Optimisation of tube voltage for adult chest digital radiography / 中华放射学杂志

ABSTRACT

Objective To explore the optimum voltage for digital chest radiography in adult. Methods PMMAs of Different thickness (7.2, 9.0, 10. 8 and 12. 6 cm) were used to simulate chest of different depth ( 17. 5, 22. 5, 27.0 and 32. 5 cm). The combinants of contrast-detail Cdrad 2.0 phantom and above PMMAs were exposed with automatic exposure control (AEC) and different tube voltages. The images of these combinants were obtained and the entrance surface dose (ESD) was recorded. The imaging quality factor (IQF) was calculated and the curves were drawn between the ESD,IQF and kV. The PMMAs of different thickness, on which a contrast object ( PMAA of 5 cm diameter and 1.8 cm thickness ) was placed, were exposed with the same condition used for above test. Their images were obtained and SNRs were calculated. Results The ESD, SNR and IQFinv of different chest depth decreased with increase of kV.When tube voltages of 70, 100 and 140 kV were used, for 17. 5 cm chest depth, the ESD was 0. 22, 0. 09 and 0. 06 mGy, the IQF was 43.3, 58. 8 and 72. 0, the SNR was 7.5, 6. 2 and 5.0; for 22. 5 cm chest depth, the ESD was 0.37, 0.12 and 0.06 mGy, the IQF was 56. 0, 61.4 and 65.3, the SNR was 6. 4, 5.2 and 3. 8; for 27. 0 cm chest depth, the ESD was 0. 52, 0. 20 and 0. 09 mGy, the IQF was 54. 2, 64. 3 and 91. 0, the SNR was 6. 0, 4. 8 and 3. 5; for 31.5 cm chest depth, the ESD was 0.53, 0.24 and 0. 10 mGy,the IQF was 53.2, 66. 8 and 95.3, the SNR was 5. 7, 4. 5 and 3. 0. Conclusion To balance ESD, SNR and IQF, proper tube voltage should be chosen for chest radiography according to thickness and constitution of patients.