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.

Author | Leah Lawrence

Articles

Educating Clinicians About LDCT May Increase Early Diagnosis

Dose Reductions Achievable in Pelvic CT with ASIR

Dose Can be Reduced in Pelvic CT with ASIR

Lower Voltage CT Angiography Effective Even with Higher BMI