Bismuth shielding . Daniel .J.P , Radiology Technologist , Khorfakhan hospital . Sharjha , UAE

Bismuth Shielding:Helpful or Harmful

DANIEL.J

TECHNOLOGISTDEPT OF RADIOLOGYKHORFAKKAN HOSPITAL

INTRODUCTION

• Bismuth shielding has been used to reduce the dosefrom CT to superficial radiosensitive organs, such asthe breast, lens of the eye, and thyroid.• Concerns include an adverse effecton image quality and absorption ofphotons exiting the patient and ontheir way to the detector• Clinical studies did not control fornoise level; primarily assessedwhether “clinically acceptable”

Bismuth Eye Shielding

BISMUTH SHEILDS

MOTIVATION

• To quantitatively assess the dose reduction and image

quality in controlled experiments:– Standard clinical protocol– Bismuth shielding– Organ-based TCM– Globally decreasing the tube current to

achieve the samedose reduction as bismuth shielding

Scanning parameters

• Reference scan parameters were chosen from ourstandard spiral head scanning protocol– 120 kV, 1s rotation, 5 mm image thickness, 300 mm

FOV• Chose a reduced effective mAs [“Low-mAs”] to yieldthe same dose reduction to the eye as bismuth shield:Low-mAs = Ref-mAs * Bi_Dose / Ref_Dose• Bi_Dose and Ref_Dose are the doses measured at

theeye with and without bismuth shielding, respectively.

Organ-based Tube Current Modulation

EYE SCANNING PARAMETERS

DOSE REDUCTION TO EYE LENS

IMAGE QUALITY EVALUATION

IMAGE QUALITY EVALUATION

EYE IMAGE EVALUATION

THORAX IMAGE EVALUATION

THORAX IMAGE EVALUATION

ORGAN BASED TCM

THORAX IMAGE EVALUATION

THORAX IMAGE EVALUATION

THORAX IMAGE EVALUATION

THORAX IMAGE EVALUATION

BISMUTH vs OTHER TECHNIQUES

COMPARISON

SUMMARY

CONCLUSION