Letter to the Editor: “Patients undergoing recurrent CT scans: assessing the magnitude”

by Pankaj Gupta, M.D. (Pankajgupta959@gmail.com)

Patients undergoing recurrent CT scans: assessing the magnitude

Dear Editor,

I read with interest the paper titled “Patients undergoing recurrent CT scans: assessing the magnitude” by Rehani et al. published in the April issue [1]. I would like to congratulate the authors for this excellent work and highlighting a less well studies aspect of CT radiation dose. I would like to make the following comments.

The minimum time needed to reach a cumulative effective dose (CED) > 100 mSv in a single day in all the institutions is alarming. This group needs further analysis. The number of patients in whom CED > 100 mSv was achieved in a single day must be reported. Although the authors have given possible explanations for achieving this high dose in a single day (multiphasic CT scans, multiple CT scans, interventional CT scans), further details are desirable. With the current CT scanners, reaching this high dose means that patients would have typically received 7-10 CT scans in a single day [2]. This must be a very unique situation and may not be generalizable. Additionally, interventional CT procedures must have being extremely complex to reach to this alarming dose in a single day. Availability of this data would have given some clarity regarding the reasons behind this unexpected observation.

The other unexplained issue in the cohort of patients with CED > 100 mSv is the basic indication for which CT examinations were performed. It is understandable that the current study was not performed with this aim as well as the fact that collecting this information retrospectively is difficult. However, this information may have been extremely useful. The broad categorization of the indications into oncology related vs. non-oncological would have at least provided some insight [3]. Even in the non-oncological indications, there are some diseases, e.g. severe acute pancreatitis, that are known to require multiple CT examinations at shorter intervals and hence more likely to expose the patients to the higher radiation doses [4].

Finally, as already highlighted by the authors, the CED reported in the study is a conservative rather than a realistic estimate given the fact that more “radiation intense” procedures like PET-CT and digital subtraction angiography were not included in the dose calculation. Moreover, the evaluation period for CED estimation was 1-5 years. This means that a higher percentage of patients in the general population may have CED > 100 mSv as well as the maximum radiation dose per patient in > 100 mSv cohort may be even higher.