Guest guest Posted June 9, 2002 Report Share Posted June 9, 2002 , It is a test to measure what your body needs for ablation. I enclose an explanation for you. " Dosimetry adjusts the therapeutic dose to compensate for patient to patient variability in the rate of iodine clearance. It is used to determine the expected dose to the whole body, blood, and sites of functioning thryoid tissue (thyroid bed, mets). A dose of 1-2 mCi of I-131 is usually adequate for dosimetry. Conditions such as renal failure, ascites, or pleural effusions can all result in prolonged retention of I-131. " Gail dx: 1968, TT, pap. & foll. well differentiated w/hurthle cell, RAI, rad.neck dissection,lung surgery, hashimoto, tg antibody 575, iodine resistant,existing thyca nodules in lungs. Last surgery 1972 > I can't seem to find out anywhere so I thought I'd try again here and post my question very specifically. > > 1. TECHNICALLY, What is a dosemitry study? > 2. What EXACTLY does it involve? > 3. How does it aid in determining a more appropriate dose of I-131? > > Thank-you so much for being here always, > Bergeron > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 10, 2002 Report Share Posted June 10, 2002 I realize why it is done I was actually looking for a more technical explanation of the entire process. I was given 4 mCi this morning. If anyone is interested in finding out more about what is involved feel free to contact me. I will know a lot more here in the next week. I am scheduled to be at the hospital on Wed, Thurs and again on Mon, Tues. Bergeron -- On Mon, 10 Jun 2002 05:32:47 fotoladyx2 wrote: >, >It is a test to measure what your body needs for ablation. I enclose an >explanation for you. > > " Dosimetry adjusts the therapeutic dose to compensate for >patient to patient variability in the rate of iodine clearance. It is >used to determine the expected dose to the whole body, blood, >and sites of functioning thryoid tissue (thyroid bed, mets). A dose >of 1-2 mCi of I-131 is usually adequate for dosimetry. >Conditions such as renal failure, ascites, or pleural effusions >can all result in prolonged retention of I-131. " > >Gail >dx: 1968, TT, pap. & foll. well differentiated >w/hurthle cell, RAI, rad.neck dissection,lung surgery, >hashimoto, tg antibody 575, iodine resistant,existing >thyca nodules in lungs. Last surgery 1972 > > > > >> I can't seem to find out anywhere so I thought I'd try again here and post my question very specifically. >> >> 1. TECHNICALLY, What is a dosemitry study? >> 2. What EXACTLY does it involve? >> 3. How does it aid in determining a more appropriate dose of I-131? >> >> Thank-you so much for being here always, >> Bergeron >> > > > _______________________________________________________ WIN a first class trip to Hawaii. Live like the King of Rock and Roll on the big Island. Enter Now! http://r.lycos.com/r/sagel_mail/http://www.elvis.lycos.com/sweepstakes Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 10, 2002 Report Share Posted June 10, 2002 I don't think you'll get much response regarding dosimetry on this listserv, because it isn't the norm for most of us to have dosimetry studies. You might try posting your questions on the Advance Thyca List because I am sure some of them have had to go thru this process. Meanwhile, we'd appreciate it if you would post the info about your week's adventure when it's all done and you know the outcome. Marilyn > I realize why it is done I was actually looking for a more technical explanation of the entire process. I was given 4 mCi this morning. If anyone is interested in finding out more about what is involved feel free to contact me. I will know a lot more here in the next week. I am scheduled to be at the hospital on Wed, Thurs and again on Mon, Tues. > > Bergeron Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 10, 2002 Report Share Posted June 10, 2002 At 11:53 PM 6/9/2002 -0400, you wrote: >1. TECHNICALLY, What is a dosemitry study? >2. What EXACTLY does it involve? >3. How does it aid in determining a more appropriate dose of I-131? > > Thank-you so much for being here always, > Bergeron A dosimetry study is a method to determine the relationship between the radiation absorbed dose of an administered dose of radioactive iodine for a single patient. There are two different doses (radiation absorbed dose and administered dose) which are different as follows: Administered Dose: This is the dose of radioactivity that your doctor gives you as in mCi of I-131. This is measured in mCi (millcuries) or GBq (gigabecquerels). Radiation Absorbed Dose: Whenever you get radiation, either internal like radioiodine or external like external beam therapy, a certain amount of radiation goes through you without being absorbed and a certain amount is absorbed by your body. Radiation may not be absorbed either because the radiation emitted from a radioactive atom did not interact with your body or because the radioactive atom was excreted before it emitted any radioactivity. The part that goes through you without being absorbed has no biological significance. The part that gets absorbed causes the intended effects and side effects of radiation. When radiation is absorbed by tissue, it is just the conversion of radiant energy (like light) to chemical energy (breaking of chemical bonds, formation of free radicals, production of new chemicals, etc.). This is the radiation absorbed dose and is measured in Rads. A Rad is not an absolute value of energy, but is a concentration of energy in a particular organ (100 ergs/gram of organ tissue). This is because the effect of radiation on an organ (like causing cell injury, cell death or inducing a cancer) is related to the concentration of energy. For any one person at any point in time there is a linear relationship between the administered dose and the radiation absorbed dose. That is if you double the administered dose, you double the radiation absorbed dose. However the exact relationship varies among different people and varies within the same person over time. The higher the radiation absorbed dose to the thyroid cancer, the more likely the cancer will be killed. However, the higher the radiation absorbed dose, the more likely you will have side effects. We know the relationship between the administered dose and radiation absorbed dose for the average patient and we know the range of individual patient variability. The usual doses given for thyroid cancer (30-200 mCi) take this variability into account. However, for some patients one wants to have a more accurate estimate of the relationship between the administered dose and the radiation absorbed dose. Usually this is because the physician knows the patient is not average (for example, they are very young, very small, or have kidney disease) or because the physician wants to give the maximum dose to the cancer that is unlikely to cause life threatening side effects. The goal of dosimetry is to determine the relationship of the administered dose and the radiation absorbed dose for a single patient. A dosimetry study involves taking a known test dose of radioiodine and then measuring the loss of radioiodine from the blood and whole body. In some cases it also include measurement of the uptake of radioiodine by areas of thyroid cancer. The blood measurement is done with blood sampling. The whole body measurement is done with whole body counting using a probe, gamma camera or whole body counter, complete urine collections or both. (Dr. Ain and I have found urine measurements to be very unreliable and do not use them.) Generally measurements are performed every day for 4-5 days. For example, we obtain blood and whole body counts at 2 hours, 1, 2, 3, and 4 days after ingestion of the radioiodine. The exact times and number of samples may vary from institution to institution. The blood and urine samples are measured. The blood, urine and whole body measurements are put into a computer to estimate the Rads (radiation absorbed dose) to the whole body and blood for each mCi (administered dose). The faster that the iodine is excreted from the body and the less the body retains at any point in time, the lower the Rads/mCi. The advantage of dosimetry is that it allows physicians to choose a dose with greater confidence that the dose will not cause serious or life threatening side effects. Generally this is to choose doses in excess of 200 mCi, but can also be used to choose doses less than 200 mCi in patients with other issues that increase the risk of serious side effects. In general dosimetry is not required for the average patient getting doses up to 200 mCi. Jeff A. , MD A@... Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 10, 2002 Report Share Posted June 10, 2002 , I am scheduled for the scan on June 27th and the RAI the 28th. I do have a few questions.. 1) Did you do the LID? What did you eat? 2) Did you go through Hipo hell? Did you work? 3) Are you planning on being isolated for awhile? 4) What is the scan like? 5) When do you do your RAI? I go off my Citomil today and a bit aprehensive about all that is to follow... I hope all works out well for you.. Given DX 5/3/02 TT 5/13/02 RAI 6/28/02 Re: HELP w/ dosemitry I realize why it is done I was actually looking for a more technical explanation of the entire process. I was given 4 mCi this morning. If anyone is interested in finding out more about what is involved feel free to contact me. I will know a lot more here in the next week. I am scheduled to be at the hospital on Wed, Thurs and again on Mon, Tues. Bergeron -- On Mon, 10 Jun 2002 05:32:47 fotoladyx2 wrote: >, >It is a test to measure what your body needs for ablation. I enclose an >explanation for you. > > " Dosimetry adjusts the therapeutic dose to compensate for >patient to patient variability in the rate of iodine clearance. It is >used to determine the expected dose to the whole body, blood, >and sites of functioning thryoid tissue (thyroid bed, mets). A dose >of 1-2 mCi of I-131 is usually adequate for dosimetry. >Conditions such as renal failure, ascites, or pleural effusions >can all result in prolonged retention of I-131. " > >Gail >dx: 1968, TT, pap. & foll. well differentiated >w/hurthle cell, RAI, rad.neck dissection,lung surgery, >hashimoto, tg antibody 575, iodine resistant,existing >thyca nodules in lungs. Last surgery 1972 > > > > >> I can't seem to find out anywhere so I thought I'd try again here and post my question very specifically. >> >> 1. TECHNICALLY, What is a dosemitry study? >> 2. What EXACTLY does it involve? >> 3. How does it aid in determining a more appropriate dose of I-131? >> >> Thank-you so much for being here always, >> Bergeron >> > > > _______________________________________________________ WIN a first class trip to Hawaii. Live like the King of Rock and Roll on the big Island. Enter Now! http://r.lycos.com/r/sagel_mail/http://www.elvis.lycos.com/sweepstakes For more information regarding thyroid cancer visit www.thyca.org. If you do not wish to belong to this group, you may UNSUBSCRIBE by sending a blank email to thyca-unsubscribe Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 10, 2002 Report Share Posted June 10, 2002 I recently had dosimetry done and here's what it entailed: 1. I went hypo and tsh had to be above 30. then, on a Monday morning I was given 1 millicurie of I131 2. Every two hours on Monday they took blood and did a whole body count (not to be confused with a whole body scan). For a whole body count you just stand on one side of the room with a detector across the room and it counts for five minutes how much radiation is coming off your body. 3. Tuesday morning and every morning until Friday morning they took blood and did the whole body count. 4. Friday they took the data and used some equations developed by a guy back in the 1940's to calculate the effective dose to the bone marrow. They then used this figure to determine the largest dose of I131 that could be administered to me without exceeding the highest allowable dose to the one marrow (i.e. you don't want to completely kill off your immune system). 5. The next Monday morning they gave me the big dose, the highest allowable dose, the one they had calculated based on the week-long dosimetry the week before. 6. I stayed inpatient isolation since it was a high dose. Of course I was doing the LID for two weeks before the dosimetry study started and stayed on it until released from the hospital. Also they had me take lithium for three days prior to the big dose until five days after, because it has been shown that lithium makes the thyca cells retain the I131 longer thus making it more effective at eradicating it. That was my experience with dosimetry... -Alyssa in Idaho Falls (still recovering from the whole experience) Bergeron wrote: > > I can't seem to find out anywhere so I thought I'd try again here and > post my question very specifically. > > 1. TECHNICALLY, What is a dosemitry study? > 2. What EXACTLY does it involve? > 3. How does it aid in determining a more appropriate dose of I-131? > > Thank-you so much for being here always, > Bergeron > > dx 12/00 pap 8 pos nodes both lobes 175 mCi > post scan showed expected activity in the neck > 12/01 TSH around 70 TG 38 > scan with tracer dose showed nothing 205 mCi > post scan showed activity in the chest > currently hypo TG 15 > under going dosimetry study for third dose of rai > > _______________________________________________________ > WIN a first class trip to Hawaii. Live like the King of Rock and Roll > on the big Island. Enter Now! > http://r.lycos.com/r/sagel_mail/http://www.elvis.lycos.com/sweepstakes > > For more information regarding thyroid cancer visit www.thyca.org. If > you do not wish to belong to this group, you may UNSUBSCRIBE by > sending a blank email to thyca-unsubscribe > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 10, 2002 Report Share Posted June 10, 2002 Oh, sorry. They gave me 400 mci. It might have been more but my white count was low to start with and then was complicated by the fact that another medication I take lowers the white count too. The worst thing about it for me was that you have to be hypo for an extra week while the dosimetry study is done and for me that took my tsh from 48 to 130 and at 130 I was miserable, barely able to walk or talk. aaltraveler wrote: > > > > > 5. The next Monday morning they gave me the big dose, > > the highest allowable dose, the one they had calculated > > based on the week-long dosimetry the week before. > > Alyssa.....you can't keep us in suspense! How much did the > dosimetry study conclude was ok? What was your dose of RAI? > Inquiring minds (me) want to know! LOL. > > Marilyn > > For more information regarding thyroid cancer visit www.thyca.org. If > you do not wish to belong to this group, you may UNSUBSCRIBE by > sending a blank email to thyca-unsubscribe > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 10, 2002 Report Share Posted June 10, 2002 > 5. The next Monday morning they gave me the big dose, > the highest allowable dose, the one they had calculated > based on the week-long dosimetry the week before. Alyssa.....you can't keep us in suspense! How much did the dosimetry study conclude was ok? What was your dose of RAI? Inquiring minds (me) want to know! LOL. Marilyn Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 10, 2002 Report Share Posted June 10, 2002 Thanks for letting us know your dose. Hope you are on the mend (didn't you travel to KY for RAI?). I can only imagine how difficult it must have been to have to become more and more hypo so that the study could be done. At least you are back on meds and will be able to salvage most of the summer! Best wishes for a speedy recovery! Marilyn > > > > > 5. The next Monday morning they gave me the big dose, > > > the highest allowable dose, the one they had calculated > > > based on the week-long dosimetry the week before. > > > > Alyssa.....you can't keep us in suspense! How much did the > > dosimetry study conclude was ok? What was your dose of RAI? > > Inquiring minds (me) want to know! LOL. > > > > Marilyn > > > > For more information regarding thyroid cancer visit www.thyca.org. If > > you do not wish to belong to this group, you may UNSUBSCRIBE by > > sending a blank email to thyca-unsubscribe@y... > > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted June 10, 2002 Report Share Posted June 10, 2002 That's the first I've heard about the lithium. I wonder how many doctors know about that? magummy@... Re: HELP w/ dosemitry I recently had dosimetry done and here's what it entailed: 1. I went hypo and tsh had to be above 30. then, on a Monday morning I was given 1 millicurie of I131 2. Every two hours on Monday they took blood and did a whole body count (not to be confused with a whole body scan). For a whole body count you just stand on one side of the room with a detector across the room and it counts for five minutes how much radiation is coming off your body. 3. Tuesday morning and every morning until Friday morning they took blood and did the whole body count. 4. Friday they took the data and used some equations developed by a guy back in the 1940's to calculate the effective dose to the bone marrow. They then used this figure to determine the largest dose of I131 that could be administered to me without exceeding the highest allowable dose to the one marrow (i.e. you don't want to completely kill off your immune system). 5. The next Monday morning they gave me the big dose, the highest allowable dose, the one they had calculated based on the week-long dosimetry the week before. 6. I stayed inpatient isolation since it was a high dose. Of course I was doing the LID for two weeks before the dosimetry study started and stayed on it until released from the hospital. Also they had me take lithium for three days prior to the big dose until five days after, because it has been shown that lithium makes the thyca cells retain the I131 longer thus making it more effective at eradicating it. That was my experience with dosimetry... -Alyssa in Idaho Falls (still recovering from the whole experience) Bergeron wrote: > > I can't seem to find out anywhere so I thought I'd try again here and > post my question very specifically. > > 1. TECHNICALLY, What is a dosemitry study? > 2. What EXACTLY does it involve? > 3. How does it aid in determining a more appropriate dose of I-131? > > Thank-you so much for being here always, > Bergeron > > dx 12/00 pap 8 pos nodes both lobes 175 mCi > post scan showed expected activity in the neck > 12/01 TSH around 70 TG 38 > scan with tracer dose showed nothing 205 mCi > post scan showed activity in the chest > currently hypo TG 15 > under going dosimetry study for third dose of rai > > _______________________________________________________ > WIN a first class trip to Hawaii. Live like the King of Rock and Roll > on the big Island. Enter Now! > http://r.lycos.com/r/sagel_mail/http://www.elvis.lycos.com/sweepstakes > > For more information regarding thyroid cancer visit www.thyca.org. If > you do not wish to belong to this group, you may UNSUBSCRIBE by > sending a blank email to thyca-unsubscribe > > Quote Link to comment Share on other sites More sharing options...
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