Category: Lab Tests and Imaging

Categories : Cardiovascular Disease Lab Tests and ImagingTags :

Comprehensive Bloodstream Lipid Level Test Can Predict CVD Decades Early

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Source: Pixabay CC0

Lipidomics, measuring many different bloodstream lipid levels, can predict the risk of developing type 2 diabetes (T2D) and cardiovascular disease (CVD) years in the future, according to a new study in PLOS Biology. Such early prediction through lipidomic profiling may provide the basis for recommending diet and lifestyle interventions before disease develops.

At present, patient history and current risk behaviours are the main predictors for T2D and CVD, along with high- and low-density cholesterol ratios and levels. But there are over one hundred other types of lipids in the blood, which are thought to at least partially reflect aspects of metabolism and homeostasis throughout the body.

Nowadays, it is possible to measure thousands of individual lipids that make up the lipidome. Nuclear magnetic resonance spectrometry (NMR) metabolomics is also being increasingly used in large cohort studies to report on total levels of selected lipid classes, and relative levels of fatty acid saturation.

To find out if detailed lipid profiles could be better predictors, the authors drew on data and blood samples from a longitudinal health study of over 4000 middle-aged participants, first assessed from 1991 to 1994, with follow-up to 2015. Using baseline blood samples, the concentrations of 184 lipids were assessed. During the follow-up period, 13.8% of participants developed T2D, and 22% developed CVD.

The authors performed repeated training and testing on the data to create a risk model. Once the model was developed, individuals were clustered into one of six subgroups based on their lipidomics profile.

Compared to the group averages, the risk for T2D in the highest-risk group was 37%, an increase in risk of 168%. The risk for CVD in the highest-risk group was 40.5%, an increase in risk of 84%. Significant reductions in risk compared to the averages were also seen in the lowest-risk groups. The increased risk for either disease was independent of known genetic risk factors, and independent of the number of years until disease onset.

Rsk could be individually defined decades before disease onset, possibly in time to take steps to avert disease. Lipidomics could be combined with genetics and patient history to provide new insights into the beginnings of the disease. Additionally, new drug candidates could be identified from the lipids  contributing the greatest risk.

“The lipidomic risk, which is derived from only one single mass-spectrometric measurement that is cheap and fast, could extend traditional risk assessment based on clinical assay,” said lead researcher Chris Lauber of Lipotype. “In addition, individual lipids in blood may be the consequences of or contribute to a wide variety of metabolic processes, which may be individually significant as markers of those processes. If that is true, Lauber said, “the lipidome may provide insights much beyond diabetes and cardiovascular disease risk.”

Lauber added: “Strengthening disease prevention is a global joint effort with many facets. We show how lipidomics can expand our toolkit for early detection of individuals at high risk of developing diabetes and cardiovascular diseases.”

Source: EurekAlert!

Categories : Lab Tests and ImagingTags :

New Biosensor Rapidly Measures ATP and Lactate in Blood Samples

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The prototype of the ATP and lactate sensor developed in the study (left); and the integrated sensor chip that detects ATP and lactate levels (right). Credit: Akihiko Ishida, Hokkaido University

Scientists at Hokkaido University have developed a prototype sensor that could help doctors rapidly measures levels of adenosine triphosphate (ATP) and lactate in blood samples from patients, aiding in the rapid assessment of the severity of conditions such as sepsis.

The scientists detailed their prototype biosensor in the journal Biosensors and Bioelectronics.

ATP is a molecule found in every living cell that stores and carries energy. In red blood cells, ATP is produced by a biochemical pathway called the Embden–Meyerhof pathway. Severe illnesses such as multiple organ failure, sepsis and influenza reduce the amounts of ATP produced by red blood cells.

As such, the severity of these illnesses could be gauged by monitoring the amounts of ATP and lactates in a patient’s blood. “In 2013, our co-authors at Tokushima University proposed the ATP-lactate energy risk score (A-LES) for measuring ATP and lactate blood levels to assess acute influenza severity in patients,” explained Akihiko Ishida, an applied chemist at Hokkaido University. “However, current methods to measure these levels and other approaches for measuring disease severity can be cumbersome, lengthy or not sensitive enough. We wanted to develop a rapid, sensitive test to help doctors better triage their patients.”

The researchers developed a biosensor that can detect levels of ATP and lactate in blood with great high sensitivity in as little as five minutes. The process is straightforward. Chemicals are added to a blood sample to extract ATP from red blood cells. Enzymes and substrates are then added to convert ATP and lactate to the same product that can be detected by specially modified electrodes on a sensor chip; the amount of by-product present in the sample increases the electrical current measured.

Schematic representation of the proposed sensor for sequentially detecting ATP and lactate levels in the blood. Through a series of chemical reactions, ATP and lactate are converted to hydrogen peroxide, the breakdown of which to water H2O causes the sensor chip to generate a signal that is detected by the sensor.

The team conducted parallel tests and found that other components present in blood, such as ascorbic acid, pyruvic acid, adenosine diphosphate (ADP), urate and potassium ions, don’t interfere with the ability of the electrodes to accurately detect ATP and lactate. They also compared their sensor with those currently available and found it allowed for the relatively simple and rapid measurement of the two molecules.

“We hope our sensor will enable disease severity monitoring and serve as a tool for diagnosing and treating patients admitted to intensive care units,” said Ishida.

The researchers plan to further simplify the measurement process by integrating an ATP extraction method into the chip itself, as well as reducing the size of the sensor system.

Source: Hokkaido University

Categories : Lab Tests and ImagingTags :

Hypersensitivity Link Between MRI and X-Ray Contrast Agents

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Photo by Mart Production on Pexels

People with a history of hypersensitivity to iodine-based contrast agents for X-ray based scans, are also susceptible to similar reactions from commonly used MRI contrast agents, according to a large, eight-year cohort study. The study, published in the journal Radiology, also found that premedication or switching to a different MRI contrast agent may reduce risk in patients who have had previous contrast agent reactions.

For a long time, gadolinium-based contrast agents (GBCA) have been used to enhance visualisation of organs, tissues and blood vessels on MRI and provide a more accurate depiction of disease. Though GBCA are relatively safe, recent studies have reported several adverse reactions related to their use, including allergic-like hypersensitivity reactions, such as rash and flushing.

These reactions are increasing in incidence with the widespread use of GBCA, prompting an urgent need for research into risk factors, according to the study’s senior author Hye-Ryun Kang, MD, PhD.

Analysing more than 330 000 cases of GBCA exposure in 154 539 patients over an eight-year period, the researchers found 1304 cases of allergic-like hypersensitivity reactions, for a rate of 0.4%. In patients who had a previous GBCE reaction, the average recurrence rate was 15%.

Acute allergic-like hypersensitivity reactions, or those that occur within one hour of contrast administration, accounted for 1178 cases, while a far smaller number of 126 cases were delayed allergic-like hypersensitivity reactions, or those that occur beyond the first hour and mostly within one week after exposure.

The risk of allergic-like hypersensitivity reactions to GBCAs was higher in those with a history of similar reactions to iodinated contrast media. Normally, having a history of iodinated contrast media hypersensitivity was not thought to be a risk factor for hypersensitivity to GBCAs and vice versa, because of their structural and compositional differences.

“The results of our study challenge this idea,” Dr Kang said.

An underlying predisposition to drug allergies in susceptible patients could be the cause, Dr Kang said, as opposed to any cross-reactivity associated with structural similarities between iodinated contrast media and GBCA. In fact, the risk of hypersensitivity reactions to iodinated contrast media was also higher in those who previously experienced a similar reaction to GBCA.

“Thus, physicians should be aware that patients with a history of hypersensitivity to one of iodinated contrast media or GBCA are at greater risk of developing hypersensitivity reactions to the other,” she said.

Analysis of the data showed that premedication, typically with steroids and antihistamines, and changing the GBCA showed preventive effects in patients with a history of acute allergic-like hypersensitivity reactions. Patients who received premedication and before MRI or were switched to a different GBCA showed the lowest rate of recurrence. Only premedication significantly reduced the incidence of reactions in patients with a history of delayed reactions.

“As the most important preventive measure is avoidance of the culprit agent, a precise record of previously used GBCA should be kept for all patients,” Dr. Kang said. “Physicians should discuss appropriate premedication strategies with their patients prior to MRI procedures.”

Dr Kang nevertheless stressed that contrast-enhanced MRI examinations are invaluable in the diagnosis and follow-up of various diseases, and the overall risk remains low.

“As most of these reactions are mild, we believe the benefits of MRI outweigh the potential risks associated with GBCA use,” she said.

Dr Kang recommended that in all patients receiving an MRI with GBCA exposure, a detailed history of previous hypersensitivity allergic reactions be conducted, and when necessary, appropriate prevention measures should be implemented, such as using premedication and switching to different GBCA types.

Future work would be to perform studies with larger populations to identify possible risk factors and effective preventive strategies for delayed hypersensitivity reactions to GBCA.

Source: Radiological Society of North America

Categories : Lab Tests and Imaging Neurodegenerative DiseasesTags :

Blood Test for Alzheimer’s Proves Highly Accurate

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Plaques and neurons. Source: NIAH

A study in the journal Neurology has shown that a less expensive blood test to detect Alzheimer’s is highly accurate at early detection, providing further evidence that the test should be considered for routine screening and diagnosis. 

“Our study shows that the blood test provides a robust measure for detecting amyloid plaques associated with Alzheimer’s disease, even among patients not yet experiencing cognitive declines,” said senior author Professor Randall J. Bateman, MD.

“A blood test for Alzheimer’s provides a huge boost for Alzheimer’s research and diagnosis, drastically cutting the time and cost of identifying patients for clinical trials and spurring the development of new treatment options,” Prof Bateman said. “As new drugs become available, a blood test could determine who might benefit from treatment, including those at very early stages of the disease.”

Developed by Prof Bateman and colleagues, the blood test assesses whether amyloid plaques have begun accumulating in the brain based on the ratio of the levels of the amyloid beta proteins Aβ42 and Aβ40 in the blood.

The gold standard PET scan evaluation requires a radioactive brain scan, at an average cost of $5000–$8000 (R75 000–R120 000) per scan. Another common test, which analyses levels of amyloid-beta and tau protein in cerebrospinal fluid, costs about $1000 (R15 000) but requires a spinal tap process.

This study estimates that prescreening with a $500 (R7500) blood test could halve both the cost and the time it takes to enrol patients in clinical trials that use PET scans. Using only blood testing for screening could be done in under six months, a tenth or less of the cost. The test is currently only available in the US and Europe.

The current study shows that the blood test remains highly accurate, even when performed in different labs following different protocols, and in different cohorts across three continents.

Scientists didn’t know if small differences in sampling methods (such as anticoagulant use) could have a big impact on test accuracy because results are based on subtle shifts in amyloid beta protein levels in the blood. Subtle interfernece in these amyloid protein ratios could have triggered a false negative or positive result.

To confirm the test’s accuracy, researchers tested blood samples from current Alzheimer’s studies in the United States, Australia and Sweden, each of which uses different protocols for the processing of blood samples and related brain imaging.

Findings from this study confirmed that the Aβ42/Aβ40 blood test using a high-precision immunoprecipitation mass spectrometry technique developed at Washington University provides highly accurate and consistent results for both cognitively impaired and unimpaired individuals across all three studies.

When blood amyloid levels were combined with another major Alzheimer’s risk factor – the presence of the genetic variant APOE4 – the blood test accuracy was 88% compared to brain imaging and 93% when compared to spinal tap.

“These results suggest the test can be useful in identifying nonimpaired patients who may be at risk for future dementia, offering them the opportunity to get enrolled in clinical trials when early intervention has the potential to do the most good,” Prof Bateman said. “A negative test result also could help doctors rule out Alzheimer’s in patients whose impairments may be related to some other health issue, disease or medication.”

Source: Washington University School of Medicine

Categories : Lab Tests and ImagingTags :

A New Test to Diagnose Dizziness without Deafening

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Source: Miika Luotio on Unsplash

Swedish researchers have developed a new way to diagnose dizziness problems in a simpler and less painful way than the old method. A bone conduction speaker, easily attached behind the ear, can make the diagnosis more efficient and safer – especially for patients with pre-existing hearing problems.

For patients with dizziness, the relationship of dizziness and hearing is used for diagnosis. Typically, a ‘VEMP’ test (Vestibular Evoked Myogenic Potentials) is performed. With loud sounds, the test evokes a muscle reflex contraction in the neck and eye muscles, triggered by the vestibular system. In their new approach, reported in Communications Medicine, researchers at Chalmers University instead made use of bone-conducted sounds to achieve better results.

“We have developed a new type of vibrating device called B250 that is placed behind the ear of the patient during the test,” said Bo Håkansson, a professor at Chalmers University. “The vibrating device is small and compact in size and optimised to provide an adequate sound level for triggering the reflex at frequencies as low as 250 Hz, which we have found to be optimal for VEMP stimulation. Previously, no vibrating device has been available that was directly adapted for this type of test of the balance system.”

In bone conduction transmission, sound waves are transformed into vibrations through the skull, stimulating the cochlea within the ear, in the same way as when sound waves normally go through the ear canal, the eardrum and the middle ear. This can be used in various technologies such as in hearing aids.

Half of over-65s suffer from dizziness, but the causes can be difficult to diagnose for several reasons. Dizziness in 50% of those cases results from vestibular system problems. But current VEMP methods have major shortcomings and can cause hearing loss and discomfort for patients. The VEMP test uses very high sound levels which can cause permanent hearing damage. Additionally, if certain types of hearing loss are already present, the test can be inconclusive.

“The previous test was like a machine gun going off next to the ear – with this bone-conduction method it will be much more comfortable. The sound levels to which patients are exposed can be minimised. The test can be performed at 40 decibels lower than today’s method, which uses air-conducted sounds through headphones. This eliminates the risk that the test itself could cause hearing damage,” said researcher Karl-Johan Fredén Jansson, who made all the measurements in the project.

“The benefits also include safer testing for children, and that patients with impaired hearing function due to chronic ear infections or congenital malformations in the ear canal and middle ear can still be diagnosed for the origin of their dizziness,” said Prof Håkansson.

The device has now been tested and developed in several patient studies that have been published internationally, both with healthy individuals to obtain normal data, and in patients suffering from various types of dizziness. The device is compatible with standardised equipment for balance diagnostics in healthcare, which makes it easy to use. In addition to the benefits for patients, the cost of the new technology is also judged to be lower than the corresponding equipment used today.

Source: News-Medical.Net

Categories : Environmental Effects Lab Tests and ImagingTags :

Lab Results are Influenced by Ambient Daily Temperatures

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Photo by Louis Reed on Unsplash

Ambient temperature influences many common lab tests, and these distortions likely affect medical decision making, such as whether to prescribe medications, according to new research published in the journal Med. 

To account for this, the researchers suggest that laboratories could statistically adjust for ambient temperature on test days when reporting lab results.

“When a doctor orders a laboratory test, she uses it to shed light on what’s going on inside your body, but we wondered if the results of those tests could also reflect something that’s going on outside of your body” said study co-author Ziad Obermeyer of the University of California, Berkeley. “This is exactly the kind of pattern that doctors might miss. We’re not looking for it, and lab tests are noisy.”

Delving into this problem, Obermeyer and Devin Pope of the University of Chicago analysed a large dataset of test results from different climates. In a sample of more than four million patients, they modelled more than two million test results based on temperature. They measured how day-to-day temperature fluctuations influenced results, over and above the patients’ average values, and seasonal variation.

Temperature was found to affect more than 90% of individual tests and 51 of 75 assays, including measures of kidney function, cellular blood components, and lipids such as cholesterol and triglycerides. “It’s important to note that these changes were small: less than one percent differences in most tests under normal temperature conditions,” Obermeyer said.

These small fluctuations did not likely reflect long-term physiological trends. For example, lipid panels checked on cooler days appeared to suggest a lower cardiovascular risk, resulting in almost 10% fewer prescriptions for cholesterol-lowering drugs called statins to patients tested on the coolest days compared to the warmest days, despite the results likely not reflecting stable changes in cardiovascular risk.

Since the study wasn’t an experiment, the exact mechanisms underlying the fluctuations in lab results could not be pinpointed. However, blood volume, specific assay performance, specimen transport, or changes in lab equipment might explain them. “Whatever their cause, temperature produces undesirable variability in at least some tests, which in turn leads to distortions in important medical decisions,” Pope said.

Laboratories could get around this by statistically adjusting for ambient temperature on the test day when reporting lab results. This could be a way to reduce weather-related variability without expensive temperature control equipment. 

In practice, decisions on adjustment would need to be at the discretion of the laboratory staff and the treating physician, potentially on a case-by-case basis.

According to the authors, the study may also have broader clinical implications. “The textbook way of thinking about medical research is bench to bedside. First, we come up with a hypothesis, based on theory, then we test it with data,” Obermeyer said. “As more and more big data comes online, like the massive dataset of lab tests we used, we can flip that process on its head: discover fascinating new patterns and then use bench science to get to the bottom of it. I think this bedside-to-bench model is just as important as its better-known cousin because it can open up totally new questions in human physiology.”

Source: Science Daily

Categories : Lab Tests and Imaging UncategorizedTags :

A New Alternative to Skin Biopsies

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Source: Pixabay

A new ‘virtual histology’ technology being developed by researchers could replace many skin tissue biopsies. The technology is detailed in Light: Science & Applications. 

Histology is the microscopic study of tissues and organs through sectioning, staining, and examining those sections under a microscope. Often called microscopic anatomy and histochemistry, histology allows for the visualisation of tissue structure and characteristic changes the tissue may have undergone.

“This process bypasses several standard steps typically used for diagnosis – including skin biopsy, tissue fixation, processing, sectioning and histochemical staining. Images appear like biopsied, histochemically stained skin sections imaged on microscope slides,” said the study’s senior author, Aydogan Ozcan, Chancellor’s Professor and Volgenau Chair for Engineering Innovation of the Electrical and Computer Engineering Department at UCLA Samueli.

The technology may enable rapid diagnosis of malignant skin tumours, reducing unnecessary invasive skin biopsies and allowing skin cancer diagnosis at an earlier stage. This technology had only previously been applied to microscopy slides of unstained tissue, acquired through a biopsy. This is the first time virtual histology has been applied to intact, unbiopsied tissue.

“The current standard for diagnosing skin diseases, including skin cancer, relies on invasive biopsy and histopathological evaluation. For patients, this often leads to unnecessary biopsies and scars as well as multiple visits to doctors. It also can be costly for patients and the health care system,” said Dr Philip Scumpia, assistant professor of dermatology and dermatopathology at the David Geffen School of Medicine at UCLA and the West Los Angeles Veterans Affairs Hospital and a member of the UCLA Jonsson Comprehensive Cancer Center. “Our approach potentially offers a biopsy-free solution, providing images of skin structure with cellular-level resolution.”

The research team, led by Ozcan, Scumpia and Dr. Gennady Rubinstein, a dermatologist at the Dermatology & Laser Centre in Los Angeles, created a deep-learning framework to transform images of intact skin acquired by an emerging noninvasive optical technology, reflectance confocal microscopy (RCM), into a format that is user-friendly for dermatologists and pathologists. Analysing RCM images requires special training because they are in black and white, and unlike standard histology, they lack nuclear features of cells.

“I was surprised to see how easy it is for this virtual staining technology to transform the images into ones that I typically see of skin biopsies that are processed using traditional chemical fixation and tissue staining under a microscope,” Dr Scumpia said.

The researchers trained a neural network to rapidly transform RCM images of unstained skin into virtually stained 3D images like the H&E (haematoxylin and eosin) images familiar to dermatologists and dermatopathologists.

“This framework can perform virtual histology on a variety of skin conditions, including basal cell carcinoma. It also provides detailed 3D images of several skin layers,” said Ozcan. “In our studies, the virtually stained images showed similar color contrast and spatial features found in traditionally stained microscopic images of biopsied tissue. This approach may allow diagnosticians to see the overall histological features of intact skin without invasive skin biopsies or the time-consuming work of chemical processing and labeling of tissue.”

“The only tool currently used in clinics to help a dermatologist are dermatoscopes, which magnify skin and polarise light. At best, they can help a dermatologist pick up patterns,” said Rubinstein, who also uses reflectance confocal microscopes in clinic.

The authors said there is a way to go before clinical use, but they aim to introduce the technology at various scales alongside other optical-imaging systems. Once the neural network is “trained,” with many tissue samples and the use of powerful graphics processing units (GPUs), it will be able to run on a computer or network, enabling rapid transformation from a standard image to a virtual histology image.

This technology could usher in a new age of “digital dermatology” and change how dermatology is practised. Additionally, the research team will see if this artificial intelligence platform can work with other AI technologies to look for patterns and further aid in clinical diagnosis.

Source: UCLA

Categories : Lab Tests and ImagingTags :

Discrepancies in Radiology Interpretation

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Source: National Cancer Institute

Researchers who conducted an analysis of nearly six million acute examinations suggest that leaders in imaging practice consider efforts to match interpretation of subspecialty examinations with radiologists’ fellowship training in the acute community setting.

Pointing out that major and minor discrepancy rates were not higher for acute community setting examinations outside of interpreting radiologists’ fellowship training, “discrepancy rates increased for advanced examinations,” acknowledged lead investigators Suzanne Chong from Indiana University in Indianapolis and Tarek Hanna of Emory University. The study was published in the American Journal of Roentgenology.

Using the databank of a large US teleradiology company, Chong, Hanna, and colleagues performed an analysis of 5 883 980 acute examinations that were preliminarily interpreted by 269 teleradiologists with a fellowship of neuroradiology, abdominal radiology, or musculoskeletal radiology. When providing final interpretations, client on-site radiologists voluntarily submitted quality assurance (QA) requests if preliminary and final interpretations were discrepant; the teleradiology company’s own QA committee categorised discrepancies as major (n=8444) or minor (n=17 208).

Among initial teleradiology interpretations of acute community setting examinations, common examinations’ major and minor discrepancies rates were not significantly different when concordant versus discordant with radiologists’ fellowship training. However, advanced examinations’ discrepancy rates were higher when concordant with radiologists’ fellowship (relative risk = 1.45 and 1.17, respectively).

Noting that their findings support multispecialty radiologist practice in acute community settings, “efforts to match examination and interpreting radiologist subspecialty may not reduce diagnostic discrepancies,” the article authors cautioned.

A supplement to the published article is available here [PDF].

Source: American Roentgen Ray Society

Categories : Cancer Lab Tests and ImagingTags :

New HPV Test Enables Precision Treatment

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Source: NCI on Unsplash

Researchers have made advances in improving detection of the human papillomavirus (HPV) in the bloodstream, which could further hone precision treatment of the illness.

The team sequenced circulating tumour DNA, which can lead to the detection of HPV in a person’s blood. Previous science in the field has proven that the virus, which causes cancers in the throat, mouth, and genital areas, can be found in the bloodstream but tests have had limited sensitivity. The new study enables ‘ultrasensitive’ detection, which could pave the way toward greater use of precision medicine for patients with cancers affecting these vulnerable areas of the body.

In a cohort of patients with advanced cervix cancer, the new sequencing method detected 20-fold lower levels of HPV circulating tumour DNA, making it a promising new method to monitor the disease.

The results come from the laboratory of Senior Scientist Dr Scott Bratman at Princess Margaret Cancer Center and are published in Clinical Cancer Research. “Increasingly, as clinicians we’re focused on precision medicine and making sure we’re not over-treating people while still curing them, that’s a very difficult balance to strike,” Dr Bratman said.

One way is to use liquid biopsy approaches or blood-based biomarkers, such as circulating tumour DNA, in order to monitor how the treatment is progressing, he added.

“We’re really at the cusp of a revolution from a technology, clinical implementation and standard of care standpoint, where five to 10 years from now we will not be treating everybody with the same dose of radiation and chemotherapy, and then waiting months to see if the treatment was effective,” he said. “I’m confident we will be giving much more tailored doses.”

When physicians scale back on these treatments, there is a risk of the cancer reoccurring. With more sensitive tests, reoccurrences can be detected early and patients returned to treatment.

“Patients who need more treatment will then be able to continue on, or different treatments can be added,” Dr Bratman said. “We can spare the vast majority of patients who will not need those interventions and provided them with a greater quality of life once they’re cured of the cancer.”

The work will enable further study in the field, refining the approach using larger study groups, and eventually, practice-changing clinical trials. This technique could also be applied to other cancer-causing viruses such as certain types of stomach cancer and lymphomas.

Source: Princess Margaret Cancer Center

Categories : Hospitals Lab Tests and ImagingTags :

Joint Statement Says Prior Radiation Should not Affect Decisions to Image

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Photo by National Cancer Institute on Unsplash

Previous radiation exposure should not be considered when assessing the clinical benefit of radiological exams, according to a statement by three scientific groups representing medical physicists, radiologists, and health physicists.

Medical radiation exposure is a hot topic. People receive average annual background radiation levels of around 3 mSv; exposure from a chest X-ray is about 0.1 mSv, and exposure from a whole-body CT scan is about 10 mSv. The annual radiation limit for nuclear workers is 20mSv.

The American Association of Physicists in Medicine, along with the American College of Radiology and the Health Physics Society, issued a joint statement opposing cumulative radiation dose limits for patient imaging, saying that there could be negative impacts on patient care. The statement opposes the position taken by several organisations and recently published papers.

“It is the position of the American Association of Physicists in Medicine (AAPM), the American College of Radiology (ACR), and the Health Physics Society (HPS) that the decision to perform a medical imaging exam should be based on clinical grounds, including the information available from prior imaging results, and not on the dose from prior imaging-related radiation exposures,” the statement reads.

“AAPM has long advised, as recommended by the International Commission on Radiological Protection (ICRP), that justification of potential patient benefit and subsequent optimization of medical imaging exposures are the most appropriate actions to take to protect patients from unnecessary medical exposures. This is consistent with the foundational principles of radiation protection in medicine, namely that patient radiation dose limits are inappropriate for medical imaging exposures.

“Therefore, the AAPM recommends against using dose values, including effective dose, from a patient’s prior imaging exams for the purposes of medical decision-making. Using quantities such as cumulative effective dose may, unintentionally or by institutional or regulatory policy, negatively impact medical decisions and patient care.

“This position statement applies to the use of metrics to longitudinally track a patient’s dose from medical radiation exposures and infer potential stochastic risk from them. It does not apply to the use of organ-specific doses for purposes of evaluating the onset of deterministic effects (e.g., absorbed dose to the eye lens or skin) or performing epidemiological research.”

The Radiological Society of North America also endorses the position.

The AAPM emphasises the importance of patient safety in their position. Radiation usage must be both justified and optimised and benefits should outweigh the risks.

“This statement is an important reminder that patients may receive substantial clinical benefit from imaging exams,” said James Dobbins, AAPM President. “While we want to see prudent use of radiation in medical imaging, and many of our scientific members are working on means of reducing overall patient radiation dose, we believe it is an important matter of patient safety and clinical care that decisions on the use of imaging exams be made solely on the presenting clinical need and not on prior radiation dose.

“AAPM is pleased to partner with our fellow societies—the American College of Radiology and the Health Physics Society—to bring a broadly shared perspective on the important issue of whether previous patient radiation exposure should play a role in future medical decision making.”

The AAPM cites the International Commission on Radiological Protection, which stresses that setting radiation exposure limits to patients is not appropriate. This is partly due to a lack of standardised dose estimates.

The position only addresses stochastic risks from radiation exposure, which are chance effects whose risk for a given imaging exam, like cancer,is unrelated to the amount of prior radiation. Deterministic effects, incremental, direct exposure responses, such as skin damage, result from different biological mechanisms and are not included.

The AAPM compiled a list of answers to frequently asked questions on the topic of medical radiation safety along with references to research papers which support the organisation’s position.

Source: News-Medical.Net