidneys, pancreas, stomach, gall bladder, spleen, bone and skin. Image noise, signal to noise ratio (SNR), contrast to noise ratio (CNR) and in-plane spatial resolution were assessed using CT-specific image quality assessment phantoms.

RESULTS

OD was found to depend on the range of arc trajectory and was higher for posterior located organs. In vascular protocols OD ranged from 4.75 mGy for skin to 0.60 mGy for bone. Image noise was higher in vascular protocols than in soft tissue ones. SNR and CNR were significantly modified among different soft tissue protocols (P < 0.05). In-plane spatial resolution was found 0.80 lp/mm in vascular as opposed to 0.41 lp/mm in soft tissue protocols.

CONCLUSIONS

The current results may be used to estimate OD for different examination protocols and enable operators choose the appropriate acquisition protocol on the preprogrammed interventional task.