OR, does the use of these radionuclide tracers, themselves, add a significant risk of causing cancer in patients?
The dose of ionizing-radiation from the tracer used in one PET scan, for example, typically exposes the patient to about 25% of the maximum allowable annual radiation exposure permitted for nuclear workers (which is a VERY high limit = to over 200 standard/modern medical chest xrays, meaning a patient is getting exposed to the equivalent of about 50x chest xrays ALL AT ONCE for each PET test).
https://en.wikipedia.org/wiki/Positron_emission_tomography
Dear Bob,
Actually, some of them appear to be not quite safe. For example, there are risks of a Gallbladder Radionuclide Scan.
The Risks of a Gallbladder Radionuclide Scan
There is a risk of exposure to radiation with this test. The gallbladder radionuclide scan uses small amounts of radioactive tracers. However, this test has been used for over 50 years and there are no known long-term side effects from such low doses of radiation. The benefits of the tests outweigh the risk of radiation exposure (Radiology, 2012).
There is, however, a rare chance of an allergic reaction, which is typically mild.
On the other hand, others were proved to be safe. For example, in the bone scan:
The amount of the radionuclide injected into your vein for the procedure is small enough that there is no need for precautions against radioactive exposure. The injection of the tracer may cause some slight discomfort. Allergic reactions to the tracer are rare, but may occur.
Hoping this will be helpful,
Rafik
Dear Bob,
Actually, some of them appear to be not quite safe. For example, there are risks of a Gallbladder Radionuclide Scan.
The Risks of a Gallbladder Radionuclide Scan
There is a risk of exposure to radiation with this test. The gallbladder radionuclide scan uses small amounts of radioactive tracers. However, this test has been used for over 50 years and there are no known long-term side effects from such low doses of radiation. The benefits of the tests outweigh the risk of radiation exposure (Radiology, 2012).
There is, however, a rare chance of an allergic reaction, which is typically mild.
On the other hand, others were proved to be safe. For example, in the bone scan:
The amount of the radionuclide injected into your vein for the procedure is small enough that there is no need for precautions against radioactive exposure. The injection of the tracer may cause some slight discomfort. Allergic reactions to the tracer are rare, but may occur.
Hoping this will be helpful,
Rafik
As Rafiq mentioned, I would say that the answer to your question is simple; generally no and specifically yes in certain circumstances (possibly in the long run affecting genetic structure and function as a whole for the species.
Do what you have to do so long you seriously consider the need vs the long term known and unknown effects of such diagnostic modalities, and or therapies.
A good question, however.
Kind regards
Suresh
thank you Lawrence for explaining the idea well
Thanx all for contributing your wisdom on the subject.
And, Dear Napoleon just a situation where someone is going to kill you with a weapon and you know that the person can be made calm with music, then it is foolish to use a weapon to kill him (no matter how strong the present statistics are) even if every time you have used a weapon you have missed the target (you could kill this present person, and for that there are no statistics and would likely be present only after 20-200 years in him or the species)
Could we settle on a common ground; that if something is very serious happening and cannot be diagnosed by all non nuclear and XR modalities, and where no action can be taken due to no knowledge of the cause, one may resort to these modalities (safest first, and unknown last).
I haven't seen a disease yet that cannot be diagnosed with other modalities but nuclear/XRs these days. Use of Gamma knife surgery on dangerous area tumors difficult to reach like brain tumors is fantastic for the reasons (certainly not the gamma radiations) well known to many surgeons, esp the neuro-surgeons. However, market forces do not let this to happen commonly and the machine are not sufficiently produced hence very expensive and most neurosurgeons will loose there skills. Moreover that is the reason a cardio surgeon will take 3-4 hours to do a bypass (most bypass surgeries - fee $10000) rather than take 3-4 hours to explain the details of how and why and lifestyle management to such patients (fee - only around $200).We reward surgery and disregard the prevention effort - what would the surgeon do - surgery ...right?
My apologies and clarification is just for the sake of explaining how we are rewarded to treat the patients, and we are not rewarded to keep them healthy. Hope you will forgive me.
Love you all
Suresh
Dear Colleagues,
Good Day,
Here is an introduction of "Radioisotopes in Medicine- (Updated 24 September 2015)"
- Nuclear medicine uses radiation to provide diagnostic information about the functioning of a person's specific organs, or to treat them. Diagnostic procedures using radioisotopes are now routine.
- Radiotherapy can be used to treat some medical conditions, especially cancer, using radiation to weaken or destroy particular targeted cells.
- Tens of millions of nuclear medicine procedures are performed each year, and demand for radioisotopes is increasing rapidly.
- Sterilization of medical equipment is also an important use of radioisotopes.
Radionuclide therapy (RNT)
Rapidly dividing cells are particularly sensitive to damage by radiation. For this reason, some cancerous growths can be controlled or eliminated by irradiating the area containing the growth.
External irradiation (sometimes called teletherapy) can be carried out using a gamma beam from a radioactive cobalt-60 source, though in developed countries the much more versatile linear accelerators are now being utilised as a high-energy x-ray source (gamma and X-rays are much the same). An external radiation procedure is known as the gamma knife radiosurgery, and involves focusing gamma radiation from 201 sources of cobalt-60 sources on a precise area of the brain with a cancerous tumour. Worldwide, over 30,000 patients are treated annually, generally as outpatients.
Internal radionuclide therapy is by administering or planting a small radiation source, usually a gamma or beta emitter, in the target area. Short-range radiotherapy is known as brachytherapy, and this is becoming the main means of treatment. Iodine-131 is commonly used to treat thyroid cancer, probably the most successful kind of cancer treatment. It is also used to treat non-malignant thyroid disorders. Iridium-192 implants are used especially in the head and breast. They are produced in wire form and are introduced through a catheter to the target area. After administering the correct dose, the implant wire is removed to shielded storage. This brachytherapy (short-range) procedure gives less overall radiation to the body, is more localised to the target tumour and is cost effective.
Treating leukaemia may involve a bone marrow transplant, in which case the defective bone marrow will first be killed off with a massive (and otherwise lethal) dose of radiation before being replaced with healthy bone marrow from a donor.
Many therapeutic procedures are palliative, usually to relieve pain. For instance, strontium-89 and (increasingly) samarium 153 are used for the relief of cancer-induced bone pain. Rhenium-186 is a newer product for this.
Lutetium-177 dotatate or octreotate is used to treat tumours such as neuroendocrine ones, and is effective where other treatments fail. A series of four treatments delivers 32 GBq. After about four to six hours, the exposure rate of the patient has fallen to less than 25 microsieverts per hour at one metre and the patients can be discharged from hospital. Lu-177 is essentially a low-energy beta-emitter (with some gamma) and the carrier attaches to the surface of the tumour.
A new field is targeted alpha therapy (TAT) or alpha radioimmunotherapy, especially for the control of dispersed cancers. The short range of very energetic alpha emissions in tissue means that a large fraction of that radiative energy goes into the targeted cancer cells, once a carrier such as a monoclonal antibody has taken the alpha-emitting radionuclide such as Bi-213 to exactly the right places. Clinical trials for leukaemia, cystic glioma and melanoma are under way. TAT using lead-212 is increasingly important for treating pancreatic, ovarian and melanoma cancers.
An experimental development of this is boron neutron capture therapy using boron-10 which concentrates in malignant brain tumours. The patient is then irradiated with thermal neutrons which are strongly absorbed by the boron, producing high-energy alpha particles which kill the cancer. This requires the patient to be brought to a nuclear reactor, rather than the radioisotopes being taken to the patient.
Radionuclide therapy has progressively become successful in treating persistent disease and doing so with low toxic side-effects. With any therapeutic procedure the aim is to confine the radiation to well-defined target volumes of the patient. The doses per therapeutic procedure are typically 20-60 Gy.
Treatment may involve significant radioactivity, e.g. 4.4 GBq is quoted as an average dose of iodine-131 for thyroid ablation, and up to 11 GBq for patients with advanced metastatic disease. According to US regulatory guidelines for I-131, the patient can be released if the activity is below 1.2 GBq, or 0.07 mSv/hr at 1 metre. Meanwhile a lot of I-131 is flushed down the hospital toilet and plumbing needs to be shielded accordingly.
So, it is definitely safe to certain level(ie it should not exceed a certain times within specific usage).
Please, see the following links for more information regarding the thread...
http://www.world-nuclear.org/info/non-power-nuclear-applications/radioisotopes/radioisotopes-in-medicine/
http://www.hopkinsmedicine.org/healthlibrary/test_procedures/neurological/positron_emission_tomography_pet_scan_92,P07654/
http://www.cancer.org/treatment/understandingyourdiagnosis/examsandtestdescriptions/imagingradiologytests/imaging-radiology-tests-nuc-scan
http://www.radiochemistry.org/nuclearmedicine/diagnostics/01_diagnostics.shtml
From the standpoint of medical ethics for all equipment for diagnosis and treatment there compliance with the conditions of safety for the patient and the doctor. Such compliance is observed if all the steps of the protocol using the device. If we take into account the situation in violation of the protocol operation of medical devices, it is the subject of a judicial investigation. Unfortunately, such examples exist.
Dear Vladimir thanx for your information, appreciate that.
Thanx, rather many thanx for your input, Lawrence and Rafik, and I am for any type of management (even that of a quack so long it makes patient's life better in any which way (more peaceful last says/weeks of life, prolong life to significant extent without making that prolonged life without making that life more unbearable for the person.
Many many thanx to you Hazim for giving such a wonderful insight into the views of scientists and research. And that was necessary to have come out in this discussion. However, I have hardly any opinion saying is is bad per se. What at times I see is at many places in our writings that say it is safe and then full stop when we haven't even past 50 years of use of nuclear medicine to see the late results. History tells us that Hiroshima bomb still has effects seen in the plants and soil of the area and their estimate of it going for decades is evident. Hiroshima has affected earth (that has lived for millions of years. In comparison to that size and capability of the earth system, human body is not even a speck.
Before going further here is a real unbelievable but true calculation; all the 7 billion people on earth if dumped in to a cube, we need only a little above 1 km cube (all populations in one KM cube ...wao). Imagine how much surface area average human being has in comparison to earth.Now imagine the size of our gene and see if the radiation we are giving to individuals these days vs gene's capacity to modify and, or mutate under that huge pressure would bring about a change some time in the future. Finally imagine the safety results found till today are studying genes for that effect in people kind of impossibility at this stage, especially when we are not looking for it, we are only looking for voluntarily reported side effects). It may take a 100 years to find that in the generations down the line. Saying that I take you back to continue with the previous paragraph of mine as follows:
Misuse of medicine, diagnostics, treatment and management of the diseases is horrifying. Ask me and please believe me (i have been up to my nose in the 40+ years of my absolute (unless mistakenly not at times) ethical medical practice I have predominantly seen, experienced and have records for proving that, in that we have gone down hill since we have abandoned clinical practice and resorted to high tech practice. I do not deny that there are professionals who have kept the image of us (physicians and scientists) still at the highest. You know and I know the misuse of science and technology and medicine industry developments.
Yes, of course nothing is good or bad, but in our hands everything can become bad if we do not know how, where and when to use, and would the alternatives could do the job or not.
Finally, I have used (advised use of) almost everything but extremely cautiously and helped people well. But I still believe we have to try avoid things we are not sure of until the the price to pay is death of the patients/grave harm to them/grave late stage of harm to our planet or species.
No matter how much we believe in them and use them, the question still remains; how safe and whether it is worth applying under the circumstances of the individual and his ailment.
It is wonderful to see you all contributing in more and more detail, and no one is wrong, but the procedures one day may be found to be wrong, for now they may be right, but not under the circumstances as has happened in Hiroshima or Chernobyl.
Really really really love you all.
Suresh
According to the source you mentioned the dose during PET-CT can be 23-26 mSv. Average dose for people in Poland is 3.35 mSv per year (from natural sources). There are regions in Norway and France were the average dose from natural sources is about 40 mSv per year and in some regions of Brazil, India and Canada it is 70 mSv per year.
It is assumed that the dangerous dose resulting with high probability of the radiation sickness is about 200-300 mSv. The lethal dose is about 3000-5000 mSv at once (3-5 Sv). Such dose is used during radical radiotherapy before the bone marrow transplantation (TBI - Total Body Irradiation).
Limits in radiotherapy are from linear model which seems to be very restrictive and used because of the population fear of radiation (some people say it is radiation phobia).
Dear Bob D. Skiles
There are two main application of radionuclides in medicine. 1) Diagnostics: More than 90 % of radionuclide imaging/diagnosis is performed with Technetium-99m and Fluorine-18. 2) Therapeutic: Some of the the radionuclides used in therapy are iodine-131, yittrium-89, lutetium-177.
Their application is governed by their mode of decay.
Typically diagnostic radionuclides decay via positron emission which subsequently interacts with electrons and release gamma rays (those radionuclides used in PET, eg, fluorine-18) and via gamma radiation (those used in SPECT, eg, Technetium-99m).
Typically therapeutic radionuclides decay via particle emission (electron emission, eg, I-131 or alpha(α) emission (essentially 2 protons and 2 neutrons, eg bismuth-212, actinium-225).
The side effects (toxicity...) of radionuclides is a result of the interaction of emitted particles or gamma rays with the environment (in our case with cells or cellular components such as DNA) and generally refered as ionizing radiation (capability of the gamma rays or particles to ionize matter). The order of magnitude of ionizing radiation of decay modes is α-particles>>beta particle (electrons)>>gamma rays. Hence, from this you can deduce that radionuclides used for therapeutic purposes have generally higher probability of causing side effects than those used in diagnostic nuclear medicine and this is indeed the case.
In short: Radionuclides used for diagnosis have minimal or no significant side effects but radionuclids used for therapy have unwanted side effects. However, all forms of treatment (diagnosis) is about benefit-to-risk and the use of radionuclides is no exception and the benefit out-weighs the risk when appropriately used.
Remember, every time you are on the beach sunbathing you are exposing yourself to gamma rays (but you still happily do it :).
Hope this helps you to have an idea to your questions
Dear Lawrence
Mine doesn't come from underestimating or negligence. Every conceivable medical treatments incur a risk (whether psychological or other form). it is about the benefit to risk ratio analysis that determines the decision. about sunbathing you missed the point deliberately or not!
New York Times once stated that
What makes Americans sick is an 'epidemic of diagnoses', that leads to an 'epidemic of treatments' which 'turns ordinary people into patients'.
Much has been already told about radiation risks from PET etc. from previous responders.
Risk benefit ratio is the guiding principle:
If the patient can die of a disease, instead of worrying about the risks of radiation, it is prudent to do the test. At the same time unnecessary tests should be avoided.
=Excess of even innocuous salt and water is poisonous=.
==Little deviation from topic, because MRI was also discussed somewhere in one of the past replies.==
Recent reports are even raising the question mark on the safety of MRI whereby they have detected that long acquisition time can induce certain pre-cancerous changes and go on to say that the MRI can also be carcinogenic.
The evidence of MRI being unsafe was accumulating from lab studies and finally latest study in human beings has given credibility to past evidence:
1. In 2008, in-vitro, Simi et al. found
MRI scan can have genotoxic effects, it causes micronuclei (MN) induction in lymphocytes, MN are early events in carcinogenesis. They found it to be reversible: as after 48 hrs, MN number returned to the control values.
2. In 2011, in-vitro, According to Lee et al.
There is genotoxic potential of 3 T clinical MRI. They studied cultured human lymphocytes in vitro and observed a significant increase in the frequency of single-strand DNA breaks
following exposure to a 3 T MRI which increased in a time-dependent manner.
3. In 2013, in-vivo, i.e. Patients, Fiechter et al. found
DNA double-strand breaks (DSBs) in human blood lymphocytes after Cardiac MR examination.
4. In 2015, in-vivo, i.e. Patients, According to Lancellotti et al. found DNA damage after CMR in their paper: Biological Effects of Cardiac Magnetic Resonance on Human Blood Cells
Source: http://circimaging.ahajournals.org/content/8/9/e003697.full#sec-24
MRI studies in 20 patients showed minor but significant immediate blood cell alterations or activations figuring inflammatory response, as well as DNA damage in T lymphocytes observed from day 2 until the first month but disappearing at 1-year follow-up.
As the last two studies are in living patient, hence should be more credible.
My Suggestion: As the
-number of MRI tests are increasing
-number of indication for MRI increasing
-strength of Magnetic field increasing
-duration of MR studies is increasing
for the current, what can be said is:
-It is advisable that MRI is used prudently, avoiding unnecessary examinations, according to the precautionary principle.
-Considering the increased use of MR scanners there is an urgent need to perform studies to provide assurance about their safety. Especially:
Contrary to what is believed that: MRI is safe for children and pregnant women that view needs a thorough review.
Now Cardiac MRI tests being increasingly used in children. The tissues in children and in fetus(es) of pregnant lady also undergo rapid division.
Therefore, MRI test that last long and repeated MRI tests should be done carefully in this group.
Further, if patient is already having some cancer, what can be the impact of MRI on existing lesions should also be investigated.
Dr. Vijay Gupta
This debate reflects the natural concern of citizens in the safety of modern methods of diagnostics and therapy. We know about the side effects of Pharmaceuticals. For example, chemotherapy, some patients are more destructive than the cancer process. But the main thing. Clinicians should consider comply with all instructions and protocols based on the patient's condition. Clinicians should also consider and implement alternative methods of diagnostics and therapy. Therefore, the covenant of the Hippocratic "do no harm to the patient" remains firm.
The small rates of radiation is considered vital for surviving the man (or any animal) as it is stimulating the immunal response of living organism. The 25% of the admittable dose is 1/4 of the dose that is considered to make NO effect to the organism (as it is comparable with the dose from natural environment including natural cosmic radiation.
Yes, Konstantin, all life developed on Earth in terms of radiation exposure. But now people are scared and taught endless technological accidents. This factor is also advisable to take into account when people are worried for their lives.
Yes, I agree. The number of Peaceful nuclear reactors operating to date is almost 500 (485 ). The number of nuclear propulsion reactors (nuclear submarines and icebreakers), operated to date is almost 500 (491). The number of accidents is 7. This makes much less than 1%. Keep in mind that one reactor can operate for 40 years.
These are just figures demonstrating the safety level to date. Hope it will improve.
I think hat physicians judge the benefit against risk before use the radioisotopes with patient else they should use other diagnostic techniques as MRI or ultrasonic.
Considering ultrasonic procedures I should draw attantion to the fact that the physics while analysing the effect of ultrasonic radiation to water propose wave mecanism including the break of homogenity and OH and H radical formation. This is almost identical to gamma-ray (E less 0.5 MeV) effect on water. Hydrogen peroxide is thus formed in the microbubbles.
Yes, radionuclides can add some risk of causing cancer in patients several years after exposure. But if I am a patient now, suspecting of having cancer now, then I would not hesitate to have PET scan done to diagnose my cancer now and get right treatment now.
ICRP Publication 128 issued in 2015 provides an update on dose to patients from radiopharmaceuticals, including those for PET studies.
http://www.icrp.org/publication.asp?id=ICRP%20Publication%20128
ICRP Task Group 101 will provide a report including discussion on risk estimates in relation to therapy with radiopharmaceuticals.
http://www.icrp.org/icrp_group.asp?id=94
If for you "safe" means "no risks", using PET is not safe. But the same is true for not using it.
Otherwise, if it means "clinical benefits are greater than risks", then the answer is definitively yes (assuming you use it according to the clinical guidelines).
For example, in radiotherapy:
- no PET: bad treatment, with risk of no local control and higher secondary effects.
- PET: good treatment, with risk of radiation induced cancer same years later (due to the PET).
Well used, PET always benefits the patient (survival and quality of life will be better).
FDG-PET is currently the best example of clinical molecular imaging techniques and unique method for testing tumors in our body. FDG-PET pro-finds its place in the new algorithms and guidelines for the management of cancer, in many countries with different systems of health care.
This all makes sense only under one condition to apply the correct algorithm for the diagnosis and this is quoting others. Dr. Vijay Gupta who gave an excellent answer with which I fully agree, this is the
"
"Risk benefit ratio is the guiding principle:
If the patient can die of a disease, instead of worrying about the risks of radiation, it is prudent to do the test. At the same time unnecessary tests should be avoided "
Regards.
Even if the benefit of the test outweighs the risk of ionizing radiation exposure, an effort to reduce radiation exposure of patients is still important, along with the protection of medical stuff.
In medicine, nothing is safe. Justification of prescribing any imaging test or any treatment is very important to ensure benefit outweigh the risk. Even nonradiation ultrasound and MR may result untoward effects from gadolinium or ultrasound contrast. Furthermore, as for now, it is still hard to judge at which level of radiation exposure limit is safe. We are living in the world of radiation. Exposure is more from long journey flight than PETCT.
To judge at which level of radiation exposure limit is safe is to consider which level of risk we tolerate.
A new whole body PET system is being built and named aptly as EXPLORER..... It is expected to reduce radiation dose from PET to 1/40th of current exposure making a scan equal to a flight journey from Heathrow to New York and back.......
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