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What Does The CT Scan Reprot Indicate?

Posted on Sat, 26 Apr 2014

Question: Dear Sir, My Son is 3.1 Yrs. And he went for plain helical head CT scan on 16 Slice Philips Scanner as he fallen from Bed CT scan carried out at 120 KV, 249 mAs CTDI is 38.08 mgy and DLP is 741 mgycm CT Scan report is normal Following are my questions 1.What will be the effective dose from this scan. 2 What will be the absorbed dose for brain & RBM from this scan 3.Any Risk in future 4.What will be effective dose, absorbed dose for brain & RBM from one SKULL ‘X’ Ray

Answered by Dr. Indu Kumar (1 hour later)

Brief Answer: Please find detail answer below. Detailed Answer: Hello XXXX Thanks for writing to HCM CTDI(CT dose index) represents the radiation dose of a single CT slice and is determined using acrylic phantoms.CTDI is CT dose index and is calculated mathematically and varies in adults and children and with the part to be scanned. The dose length product (DLP) is the CTDIvol multiplied by the scan length (slice thickness × number of slices) in centimeters. DLP is independent of the part scanned.Conversion factor is used to estimate the effective dose equivalent.Conversion factor varies with the organs involved. DLP gives exact amount of radiation received. Total effective dose for your son head is 0.017 x DLP So,effective dose for your son is 12.597 mGy The brain dose is 29 mGy and RBM dose is 9 mGy. This much amount of radiation will not cause any problem in future and it is far less below the maximum allowable dose. Skull X-ray (lateral view) effective dose is 0.01mSv. Skull X-ray (AP view) effective dose is 0.03 mSv. Hope i have answered your query. Further queries are most welcome. Take Care Dr.Indu XXXXXXX

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

Follow up: Dr. Indu Kumar (41 minutes later)

Dear Sir, Thank you very much for your immediate & quick response. I have following questions please do the needful. 1. You have mentioned that effective dose for head is 12.597 mgy, in msv what will be value. 2. Conversion factor .017 is used only for head organ or it contents other organs also. 3. In ICRP age specific organ conversion factor, .005 is mentioned for head for 3Yrs. child please confirm. 4. How much amount of radiation will cause any problem . 5. What is the maximum allowable dose. 6. Skull X-ray (lateral view) effective dose is 0.01mSv.Skull X-ray (AP view) effective dose is 0.03 mSv, What will be brain & RBM absorbed dose in this case. Thanks

Answered by Dr. Indu Kumar (20 hours later)

Brief Answer: Please find detail answer below Detailed Answer: Hello XXXX, Thanks for writing back 1.mgy and msv both are S.I units and values are same. 2.Conversion factor .017 is constant to all organs. 3.Up to 5 mSV is the maximum allowable annual dose limit. You shouldn't be worried about radiation hazard due to CT Brain.It is far less than the hazardous dose. Hope i have answered your query. Further queries are most welcome. Take Care Dr.Indu XXXXXXX

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

Follow up: Dr. Indu Kumar (37 minutes later)

Dear Sir, Thank you very much for your immediate & quick response. 1.My question is that you have used .017 in your calculation whether it is for head organ or it involves other organs also. 2. Whether conversion factor .005 is correct or not. 3. How many ct scan can increase risk 4. What will be the absorrbed brain and rbm dose from one skull x ray. Thanks

Answered by Dr. Indu Kumar (19 hours later)

Brief Answer: Please find detail answer below. Detailed Answer: Hello XXXX, Thanks for writing back (1) .017 is constant for all organs. (2)Conversion factor .017 is constant to all organs.Conversion factor .005 is also correct and it is more apppropriate. (3)Below 16 years of age,risk increases after two CT Scans. (4) Absorbed brain dose in one skull X-ray is 1.5 mGY whereas RBM dose is insignificant. Hope i have answered your query. Further queries are most welcome. Take Care Dr.Indu XXXXXXX

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

Follow up: Dr. Indu Kumar (1 hour later)

Dear Sir, Thanks for your update my last query is 1. In head ct scan, which organs are scanned. 2. For Effective dose calculation which conversion factor is to be used .017 or .005 3. Below 16 Yrs. of age two head ct scans is safe or it involves any risk. Thanks

Answered by Dr. Indu Kumar (5 hours later)

Brief Answer: Please find detail answer below. Detailed Answer: Hello XXXX, Thanks for writing back 1.In head CT scan,head part is only scanned. 2.Conversion factor .017 or .005 both are correct.We can use either.There is very negligible difference in between them. 3.Up to two scans it is considered as harmless. Hope i have answered your query. Further queries are most welcome. Take Care Dr.Indu XXXXXXX

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