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

by Madan. M. Rehani (madan.rehani@gmail.com))

Patients undergoing recurrent CT scans: assessing the magnitude

Dear Editor-in-Chief,

We have read with interest the letter to the editor by Dr. Pankaj Gupta on our recent paper “Patients undergoing recurrent CT scans: assessing the magnitude” [1]. We thank Dr. Gupta for the observations, comments and will like to respond to concerns and questions raised.

The first question is on further information about patients who received 100mSv+ in a single day. We were conscious of several questions to arise if we had published only above paper alone that assesses mainly the size of the cohort [1]. Therefore, we published other two papers also [2, 3] simultaneously which automatically handled many questions on what this cohort consists of, their age, gender distribution and partly the classification into malignant and non-malignant diagnosis [3]. Yes, the characterization of cohort with 100 mSv+ on a single day was only flagged in our paper but not deliberated further and Dr. Gupta’s question on that issue is very pertinent. We have submitted a paper analyzing 34 patients who underwent 37 CT guided interventional procedures, each procedure resulting in over 100 mSv. Thus, it is not only > 100 mSv in a single day but all these are cases in a single procedure. Since the study is under publication, Dr. Gupta and readers are requested to watch for our paper which has been submitted. We agree with Dr. Gupta that this observation is nothing short of alarming. In fact, the size of the 100 mSv+ cohort in our papers [1, 2] is itself alarming. We believe that most centers active in CT-guided interventions will find such patients and we encourage investigators to publish their data so as to confirm our findings and create better awareness that is so much needed. We have another paper appearing very soon in American Journal of Roentgenology on patients who received over 100 mSv through fluoroscopic guided interventional procedures. It provides detailed analysis of type of procedures and their frequency. We have yet another paper that should appear in few months analyzing data of thousands of patients who received over 100 mSv in a single day through CT exams, whether multiphase CT or CT guided interventions. The comment on unique or generalizable tends to get cleared with size of cohort and number of facilities covered and creates pressing condition for others to verify.

Another point raised by Dr. Gupta is on basic clinical conditions involved in cohort of patients with 100 mSv+ through recurrent imaging. Our paper [3] provides this information in which Table 2 provides top 50 most frequently occurring clinical reasons for CT imaging in patients with non-malignant diagnoses and of age ≤ 40 years. It provides frequency of occurrences in the 100 mSv+ cohort. Such information cannot be available in large multicentric studies such as in paper [1] in view of IRB clearance/ ethical committee requirements and patient data sharing obstacles. But the single institution data from a large hospital [3] does provide needed information. Our studies provide the path for other institutions to explore in their set up. We appreciate work on severe acute pancreatitis by Gupta et al. [4] as that is one condition which has not received so much attention when it comes to high doses.

On the final comment by Dr. Gupta, we are happy that our message that our estimates are conservative rather than realistic has been rightly noted. Yes, when nuclear medicine exams and interventional procedures are added, the percentage will be higher. Further, the comment that higher percentage will be found if the data collection period is increased is also correct.

Patients with such high cumulative doses as 100 mSv+ is a relatively new area and we expect there will be many papers appearing in coming months and years that will provide answers to many questions that arise from our papers, besides confirming our findings reported in [1-3].