Thyroid dose during neurointerventional procedures: does lead shielding reduce the dose?
OBJECTIVE
To assess radiation dose to the thyroid in patients undergoing neurointerventional procedures and to evaluate dose reduction to the thyroid by lead shielding.


METHODS
A randomized patient study was undertaken to evaluate the dose reduction by thyroid lead shields and assess their practicality in a clinical setting. Sixty-five patients attending for endovascular treatment of arteriovenous malformations (AVMs) and aneurysms were randomized into one of 2 groups a) No Thyroid Shield and b) Thyroid Lead Shield. Two thermoluminescent dosimeters (TLDs) were placed over the thyroid gland (1 on each side) at constant positions on each patient in both groups. A thyroid lead shield (Pb eq. 0.5 mm) was placed around the neck of patients in the thyroid lead shield group after the neurointerventional radiologist had obtained satisfactory working access above the neck. The total dose-area-product (DAP) value, number and type of digital subtraction angiography (DSA) runs and fluoroscopy time were recorded for all patients.


RESULTS
Of the 72 patients who initially attended for neurointerventional procedures, 7 were excluded due to failure to consent or because of procedures involving access to the external carotid circulation. Of the remaining 65 who were randomized, a further 9 were excluded due to; procedureabandonment, unfeasible shield placement or shield interference with the procedure. Patient demographics included mean age of 47.9 yrs (15-74), F:M=1.4:1. Mean fluoroscopy time was 25.9 min. Mean DAP value was 13,134.8 cGy x cm(2) and mean number of DSA runs was 13.4. The mean relative thyroid doses were significantly different (p< 0.001) between the unshielded (7.23 mSv/cGy2 x 105) and shielded groups (3.77 mSv/cGy2 x 105). A mean thyroid dose reduction of 48% was seen in the shielded group versus the unshielded group.


CONCLUSIONS
Considerable doses to the thyroid are incurred during neurointerventional procedures, highlighting the need for increased awareness of patient radiation protection. Thyroid lead shielding yields significant radiation protection, is inexpensive and when not obscuring the field of view, should be used routinely.
Shortt
C P
CP
Department of Radiology, Beaumont Hospital, Dublin 9, Ireland.
Fanning
N F
NF
Malone
L
L
Thornton
J
J
Brennan
P
P
Lee
M J
MJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D015901:Angiography, Digital Subtraction / Q000009:adverse effects*; D004867:Equipment Design; D005260:Female; D005471:Fluoroscopy / Q000009:adverse effects; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging* / Q000601:surgery; D002538:Intracranial Arteriovenous Malformations / Q000000981:diagnostic imaging* / Q000601:surgery; D007854:Lead; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures; D011446:Prospective Studies; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control; D011835:Radiation Protection / Q000295:instrumentation*; D015641:Radiography, Interventional / Q000009:adverse effects*; D013961:Thyroid Gland / Q000528:radiation effects*; D013997:Time Factors
D007854:Lead