Reducing the dose of CT of the paranasal sinuses: potential of an iterative reconstruction algorithm

Abstract

Objective: To evaluate the feasibility and image quality of low-dose CT of the paranasal sinuses using iterative reconstruction with adaptive-iterative dose reduction in three dimensions (AIDR 3D) in comparison with conventional image protocols of older scanner generations. Methods: Sinus CT scans of 136 patients were assessed retrospectively. Patients underwent CT either with low-dose settings (Protocol A: 80 kV, 30 mA s; Protocol B: 120 kV, 15 mA s or C: 80 kV, 90 mA s) reconstructed using AIDR 3D (Protocols A and B) or filtered back projection (FBP) (Protocol C) or with standard dose (Protocol D: 120 kV, 80 mA s) and FBP. Image quality was assessed in consensus by two blinded readers scoring the diagnostic image quality (from 1 5 excellent to 5 5 non-diagnostic) and conspicuity of important anatomic landmarks (from 0 5 not visible to 2 5 completely visible; maximum score of 16 points) as well as osseous structures (maximum score of 12 points). Dose-length product, effective dose (ED), CT dose index and scan length were retrieved for each scan and compared. Results: Mean ED could be lowered by 82% when using Protocol A. The best image quality was found using Protocol B (mean score 5 2.1 ± 0.51). Conspicuity of relevant anatomic landmarks was best with Protocol A (mean score 5 11.97 ± 1.88). Protocol B provided the highest conspicuity of osseous structures (mean score 5 8.27 ± 1.58). Image noise was highest in images obtained using Protocol A. Conclusions: AIDR 3D allows a significant dose reduction while maintaining a good diagnostic image quality and conspicuity of relevant anatomic structures.

A local guideline reduces inappropriate requests for computed tomography imaging of the paranasal sinuses

“…The effective dose range is approximately 0.1‐1 mSv for a CT PS—for comparison the average annual background radiation for a person living in the UK is 2.7 mSv. Although the baseline increase risk of cancer of the thyroid and other radiosensitive structures is very low following the effective dose of CT PS (one in 37 189), the cataractogenic potential of this level of radiation is not yet known (a cumulative dose of 100 mGY has been suggested as a threshold) . Many patients are young (mean age 42 in this cohort), and thus the cumulative exposure to ionising radiation should be sought to be minimised by reducing inappropriate CT PS ordering.…”

“…The effective dose (ionising radiation dose) from a CT PS is subject to significant variation based on scan technique, coverage, patient size and equipment used. The effective dose range is approximately 0.1-1 mSv for a CT PS-for comparison the average annual background radiation for a person living in the UK is 2.7 mSv.Although the baseline increase risk of cancer of the thyroid and other radiosensitive structures is very low following the effective dose of CT PS (one in 37 189), the cataractogenic potential of this level of radiation is not yet known (a cumulative dose of 100 mGY has been suggested as a threshold) 11. Many patients are young (mean age 42 in this cohort), and thus the cumulative exposure to ionising radiation should be sought to be minimised by reducing inappropriate CT PS ordering.Keypoints• Introduction of a computed tomography (CT) guidance protocol significantly reduces the number of inappropriate CT paranasal sinuses being performed.• Departmental education is critical to the introduction of such a protocol.• Total radiation exposure is therefore reduced.• Patients without rhinosinusitis requiring imaging investigation for intractable pain in the distribution of the trigeminal nerve would benefit from MRI in order to save unnecessary exposure to ionising radiation from CT.F I G U R E 1 CT sinuses guideline as displayed prominently in clinic rooms and disseminated in focussed clinician education.…”

Application value of iterative reconstruction with CTA to intractable headache patients

“…Also, the absorbed dose and ED of the tested blood vessels and muscles in the patients showed decrease in variable degrees. The utilization of iterative reconstruction technique could elevate the detection efficiency of iodine signals, and the examination results would not be affected even though the tube voltage was appropriately lowered, thus providing some space for decreasing CTDI vol , DLP and ED ( 20 ).…”

Comparing subjective and objective image quality at two different radiation exposure ranges of the paranasal sinus CT examinations using a volumetric 320-row detector CT system

“…These anatomic landmarks were chosen based on the two previous studies. 5,13 Evaluation of the objective image quality To compare the objective parameters between the control and study group images, noise was measured by three 10 mm 2 region of interest placed with consensus on the axial soft tissue reconstructions in both eye bulbs, retrobulbar fat and maxillary sinuses to obtain different values for aqueous tissue, soft tissue and air, respectively. Noise was defined as the mean standard deviation of attenuations measured in Hounsfield units.…”

“…11,12 In recent years, various articles about dose reduction strategies in paranasal sinus CT imaging have been published. 2,4,5,7,13 However; to the best of our knowledge, our study is the first original research evaluation of the paranasal sinus CT imaging protocols using volumetric 320-row detector CT system. In this study, we aim to compare two paranasal CT protocols: one with 135 kVp tube voltage and 5 mAs current and one with 80 kVp tube voltage and 5 mAs current.…”