Brian Lott

Despite the image of young snowboarders recklessly bombing downhill, the popular sport actually has no greater percentage of injuries than does skiing. Snowboarders have their own types of injuries, however, related to factors unique to the sport. 

Until five years ago, many doctors failed to recognize the differences in injuries between snowboarding and downhill skiing, according to Dr. Klaus Dann, a sports medicine specialist at Top-Med. His practice has an average of 100 snowboarding patients per year. 

Common to beginners is a wrist injury that occurs when they fall backward or forward onto a hyperextended wrist, said Dann, an avid athlete in Vienna, Austria. Novice snowboarders often fall while learning to balance on a board without ski poles for support, but these injuries represent a small percentage of the total related to the sport.

There are about 10 million snowboarders around the world, and all are susceptible to clavicle fractures, rotator cuff strains, and acromioclavicular joint dislocations. Radiographic evaluation for a possible fracture is justified in shoulder injuries when an attempt to reduce the dislocation has failed.

"For shoulder injuries, we tend to use MRI, if there is a situation that might be complicated," Dann said. 

Dann recommends CT in cases that are directly related to sprains and fractures in the front leg on the board, when stress in placed on the leading leg and the boarder is wearing a soft boot. 

Fractures of the lateral process of the talus are known in some quarters as "snowboarder's fracture" because they are seen far more often among the sport's enthusiasts than in the general population.

"Standard radiology methods are not as accurate, so many professionals prefer to use CT, as it provides a better image in cases such as subankle injuries," he said.

More experienced snowboarders have different types of injuries, as they try to perfect stunts known as "Hospital-Air." These aerial tricks cause various injuries due to the radical extension of limbs, the brutal pounding applied to internal organs, and inadequate or lack of specialized equipment. 

"While there are similarities among injuries, each case is unique. The key to proper diagnosis is using the best method per case, rather than generalized procedures," Dann said.

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Articles

Despite the image of young snowboarders recklessly bombing downhill, the popular sport actually has no greater percentage of injuries than does skiing. Snowboarders have their own types of injuries, however, related to factors unique to the sport.

Snowboarders face different injuries from skiers

The choice of a contrast agent for MR imaging of the liver is highly dependent on the clinical problem. Extracellular gadolinium can characterize most lesions and detect hypervascular tumors, while superparamagnetic iron oxide (SPIO) particles detect smaller metastases and characterize hepatocellular lesions, according to Prof. Philip J. Robinson, a clinical radiologist at St. James' Hospital in Leeds, U.K.

"Combined use of Gd-SPIO agents is the most effective technique for detecting hepatocellular carcinoma in cirrhosis, characterizing focal nodular hyperplasia and adenoma, preoperative mapping of cholangiocarcinoma, and problem-solving with difficult lesions," he told ECR delegates at a special session on contrast-enhanced liver imaging.

SPIO particles help increase the time window for imaging, improve lesion/liver contrast, and provide access to pathology at the cellular level, enabling characterization of hepatocellular lesions and hemangiomas. They are strongly paramagnetic and cause local field inhomogeneities and loss of signal from the normal liver. Particles are cleared from plasma by reticuloendothelial cells in the first few minutes after injection (blood half-life of three to five minutes). About 80% are taken up into the liver, 15% into the spleen, and the remainder into bone marrow, Robinson said.

The two SPIO agents available for liver MRI are ferumoxides (Endorem, Guerbet) and ferucarbotran (Resovist, Schering). Ferumoxides comprise iron oxide crystals coated with dextran. The mean particle size is 150 nm, and the recommended dose is 15 micronol/kg of body weight, or half that amount at 1T and 1.5T. The contrast is diluted in 100 mL of 5% glucose solution and infused over 30 minutes. Images are optimal 30 to 120 minutes postinjection.

The ferucarbotran iron oxide particles are coated with carboxydextran, and the mean particle size is 60 nm. The agent has a blood half-life of three to five minutes, and optimal T2-weighted images are acquired at 10 to 40 minutes after injection. The recommended dose is 7 to 11 micronol/kg of body weight, administered as a bolus injection, which allows dynamic T1 acquisitions that show transient enhancement.

"As is always the case, it is the choice of techniques and treatments that are critical to the status and well being of the patient. Whether or not to use SPIO or another process is of course very subjective. It wholly depends on the needs of the patient," Robinson said. "Acquisition technique is critical. The efficacy of post-SPIO imaging is determined by the choice of pulse sequence parameters."

The use of contrast agents dramatically improves ultrasound's ability to detect and characterize focal liver lesions, said Dr. Thomas Albrecht, a radiologist at Freie University in Berlin. Contrast-enhanced ultrasound is about as sensitive as CT for detecting metastases and is comparable to MRI in characterizing focal lesions.

In the liver, ultrasound contrast agents are used for dynamic assessment of enhancement during the arterial, portovenous, and delayed phases. In the delayed phase, which is of particular value for detecting tumors, the bubbles pool in normal liver and spare malignant focal lesions such as metastases.

Ultrasound contrast can also be used as a tracer for functional studies of liver perfusion. Hepatic transit time is shortened in certain diseases, including cirrhosis and metastases. Transit time analysis of a microbubble bolus is a promising research tool for early detection of these diseases, Albrecht said.

Brian Lott

Articles

Snowboarders face different injuries from skiers

Contrast and acquisition technique prove critical in liver imaging