PET CT with Radioactive isotope F18-FDG

[JLee]

Hi,
I am having a PET-CT with F18-FDG isotope. My question is firstly related to how long not to be around my children, the recommdendation is 6 hours after the scan although I see various instructions throughout the internet of up to 24 hours.

Second, how long should I avoid feeding my 6 month old baby - she is breastfed and taking some solids but refuses a bottle. (We will need to use a syringe). The advice is not to feed for 6 hours, although we can use the milk from 3 hours - but again I have seen alot of differing advice on the web. Are there any specific studies regarding this - I have attempted to research this but have come up with nothing thus far in my sleep deprived and worried state! (I am also a physician).

Many thanks in advance for any suggestions.

[admin]

JLee:

Fludeoxyglucose F 18 is a positron-emitting radiopharmaceutical used in conjunction with positron emission tomography (PET Scanning) to detect alterations in tissue glucose metabolism and is useful in detecting brain tumors, certain malignancies, chronic coronary artery disease, partial epilepsy, and Alzheimer's disease.[1,2,3]

FDG, as a glucose analog, is taken up by high-glucose-metabolizing cells throughout the body. About 75% is sequestered within the cell until metabolized or decayed. The radioactive Fluorine-18 decays rapidly within the cell with a half-life of 110 minutes. About 20% of the dose is rapidly cleared renally by 2 hours. The urine is therefore radioactive for several hours after administration of this isotope. Thus, about 20% of the dose is rapidly cleared from the body. Only 80% remains to decay. By 24 hours (13 half-lives) only 1 part in 8200 parts of the initial radiation remains.[4]

Fludeoxyglucose F 18 is rapidly distributed to all parts of the body that have significant glucose metabolism, including the breast. In a group of 6 lactating women, who received between 50-160 MBq FDG, amounts reported in milk were very low.[5] Decay-corrected activity measurable in breast milk ranged from 5.54 to 19.3 Bq/mL/MBq injected. Interestingly, the levels in breast tissue were quite high, but this product seems to be sequestered in lactocytes in breast tissue without penetrating into milk. The calculated maximum cumulative dose to the infant, 0.085 mSv with no interruption of breastfeeding, is well below the recommended limit of 1 mSv. Indeed, a higher radiation dose is received by the infant from close contact with the breast than from ingestion of radioactive milk. The authors suggest pumping of the milk and feeding in bottles by another individual to reduce direct exposure to radiation.

The half-life of the F-18 is short, only 110 minutes. Due to concentration in some tissues such as the bladder, radiation exposure could be a problem and emptying of the breast at routine intervals would reduce radiation exposure to breast tissue. The USPDI(1994) recommends interruption of breastfeeding for 12-24 hours. At 9 hours, 97% of the radioisotope remaining in the tissues would be decayed away.[6] It is likely that after 12 hours, almost all radioisotope would be decayed to almost background levels. Recommend pumping and dumping of breastmilk after the procedure for at least 12 hours to avoid all radiation. Close contact with infants should probably be avoided for about 9 hours, due to release of gamma radiation from the mother.


1.Jamieson D, Alavi A, Jolles P, Chawluk J, Reivich M. Positron emission tomography in the investigation of central nervous system disorders. Radiol Clin North Am 1988; 26(5):1075-1088.
2.Jones SC, Alavi A, Christman D, Montanez I, Wolf AP, Reivich M. The radiation dosimetry of 2 [F-18]fluoro-2-deoxy-D-glucose in man. J Nucl Med 1982; 23(7):613-617.
3.Som P, Atkins HL, Bandoypadhyay D, Fowler JS, MacGregor RR, Matsui K, Oster ZH, Sacker DF, Shiue CY, Turner H, Wan CN, Wolf AP, Zabinski SV. A fluorinated glucose analog, 2-fluoro-2-deoxy-D-glucose (F-18): nontoxic tracer for rapid tumor detection. J Nucl Med 1980; 21(7):670-675.
4.Fludeoxyglucose F-18, http://en.wikipedia.org/wiki/Fludeoxyglucose_(18F)
5.Hicks RJ, Binns D, Stabin MG. Pattern of uptake and excretion of (18)F-FDG in the lactating breast. J Nucl Med. 2001 Aug;42(8):1238-42. PubMed PMID: 11483686.
5.Jones SC, Alavi A, Christman D, Montanez I, Wolf AP, Reivich M. The radiation dosimetry of 2 [F-18]fluoro-2-deoxy-D-glucose in man. J Nucl Med 1982; 23(7):613-617.


Regards

Tom Hale Ph.D.

[JLee]

Many thanks Tom, that has been really helpful.

Just a quick question I neglected to include:- how long do I need to be away from my 2 year old? (Could I be in the room next door for example). I'm just trying to work out where to go after the scan and dont want to put her in danger. They have advised 3 hours of being away from her but I wonder if it really needs to be longer.
Thanks


[QUOTE=admin;321]JLee:

Fludeoxyglucose F 18 is a positron-emitting radiopharmaceutical used in conjunction with positron emission tomography (PET Scanning) to detect alterations in tissue glucose metabolism and is useful in detecting brain tumors, certain malignancies, chronic coronary artery disease, partial epilepsy, and Alzheimer's disease.[1,2,3]

FDG, as a glucose analog, is taken up by high-glucose-metabolizing cells throughout the body. About 75% is sequestered within the cell until metabolized or decayed. The radioactive Fluorine-18 decays rapidly within the cell with a half-life of 110 minutes. About 20% of the dose is rapidly cleared renally by 2 hours. The urine is therefore radioactive for several hours after administration of this isotope. Thus, about 20% of the dose is rapidly cleared from the body. Only 80% remains to decay. By 24 hours (13 half-lives) only 1 part in 8200 parts of the initial radiation remains.[4]

Fludeoxyglucose F 18 is rapidly distributed to all parts of the body that have significant glucose metabolism, including the breast. In a group of 6 lactating women, who received between 50-160 MBq FDG, amounts reported in milk were very low.[5] Decay-corrected activity measurable in breast milk ranged from 5.54 to 19.3 Bq/mL/MBq injected. Interestingly, the levels in breast tissue were quite high, but this product seems to be sequestered in lactocytes in breast tissue without penetrating into milk. The calculated maximum cumulative dose to the infant, 0.085 mSv with no interruption of breastfeeding, is well below the recommended limit of 1 mSv. Indeed, a higher radiation dose is received by the infant from close contact with the breast than from ingestion of radioactive milk. The authors suggest pumping of the milk and feeding in bottles by another individual to reduce direct exposure to radiation.

The half-life of the F-18 is short, only 110 minutes. Due to concentration in some tissues such as the bladder, radiation exposure could be a problem and emptying of the breast at routine intervals would reduce radiation exposure to breast tissue. The USPDI(1994) recommends interruption of breastfeeding for 12-24 hours. At 9 hours, 97% of the radioisotope remaining in the tissues would be decayed away.[6] It is likely that after 12 hours, almost all radioisotope would be decayed to almost background levels. Recommend pumping and dumping of breastmilk after the procedure for at least 12 hours to avoid all radiation. Close contact with infants should probably be avoided for about 9 hours, due to release of gamma radiation from the mother.


1.Jamieson D, Alavi A, Jolles P, Chawluk J, Reivich M. Positron emission tomography in the investigation of central nervous system disorders. Radiol Clin North Am 1988; 26(5):1075-1088.
2.Jones SC, Alavi A, Christman D, Montanez I, Wolf AP, Reivich M. The radiation dosimetry of 2 [F-18]fluoro-2-deoxy-D-glucose in man. J Nucl Med 1982; 23(7):613-617.
3.Som P, Atkins HL, Bandoypadhyay D, Fowler JS, MacGregor RR, Matsui K, Oster ZH, Sacker DF, Shiue CY, Turner H, Wan CN, Wolf AP, Zabinski SV. A fluorinated glucose analog, 2-fluoro-2-deoxy-D-glucose (F-18): nontoxic tracer for rapid tumor detection. J Nucl Med 1980; 21(7):670-675.
4.Fludeoxyglucose F-18, http://en.wikipedia.org/wiki/Fludeoxyglucose_(18F)
5.Hicks RJ, Binns D, Stabin MG. Pattern of uptake and excretion of (18)F-FDG in the lactating breast. J Nucl Med. 2001 Aug;42(8):1238-42. PubMed PMID: 11483686.
5.Jones SC, Alavi A, Christman D, Montanez I, Wolf AP, Reivich M. The radiation dosimetry of 2 [F-18]fluoro-2-deoxy-D-glucose in man. J Nucl Med 1982; 23(7):613-617.


Regards

Tom Hale Ph.D.[/QUOTE]

[admin]

I would suggest you stay away from her for about 12 hours. As for the distance to the next room, I don't really know how far this should be, but I would suggest at least 10-20 feet. I'm not sure how much energy this gamma ray has.

Tom Hale Ph.D.

[CTsings]

Question - if rads seem to concentrate in breast tissue, and not breastmilk, why would the frequent emptying of the breast reduce radiation exposure in the breast tissue?

It's very tricky to advise a nursing mother whose radiology department tells them 6-8 hrs and I'm giving information that says 12-24 hrs!

[admin]

CTsings:

Because nothing is absolute, some radiation is certain to enter milk, although most resides in the lactocytes themselves. Lactocytes are always dying off and being sluffed off in milk. Thus an exceedingly small amount would probably enter milk.

It is well known that afer 5 half-lives, about 98.5% of any radioisotope is decayed to background. However, its the 1.5% that in some instances ( I-131) is worrying because of the massive doses sometimes used.

In this case, about 5 half-lives is probably long enough to wait and 'reduce' the exposure of the infant via milk. This would be about 9.2 hours. But there would still be a small amount retained for the next few hours.

Regards

Tom Hale Ph.D.
InfantRisk Center