Space radiation: Should frequent flyers worry?

We’re bombarded with the radiation of supernovae and other cosmic sources when we fly – how concerned should we be?

Plane surrounded by sun flare (Getty Images)

One day, shortly before boarding a flight from Paris to Montreal, I began to think about the risks of flying for the first time. It was not the fear of engine failure or crashing into a mountain that worried me. Rather I realised I was about to make my 39th plane journey of the year, and as a result was exposing myself to higher than normal levels of radiation from space.

Like most holidaymakers, I had checked the weather forecast. But now, as I waited to board the plane, I wondered whether I and other frequent flyers should be more concerned with checking the space weather before we take off.

The Earth is constantly being bombarded by high speed, sub-atomic particles. These interact with the atmosphere and our planet’s magnetic field to generate cosmic radiation which rains down on us. Our exposure levels rise when we travel by plane, especially at higher altitudes and latitudes.

What do scientists know about the dangers that cosmic radiation might pose during regular flights, and is there anything that aviation authorities or passengers can do to minimise risk?

Cosmic radiation consists mainly of protons and helium nuclei that originate outside our galaxy. Scientists have long speculated over their origins, with likely candidates being powerful events such as star collisions, gamma ray bursts, black holes and supernovae – explosions that mark the death of large stars. Earlier this year US astronomers concluded supernovae were indeed a significant source of cosmic radiation hitting Earth. Particles thrown out by our Sun are another source.

These sub-atomic particles can be both low- and high-energy. Many are deflected by the Earth’s magnetosphere, without which cosmic rays would wipe out complex life forms pretty quickly by damaging tissue, DNA and causing lethal radiation sickness. Only very high-energy cosmic rays can reach our atmosphere at latitudes close to the equator, however lower-energy ones can reach polar latitudes.

Those that do penetrate the Earth’s magnetic shield collide with nitrogen, oxygen and other atoms in the air, generating highly energetic and invisible showers of ionised “secondary particles”, which cascade down on us in vast numbers, penetrating everything and everyone. The atmosphere provides good protection for those on the ground because particles hitting them will have undergone more collisions with atoms, but exposure is greater at high altitudes because the air is thinner.

Body shock

What can this do to the body? Cosmic radiation is ionising, which means the particles involved are energetic enough to knock charged particles from atoms – potentially causing chemical changes in body tissue that can increase risks from cancers and genetic abnormalities.

While this might sound scary, it should be made clear that we are regularly exposed to low doses of ionising radiation in other forms with no apparent health consequences in the overwhelming majority of cases – from radon in the air, naturally occurring radioactive substances in the ground such as uranium, building materials and during medical procedures.

The risks of individuals suffering health effects as a result of being exposed to ionising radiation of any kind – whether from cosmic rays, a nuclear power plant, an X-ray machine, or airport full body scanner – are measured in sieverts or rems (1 sievert equals 100rem). “The same potential risks exist,” says Major Alan Hale at the US Air Force School of Aerospace Medicine, based at Wright-Patterson Air Force Base, Ohio. “Health risk assessments are based on frequency, duration, and intensity level.”

The average person on Earth is exposed to around 350 millirems (mrem) per year. The average annual dose for US citizens is 620mrem , according to the US National Council on Radiation Protection and Measurements. About half of this comes from man-made sources such as X-ray, mammography and CT scans, while the other half comes from natural sources, of which only about 9% comes from cosmic radiation.

Cosmic radiation exposure levels during flights vary according to altitude, latitude and the space weather at the time. Typically, passengers flying from London to Chicago could expect to be exposed to around 4.8mrem, and those travelling from Washington DC to Los Angeles would be exposed to close to 2mrem. This compares to an airport body scanner which delivers around 0.1mrem and a chest X-ray that can vary between 2mrem and 10mrem.

As people travel more often and further away, frequent travellers should be aware of their exposure levels, says Mike Lockwood, professor of space environment physics at Reading University in the UK. “No need to panic, but cosmic radiation should not be ignored,” he says.

Your flight route is particularly important to consider, because exposure rises at higher latitudes. Because cosmic radiation particles are charged, they are deflected towards the North and South Poles by the Earth’s magnetic field lines. At these latitudes the magnetic field lines are closer to vertical, making it easier for cosmic ray particles to enter the atmosphere.

Airlines, however, prefer polar routes because they are shorter with lower head winds, meaning shorter journey times and lower fuel costs. A number of flights from the US to northern Europe and Asia pass directly over the North Pole – for example from San Francisco to Paris. The same goes for flights from, say, Santiago in Chile to Sydney in Australia, which cross the South Pole. “Airlines rotate staff around flight routes so nobody does exclusively polar routes,” says Lockwood.

Risky business

In the US, pilots and flight attendants have been officially classed as “radiation workers” by the Federal Aviation Administration since 1994. Staff regularly working on high-latitude flights are exposed to more radiation than workers in nuclear power plants. Despite this, the airlines don’t measure the radiation exposure of their staff, or set safe limits on the doses they can safely receive.

Among flight crews, there has been a lot of research into links between cosmic radiation and health risks, especially cancer. However, attempting to work out whether small additional doses of ionising radiation are linked to actual disease is far from straightforward.

In 2002, Scandinavian researchers analysed data from 10,000 male airline pilots over 17 years, and found they were at greater risk of developing melanoma and prostate cancer. However the charity Cancer Research UK says this may be related to other lifestyle factors such as the pilots spending more time sunbathing than the average person.

Two different groups of scientists from Japan and Italy combined their efforts in 2006 to look at health risks to female flight crew members from cosmic radiation. They found that women working on planes were more likely than average to develop breast cancers and melanomas, but again the authors admitted they could not be sure this was to do with cosmic rays. A meta-analysis published last year in the Journal of Radiological Protection concluded that overall cancer risk was not elevated, but that “malignant melanoma, other skin cancers and breast cancer in female aircrew have shown elevated incidence.”

Most plane passengers, however, needn’t worry too much, unless they fly regularly over the poles, says Lockwood. Even though their exposures might take them over the recommended annual dose, these limits have been set well below the level likely to cause actual health problems, he says. More dangerous would be spending a lot of time in Cornwall, in the UK, where naturally-occurring radon gas seeping from the ground means inhabitants are exposed to 780mrem per year, nearly three times the national average.

And while some fear that unborn babies could be at risk from cosmic radiation during flights, this is unlikely to be the case unless the women are flying several times a week, according to the US Aerospace Medical Association.

Sun trap

There are however times when cosmic radiation becomes more of a concern because of emissions from our Sun. Usually the solar energetic particles (SEPs) that reach us are of low energy, but the Sun is temperamental.

Levels of radiation and brightness from our star vary, with peaks in both occurring approximately every 11 years. The more sunspots appear on the surface, the more active the sun becomes and the more protons it sends our way. But the sun also has much longer phases, and currently, it is at a grand solar maximum – a phase that began in the 1920s. During this phase, the peaks of the solar cycle are larger and huge magnetic storms on the surface of the Sun, called coronal mass ejections (CMEs) or solar flares, are more frequent. These events fill space with streams of high-energy protons and electrons, some of which quickly reach Earth.

Measurements show solar activity has begun to calm recently and past experience indicates that it will continue to fall over coming decades. Once the Sun leaves its grand maximum, there will be fewer solar storms, but theory suggests those that do occur could be more powerful, ejecting more dangerous high energy particle in our direction. In short, passengers should expect higher exposures in the coming decades.

“Solar energetic particles events are difficult to assess, but being aloft at high latitudes during a big solar storm would be a large dose,” says Lockwood. “There are no studies that give the actual risk factor, but you certainly wouldn’t want it to happen twice to one individual.”

People who have been unlucky enough to get caught in such an event should be informed, he adds. “It would not be wise for them to risk a second such exposure, and more regular health checks would be a good idea, as we already do for recognised radiation workers”. According to NASA, a strong solar storm in late October 2003 subjected passengers on polar flights – from Chicago to Beijing, for instance – to radiation well above the limit recommended by the International Commission on Radiological Protection.

Cosmic forecasting

Very few passengers check the space weather when they fly, but airlines do. In some instances they have varied flight paths to lower latitudes because of predicted solar activity, particularly SEP events during solar flares. “The most pressing reason for this is that the SEP cause radio blackouts,” says Lockwood.

So what can passengers concerned about their exposure to cosmic radiation do, short of stopping flying? Could they perhaps choose to sit in parts of planes that are subject to a lower dose of particles, or fly only at night, in order to put the Earth between them and the Sun? Unfortunately all seats on aircraft are equally affected and exposures are just as high at night.

Would it be possible to shield planes? After all, crew quarters onboard the International Space Station, which is located at the outskirts of the Earth’s magnetosphere, are lined with high-density polyethylene several centimetres thick. The hydrogen atoms in it are great at absorbing and dispersing radiation.

The airline industry is increasingly using carbon fibre-based composites to build planes because of their strength and low weight. These are much better protection against cosmic radiation than standard aluminium, and metals in general, says physicist Nasser Barghouty at Nasa’s Marshall Space Flight Center in Huntsville, Alabama.

In the meantime, the US Federal Aviation Administration’s Civil Aerospace Medical Institute has an online tool that allows individuals who are concerned to calculate their cosmic radiation exposure levels on specific routes.

Cosmic radiation comes in a wide variety of forms at varying energy levels, and calculating the health effects of low doses of radiation on specific individuals is complex, and inevitably involves simplification and estimation. The research that has been carried out on those who fly most frequently – airline crew – is far from conclusive.

The available evidence suggests that those who fly occasionally have little to worry about. Likewise most frequent flyers are also probably fine but could protect themselves with more frequent medical check-ups if they are worried.

So next time you fly, consider the galactic radiation from supernovae all around you – but try not to let it spoil your trip.

Routine Urinalysis Not Helpful After Blunt Abdominal Trauma.

Routine urinalysis after blunt abdominal trauma won’t help find urogenital injury, Dutch researchers say.

“With the advancements made in CT scanning, there is now much greater accuracy in the detection (or ruling out) of injury to the urogenital system,” Dr. J. Carel Goslings from Academic Medical Center in Amsterdam told Reuters Health.

“In this study,” Dr. Goslings added, “we found the value of the routine performance of urinalysis in patients with a blunt trauma mechanism to be limited.”

The retrospective study involved 1815 patients. Most patients — 1031, or 57% — also had imaging studies, according to a paper online September 16th in Emergency Medicine Journal.

Among the patients who had imaging studies done, 795 (77%) had no hematuria, 220 (21%) had microscopic hematuria, and 16 (2%) had macroscopic hematuria.

Of the 220 patients with microscopic hematuria, eight had abnormal urogenital imaging studies, but only three of the eight had clinical consequences. Another eight patients with microscopic hematuria did have clinical consequences despite normal-looking imaging.

There were 332 patients who had urine collected but no imaging studies. In this group, 278 patients (84%) had no hematuria. In the 54 patients (16%) who did have microscopic hematuria, there were no clinical consequences, according to the authors.

Two hundred sixty-eight patients (15%) had urogenital imaging but no urinalysis. Only 10 had abnormal findings; four of the 10 had clinical consequences.

Ten percent of patients had neither urine collection nor imaging.

“The potential danger of performing urinalysis without imaging is to miss clinically relevant injuries (e.g., bleeding sites in the kidney parenchyma), which can only be shown by imaging,” the authors wrote. “Bypassing urinalysis and going straight for imaging…results in clinical consequences in 1.5% of the patients (4 out of 268). This is comparable to the percentage of clinical consequences in the patients who receive both urinalysis and imaging (2%; 22 out of 1031).”

They added, “The remaining 0.5% difference in clinical consequences consists of relatively minor consequences such as additional imaging and re-evaluation at the outpatient department, and this indicates little added value of the performance of urinalysis.”

Dr. Goslings told Reuters Health that the researchers “advise omitting this investigation as a routine part of the assessment of trauma patients, given that (good) imaging facilities are available in the hospital.”

But in specific circumstances, urinalysis might still be appropriate. Repeating by email some points from the paper, Dr. Goslings wrote, “In particular, patients with specific trauma mechanisms (e.g., fall from height, fall from horse or direct blow to the flank) or patients with a suspicion of pelvic (ring) injuries or thoracolumbar spinal cord injuries might benefit from urinalysis.”

“Future studies should focus on identifying the subgroups of patients in whom urinalysis is helpful,” Dr. Goslings added.

Chronic kidney failure no barrier to CT angiography.

CT angiography (CTA) using moderate doses of IV contrast in patients with advanced renal failure is a safe procedure that negatively affects renal function in only a small percentage of patients, according to researchers from Baltimore.

But the imaging options are even better with newer MDCT scanners. CTA protocols with low kVp and using half the normal dose of iodinated contrast have even less impact on kidney patients and produce excellent images, said Dr. Barry Daly from the University of Maryland.

In a study presented at last month’s International Society for Computed Tomography (ISCT) meeting in San Francisco, Daly showed how even normal contrast doses had little effect on serum creatinine levels in most patients. Information gained by the studies far outweighs the chance of adverse effects in patients with chronic renal failure, he said.

Daly also showed his latest protocol for low-contrast-dose, low-kV CTA imaging that delivers high image quality with even less risk for these patients.

Don’t skip the CTA

CTA isn’t something you want to skip, even though many centers do just that, he said. Before renal transplant surgery, for example, surgeons need to see what they’re going to be dealing with in the operating room.

“There are big risks going into surgery without CTA in this group because they have the risk of a major change in operative procedure, prolonged surgery, poor graft outcomes, failure to engraft, loss of the organ — which is a total disaster, especially in the setting of matched renal donor transplantation — and, of course, the possibility of missing important pathologies,” Daly said.

Incidental right iliac venous stent
Patient is in renal failure but not yet on dialysis. CTA was acquired at 80 kVp and 360 mAs following administration of 50 mL of 350 mg/mL contrast. Contrast density in the iliac arteries is > 400 HU. Radiation dose is 4.3 mSv. There is an incidental right iliac venous stent. Images courtesy of Dr. Barry Daly.

Daly and colleagues reviewed the use of CTA in 180 potential renal transplant recipients, all with matched donors, “but we were especially interested in looking at a predialysis cohort of 40 patients,” he said.

Patients were assessed for aortoiliac and calcific atherosclerosis, venous thrombosis, and increased incidence of renal cell carcinoma (four to seven times the normal rate in native kidneys). The only prophylaxis was aggressive oral hydration both before and after CTA, he said.

It’s important to find an appropriate place for the engraftment, Daly said. Many patients may require surgical correction with bypass grafts before transplantation can be done.

“Because a lot of these folks have had chronic hemodialysis, it’s not uncommon to find occlusion of the iliac veins,” he said. In a couple of cases, this has become obvious only in the operating room — “with disastrous consequences.”

The study measured serum creatinine (SeCr) and estimated glomerular filtration rate (eGFR) before and after imaging in the 40 predialysis patients. “There was almost no difference between the two groups in mean measurements,” Daly said.

“Nobody had to undergo dialysis, but looking at the changes, there clearly were some shifts that we shouldn’t ignore,” he said.

Post CTA, 27 patients had stable or mean decreased SeCr of 10.2%. Thirteen patients had a mean increase of 6.3%, with one patient showing a 32% rise, and three saw almost no change (0.5-1.5 mg/dL increase).

Change in SeCr after CTA in predialysis cohort of 40 patients

SeCr mean SeCr range eGFR mean
Pre-CTA 5.2 2.9-14.1 20.5
Post-CTA 5.1 2.4-14.2 21.0

A low rate of contrast-induced nephropathy (CIN) in renal patients isn’t all that surprising, Daly said. Newhouse, Katzberg, and others have shown that the risks of IV low-osmolar contrast precipitating CIN have been overestimated.

These previous studies demonstrate that moderate doses of IV contrast are much less nephrotoxic than arterial administration, he said. Many studies without controls failed to allow for other factors affecting renal function, especially in hospital populations. Finally, a 2010 study in Radiologyshowed that low-osmolar contrast may be as safe as iso-osmolar contrast, he noted.

Low-kVp, low-contrast-dose CTA

Daly and colleagues also performed a study of low-kVp, low-contrast-dose CTA in chronic renal failure patients. Why is this necessary if the regular dose is safe?

“The answer, of course, is that lower is always better,” Daly said. Even if the negative effects aren’t as bad as they were feared to be, “there is still a small portion of patients in our group who are still at risk with the conventional dose,” he said, adding that “new CT scanners have enabled new techniques for getting more out of each gram of iodine.”

The technique involves dropping the kV and increasing the mAs. For example, if you drop the tube current from 120 kV to 80 kV, you would increase the mAs by a factor of 2.7. Thus, 120 kVp and 250 mAs become 80 kV and 600 mAs, he said, and for large patients the tube may reach the maximum mAs.

MDCT can be used with extended z-axis coverage to shorten scan times to correspond to a shorter bolus train. Ideally, there should be at least 40 mm to 80 mm of coverage, he advised.

How it works is by now well-known, he said. “The k-edge of iodine is only [33.2] keV, so by dropping our kVp we can actually get considerably increased x-ray absorption. There’s a nearly a twofold increase in iodine attenuation at 80 kV compared to 120 kV.” Thus, the iodine dose can be cut in half while producing similar CT values, according to Daly.

The researchers perform the 80-kV studies on a Brilliance iCT 256 or a Brilliance 64 scanner (Philips Healthcare) using 320 to 350 mgI/mL of contrast.

They inject 35 to 50 mL of contrast at 4 mL per second in a peripheral vein, followed by 40 to 60 mL of a saline chaser at 4 mL per second. Automated bolus tracking is set for a 120- to 150-HU threshold in the aorta just below the hiatus, and the automated minimum scan delay is set to 4.2 to 6.5 seconds, he said.

Tube rotation speed is 0.75 seconds for a 256-slice scanner and 0.75 to 1 second for a 64-detector-row scanner. mAs values are based on patient body mass index (noise present at precontrast phase) with pitch set at maximum for the mAs selected, Daly said.

The resulting images look great, but using iterative reconstruction (iDose5, Philips) allows even lower doses, or the scanning of larger patients using low-kV, low-contrast protocols, he said.

In summary, CTA with a moderate 100-mL dose of iso-osmolar contrast in advanced renal failure “is a safe procedure with a negative impact on renal function in only a small percentage of patients,” Daly said, adding that “these aren’t patients with creatinine of 1.8, these are patients with major renal compromise.”

However, even though the 100-mL contrast protocol has a “very limited negative effect on people … a better option today is low 80-kVp, low-contrast-dose CTA technique with 35 to 50 mL of iso-osmolar contrast,” Daly said.

This very safe technique yields high diagnostic quality and works on most newer CT scanners, he added.

“Finally, if you have the benefit of iterative reconstruction, it improves image quality and allows us to use this technique even in very large patients,” Daly said.

CT nanoparticle contrast: Good as gold?

CT nanoparticle-based contrast agents are all investigational — and at this point all preclinical — but they’re out there. In a few years, the tiny contrast agent delivery vehicles, which work well in animals, could greatly affect the diagnosis and treatment of disease in humans.

That’s according to David Cormode, PhD, assistant professor of radiology at the University of Pennsylvania. He spoke on nanoparticle CT contrast media at last month’s International Society for Computed Tomography (ISCT) annual meeting in San Francisco.

The integration of nanoparticle CT contrast into the clinical mainstream will take a while, Cormode said, but the process might be speeded up if elements are developed that are cheaper than gold, which is currently used to make the nanoparticles.

Nanoparticles for CT imaging aren’t so different in design and structure from those built for other imaging modalities such as MRI, except that they contain CT contrast agents in their lipid-based cores. Inside every nanoparticle agent is an inner core surrounded by various layered and scattered components including liposomes, micelles, emulsions, and nanocrystals with biocompatible coatings, Cormode said.

CT contrast agents have bigger cores than, for example MR agents, because they need them. Due to CT’s relative insensitivity to contrast compared to other imaging modalities, high-contrast payloads are required for better sensitivity, Cormode said. Nevertheless, they are still quite small, typically less than 4 nm in diameter.

“If you compare the Earth to the size of a soccer ball, it’s about 58 millionth of the size,” he said. “Going from [the soccer ball] to a nanoparticle, it’s about the same factor of difference in sizes.”

In recent years, interest in imaging nanoparticles has soared, with about 80 peer-reviewed studies being published a year, compared with fewer than 10 as recently as 2006, Cormode said. The reason is, quite simply, their vast potential in diagnosing and treating disease.

Nanoparticles are designed to be long-lasting contrast agents that do not need to be readministered in the case of multiple exams being acquired over several hours or potentially even days, Cormode said.

“Compared to agents we are currently using, nanoparticles have long circulation half-lives,” he said. “They can be targeted to allow molecular imaging or specific cells or specific processes. They can be used with spectral CT, and they can also be multifunctional, providing contrast for more than one imaging technique.”

Although no nanoparticle agents are approved for CT, a couple have been cleared for use with MRI, including Doxil, a liposomal formulation of doxorubicin approved for head and neck cancers in the mid-1990s, and Feridex, an iron-oxide nanoparticle contrast agent.

The tiny structures have become more complex in recent years, featuring multiple layers of different coatings, and an antibody or protein used to direct the agent to a biological target. For example, a 2009 in vitro and rat study by Pan and colleagues examined an iodine-loaded agent targeted to fibrin for thrombus imaging, he said.

Representing a new class of nanoparticles designed for CT, the colloidal, radio-opaque and metal-encapsulated polymeric (cROMP) particle offered severalfold enhancement both in vivo and in a rat model, its authors reported, with sensitivity reaching to the low nanomolar particulate .

Key CT nanoparticle studies

In 2006, Mukundan and colleagues tested a blood-pool contrast nanoparticle encapsulating a high concentration of iodine. They injected the agent into five mice and scanned them with micro-CT. The researchers measured high initial enhancement of about 900 HU in the aorta, which plateaued at about 800 HU when measured again two hours later, and there was excellent contrast discrimination between the myocardium and cardiac blood pool .”I imagine if they had continued the study for a longer time, you would have seen the same amount of contrast,” Cormode said.

In a 2010 study of a gold high-density lipoprotein nanoparticle targeted at atherosclerosis, Cormode and colleagues showed that nanoparticles can distinguish several different components in a single scan. The group performed spectral imaging on a preclinical CT scanner developed by Philips Healthcare to differentiate gold (Au-HDL), iodine-based contrast, and calcium phosphate in phantoms. The gold nanoparticles were injected in mice and followed 24 hours later by an iodine-based contrast agent.

The gold particles were detected in the aortas of the mice, while the iodine-based contrast agent was highlighted in the blood and the calcium-rich tissue of the skeleton during a single CT scan. Microscopy showed that the gold was primarily localized in macrophages in the aorta, thereby showing that spectral CT also provided information about the macrophage burden 

“You can use nanoparticles … to extract several different parameters at the same time,” Cormode said of the study.

Also in 2010, Cormode collaborated with van Schooneveld et al to examine an all-in-one contrast agent for MRI, CT, and fluorescence imaging. The researchers created a gold/silica nanoparticle agent to enhance macrophage cells in vitro using MRI, CT, and fluoroscopy and mice livers in vivo using MRI and CT. The agent is useful in many applications, including cell tracking and target-specific molecular imaging, and is “a step in the direction of truly multimodal imaging,” the authors wrote.

Diagnostic and therapeutic

Gold nanoparticle-based contrast was also the agent of choice in a study by von Maltzahn et al, who used a gold nanorod agent to visualize and then ablate tumors in mice. The nanomaterials improved the specificity of cancer ablation by homing into tumors and acting as antennas for externally applied radiofrequency ablation, the authors .

The polyethylene glycol (PEG)-protected gold nanorods “actually absorb laser radiation very strongly, and when they do they heat up the surrounding material,” Cormode said of the study. “This can be used as a kind of hyperthermia technique” to completely eradicate the tumors, he noted.

In summary, CT nanoparticle contrast agents “are out there, but gold is sort of expensive and we need to create cheaper agents,” Cormode said. In addition, “extensive clearance and toxicity testing” will be needed before the agents are ready for routine clinical use.

Higher creatinine can occur after CT — even without contrast.

Contrast media is often blamed for what appears to be contrast-induced nephropathy (CIN) in patients getting CT scans. But Chinese researchers have found that elevated rates of serum creatinine — a marker for CIN — can occur after CT even in

There are lots of reasons why patients could have higher serum creatinine levels after CT exams, according to two studies presented by researchers from Peking University First Hospital in Beijing at the 2013 International Symposium on Multidetector-Row CT. Clarifying those reasons is critical, according to the group.

“There are many factors affecting creatinine levels, especially among inpatients,” said Dr. Xiaoying Wang in her presentation. “Many patients have severe diseases where, due to the disease, doctors find it is not appropriate for them to have contrast-enhanced CT.”

Nailing down renal impairment

The findings don’t necessarily fit with conventional wisdom on contrast-induced nephropathy; however, they do highlight the multifactorial nature of impaired renal function and remind clinicians that several factors must be present for a CIN diagnosis, Wang said.

“The definition of CIN is clear and simple, but in practice it’s not easy to define,” she said. CIN requires an absolute or relative increase in serum creatinine (SCr) compared to baseline values, a temporal relationship between the rise in SCr and exposure to a contrast agent, and the exclusion of alternative explanations for renal impairment — which means looking for these explanations.

“Generally, as radiologists it is easy for us to detect an increase in serum creatinine, but it is not very easy for us — sometimes not even easy for nephrologists — to exclude alternative reasons for renal impairment,” Wang said.

In an effort to identify at-risk patients, in Wang’s practice, patients making appointments for contrast-enhanced CT are asked about a range of factors suggestive of CIN risk. The literature shows higher levels of risk for patients with a history of diabetes mellitus, hypertension, renal impairment, liver disease, renal-toxic medications, and a few other circumstances, though the studies used to identify the risk factors involved intra-arterial injection of contrast agents, Wang said.

Study 1: Are at-risk patients really more at risk for CIN?

For patients undergoing contrast-enhanced CT between 2010 and 2012, her group analyzed the association between risk factors and the subsequent development of CIN. The researchers examined a total of 2,556 patients, of whom 1,243 formed an observation group. The patients were measured for SCr before contrast-enhanced CT as well as 48 to 72 hours after CT; if SCr levels rose by the second test, the patient was referred to a nephrologist, and SCr was measured again seven to 10 days later.

In all, 68 (5.5%) of the 1,243 patients were diagnosed with CIN, including 12 with acute renal failure. (Fifty-one patients recovered and five were lost to follow-up.) However, the study showed no statistically significant difference in the development of CIN between the patients with risk factors and those without.

Of the patients who were not at risk, 4.5% (17/375) developed CIN, while in the at-risk group, 5.9% (51/868) developed the condition (p = 0.21). Among patients with no history of chronic kidney disease, only female gender (p = 0.03) and the use of low-osmolar contrast media (p = 0.03) were associated with a significantly increased risk of CIN.

Logistic regression analysis of risk factors showed several that increased the odds of CIN, including a history of diabetes mellitus (odds ratio [OR] = 1.83), history of tumor (OR = 1.54), use of nephrotoxic drugs (OR = 1.69), frequent use of contrast media (OR = 1.13), and use of low-osmolarity contrast media (OR = 2.28). In addition, women had an odds ratio of 1.69, and those older than 75 had an odds ratio of 1.26. The difference was only statistically significant in women (p = 0.04), however.

“These [risk] factors are not very strong to [predict] the incidence of CIN,” Wang said.

Study 2: Is ‘CIN’ risk really higher after noncontrast CT?

To continue to refine risk-factor prediction, the group recently completed a prospective cohort study of 623 patients who underwent CT with and without contrast. Of the 623 patients, 171 formed an observation group that received multiple SCr tests to allow the nephrologist to confirm a temporal association between increased SCr and contrast administration.

Among these 171 patients, 99 underwent contrast-enhanced CT and 72 had CT without contrast. There was no statistically significant difference in demographics and CIN-related risk factors between the 171 patients and the remaining 452, Wang said.

In all, 17 (9.9%) of the 171 patients developed what appeared to be CIN. Dividing up the patients between those who received contrast and those who did not, seven (7.1%) of the 99 who got contrast developed CIN. Meanwhile, 10 (13.9%) of the 72 patients who did not receive contrast developed “CIN.” Again, the difference in CIN rates between those who did and did not receive contrast was not statistically significant (p = 1.414).

Many factors affect creatinine levels, especially among those like the inpatients in this study, who have a wide range of medical conditions and are prescribed a variety of medications, Wang concluded. Even factors ranging from higher muscle mass to recent ingestion of cooked meat can result in higher SCr levels.

“That’s how we explain the higher SCr levels among noncontrast CT patients,” she said. “The increase of serum creatinine level after CT examination may occur without iodine contrast administration.”

She cautioned, though, that the sample sizes were small in both studies.

Excluding alternative explanations for renal impairment is crucial for diagnosing CIN, Wang concluded, and large, prospective cohort studies are needed to determine the true incidence of CIN in contrast-enhanced CT.


Children’s hospital installs pirate-themed CT-scanner to make medical test a little less scary.

A New York children’s hospital recently purchased a a pirate-themed CT scanner to make the medical tests less of a ‘horrible, scary chore’. 

Child patients lay down on a mock plank which then slides into the scanner, a hoop in the shape of a ship’s wheel. Swash-buckling pirate animals decorate the walls to distract the children from the test.

GE provided the scanner to New York-Presbyterian Morgan Stanley Children’s Hospital, and gave the hospital two choices for a child theme – fish or pirates – sparking a heated debate among the staff. 

An exam adventure: A new CT scanner at a New York City children's hospital helps distract patients from the stressful test

An exam adventure: A new CT scanner at a New York City children’s hospital helps distract patients from the stressful test

Tough choice: The hospital was given two choices for a children's scanner by manufacturer GE, either pirates or fish

Tough choice: The hospital was given two choices for a children’s scanner by manufacturer GE, either pirates or fish

Dr Carrie Ruzal-Shapiro, the hospital’s chief of pediatric radiology, said the pirates won out because they ‘were cute’ and the scanner was installed in August.

And so far the reaction has been positive. Registered nurse Naomi Hawkins told Buzzfeed that the best response she’s gotten is a patient saying: ‘Hurry up and get out so I can play’.

Although the test only lasts a minute, it takes about 10 to 15 minutes to get children prepared for the test, which can be stressful. 

‘It allows children to imagine all sorts of things,’ Dr Ruzal-Shapiro told the New York Daily News. ‘So it doesn’t seem like a horrible scary chore.’

Decision: Dr Carrie Ruzal-Shapiro, head of the pediatric radiology department, said they chose the pirates because they were cute

Decision: Dr Carrie Ruzal-Shapiro, head of the pediatric radiology department, said they chose the pirates because they were cute

Not so bad: Dr Ruzal Shapiro said the decor helps make the test a little less of a 'horrible, scary chore'

Not so bad: Dr Ruzal Shapiro said the decor helps make the test a little less of a ‘horrible, scary chore’

Prep: The test only takes a minute, but around 10 to 15 minutes to prepare patients for

Prep: The test only takes a minute, but around 10 to 15 minutes to prepare patients for

Procedure: Patients are set up on the table which resembles a plank and are then pushed into scanner in the shape of a ship's wheel

Procedure: Patients are set up on the table which resembles a plank and are then pushed into scanner in the shape of a ship’s wheel

Before the test, nurses get kids settled onto the table and hooked up to an IV. The room’s decor helps kids take their mind off the IV and the anxiety of the test.

The children being scanned could be dealing with something as serious as cancer to checking on bone fractures.

The hospital’s radiology department conducts about five to 10 scans in the room every day, on patients ranging from infants to 21-year-olds. 

‘The teens roll their eyes at the cat with the eye-patch and the hippo mermaid,’ Dr Ruzal-Shapiro said. ‘But they like it as much as the kids.’

Entertained: Imagery of swash-buckling animals like monkeys and tigers adorn the walls to give patients something to look at

Entertained: Imagery of swash-buckling animals like monkeys and tigers adorn the walls to give patients something to look at

Patients: The hospital performs between five and 10 scans a day on patients as young as infants and as old as 21

Patients: The hospital performs between five and 10 scans a day on patients as young as infants and as old as 21

Different issues: Those getting scanned could be dealing with something as serious as cancer or just a fractured bone

Different issues: Those getting scanned could be dealing with something as serious as cancer or just a fractured bone

Never too old: While teens roll their eyes at the decorations, Dr Ruzal-Shapiro says that they like it just as much as the younger ones

Never too old: While teens roll their eyes at the decorations, Dr Ruzal-Shapiro says that they like it just as much as the younger ones

Source: Daily Mail.

Living Longer With Obesity Increases Heart Risk.

We all know that carrying around extra weight increases the risk of heart disease, but the length of time a person has been toting that weight appears to be a factor as well. Children and adolescents who are obese — about 18% of the adolescent population right now — are in far more danger of developing heart disease than anyone ever considered.

Heart disease is the leading cause of death among men and women in the US, accounting for 600,000 deaths per year. Coronary heart disease, the most common form, develops when the arteries that supply the heart with blood, oxygen, and nutrients become damaged or diseased.

The usual cause is plaque, a combination of calcium, fat, cholesterol, and other substances. The accumulation of plaque, called atherosclerosis, is often the precursor to a heart attack or stroke.

Among those who were obese for over 20 years, 38 percent had calcification in the coronary arteries compared to 25 percent of those who never were obese. Higher rates of type 2 diabetes were also present in those who had been obese the longest.

Twenty-five years ago, at what we now know was the start of the obesity epidemic, researchers enrolled nearly 3,300 white and African-American adults between the ages of 18 and 30 in a study designed to look at the development of coronary artery disease in young adults. The participants were examined by a physician every two to five years and had CT scans at 15, 20, and 25 years into the study to detect calcification (hardening) in the coronary arteries.

The information collected on each participant included their body mass index, whether they smoked or not, cholesterol, blood pressure, physical activity level, and whether or not they developed type 2 diabetes.

How long a person had been overweight or obese was linked to accelerated atherosclerosis. Coronary artery calcification was discovered in nearly 28 percent of the participants. The length of time each person was obese, based on their physical exams over the years, correlated with the presence and the extent of blockage in the arteries. Among those who were obese for over 20 years, 38 percent had calcification in the coronary arteries compared to 25 percent of those who never were obese.

The risk of developing plaque increased by two to four percent for every year the young adults were obese, independent of all other factors measured on the participants. Those who had been obese the longest and who had abdominal obesity had increased odds of developing high blood pressure and elevated cholesterol and were more likely to be onmedications to control those conditions. Higher rates of type 2 diabetes were also present in those who had been obese the longest.

Overall, the study implies that the earlier one becomes obese, the more likely it is that major heart problems will develop by middle age. Given the fact that over the past thirty years the rate of obesity has doubled among children and tripled among adolescents, more of today’s children and teens are likely to experience coronary events as they reach mid-life.

People are becoming obese at younger ages than previous generations. The results of this study make clear that this will likely have significant implications on the incidence of heart disease in the future and underscore the need for programs aimed at tackling obesity among our children and teens.

Source: Journal of the American Medical Association.


Chilaiditi’s sign.

A 79-year-old man presented with symptoms and signs of upper respiratory tract infection; he had a history of permanent pacemaker implantation. An upright postero-anterior chest radiograph showed a raised right hemidiaphragm delineated by subdiaphragmatic air. Unlike free air, which forms an uninterrupted crescent-shaped subdiaphragmatic radiolucency, this radiograph showed a haustral pattern of subdiaphragmatic lucency, overlapping the upper border of the liver shadow. On examination, clinical findings suggesting acute abdomen from rupture of a hollow viscus were absent and there was no recent history of abdominal surgery to account for the presence of subdiaphragmatic air.


The visualisation of a gas filled transverse colon lumen interpositioned between the right hemidiaphragm and the liver on a chest film is called Chilaiditi’s sign. A CT scan may confirm these anatomical relations. In our patient’s radiograph, the haustral pattern of air was indicative of colonic origin, and the continuity of the subdiaphragmatic air was broken up by the shadow of the vertical plicae semilunares of the colon. Chilaiditi’s sign was first described in 1910 by Demetrious Chilaiditi and it is an incidental radiographic finding. This sign can be mistaken for pneumoperitoneum and can lead to needless surgical intervention. Our patient was treated only for his upper respiratory tract infection.

Source: Lancet

Striking cysts: recurrent haematuria in a kickboxer.

A 42-year-old man presented with recurrence of haematuria after extensive body-building exercises.


He had a history of renal failure due to polycystic kidney disease, complicated by recurrent bleeding, particularly after kickboxing or body-building exercises. Ultrasonography  and abdominal CT scan without contrast  showed widespread polycystic kidney and liver disease. However, the source of bleeding could not be identified. MRI (T2-weighted, half-Fourier acquired single-shot turbo spin echo) showed multiple cysts with decreased signal density , suggestive of recent bleeding; this was further confirmed by distinct fluid levels in some of the cysts. Cyst bleeding is a common complication of polycystic kidney disease, occurring in 30—50% of cases. Our case shows that trauma can be a causative factor. MRI can elegantly reveal the exact location of cysts in which recent bleeding has occurred.

Source: Lancet

N-Acetylcysteine Plus Intravenous Fluids Versus Intravenous Fluids Alone to Prevent Contrast-Induced Nephropathy in Emergency Computed Tomography.



We test the hypothesis that N-acetylcysteine plus normal saline solution is more effective than normal saline solution alone in the prevention of contrast-induced nephropathy.


The design was a randomized, double blind, 2-center, placebo-controlled interventional trial. Inclusion criteria were patients undergoing chest, abdominal, or pelvic computed tomography (CT) scan with intravenous contrast, older than 18 years, and at least one contrast-induced nephropathy risk factor. Exclusion criteria were end-stage renal disease, pregnancy, N-acetylcysteine allergy, or clinical instability. Intervention for the treatment group was N-acetylcysteine 3 g in 500 mL normal saline solution as an intravenous bolus and then 200 mg/hour (67 mL/hour) for up to 24 hours; and for the placebo group was 500 mL normal saline solution and then 67 mL/hour for up to 24 hours. The primary outcome was contrast-induced nephropathy, defined as an increase in creatinine level of 25% or 0.5 mg/dL, measured 48 to 72 hours after CT.


The data safety and monitoring board terminated the study early for futility. Of 399 patients enrolled, 357 (89%) completed follow-up and were included. The N-acetylcysteine plus saline solution group contrast-induced nephropathy rate was 14 of 185 (7.6%) versus 12 of 172 (7.0%) in the normal saline solution only group (absolute risk difference 0.6%; 95% confidence interval -4.8% to 6.0%). The contrast-induced nephropathy rate in patients receiving less than 1 L intravenous fluids in the emergency department (ED) was 19 of 147 (12.9%) versus 7 of 210 (3.3%) for greater than 1 L intravenous fluids (difference 9.6%; 95% confidence interval 3.7% to 15.5%), a 69% risk reduction (odds ratio 0.41; 95% confidence interval 0.21 to 0.80) per liter of intravenous fluids.


We did not find evidence of a benefit for N-acetylcysteine administration to our ED patients undergoing contrast-enhanced CT. However, we did find a significant association between volume of intravenous fluids administered and reduction in contrast-induced nephropathy.

Source: Pubmed