A head phantom study for intraocular dose evaluation of 64-slice multidetector CT examination in patients with suspected cranial trauma

Development of a novel artifact-free eye shield based on silicon rubber-lead composition in the CT examination of the head

The aim of this work was to develop a novel artifact-free eye shield and evaluate its effect on the dose received by the eye lens and the resulting image quality in the CT examination of the head. A new material for an eye shield was synthesised from silicon rubber (SR) and lead (Pb) using a simple method. The percentage of Pb was varied from 0 to 5% wt. An anthropomorphic head phantom was scanned with and without the SR-Pb eye shield, and compared with a tungsten paper (WP) eye shield. The distance from the eye shield and head was varied from 0 to 5 cm. The dose to the eye lens was measured using photo-luminescence detectors (PLDs). The presence of artifacts was determined by measuring CT numbers at different eye lens locations and by subtracting images with and without the eye shield. The dose reduction increases with increasing Pb content in the SR-Pb eye shield. A 5% wt SR-Pb eye shield reduced the eye lens dose by up to 50%, whereas the WP eye shield reduced the dose by up to 86%. The CT numbers in images with the SR-Pb eye shield in the regions of both eyes and the center of the head phantom is similar to those without the eye shield, indicating that there is no artifact in the resulting image. Using the WP eye shield, there is considerable artifact with the CT number increasing by up to 700% in the regions of both eyes and the center of the head. It is found that the distance between the SR-Pb eye shield and the head does not affect either the dose or the resulting images. A SR-Pb-based eye shield can be applied in clinical environments and should be placed directly above the eye surface for dose optimisation.

Estimation of Eye Lens Dose During Brain Scans Using Gafchromic Xr-QA2 Film in Various Multidetector CT Scanners

The purpose of this study was to estimate eye lens dose during brain scans in 16-, 64-, 128- and 256-slice multidetector computed tomography (CT) scanners in helical acquisition mode and to test the feasibility of using radiochromic film as eye lens dosemeter during CT scanning. Eye lens dose measurements were performed using Gafchromic XR-QA2 film on a polystyrene head phantom designed with outer dimensions equivalent to the head size of a reference Indian man. The response accuracy of XR-QA2 film was validated by using thermoluminescence dosemeters. The eye lens dose measured using XR-QA2 film on head phantom for plain brain scanning in helical mode ranged from 43.8 to 45.8 mGy. The XR-QA2 film measured dose values were in agreement with TLD measured dose values within a maximum variation of 8.9%. The good correlation between the two data sets confirms the viability of using XR-QA2 film for eye lens dosimetry.

The "Air in the CT X-ray Tube Oil" Artifact-Examples of the Quality Control Images and the Evaluation of Four Potential Clinical Patients' Head Computed Tomography Cases

We present a newly reposted scanner-based artifact-with 4 potential patients' head computed tomography (CT) cases-the "Air in the CT X-ray Tube Oil" artifact with a 64-slice multidetector CT. This artifact mimics diseases, which cause hypodense findings in CT images. It can be difficult to notice in the clinical patient imaging but can be also very difficult to verify in quality control tests.

The Ongoing Gap in Availability of Imaging Services at Teaching Versus Nonteaching Hospitals

RATIONALE AND OBJECTIVES

This study aimed to characterize associations between availability of imaging services and intensity of teaching among US hospitals.

MATERIALS AND METHODS

Using the American Hospital Association Annual Survey Database, we studied information regarding the availability of imaging services at general hospitals nationwide in 2007 (4102 hospitals) and in 2012 (3876). Teaching intensity was categorized as Council of Teaching Hospitals (COTH) member, non-COTH teaching hospital (non-COTH member with affiliated medical school and/or residency), and nonteaching hospital. Availability in hospitals of reported basic and advanced imaging modalities, as well as beds, number of employed physicians, and case mix index, was analyzed. Univariable and multivariable trends were assessed.

RESULTS

All 15 assessed modalities showed significant increases in availability with increasing hospital teaching intensity (P < 0.001). Modalities showing the largest differences between COTH and nonteaching hospitals in 2012 were image-guided radiation therapy (78% vs. 14%), positron emission tomography/computed tomography (74% vs. 17%), and single-photon emission computed tomography (88% vs. 35%). The gap between COTH and nonteaching hospitals increased from 43% in 2007 to 57% in 2012 for positron emission tomography/computed tomography, and from 34% to 48% for virtual colonoscopy. COTH status was a significant predictor, independent of beds and employed physicians, for 10 modalities (P < 0.001-0.038). Greater case mix index was significantly associated with availability of advanced, although not basic, modalities.

CONCLUSIONS

Availability of imaging services increased with greater hospital teaching intensity. Differences were most pronounced and sustained over time for advanced modalities. Our findings reflect the greater advanced imaging resources necessary to support the complexity of care rendered at teaching hospitals. This differential must be considered when exploring adjustments to teaching hospitals' funding levels.