Patient dose and associated risk due to radiological investigation of the internal auditory meatus

Endolymphatic Sac Tumor Screening and Diagnosis in von Hippel-Lindau Disease: A Consensus Statement

Objective Endolymphatic sac tumors (ELSTs) are a frequent cause of hearing loss and other audiovestibular dysfunction in patients with von Hippel-Lindau disease (VHL). Unified screening recommendations for VHL patients have not been established. To develop consensus guidelines, the VHL Alliance formed an expert committee to define evidence-based clinical screening recommendations.

Patients and Methods Recommendations were formulated by using the Grading of Recommendations, Assessment, Development, and Evaluation framework after a comprehensive literature review.

Results Diagnosis of ELSTs in VHL requires a combination of clinical evaluation and imaging and audiometric findings. Audiovestibular signs/symptoms are often an early feature of small ELSTs, including those that are not visible on imaging. Diagnostic audiograms have the greatest sensitivity for the detection of ELST-associated sensorineural hearing loss and can help confirm clinically relevant lesions, including those that may not be radiographically evident. Magnetic resonance imaging (MRI) can be a more specific test for ELSTs in VHL particularly when supplemented with computed tomography imaging for the identification of small tumors. VHL patients between the ages 10 and 60 years carry high preponderance for ELST presentation.

Conclusion We recommend that clinical evaluation (yearly) and diagnostic audiograms (every other year) be the primary screening tools for ELSTs in VHL. We suggest that screening be performed between the ages 11 and 65 years or with the onset of audiovestibular signs/symptoms for synchronicity with other testing regimens in VHL. We recommend that baseline imaging (MRI of the internal auditory canals) can be performed between the ages of 15 and 20 years or after positive screening.

Radiation dose to the lens using different temporal bone CT scanning protocols

BACKGROUND AND PURPOSE

Temporal bone CT is performed frequently in clinical practice. At the same time, the eye lens are exposed to ionizing radiation without any useful diagnostic information delivered. Our aim was to investigate the radiation dose to the lens of the eye by using temporal bone CT scanning with different protocols.

MATERIALS AND METHODS

Direct axial and coronal CT by using a conventional sequential scanning mode (140 kV, 220 mAs/section, 1.25-mm thickness, 1.25-mm increment, 16 x 0.625 mm collimation, the glabellomeatal line as a scanning baseline), a routine helical scanning mode (140 kV, 220 mAs/section, 0.315 pitch, 0.67-mm thickness, 0.33-mm increment, 16 x 0.625 collimation, the orbitomeatal line as a scanning baseline), and a modified helical scanning mode (acanthiomeatal line as a scanning baseline; other parameters, same as above) was performed on an exsomatized cadaveric head. CTDI(vol) and DLP were recorded for each scanning mode, and effective doses were calculated. Organ doses for the lens were measured with TLDs.

RESULTS

When the sequential scanning mode was used, the gross effective dose was 1.21 mSv and the organ dose to the lens was 50.96 and 1.73 mGy, respectively, for direct axial and coronal imaging. The effective dose was 0.803 mSv in routine helical scanning, while the lens dose was 40.17 mGy. With the modified helical scanning mode, the effective dose was as same as that for the routine helical scanning, but the lens dose was reduced significantly to 10.33 mGy.

CONCLUSIONS

The effective doses resulting from sequential axial and coronal scanning were 1.51 times higher than the dose from helical scanning, and the lens dose was 1.31 times higher. With the modified helical scanning mode, thinner section images could be used to reformat axial, coronal, and sagittal images with a further 74.3% reduction in lens dose beyond that achieved with the conventional helical protocol.

Evaluation of radiation doses from MDCT-imaging in otolaryngology

The purpose of this study was to clarify patient doses in the current otolaryngological multi-detector row computed tomography (MDCT) examinations. Patient doses were measured with an in-phantom dosimetry system which was composed of 48 photodiode dosimeters embedded within an anthropomorphic phantom. Organ and effective doses were evaluated according to the International Commission on Radiological Protection Publication 103. In neck CT, doses for salivary glands and for thyroid were high, 7.6-29.9 and 13.4-60.3 mGy, respectively. In sinus CT, brain and lens doses were high, 7.6-24.6 and 10.6-32.0 mGy, respectively, and in inner ear CT, lens dose was 8.0-35.3 mGy. Effective doses were 1.8-6.6 mSv in neck CT, 0.5-0.9 mSv in sinus CT and 0.3-0.6 mSv in inner ear CT. The present dose data would be used to estimate radiation risks for patients undergoing otolaryngological MDCT examinations.

Radiation dose to the lens from computed tomography scanning in a neuroradiology department

The radiation dose to the lens was measured by thermoluminescent dosimetry on 194 patients undergoing routine head and neck computed tomography scanning in a neuroradiology department. The results are lower than previously reported: brain scans, mean value 5.1 mGy; orbital scans, mean value 18.5 mGy; and direct coronal pituitary scans, mean value 1.9 mGy. These lower values in axial brain scans are due to use of the supraorbital meatal baseline for radiographic positioning.