Author: Stephen R. Baker, MD. Special Presentation for Practical Reviews in Radiology

Other Signs of Free Air on Radiography

This third section of the review on diagnosing pneumoperitoneum considers supine plain film signs of abdominal free air outside the right upper quadrant.

In the anterior paramedian superior position of the abdomen, the most common manifestation is the cupola sign, which is much more frequent than the presence of air in the lesser sac.

Like a cupola, free air in this location is well delimited superiorly, but indistinctly bordered inferiorly.

Occasionally, the only evidence of pneumoperitoneum can be found in the left upper quadrant.

In the mid-abdomen, the classic finding is Rigler’s sign, otherwise known as the bas-relief sign.

It is, unfortunately, insensitive and non-specific, requiring for its presence almost a liter of extraluminal air and accompanying ascites.

However, in patients with intestinal perforation and intra-abdominal adhesions, Rigler’s sign may be encountered even though the more subtle right upper quadrant patterns of free air are absent, because the rostral migration of free air is retarded by the presence of adhesions.

Summary
In patients with intestinal perforation and intra-abdominal adhesions, Rigler’s sign may be encountered even though the more subtle right upper quadrant patterns of free air are absent, because the rostral migration of free air is retarded by the presence of adhesions.

Author: Stephen R. Baker, MD. Special Presentation for Practical Reviews in Radiology

Signs of Free Air on Radiography

The best place to look on plain films for findings of pneumoperitoneum is in the right upper quadrant, because the homogeneous shadow of the liver affords an excellent background upon which even very small collections of free air can be displayed.

However, to take advantage of the hepatic background, the entirety of the peritoneal cavity from the top to bottom must be encompassed.

That is, the radiograph or radiographs must extend from the obturator foramina inferiorly to the apex of the higher hemidiaphragm superiorly.

For most adults, a standard KUB (Kidney-ureter-bladder) cannot include the full expanse of the peritoneal cavity, and a second film of the upper abdomen must be obtained.

The most common right upper quadrant sign of free air is the anterior superior bubble which, contrary to traditional notions, can be discerned even when its diameter is much less than 1 cm and its volume less than ice.

Summary:
The most common right upper quadrant sign of free air is the anterior superior bubble which, contrary to traditional notions, can be discerned even when its diameter is much less than 1 cm and its volume less than ice.

Other signs of free air superimposed on the liver or even within it will be outlined in Part III of this discussion.

Currently the FDA has approved eight digital mammogram systems. However, none of the literature on image quality among these systems addresses measurement accuracy, the Colorado researchers say.

Using an acrylic disk. the team took measurements in various magnification views across different systems, then compared them with measurements made with electronic calipers. Here’s how the 1-cm disk measured:

First system:

• 1.05 cm (nonmagnification)
• 1.64 cm (1.6x magnification)

Second system:

• .99 cm (non magnification)
• .66 cm (1.5x magnification)

Third system:

• Accurate in both views (this system used Selenia from Hologic for acquisition and a PACS viewing station designed by Horizon Medical Imaging from McKesson.)

“This brief yet informative paper tells us that simply assuming that DICOM-compatible FDA-approved equipment will work together seamlessly is unacceptable,” says reviewer Basil Hubbi, MD. “Any practice that is transitioning to digital soft copy reading or employs equipment from various manufacturers should be aware of this potential problem.”

Related seminar: Pittsburgh Breast Imaging Seminar

]]> http://www.radiologydaily.com/daily/breast-imaging/in-digital-mammography-different-equipment-may-mean-different-measurements/feed/ http://www.radiologydaily.com/daily/chest-radiology/vq-scanning-better-choice-for-detecting-pe/ http://www.radiologydaily.com/daily/chest-radiology/vq-scanning-better-choice-for-detecting-pe/#comments Thu, 04 Mar 2010 16:00:59 +0000 Laurie Herr http://www.radiologydaily.com/?p=3879 Over the past 10 years, CT angiography (CTA) has been replacing ventilation/perfusion (VQ) imaging as “the gold standard” for imaging pulmonary embolism (PE). Some would say that’s with good reason: CT is faster, produces sharper images, and is usually readily available in most hospitals. However, using CT for diagnosing PE is a big concern for

“For women at the highest risk of breast cancer, using both breast MRI and mammography together for screening will likely reduce their chances of dying from breast cancer and help them live longer, healthier lives,” said lead study author Janie M. Lee, M.D. in a press release.

In the study, Dr. Lee and her colleagues compared the costs and benefits of film mammography, MRI, and a combination of mammogram plus MRI in a hypothetical group of women with BRCA1 mutations, a genetic factor that increases a woman’s chances of developing breast cancer.

The researchers then used stastistical modeling to estimate the number of quality adjusted life years (QALYs) gained by screening, along with lifetime costs. (QALYs are a measure of both the quantity and quality of life.)

Results showed that annual combined screening was best at detecting early stage cancers and prevented the most deaths from cancer. Combined screening became more cost-effective as breast cancer risk increased, and less cost-effective as risk decreased.

MRI screening was linked with an increase in false-positive results. Annual mammograms led to 37 false-positive screening exams for every breast cancer death avoided. Adding an annual MRI increased that number to 137 false-positive results for every breast cancer death avoided.

“The benefits provided by MRI are balanced by an increased chance of needing additional tests to evaluate a possible abnormality, and perhaps even a biopsy that might in the end show no cancer,” Dr. Lee said.

Source: Radiological Society of North America

FREE Report: Computer-Aided Detection in Mammography: Five Key Breast Imaging Questions and Answers

“This method can be used to determine if the cancer has spread from stage 2, where the melanoma is still just in the skin lesion, to stage 3, where the melanoma has spread to the lymph nodes,” said John Viator, assistant professor in the Department of Biological Engineering and Department of Dermatology. “If the cancer is still at stage 2, a simple procedure can remove that lesion. If the cancer has progressed from the initial skin lesion into the lymphatic region and possibly the bloodstream, doctors have to make serious decisions about patient care. The cancer may have possibly spread to other organs, such as the liver, lungs or brain.”

Currently, pathologists must perform several specific and detailed tests to determine if there is cancer in the lymph nodes. This new technology could make the search less time-consuming by identifying a general area of the lymph node that might contain cancer.

“It’s very similar to identifying a prize inside a cake,” Viator said. “Instead of looking through the entire cake, we can use our ultrasound to pinpoint a slice or two that might contain the ‘prize.’ In the case of the lymph nodes, when you get a signal, this alerts the pathologist that this is an area of the node that might contain cancer cells. At that point, a pathologist would be able to narrow down the search, saving time and money.”

In the photoacoustic method, a tabletop device scans a lymph node biopsy with laser pulses. About 95 percent of melanoma cells contain melanin, the pigment that gives skin its color, so they react to the laser’s beam, absorbing the light. The laser causes the cells to heat and cool rapidly, which makes them expand and contract. This produces a popping noise that special sensors can detect. This method would examine the entire biopsy and identify the general area of the node that has cancer, giving pathologists a better idea of where to look for the cancer.

“This method is quicker and simpler and could be used to improve the efficiency of how doctors determine if the cancer has spread from the original skin lesion into the lymphatic system,” Viator said. “This technology could be an important tool in our fight against cancer.”

In the study, Viator took human cancer cells and placed them inside canine lymph nodes. Then, using the laser, he determined the best ways to locate the cancer cells. The next step is to try the procedure using human lymph nodes.

The study, “Photoacoustic Detection of Melanoma Micrometastatis in Sentinel Lymph Nodes,” was published in the Journal of Biomedical Engineering.

Source: University of Missouri - Columbia

Related seminar: Head to Toe Imaging

According to the FDA’s federal notice, the goal of the meeting is “to receive public input on steps manufacturers of CT and flouroscopic devices should take to help reduce unnecessary patient exposure to ionizing radiation from these medical imaging modalities.”

Day 1 will focus on equipment features that manufacturers should incorporate into CT scanners (morning session) and fluoroscopes (afternoon session). Day 2 will focus on steps manufacturers should take to improve training of individuals who use these devices (morning session) and steps to improve quality assurance at medical imaging facilities with respect to these two modalities (afternoon session).

Anyone interested in attending should email CDRHImagingInitiative@fda.hhs.gov. Include your name, title, organization, address, email, and phone number. Registration requests must be received by March 15, 2010.

Related seminar: Radiation Overexposure: Are Your Patients at Risk?

Using anonymous data from the American College of Radiology’s 2007 Survey of Diagnostic Radiologists, researchers from the American College of Radiology (ACR), Yale, Johns Hopkins, and the University of California at San Francisco looked at factors such as type and size of practice, radiology subspecialty, and geographic region. They also looked at probable links between desired workload change and characteristics of radiologists and the practices where they worked. The researchers compared responses to those in the ACR’s 2003 Survey of Radiologists.

Results showed the desired workload change increased by about 3 percent. Back in 2003, radiologists desired no signficant change in workload. The overall balance between supply and demand of radiologists also tipped toward a surplus. “According to our measure, we judge there was a close balance in 2003, but a 3 percent surplus in 2007,” the authors wrote in the study. They noted that the employment market usually seems to self-correct over a few years.

Related seminar: National Diagnostic Imaging Symposium Discount expires March 1.

• nuclear detonation
• biological aerosol attack with anthrax
• biological disease outbreak from pandemic influenza
• biological attack from pneumonic plague
• chemical attack from industrial chemicals
• chemical attack from chlorine tank explosion
• radiation dispersion attack
• explosive attack using improvised explosive devices

According to the article, radiologists may be called upon for everything from managing acute radiation exposure (in the event of a nuclear attack) to helping treat blast, thermal, and overcrowding injuries in the event of an explosion in, say, a crowded concert hall or sports complex.

These are findings that “every radiologist should know,” said Rahul Pawar, MD, who reviewed the article.

Read or listen to more expert reviews: Practical Reviews in Radiology

Conducted by researchers at Columbia University Medical Center and the National Heart, Blood, and Lung Institute, the study focused on the newest type of CT technology, a 320-detector row volume CT scanner, which can image the entire length of the heart (16 centimeters) in a single rotation and within a single heartbeat. Many current tests use 64-detector row scanners, which can image 4 centimeters at a time.

In the study, researchers compared the radiation exposure from a 320-detector row scanner to the amount given from a scanner with 64 detector rows. Using standard 64-detector row scanning as the norm, the effective radiation dose was cut by 91 percent from 35.4 millisieverts (mSV) to 4.4 mSV using optimized 320-detector row volume scanning.

“By imaging the entire heart in one piece, volume scanning eliminates artifacts due to seams or gaps between image sections,” said Columbia University’s Andrew J. Einstein, MD, PhD, in a press statement. “Moreover, the X-ray tube is left on for only a brief duration, as little as .35 seconds.”

Related seminar: CT Angiography and 3D Imaging: Current State-of-the-Art