What Do These CTDI And DLP After An Injury Indicate?

Posted on Mon, 21 Apr 2014

Question: My son is 3.1 Yrs and he went for a helical head ct scan plain on 16 slice Philips scanner as he fallen from height. CT scan report is normal . Displayed CTDI is 38.08 mgy and DLP is 741 mgycm. What will be the absorbed brain and RBM dose. CT scan performed at 249 mAS and 120KV

Answered by Dr. Vivek Chail (3 hours later)

Brief Answer: Please find detailed answer below Detailed Answer: Hi XXXXX, Thanks for writing in to us. Your query is very important and I am glad to be answering it. CTDI is CT dose index and is calculated mathematically and varies in adults and children and with the part to be scanned. DLP is a more accurate measurement of radiation received. Effective dose E = 0.017 x DLP The effective dose is a quantity which is a risk metric, and is not a dosimetric quantity per se. The computation of effective dose is performed by estimating organ absorbed doses (for a list of 15 different organs), and then multiplying each of those by a tissue weighting factor. The tissue weighting factors were computed from radiation epidemiological data, and takes into consideration that some organs (e.g. breasts, stomach, lung) are more radiosensitive than others (e.g. brain, skin). The total effective dose is the sum of all of these products. The effective dose for your son is 12.597 mGy The brain dose is 28 mGy and RBM dose is 9 mGy Hope your query is answered. Do write back if you have any doubts. Regards, Dr.Vivek

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Vivek Chail (1 hour later)

Dear Sir, Thank you very much for your valuable guidance. You have mentioned that effective dose is 12.97 mgy. This Effective dose is for head or Whole body. Is there any risk. Thanks.

Answered by Dr. Vivek Chail (1 hour later)

Brief Answer: Please find detailed answer below Detailed Answer: Hi XXXXX, Welcome and thanks for writing in with an update. The effective dose is for the whole body considering various organs and the amount of dose they get. In my knowledge one CT scan has negligible risk. The risk of radiation effects in a child progressively increases with the third and subsequent CT scans of brain or any other part done within 15 years of age. Hope your query is answered. Do write back if you have any doubts. Regards, Dr.Vivek

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Vivek Chail (11 hours later)

Dear Sir, Thank you once again for your guidance One last question is that as per ICRP103 tisue weight factor for head for 3 Yrs. Child is approximate .005, Which will give effective dose E = 3.7 msv. Please Guide. Thanks

Answered by Dr. Vivek Chail (6 hours later)

Brief Answer: Please find detailed answer below Detailed Answer: Hi XXXXX, Welcome and thanks for writing in with an update. An effective dose of 3.7 mSv is acceptable and not considered to have any impact on his health in the future. Keeping ICRP 103 in practice and after taking all the variables into account the effective dose for your son is within permissible limits. Please do not worry for any increased risk to his health due to radiation. The risk significantly increases with the third CT scan within 15 years of age. Hope your query is answered. Do write back if you have any doubts. Regards, Dr.Vivek

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar