Fidest – Agenzia giornalistica/press agency

Quotidiano di informazione – Anno 31 n° 259

Posts Tagged ‘radiation’

Study reveals low adoption of advice to reduce nuclear cardiology radiation exposure

Posted by fidest press agency su giovedì, 11 maggio 2017

viennaVienna, Austria. A study in 65 countries has revealed low adoption of International Atomic Energy Agency recommendations to reduce nuclear cardiology radiation exposure. The research is presented today at ICNC 2017 by Dr Edward Hulten, a cardiologist at the Walter Reed National Military Medical Center, Bethesda, USA. Nuclear cardiology uses small amounts of radioactive tracers which are injected into the veins and taken up by the heart. A gamma camera images the radiation from the tracer. The cardiac images are used to measure the heart size and function, identify coronary heart disease, and predict the risk of a heart attack.Dr Hulten said: “Nuclear cardiology is a key part of contemporary cardiology management and around 15 to 20 million procedures are performed annually. It gives information regarding diagnosis, prognosis, and the effects of therapeutic interventions.”“Concerns have been raised about tests, including nuclear cardiology, that expose patients to ionising medical radiation,” he continued. “Medical radiation potentially raises the lifetime risk of cancer which is important for all patients, especially younger patients or when considering additional radiation over time from further medical studies.”
A goal of 9 mSv or less radiation exposure per scan was recommended by the American Society of Nuclear Cardiology (ASNC) in 2010. It was noted in a 2016 International Atomic Energy Agency (IAEA) nuclear cardiology guideline but not formally endorsed as a recommendation.
The IAEA developed eight quality metrics for responsible radiation use in nuclear cardiology: avoiding thallium 201 stress testing, avoiding dual isotope testing, avoiding too much technetium-99m and thallium 201, using stress only imaging, use of camera technologies to reduce dose, use of weight based dosing strategies for technetium-99m, and avoiding inappropriate dosing that can lead to “shine-through” artefacts.The IAEA Nuclear Cardiology Protocols Study (INCAPS) assessed adherence to the eight quality metrics. The present analysis investigated which metrics were most helpful in meeting the ASNC’s 9 mSv target. During one week in 2013, 308 nuclear cardiology laboratories were studied in 65 countries in Africa, Asia, Europe, Latin America, North America, and Oceania. The survey included 7911 nuclear cardiology scans. There was significant variability in adherence to the quality metrics across laboratories and regions. There was low adherence overall, with the majority of sites implementing less than half of the quality metrics.
When the researchers performed multivariable logistic regression analysis, they found that the practices most strongly associated with achieving a 9 mSv or less scan were the use of stress or rest only imaging, avoiding thallium, and use of camera technologies to reduce radiation dose. Dr Hulten said: “When the 9 mSv recommendation was made in 2010 it was suggested that it should be achieved in 50% of scans by 2014. The INCAPS survey shows that there is still work to do. It is possible to reduce radiation exposure with existing techniques. Cadmium zinc telluride (CZT) cameras are more sensitive and allow for reduced dose scanning. With certain tracers you can achieve 1 mSv or less. But some scans use more than 30 mSv, so there is huge variability.” Not every site has all of the hardware and technology, said Dr Hulten, so the first step is to look at what is possible within each lab. He said: “There are improvements every lab can make regardless of money – for example multiple position imaging, weight based dosing and stress only techniques. They do require adapting existing workflows which takes leadership but they should be feasible in most labs.” He added: “Eventually cameras wear out and perhaps the decision on a replacement could factor in a reduced radiation dose which also lowers false positive tests and has the potential to reduce lab costs.” Dr Hulten concluded: “The INCAPS survey is a crucial step towards improving patient care in the field of nuclear cardiology by quantifying worldwide adherence to best practices. Any test involving ionising radiation will increase cancers within a population but the risk must be weighed against the benefit of gaining information about heart disease. The 9 mSv goal is achievable, and the lower the better.”

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Large nuclear cardiology laboratory slashes radiation dose by 60% in eight years

Posted by fidest press agency su domenica, 7 maggio 2017

viennaVienna, Austria. A large nuclear cardiology laboratory has slashed its average radiation dose by 60% in eight years, according to new research presented today at ICNC 2017 and published in JACC: Cardiovascular Imaging.1,2 The study in over 18 000 patients shows dose reductions were achieved despite a large number of obese patients.
“There has been concern amongst the medical community and the public that the radiation from medical diagnostic tests could increase the risk of cancer,” said Professor Randall Thompson, a cardiologist at the Mid America Heart Institute, Kansas City, Missouri, US.
He continued: “Although the risk of harm from an individual nuclear cardiology test is very low – even very conservative estimates suggest only one in 1 000 extra patients would develop cancer 20 years later – the cumulative dose from multiple medical diagnostic tests may be a concern.” Medical societies advocate getting radiation doses as low as is reasonably achievable. There are ways to do this but surveys show that adoption of new technologies, which cost money, and new testing algorithms, which take more physician time, has been slow.
This study assessed the impact on radiation dose of modifying protocols and introducing new hardware (cameras) and post processing software in a large nuclear cardiology laboratory network in Kansas City.The study included the 18 162 single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) studies performed at all four of the Saint Luke’s Mid America Heart Institute nuclear cardiology laboratories from 1 January 2009 to 30 September 2016. SPECT MPI shows how well blood flows through the muscle of the heart and is primarily performed to diagnose the cause of chest pain or to help manage patients with known coronary artery disease. Protocols were modified by performing stress-only tests where possible, which saves the radiotracer dose from the rest scan. Stress and rest scans are still required in some patients since shadowing from body parts can look like a lack of blood flow and two scans can clarify the findings. Technetium tracers are now used instead of thallium 100% of the time at one-third of the radiation dose.Small field of view cameras which have advanced post processing, and a new generation of camera systems which are more sensitive and need less radiotracer injected into the body, have both been introduced. These camera systems are equipped with advanced processing which enhances the nuclear pictures and need less radiation or shorter image acquisition times. Professor Thompson’s laboratory focussed primarily on reducing the radiation dose.
The average radiation dose fell from 17.9 mSv in 2009 to 7.2 mSv in 2016 and the median dose (the 50th percentile) dropped from 10.2 mSv to 2.5 mSv. Professor Thompson said: “There was a dramatic lowering of the radiation dose with all of these concerted efforts. The average dose fell by 60% and the median dropped by 75%.” “The average dose had fallen to 5.4 mSv in 2012 but crept up as we’ve had more obese patients referred in whom we have to use the higher dose protocols,” he added. “But more than half of patients now are tested with a low-dose, stress-only test using the new technology, which is why the median dose of radiation has fallen so dramatically.”
The average background dose for people living in Europe and North America from radon underground and cosmic background sources is about 3 mSv a year. Medical societies consider higher and lower dose tests to be above 10 mSv and below 3 mSv, respectively. In 2010 the American Society of Nuclear Cardiology set a target of 9 mSv or less for the majority of tests. Professor Thompson said: “The majority of studies were in the high dose range back in 2009 and now most tests have a radiation dose that is about a third of the target. This is despite being referred a larger number of obese patients. In the last 2.5 years, 17% of patients have needed the large field of view camera as their average body mass index was 46 kg/m2 and they were simply too big for the small cameras.”He concluded: “By adopting contemporary protocols and technologies it is feasible to substantially lower radiation doses in nuclear cardiology in very large numbers of patients in real world clinical practice.”

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New cardiac imaging technique improves accuracy by removing need to breathe

Posted by fidest press agency su lunedì, 16 maggio 2016

firenzeFlorence, Italy A new technique for cardiac magnetic resonance (CMR) imaging improves accuracy by removing patients’ need to breathe, reveals research presented today at EuroCMR 2016 by Professor Juerg Schwitter, director of the Cardiac MR Centre at the University Hospital Lausanne, Switzerland.1 The lack of motion allows acquisition of higher quality images in less time.
“In many imaging techniques, but particularly in CMR, you need a relatively long acquisition time and must correct for respiratory motion,” said Professor Schwitter. “For decades we have had to correct for respiration when estimating the position and motion of the heart by CMR, and this is not always accurate.” He continued: “In Lausanne, radio-oncologists are exploring a technique called high frequency percussive ventilation. Patients do not need to breathe naturally and no correction for respiratory motion is required. This enables the physicians to more accurately plan the field of radiation to apply in each patient.” For the technique, patients put a mask over their mouth which is connected to a ventilator that delivers small volumes of air, called “percussions”. Instead of the 10 to 15 large breaths patients would take naturally per minute, air is provided in 300 to 500 small ventilations per minute. Air volumes are small so the chest does not move. The procedure is noninvasive, patients are conscious, not sedated, and do not need to breathe.For the current study, the ventilator was adapted for use in the CMR environment. CMR uses a magnet which means that metal parts had to be swapped for MR-compatible ones. Tubes were used to connect equipment inside and outside the scanning room.Professor Schwitter said: “Patients lie face up in the CMR machine and do not need to breathe. They say their chest feels a bit inflated during the ventilation but otherwise it feels okay.”The study was designed to test the feasibility and tolerability of high frequency percussive ventilation during CMR. It included one healthy volunteer aged 38 years and one patient aged 55 years with a thymic lesion. The procedure was well tolerated in both cases. The average time without breathing was ten minutes in the volunteer and six minutes in the patient.The investigators could clearly see the coronary arteries. Lung volumes were “frozen” in full inspiration and the pulmonary vessels were also seen clearly. There was no need to correct for respiratory motion.Professor Schwitter said: “We found that this type of ventilation was feasible and there was no problem with tolerating it. Of course, we are in a very early stage of development and we now need to test it in more patients. Some patients may find it difficult because the CMR machine is small and on top of that they will be ventilated by a machine.”CMR images are currently acquired in steps. Patients breathe in and then hold their breath for each image, then recover before repeating the process for the next image. High frequency percussive ventilation offers the potential to acquire all images in one go, with no need to correct for respiratory motion.
“The possibilities with high frequency percussive ventilation are huge,” said Professor Schwitter. “You could run all the CMR sequences in one batch, which would be much faster. Data could be acquired constantly with fewer artifacts. We might be able to use this technique for diagnosis of sicker patients, who find breath holding difficult and need the imaging to be done quickly.”He continued: “This technique would help us to collect high resolution images where we want millimetric precision, for example to localise scar in the myocardium or to see the anatomy of coronary arteries or valves and malformations. We would have much better conditions because we would not need to correct for motion.”Professor Schwitter concluded: “We have made promising first steps with high frequency percussive ventilation in CMR. In future we could even imagine that if the patient is not breathing for 20 minutes or even longer this technique could give a precise 3D representation of cardiac structures and help guide electrophysiology procedures such as ablation.”
The European Society of Cardiology (ESC) represents more than 95 000 cardiology professionals across Europe and the Mediterranean. Its mission is to reduce the burden of cardiovascular disease in Europe.

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