Radiation dose reduction by using low dose CT protocol of thorax

CT makes up to 67% of radiation from medical sources. Therefore emphasizes is especially on the importance of reducing doses and the introduction of procedures with the lowest possible dose received by the patient. The so called low dose CT protocol was studied for some chest diagnosis however it was not investigated for the patients with lymphoproliferative diseases. Lymphoproliferative diseases, including most lymphomas involve a large number of younger and middle age patients i.e. patients in the reproductive period of life. A CT exam of these patients is indispensable method for the diagnosis, and later for long life monitoring of the effectiveness of therapy. The aim of this work was to compare the patient doses between two different CT protocols of thorax in patients with this diagnosis. The entrance surface doses were measured and compared using standard CT protocol of thorax which implies 120 kV and 160 mA conditions and low dose CT protocol using 120 kV and 30 mA conditions while maintaining image quality. The study involved 60 patients. Each patient underwent two different CT thorax protocols during regular follow up of the disease. The doses were measured using LiF:Mg,Ti (TLD-100) thermoluminescent (TL) and GD-352M radiophotoluminescent (RPL) dosimeters on the thyroid, eye lens, sternum and gonads. The results showed that low dose protocol yielded with the reduction of doses by the factor of 1.8–15 on the eye lens, 1.0–9.1 on the thyroid, 2.5–7.0 on sternum and 0.3–12.8 on gonads, respectively. The doses were significantly lower using low dose CT protocol while the image quality for lymph node presentation was satisfactory according to European criteria. Therefore the use of low dose CT protocol as a standard for patients with lymphoproliferative disorders is highly recommended.