Introduction

Lymphomas is a heterogeneous group of malignant tumors characterized by lymph nodes and extralymphatic organs involvement. There are more than 30 different morphological variants of lymphomas that combined into two large groups – Hodgkin Disease (HD) and Non-Hodgkin's Lymphomas (NHL). In a view of the systemic nature of disease, whole body CT scan is carried out before start of treatment for tumor staging [1]. Additionally, CT is used for intermediate control in the course of chemotherapy, for radiotherapy treatment planning, and to monitor patients after treatment.

It is well known that CT is a relatively high radiation dose diagnostic imaging modality [2]. In oncology CT is the most commonly used diagnostic technique and its contribution to the radiation exposure of the population increases. So, share of CT examinations in roentgenodiagnostics in Belarus in 2007 was 1.8% but 25% in N.N. Alexandrov National Cancer Center of Belarus (35049 CT examinations). In 2012 the proportion of CT examinations at our institution increased to 43% (43717 examinations).

Concerns about radiation doses in diagnostic imaging are associated, in particular, with stochastic effects of irradiation such as radiation-induced cancer and heritable effects. According to the International Commission on Radiological Protection (ICRP), there is no minimum threshold of radiation dose below which cancer induction is not possible (linear no-threshold concept). The risk of radiation- induced cancer is 1 in 20000 after irradiation at a dose of 10 mSv [3], which roughly corresponds to one CT scan of abdomen and pelvis. Irradiation of patients during medical X-ray diagnostic procedures can be the cause of 1-3 % of cancers [4].

The aim of our study was to determine the number, types and timing of CT examinations in patients with lymphoma, to estimate cumulative effective dose and attributable risk of cancer.