Category: CT Scanners

CT Cancer Risk Study Raises Questions

Posted on by Brian Casey

The radiology world was turned on its head this week with the publication of a new paper in JAMA Internal Medicine on CT radiation risk. Researchers estimated that all the CT scans performed in the U.S. in a single year would cause more than 100k cancers over the lives of the patients who got them. 

Radiation risk has always been the Achilles heel of CT, radiology’s workhorse modality for advanced imaging. 

  • But CT is plagued by dose variation and a lack of reporting on exactly how much dose patients are getting – especially when it exceeds guidelines.

In the new study, researchers led by radiation safety expert Rebecca Smith-Bindman, MD, of UCSF used existing estimates of low-level radiation risk to calculate how many cancers would result from the 93M CT scans performed in the U.S. in 2023, finding …

  • CT radiation dose would cause 103k future cancers over the lifetimes of the patients.
  • At the current rate, “CT-associated cancer” would account for 5% of all cancers – about the same number caused by alcohol. 
  • The study’s projection of CT-linked cancers is 3X-4X higher than previous estimates, mostly due to the growth in CT utilization. 

The paper generated pushback from sources including the ACR and AAPM, who questioned whether it really reveals any new information about the risks of CT radiation. 

  • They reiterated the medical value of CT scans, noting that the research was based on statistical models and that there are no published studies directly linking CT scans to cancer.

Another thing the paper doesn’t touch on are the dramatic reductions in CT radiation dose that have occurred in recent years. 

  • CT protocol optimization and AI-based data reconstruction – as well as technologies like photon-counting CT – have enabled imaging professionals to reduce doses to levels previously thought impossible, such as under 1 mSv for a routine chest exam. 

To help providers manage dose, CMS this year launched new dose reporting quality measures, CMS1074v2, designed to reward radiology practices for tracking and reporting radiation dose. 

  • Smith-Bindman is a co-founder of Alara Imaging, which provides software to help radiology providers comply with the new CMS measures. ACR also offers a variety of dose optimization and monitoring tools.

The Takeaway

So what to make of the new study? On the one hand, the sensational headlines it generated could scare many patients away from getting medically necessary CT scans. On the other, any attention toward radiation dose reduction and appropriate imaging is a good thing, and if it spurs new efforts toward more judicious and consistent use of CT at lower radiation levels, so much the better. 

How to Improve CT Lung Screening Outcomes

Posted on by Brian Casey

Getting patients to attend cancer screening exams is one of the biggest challenges in healthcare. But a new study in JAMA Network Open should provide motivation, showing that people who showed up for annual CT lung cancer screening exams had better clinical outcomes than those who didn’t. 

Low cancer screening adherence frustrates clinicians and healthcare policy experts alike, but nowhere is the situation as dire as in CT lung cancer screening.

  • U.S. lung screening adherence rates languished in the single digits for years after the exam was approved by the USPSTF, and while there has been some recent improvement, screening rates are nowhere near those of more established exams like mammography. 

At the same time, statistical modeling studies (and common sense) suggest that complying with screening would reduce lung cancer mortality. 

  • So researchers from multiple institutions in the U.S. and Canada decided to track adherence to a real-world CT lung screening program consisting of a baseline scan and then two follow-up scans roughly a year apart. 

In all, 10.2k eligible adults were screened from 2015 to 2018, with researchers finding …

  • Screening adherence rates fell from the first follow-up round to the second (61% to 51%).
  • People who attended the first follow-up round were more likely to attend the second (67% vs. 25%). 
  • Patients who completed both screening rounds had higher lung cancer diagnosis rates (1% vs. 0.2%).
  • Patients who attended the second round and got a lung cancer diagnosis were more likely to have early-stage disease (73% vs. 25%) and less likely to have late-stage disease (21% vs. 58%). 

In analyzing the results, researchers said the drop-off in adherence rates between the first and second follow-up screening rounds represented an opportunity to reach out to people who missed the first round and get them to the second.

  • This position dovetails with other recent research underscoring the importance of patient navigators in guiding eligible people to lung cancer screening. 

The Takeaway

So as radiology and other disciplines look to build on the momentum behind CT lung cancer screening, what’s the key to success in improving patient outcomes? Sometimes, it’s just getting people to show up. 

Are CT Scans Too Slow?

Posted on by Brian Casey

Is your imaging practice paying attention to the acquisition speed of your CT scans? A new study in AJR suggests that CT pulmonary angiography patients are being scanned at an average speed that’s 30% slower than optimal, resulting in unnecessary imaging artifacts. 

CT is radiology’s workhorse modality, but recent studies have found wide variation in CT scanning parameters, sometimes between scanners in the same health system or even the same facility. 

  • This can result in patients getting different levels of radiation dose for the same type of study, or differences in image quality that can make image comparisons more difficult. 

To even out the variation, imaging groups have proposed best-practice scanning protocols for different exams and anatomical regions. 

  • Most of these protocols focus on reducing radiation dose, but there are other elements – such as scan acquisition speed –  that are also important.

For CT pulmonary angiography exams, scans that are performed too slowly run the risk of motion artifacts caused by patients breathing.

  • Imaging sites, therefore, should try to optimize scan speed, which is determined by a mix of collimation, pitch, and gantry rotation time. 

Researchers in the new study — from UC San Francisco and University of Wisconsin — found that many sites were using a fixed scan speed for CTPA regardless of patient characteristics. 

  • They analyzed data for 167k CTPA scans acquired from 2016 to 2021, with data coming from 121 sites using 28 different scanner models from various manufacturers.

Researchers compared scan speeds to best-practice levels, revealing … 

  • Scans on average were 30% slower than the best-practice speed.
  • 87% of acquisitions were slower.
  • 62% were more than 20% slower.
  • Scan speeds varied widely by vendor and by scanner model.

Researchers concluded that CT sites weren’t optimizing their equipment and not implementing the fastest scan speeds available.  

  • As a result, they could be generating widespread motion artifacts, especially for smaller patients. 

The Takeaway

The new findings show that radiation dose isn’t the only CT scanning parameter that needs optimization. Imaging practices should take a look at their CT protocols to ensure they have the optimal settings, especially for CTPA scans of smaller patients. 

Is Radiation Dose Too Low?

Posted on by Brian Casey

A new study raises a provocative question: Is radiation dose from medical imaging exams too low? The authors propose in a paper in Nature’s Communications Medicine that lowering radiation dose too much negatively impacts patient care by making exams less diagnostic. But radiation dose experts are pushing back on the claim.

Efforts to minimize medical radiation dose are almost as old as radiology itself. 

  • The arrival of CT in the 1970s saw a sharp rise in radiation dose exposure, but a series of radiation overdose incidents in the 2000s spurred new efforts to  monitor and reduce dose. 

Today, CT radiation doses are remarkably low, with some ultra-low-dose protocols enabling exams at levels below 1 mSv – only slightly higher than a chest X-ray at 0.1 mSv. 

What’s more, CMS this year is launching new dose reporting quality measures designed to reward radiology practices for tracking and reporting radiation dose. 

  • Imaging practices will be able to secure additional reimbursement by complying with an electronic clinical quality measure (eCQM), CMS1074v2, issued by CMS to reduce excessive CT dose exposure. 

That brings us to the new paper. Researchers from Duke University developed a statistical model that they believe balances radiation risk from imaging exams with imaging’s clinical benefit.

  • They created a “detectability index” to quantify the benefit of imaging’s precise characterization of disease – which could lead to misdiagnosis if pathology isn’t adequately visualized – and weigh it against the lifetime cancer risk from an exam. 

They then tested the model in a simulated dataset of 1M liver cancer patients, finding …

  • The clinical risk of lower dose outweighed the radiation risk by 400%.
  • Radiation dose should be increased for over 90% of abdominal CT scans under their formula.

But pushing back against the paper are some advocates for radiation dose reduction, including radiologist Rebecca Smith-Bindman, MD, of UCSF. 

  • She points out that the use of imaging continues to grow exponentially, with little evidence to justify its benefit for many uses, and therefore every effort should be taken to minimize harms like radiation risk. 

The Takeaway

The new paper shows that even concepts thought to be self-evident – like the benefit of radiation dose reduction – can still be open to debate. Time will tell whether the new paper gains traction in the discussion over radiation dose management.

CT Lung Screening’s Weak Link

Posted on by Brian Casey

CT lung cancer screening rates in the U.S. remain abysmally low, over a decade after the exam was recommended. Is part of lung screening’s problem its reliance on provider referrals? A new research letter in JAMA Network Open examines this question. 

Unlike breast screening, in which eligible women are able to self-refer themselves for exams, CT lung screening revolves around provider referrals to start the process. 

  • CMS requires a shared decision-making session that results in a written order from a practitioner for a CT lung screening exam in order to pay for screening through Medicare and Medicaid. 

When CMS created the rules in 2015, provider referrals and shared decision-making were seen as ways to get patients involved in their own care by making choices in coordination with their caregivers.

  • But many are starting to see the requirements as a barrier, especially given low CT lung screening rates in the U.S.

In the new article, researchers investigated how easy it would be for an eligible individual to secure a CT lung screening appointment by just calling hospitals – without a provider referral. 

  • They note that one-third of Americans don’t have primary care clinicians, and are often told to call hospitals directly to set up appointments.

So they did just that, placing phone calls to 527 hospitals asking to arrange CT lung screening appointments, finding …

  • 317 calls (60%) failed because the caller did not have a primary care provider’s order.
  • Only 51 hospitals (9.7%) were able to connect callers to any component of a lung cancer screening process. 

The study authors note that the provider referral requirement isn’t the only thing holding CT lung cancer screening back, as even patients with primary care providers aren’t getting screened, and managing nodule follow-up can also be challenging. 

  • But Medicare’s cumbersome reimbursement rules certainly don’t help bring new people into the fold.

The Takeaway

Given CT lung cancer screening’s undisputed life-saving value, there’s no reason to put unnecessary barriers in its way. The provider referral and shared decision-making requirements are lung screening’s weak link to securing greater adoption, and CMS should rescind them to put CT lung cancer screening on the path to greater adoption.

FFR-CT Reduces Invasive Angiography Rates

Posted on by Brian Casey

Performing automated CT-derived fractional flow reserve with Shukun Technology’s software reduced referrals to invasive coronary angiography by 19% in a new study in Radiology. The findings suggest that software-based FFR-CT can serve a gatekeeper role in managing workup of patients with suspected coronary artery disease. 

Cardiac CT has been a revolutionary tool for assessing people with heart problems, evolving rapidly into a first-line modality that’s eclipsed other more traditional imaging technologies. 

  • But CCTA’s prowess also has a downside – more referrals to invasive coronary angiography, in some cases for patients without obstructive disease.

Rising to this challenge is FFR-CT, which uses automated software to calculate maximum blood flow in the coronary arteries and detect dangerous coronary lesions that could be early signs of a cardiac event. 

  • The segment to date has been dominated by HeartFlow, thanks to its early start in the field: its FFRCT software got FDA clearance in 2014 and the company has used its dominance to build a massive cash position.

In the new China CT-FFR Study 3, researchers in China used another FFR-CT application, Shukun’s skCT-FFR, and compared angio referral rates for 5.3k patients with suspected coronary artery disease who were scanned with either CCTA alone or CCTA and FFR-CT. They found …

  • Referral rates were lower for those who got FFR-CT (10% vs. 12.4%), a 19% relative difference.
  • Fewer cardiac events occurred in the FFR-CT group at one year (0.5% vs. 1.1%).
  • There was no statistically significant difference in major adverse cardiac event rates at 90 days (0.5% vs. 0.8%, p=0.12) and one year (2.9% vs. 2.8%, p=0.9).

Shukun is not as well known in the West as other developers of FFR-CT software like HeartFlow, but the company has raised over $250M to date – enough to land it in the top echelon of AI developers. 

  • One advantage of Shukun that was evident with the new study is that image processing was performed on-site, rather than being shipped off-site as is the case with other applications. 

The Takeaway

The study shows that FFR-CT can make cardiac CT more precise while tamping down on referrals to invasive angiography that have come from growing CT use. The results should also help put Shukun on the radar of many industry observers in a segment that so far has been dominated by HeartFlow.

Did Malpractice Risk Kill V/Q Exams?

Posted on by Brian Casey

CT perfusion angiography exams have largely replaced nuclear medicine-based ventilation/perfusion (V/Q) studies for detecting pulmonary embolism. But a new article in Academic Radiology suggests that CT’s rise wasn’t entirely based on clinical efficacy – fears of malpractice risk may have played a role. 

V/Q studies can help diagnose PE by enabling clinicians to visualize lung perfusion, showing defects such as blockages in pulmonary vessels. The scans are typically performed in three phases … 

  1. An albumin injection to show pulmonary vasculature.
  2. A radiopharmaceutical that’s inhaled and imaged with a gamma camera.
  3. A chest radiograph to correlate findings. 

The scans dominated PE imaging in the 1980s, but the rise of CT saw radiology facilities begin to shift.

  • CTPA was seen as having higher spatial resolution and was easier to perform than nuclear medicine exams. 

But the new article suggests that there were other forces at work as well – in particular, fear of malpractice risk from PEs that weren’t adequately followed after inconclusive V/Q exams.

  • The problem originated with clinical guidelines for V/Q reporting that classified some 20% of V/Q studies as “low probability” for PE when they probably would have better been classified as “inconclusive” or “non-diagnostic.”

As a result, a number of “low probability” patients weren’t followed up adequately, with tragic results that later figured into medical malpractice cases …

  • A patient who was diagnosed with pneumonia after an inconclusive V/Q exam, sent home, and died one day later of a “massive” PE.
  • A patient with leg and chest pain who was given heparin after a negative V/Q scan and later suffered internal hemorrhage; fortunately she survived.
  • A patient with “vague symptoms” who had an inconclusive V/Q scan and later died of an undiagnosed PE that some claimed would have been detected on CTPA.

Indeed, the theme of PE malpractice cases began to shift over time, from failure to diagnose V/Q scans to failure to order CTPA exams – which were soon seen as the clinical gold standard.

The Takeaway

Given the fast pace of development in radiology, it’s inevitable that some technologies that were once clinical staples fall by the wayside. But the new article offers a fascinating look at how clinical language can lead to medico-legal concerns that influence physician behavior – often in ways that are impossible to detect as they happen.

Low-Dose CT Confounds CAD in Kids

Posted on by Brian Casey

When it comes to pediatric CT scans, clinicians should make every effort to reduce dose as much as possible. But a new study in AJR indicates that lower CT radiation dose can affect the performance of software tools like computer-aided detection. 

Initiatives like the Image Wisely and Image Gently projects have succeeded in raising awareness of radiation dose and have helped radiologists find ways to reduce it.

But every little bit counts in pediatric dose reduction, especially given that one CT exam can raise the risk of developing cancer by 0.35%. 

  • Imaging tools like AI and CAD could help, but there have been few studies examining the performance of pulmonary CAD software developed for adults in analyzing scans of children.

To address that gap, researchers including radiologists from Cincinnati Children’s Hospital Medical Center investigated the performance of two open-source CAD algorithms trained on adults for detecting lung nodules in 73 patients with a mean age of 14.7 years. 

  • The algorithms included FlyerScan, a CAD developed by the authors, and MONAI, an open-source project for deep learning in medical imaging. 

Scans were acquired at standard-dose (mean effective dose=1.77 mSv) and low-dose (mean effective dose=0.32 mSv) levels, with the results showing that both algorithms turned in lower performance at lower radiation dose for nodules 3-30 mm … 

  • FlyerScan saw its sensitivity decline (77% vs. 67%) and detected fewer 3mm lung nodules (33 vs. 24).
  • MONAI also saw lower sensitivity (68% vs. 62%) and detected fewer 3mm lung nodules (16 vs. 13).
  • Reduced sensitivity was more pronounced for nodules less than 5 mm.

The findings should be taken with a grain of salt, as the open-source algorithms were not originally trained on pediatric data.

  • But the results do underscore the challenge in developing image analysis software optimized for pediatric applications.

The Takeaway

With respect to low radiation dose and high AI accuracy in CT scans of kids, radiologists may not be able to have their cake and eat it too – yet. More work will be needed before AI solutions developed for adults can be used in children.

AI Recon Cuts CT Radiation Dose

Posted on by Brian Casey

Artificial intelligence got its start in radiology as a tool to help medical image interpretation, but much of AI’s recent progress is in data reconstruction: improving images before radiologists even get to see them. Two new studies underscore the potential of AI-based reconstruction to reduce CT radiation dose while preserving image quality. 

Radiology vendors and clinicians have been remarkably successful in reducing CT radiation dose over the past two decades, but there’s always room for improvement. 

  • In addition to adjusting CT scanning protocols like tube voltage and current, data reconstruction protocols have been introduced to take images acquired at lower radiation levels and “boost” them to look like full-dose images. 

The arrival of AI and other deep learning-based technologies has turbocharged these efforts. 

They compared DLIR operating at high strength to GE’s older ASiR-V protocol in CCTA scans with lower tube voltage (80 kVp), finding that deep learning reconstruction led to …

  • 42% reduction in radiation dose (2.36 mSv vs. 4.07)
  • 13% reduction in contrast dose (50 mL vs. 58 mL).
  • Better signal- and contrast-to-noise ratios.
  • Higher image quality ratings.

In the second study, researchers from China including two employees of United Imaging Healthcare used a deep learning reconstruction algorithm to test ultralow-dose CT scans for coronary artery calcium scoring. 

  • They wanted to see if CAC scoring could be performed with lower tube voltage and current (80 kVp/20 mAs) and how the protocol compared to existing low-dose scans.

In tests with 156 patients, they found the ultralow-dose protocol produced …

  • Lower radiation dose (0.09 vs. 0.49 mSv).
  • No difference in CAC scoring or risk categorization. 
  • Higher contrast-to-noise ratio.

The Takeaway

AI-based data reconstruction gives radiologists the best of both worlds: lower radiation dose with better-quality images. These two new studies illustrate AI’s potential for lowering CT dose to previously unheard-of levels, with major benefits for patients.

Combo CT Screening Detects More Disease

Posted on by Brian Casey

A CT lung cancer screening program that also offered abdominal non-contrast CT scans detected a large number of abnormalities outside the lung in a population of people with smoking histories. The combined approach could offer a more efficient way to detect multiple pathologies in a single patient visit. 

CT lung cancer screening is gaining momentum globally, but clinicians and researchers continue to look for ways to make it more valuable. 

  • That’s a good thing, because smoking is a risk factor not just for lung cancer, but also other pathologies like abdominal aortic aneurysm (AAA) – so why not screen for those at the same time?

In a paper in European Urology, U.K. researchers describe their Yorkshire Kidney Screening Trial (YKST), which sought to detect kidney cancer by piggybacking on the county’s existing CT lung cancer screening program. 

  • Abdominal non-contrast CT exams were offered at the same time as thoracic CT lung screening scans to high-risk people who met the lung program’s screening criteria, namely aged 50-85 and more than 30 pack-years of smoking history. 

In all, 4k people accepted the offer to get additional abdominal CT scans, which had the following findings …

  • 64% of patients had normal findings, while another 20% had images that required additional review but no further action.
  • 5.3% had a new serious finding.
  • Serious findings were broken down as follows: renal stones ≥ 5 mm (3%), AAA (1.5%), renal mass/complex cysts (0.62%), kidney cancers (0.25%), and other cancers (0.25%).
  • It took 13 minutes of additional time to perform the abdominal CT scan.

Researchers said the prevalence of additional disease in YKST was within the range of other U.K. screening programs, such as for colorectal cancer (0.16-0.61%) and breast cancer (0.92%). 

  • The high prevalence of AAA was “unexpected,” especially since many AAA cases were found in people who aren’t covered by existing AAA screening programs. 

The Takeaway

As with recent research combining CT lung screening with coronary artery calcium (CAC) scoring, the new study shows that lung screening offers an opportunity to screen for more than just lung cancer. By detecting additional disease, combo screening has the potential to flip the script when it comes to screening’s cost-benefit ratio. 

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