Leah Lawrence

By providing general practitioners with direct access to low-dose computed tomography (LDCT), a greater number of symptomatic lung cancers were diagnosed in a favorable stage, according to results of a Danish study published in 

In Denmark, a fast-track referral system was introduced that allows general practitioners to refer patients who they believe might have lung cancer to undergo screening within the next 72 hours.

“Only 25% of Danish lung cancer patients are diagnosed that way,” said study author

Louise Mahncke Guldbrandt, PhD, of Aarhus University, Aarhus, Denmark. “For the rest of the patients, there is only the use of a conventional x-ray and approximately 20% of patients will have a false negative x-ray prior to a lung cancer diagnosis.”

In this study, the researchers were testing if a technological and organizational upgrade would increase the use of the fast-track referral system. The study included 266 general practitioners who were randomized into two groups. One group was offered direct access to a chest LDCT with continuing medical education on lung cancer diagnosis.

Over a period of 19 months, general practitioners referred 649 patients to direct CT, with 648 actually performed. Most patients were referred to CT with coughing as their most prominent symptom. General practitioners referred 335 patients to the lung cancer fast track during the study period; 33 lung cancers were diagnosed as a result. Of all patients referred for LDCT, 2.3% were diagnosed in a favorable stage and about half of the patients required further work-up.[[{"type":"media","view_mode":"media_crop","fid":"30073","attributes":{"alt":"Louise Mahncke Guldbrandt, PhD","class":"media-image media-image-right","id":"media_crop_9344098226312","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"3140","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 225px; width: 150px; border-width: 0px; border-style: solid; margin: 1px; float: right;","title":"Louise Mahncke Guldbrandt, PhD, study author","typeof":"foaf:Image"}}]]

Of the study group, 133 practitioners had access to direct CT, of whom 91(68.4%) used this route. Although one general practitioner referred as many as 40 patients to LDCT, the median number of referrals was two. The researchers found no difference between those who referred patients and those who did not in terms of age, sex, or type of clinic.

“We did hope for more patients with lung cancer to be diagnosed this way,” Guldbrandt told 

. “The positive predictive value for lung cancer in the existing fast-track is 10% and the patients referred to LDCT are different from the patients referred to the fast-track as these patients are more obviously ill and, therefore, there are more patients with advanced disease. The ones referred to LDCT were the not as obviously ill and, therefore, the proportion of cancer was lower.”

Less than half of the general practitioners (48.1%) participated in the CME meeting about lung cancer diagnosis. However, the referral rate was 61% higher among general practitioners who worked in a clinic where at least one practitioner participated in the CME meeting compared with clinics where no one participated.

The researchers do not yet know if the study intervention will reduce mortality from lung cancer.

“Early stage identification is beneficial only if the proportion of late stage cancers is reduced and this will be analyzed in a randomized controlled trial,” Guldbrandt said.

Articles

When general clinicians were educated about and given access to low-dose computed tomography, more lung cancers were diagnosed. 

Educating Clinicians About LDCT May Increase Early Diagnosis

Patients may be exposed to significantly less radiation when undergoing pelvic computed tomography (CT) if the imaging study is done with a filtered back projection and 50% adaptive statistical iterative reconstruction blending ratio reconstruction (ASIR

), according to the results of a study published recently in 

Specifically, use of this technique on 45 patients by researchers from Qianfoshan Hospital, China, resulted in greater than 50% reductions in CT dose index volume, dose-length product, and effective dose compared with a routine-dose CT with filtered back projection.

“The current study revealed that when compared to low-dose CT images with filtered back projection, low-dose CT images with ASIR

 more clearly displayed lesion edges and contours, and further improved diagnostic acceptability,” the researchers wrote. “In addition, low-dose CT images with ASIR

 allowed the visualization of various pelvic organs that was comparable to routine-dose CT images with filtered back projection, and fully met the requirements for disease diagnosis and treatment.”

Currently, there are limitations in how much radiation dose can be reduced without affecting image quality. These limitations are caused in part because of the standard filtered back projection reconstruction used in CT systems. In contrast, early studies of adaptive statistical iterative reconstruction has shown an association with better image quality and reduced image noise.

This study evaluated 45 patients who underwent a routine CT with filtered back projection, or a low-dose CT with filtered back projection and ASIR

. Patients who underwent the low-dose procedure had a mean CT dose index volume of 10.80 mGy, a mean dose limiting product of 265 mGy/cm, and a mean effective dose of 3.97 mSv. When compared with the standard-dose CT protocol, these rates resulted in decreases of 62%, 55%, and 56%, respectively, for the three measures.

Image quality scores were significantly lower when looking at low-dose CT with filtered back projection compared with the same procedure with ASIR

 or standard-dose CT with filtered back projection. In addition, the reviewers ranked image quality of low-dose CT with ASIR

 as significantly better than low-dose CT with filtered back projection. Overall, the results showed no subjective or objective differences in image quality between the three procedure types.

The researchers noted that this study was small and retrospective in nature. Further study is needed to confirm the utility of low-dose CT with filtered back projection and ASIR

Pelvic CT with filtered back projection and 50% ASIR reduces dose.

Dose Reductions Achievable in Pelvic CT with ASIR

Currently, there are limitations in how much radiation dose can be reduced without affecting image quality. These limitations are caused, in part, because of the standard filtered back projection reconstruction used in CT systems. In contrast, early studies of adaptive statistical iterative reconstruction have shown an association with better image quality and reduce image noise.

Filtered back projection and ASIR50 reduces dose in pelvic CT.

Dose Can be Reduced in Pelvic CT with ASIR

Despite an increased body mass, radiologists could still accurately read computed tomography pulmonary angiography (CTPA) results at the lower 100 kVp tube voltage in patients weighing up to 125 kg, according to the results of a study published recently in 

According to the study, industry standard for CTPA is slowly moving towards the use of 100 kVp tube voltage in place of the former protocols of 120 to 140 kVp.

“The most important reason to use a lower peak tube voltage for CT angiography is to reduce the radiation dose to the patient,” wrote Boglarka Megyeri of the University of Debrecen, and colleagues. “Although low voltage CT angiography is feasible in virtually all body regions, it is especially attractive for the chest, as the image noise increases less steeply at lower tube voltage in this body region than in the abdomen because of the low X-ray absorption of the air-filled lungs.”

The researchers conducted a retrospective study of 216 patients with body weights ranging from 75 kg to 150 kg. Almost 60% of the patient population was obese. Patients received CTPA at 100 kVp to exclude a diagnosis of pulmonary embolism. The study measured size-specific dose estimates as well as contrast-to-noise ratio. Three radiologists reviewed the images for quality and diagnostic confidence.

Results showed that vessel attenuation in the main pulmonary artery was significantly higher for patients weighing 75 to 99 kg compared with all other weight groups. However, once patients reached a body weight greater than 100 kg, there was no difference in vessel attenuation between groups. In addition, contrast-to-noise ratio was significantly higher in patients in the 75 to 99 kg body weight group (

The researchers found that the size-specific dose estimates were significantly lower in patients weighing 75 to 99 kg compared with patients in the higher body weight groups. However, again, no difference in size-specific dose estimate was found between patients weighing 100 to 125 kg and those weighing 125 to 150 kg.

“Objective image quality parameters such as vessel attenuation and contrast-to-noise ratio were dependent on patient body weight but not on body mass index,” the researchers wrote. “In contrast, subjective quality rating and diagnostic confidence were influenced neither by body mass index nor by body weight.”

Megyeri and colleagues concluded that the 100 KvP tube voltage could be accurately used in patients weighing up to 125 kg, but that more study should be done of image quality and diagnostic confidence in patients weighing 125 to 150 kg.

Study measures size-specific dose estimates and contrast-to-noise ratio in overweight patients.

Lower Voltage CT Angiography Effective Even with Higher BMI

The use of a low-dose computed tomography (CT) protocol with 50% adaptive statistical iterative reconstruction (ASIR) resulted in a greater than 57% radiation dose reduction in pediatric chest CT examinations of both normal and overweight children, according to the results of a 

 that compared this technique with the use of a conventional dose protocol reconstructed with filtered back projection.

The study, led by Mi-Jung Lee MD, PhD, assistant professor of radiology at Severance Children's Hospital, Yonsei University College of Medicine, also found that this dose reduction occurred without a significant loss of image quality.

“In both normal weight and overweight children, the ASIR technique is associated with a greater than 57% mean dose reduction, without significantly impacting diagnostic image quality in pediatric chest CT examinations,” Lee told 

. “However, CT scans in overweight children may have a greater noise level, even when using the ASIR technique.”

Lee and colleagues performed this study to confirm the feasibility of radiation dose reduction during chest CT using iterative reconstruction technique in children in consideration with the effect of body mass index or weight, which also can affect image quality.

They retrospectively reviewed 40 pediatric chest CT exams and compared radiation dose and imaging quality, including noise. There were eight overweight children in the ASIR group and seven in the control group.

Results showed that patients who underwent CT with ASIR had a significant (62.3%) radiation dose reduction compared with the control group, with an average size specific dose estimate of 5.5 mGy compared with 14.6 mGy (

Looking at estimated effective doses, there was a 57.4% dose reduction for children in the ASIR group when considering the estimated effective dose of 2.0 mSv compared with 4.7 mSv (

When analyzing objective image quality, the study showed no significant difference in image noise in the aorta between the two groups. However, image noise in the paraspinal muscle of the ASIR group was significantly higher (

<0.001), especially in overweight children. When examining subjective image quality, the reviewers rated only one ASIR scan as “diagnostically suboptimal” and rated none as unacceptable.

The researchers noted that the three image reviewers in the study “did not generally agree on subjective image quality, including noise, sharpness, artifacts and diagnostic acceptability” adding that this lack of agreement is a limitation to the study results.

In addition, Lee and colleagues noted that their sample of overweight children was too small to draw conclusions and mentioned that additional studies including a larger number of overweight or obese individuals will be needed.

Study examines ASIR effect on normal and overweight children who underwent chest CT.

Iterative Reconstruction Reduces Pediatric Chest CT Dose

In a healthy population of patients aged 65 or older, low-dose computed tomography (LDCT) screening for lung cancer appears to provide a generally similar benefit to harm tradeoff as it does for younger patients, according to the results of a sub-analysis of data from the National Lung Screening Trial (NLST) published in 

“The benefits and harms of LDCT screening in NLST were roughly similar by age group (under 65 vs. 65+),” study author Paul F. Pinsky, PhD, of the National Cancer Institute, told 

. “The findings should help inform [The Center for Medicare and Medicaid Services] in making their LDCT coverage decision.”

The Center for Medicare and Medicaid Services (CMS) is currently evaluating whether to offer coverage of LDCT screening for lung cancer to Medicare recipients. In April, Medicare Evidence Development and Coverage Advisory Committee (MEDCAC) panel voted low confidence that there was enough evidence to conclude that the benefits of LDCT screening outweighed its harms in the Medicare-aged population.

According to Pinsky, this low level of confidence was based, in part, on the fact that the NLST, the main body of evidence used by the United States Preventive Services Task Force (USPSTF) in making its recommendation for LDCT screening, was comprised primarily of patients younger than age 65, with only 25% of NLST patients 65 or older at entry. Therefore, it was not clear whether the overall favorable results of NLST also held in the 65+ population.

In this study, Pinsky and colleagues compared a spectrum of screen-related outcomes by age group in NLST to see if there were any systematic differences by age. There were data available from 19,210 participants aged younger than 65 and 7,110 aged older than 65. Patients in the older group were more likely to be former smokers and had a greater median pack-year history compared with the younger group.

Results showed that participants in the older group had higher rates of both positive and false-positive screens. In patients aged 65 or older, the rate of false positive was 27.7% compared with 22% in the younger group (

<.001). Additionally, the rates of invasive procedures after a false-positive screen were also slightly higher in the older group (3.3% vs. 2.7%; 

The researchers also found that the positive predictive value was higher in the older cohort (4.9% vs. 3.0%; 

<.001). This was due to a higher prevalence of lung cancer in the older group (1.5% vs. 0.7%; 

“Screen detected cancers were treated similarly with curative resection in each age group,” Pinsky said. “The rate of surgical mortality was low in each group.”

Pinsky also pointed out a caveat, that the older population in the NLST was healthier and had fewer comorbidities than the overall U.S. population in that age group who would be eligible for LDCT screening. Therefore, he said, it is not clear whether these same findings would hold up with population screening. 

In an editorial that accompanied the article, Michael K. Gould, MD, MS, of Kaiser Permanente Southern California, wrote that this new evidence should help to inform both policy makers and physicians.

“For policymakers, LDCT screening seems to involve similar tradeoffs for persons who meet NLST eligibility criteria in both the older and younger age groups. Until there is new and direct evidence to the contrary, it does not seem reasonable to exclude persons aged 65 to 74 years from access to screening,” Gould wrote. “For clinicians, it will be helpful to provide age-specific estimates of benefits and harms when engaging patients in a process of shared decision making that enables each to weigh the tradeoffs and make an informed choice.”

Study evaluates whether LDCT lung cancer screening is equally beneficial for younger and older patients.

LDCT Lung Cancer Screening: More Data for CMS

There was not that great a difference between cone-beam computed tomography (CBCT) and multislice spiral computed tomography (MSCT) with respect to dose and image quality, according to the results of a study published recently in 

. However, study results did show that use of MSCT was preferential for soft-contrast objects and CBCT for hard-contrast objects.

These results were taken from a study by Alexander A. Schegerer, PhD, of the department of medical and occupational radiation protection, Federal Office for Radiation Protection, Neuherberg, and colleagues who compared patient exposure and image quality of various CBCT and MSCT protocols for abdominal and genitourinary imaging.

According to Schegerer, the application of CBCT for image-guided interventions outside the radiology department has strongly increased.

“Cone-beam computed tomography has been established in many different clinical fields, for example, neurology, otolaryngology, cardiology, abdominal angiography, musculoskeletal imaging, and, urology,” Schegerer said. “To date, there are only few reports in the literature on radiation doses and image quality for CBCT.”

Schegerer and colleagues examined the CBCT and MSCT protocols for imaging soft tissue and hard-contrast objects at varying dose levels.

CBCT protocols had an effective radiation dose that ranged between 0.35 mSv to 18.1 mSv, with the local skin dose reaching doses as high as 190 mGy.

“The effective dose necessary to realize the same contrast-to-noise ratio with CBCT and MSCT depended on the MSCT convolution kernel: the MSCT dose was smaller than the corresponding CBCT dose for a soft kernel but higher than that for a hard kernel,” Schegerer said.

The researchers also compared noise-power spectrum of the two protocols and found that the spectrum of images taken with CBCT at tube voltages of 85/90 kV(p) were at least half of that of images measured at 103/11 kV(p) at any chosen spiral frequency.

“As compared with MSCT using a medium-hard convolution kernel, CBCT produces images at medium noise levels and, simultaneously, medium spatial resolution at approximately the same dose,”  Schegerer said. “It is well suited for visualizing hard-contrast objects in the abdomen with relatively low image noise and patient dose.” 

He added that for the detection of low-contrast objects at standard tube voltages of approximately 120 kV(p), however, MSCT should be preferred.

Finally, the researchers noted that it is indispensable to carefully justify and optimize the CBCT protocols predefined by the manufacturer to the specific clinical needs of different types of examinations. The collimation of the radiation field has to be adapted to the clinically relevant body region to reduce patient exposure.

Cone-beam CT is preferential to multislice spiral CT for hard-contrast objects, study says.

Cone-Beam CT Best for Visualizing Hard-Contrast Objects

A retrospective review of an additional group of patients at high-risk for lung cancer - or National Comprehensive Cancer Network Group 2 patients - showed that annual lung screening had similar rates of positivity and lung cancer diagnoses in these patients as those seen in patients in the National Lung Screening Trial (NLST). 

“Similar initial clinical CT lung screening results between the NLST population and NCCN high-risk Group 2 suggests it may be possible to save thousands of additional lives each year by allowing Group 2 individuals to enroll in CT lung screening programs,” study author Brady J. McKee, MD, of the department of radiology at Lahey Hospital and Medical Center, told 

. “We recommend CMS provide ‘coverage with evidence’ for Group 2, as is being requested by the national multi-stakeholder coalition currently providing evidence to CMS as part of the National Coverage Determination process.”[[{"type":"media","view_mode":"media_crop","fid":"28098","attributes":{"alt":"","class":"media-image media-image-right","id":"media_crop_85319305956","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"2810","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 238px; width: 166px; border-width: 0px; border-style: solid; margin: 1px; float: right;","title":"Brady J. McKee, MD, study author","typeof":"foaf:Image"}}]]

Based on results of the NLST, annual CT screening is currently recommended in patients aged 55 to 74  with a 30 pack-year or greater smoking history or current or former smokers who quit within the past 15 years. The NCCN Group 2 is patients aged 50 or older with a greater than 20 pack-year smoking history, current or former smokers who quit for any length of time, and those with at least one additional lung cancer risk factor, excluding second hand smoke exposure.

The study by McKee and colleagues, published in the 

Journal of the American College of Radiology

 is the first to report the performance of NCCN Group 2 in a clinical CT lung screening program. They looked at 1,760 CT lung screening examinations performed between January 2012 and December 2013 (464 in group 2; 1,296 in group 1 equivalent to NSLT). The results of the CT examinations were analyzed by radiologists credentialed in structured CT lung screening reporting. Positive results required a solid nodule 4 mm or greater, a ground-glass nodule 5 mm or greater, or a mediastinal or hilar lymph node greater than 1 cm, not stable for two years or longer.

“Despite statistically significant differences in age, smoking history, and duration of smoking cessation between NCCN Group 2 and Group 1 (the NLST population) the positive test and cancer detection rates for both groups were similar,” McKee said.

Results of the imaging examination showed positive results, clinically significant incidental findings, and suspected pulmonary infection in 25%, 6%, and 6% of patients in group 2 and 28.2%, 6.2% and 6.6% in group 1, respectively.

“In our program, for every three NLST high-risk individuals screened, we screened one from NCCN Group 2. Applying a similar ratio nationwide would yield 2 million Americans in Group 2,” McKee said. “Should CT lung screening generate a Group 2 mortality benefit similar to the NLST we could save thousands of additional lives each year by including Group 2 in clinical CT lung screening programs.”

NCCN Group 2 high-risk patients to benefit from CT lung screening, study says.

Data Backs CT Lung Screening in More High-Risk Patients

Physician reviewers were able to identify an equal number of findings from liver computed tomography (CT) images with a 59 percent reduced radiation dose reconstructed with model-based iterative reconstruction (MBIR) as they were from standard-dose adaptive statistical iterative reconstruction (ASIR), according to the results of a recent study.

“We found that clinically reportable findings identified on the images from the stan­dard dose ASIR series were all identi­fied by two separate reviewers on the images from the reduced dose MBIR series,” wrote William P. Shuman, MD, from the department of radiology at the University of Washington School of Medicine, and colleagues in 

. “In 94% of the 136 liver findings, subjective conspicuity, subjective spa­tial resolution, and subjective assess­ment of image noise were assigned a score as the same or better with MBIR than with ASIR; none were assigned scores as nonvaluable.”  

According to the background information in the article, ASIR is a partially iterative technique that lowers image noise allowing technicians to obtain better image quality than reconstruction with filtered back projection or to lower radiation dose. In contrast, MBIR is a fully iterative technique that lowers image noise using back and forward projections. The lower noise gained with MBIR can be used to obtain a comparable image quality or to reduce radiation dose.

“However, the different appearance of CT images re­constructed with MBIR may raise con­cerns about depiction of clinically rele­vant findings,” the researchers wrote.

In this study, Shuman and colleagues wanted to compare images taken with reduced radiation dose MBIR and standard dose ABIR. Fifty patients were enrolled in the study and underwent liver CT. Two passes were made in the portal venous phase, one using standard-dose ABIR and one using reduced -dose MBIR.

The images were then reviewed by one physician who scored the ASIR image quality and marked any findings. Two additional reviewers then reviewed the MBIR images and noted if marked ASIR findings were present on the MBIR images, and assigned the images scores for relative conspicuity, spatial resolution, image noise, and image quality. 

The ABIR reviewed, identified and marked 136 liver findings, all of which were identified by the two MBIR reviewers. The MBIR reviewers scored each of the liver findings as equal to or better than the ASIR images for conspicuity in 94.1 percent of MBIR images; for spatial resolution in 96.7 percent of MBIR images, and for image noise 99.3 percent of the MBIR images.

The volume CT dose index for the ASIR images was 15.2 mGy compared with 6.2 mGy for the MBIR images (

<.001). Similarly, the mean size-specific dose estimate for ASIR images was 16.4 mGy compared with 6.7 mGy for MBIR images, a reduction of 59 percent.

“This da­tum suggests that MBIR reconstruction may allow substantial radiation dose reduction in portal venous phase liver CT without compromising depiction of clinically relevant findings and with acceptable or improve image quality,” the researchers concluded.

CT images reconstructed with low dose model-based iterative reconstruction did not compromise image quality.

Model-Based Iterative Reconstruction Allows Lower Dose

A new study has found that more low-dose computed tomography (LDCT) screening centers may be needed in certain geographic areas as the acceptance and practice of LDCT for lung cancer screening continues to grow.

Specifically, Jan M. Eberth, PhD, of University of South Carolina and colleagues, found that several states with a high percentage of people at risk for lung cancer, such as Oklahoma, Nevada, Mississippi and Arkansas, do not have an adequate number of screening centers.

“Organizations such as the American Cancer Society and American College of Radiology recommend that lung cancer screening take place at organized programs with access to multidisciplinary teams and experienced physicians doing a high volume of procedures,” Eberth told 

. “There is little information available to date to show exactly where such programs are located. Our study is a first step to identify where low-dose screening programs are located in the United States.” 

Eberth and colleagues studied the geographic locations of 203 LDCT screening centers from the Lung Cancer Alliance Screening Centers or Excellence database, a list of active National Lung Screening Trial and International Early Lung and Cardiac Action Program, and an independent survey of Society of Thoracic Radiology members. Eberth and colleagues compared these locations with rates of lung cancer incidence, mortality, and smoking prevalence. They published their results recently in 

Nationwide, each state, including Washington DC, had a mean of four screening centers; however, 11 states had no screening centers identified. There was an average of 0.3 screening centers per 100,000 people aged 55 to 79. Among the states with the best capacity of LDCT screening centers were Washington, DC, Connecticut, Virginia, Colorado and Maryland.

“It is expected that the number of screening centers will continue to increase in the coming years, as data show that 90% of centers without an active LDCT screening program are considering adding the service in the near future,” the researchers wrote. “Factors such as the changing status of LDCT screening guidelines and the lack of reimbursement for screening were commonly listed by radiologists as factors that contributed to their institutions’ decision to not offer screening.”

The Northeast and East North Center U.S. were identified as the geographic areas with the most LDCT screening centers. Although they had countries with some of the highest quartiles of lung cancer incidence and mortality, counties in Oklahoma, Louisiana, Mississippi, Arkansas, West Virginia and Missouri had the least screening availability.

One notable exception was Kentucky, where despite a high lung cancer incidence and mortality there was a high screening capacity, “suggesting the positive effect of initiatives such as the Kentucky Cancer Consortium Lung Cancer Prevention and Early Detection Network (funded by the Centers for Disease Control and Prevention),” the researchers wrote.

Data from the study also indicated that those people living in rural areas face greater barriers to screening. “Among these populations, obtaining services is not merely a matter of community to the closest metropolitan area, but may require ‘cross-state’ travel,” the researchers added.

“States with high rates of lung cancer incidence and mortality, smoking, and occupations that predispose workers to lung carcinogens should be particularly concerned with their capacity to screen their high-risk population for lung cancer,” Eberth said. “Policies that ensure the availability and affordability of screening, including mandating reimbursement for screening of high-risk persons, are vital for increasing development of screening programs and their utilization.”

States found to have a high percentage of people at risk for lung cancer do not have an adequate number of LDCT screening centers.