Tc-99m PYP scanning following low voltage electrical injury

Tc-99m pyrophosphate imaging of poloxamer-treated electroporated skeletal muscle in an in vivo rat model

OBJECTIVE

This study investigates whether (99m)Tc pyrophosphate (PYP) imaging provides a quantitative non-invasive assessment of the extent of electroporation injury, and of the effect of poloxamer in vivo on electroporated skeletal muscle.

METHODS

High-voltage electrical shock was used to produce electroporation injury in an anesthetized rat's hind limb. In each experiment, the injured limb was treated intravenously by either poloxamer-188, dextran, or saline, and subsequently imaged with (99m)Tc PYP. The radiotracer's temporal behavior among the experimental groups was compared using curve fitting of time-activity curves from the dynamic image data.

RESULTS

The washout kinetics of (99m)Tc PYP changed in proportion to the electric current magnitude that produced electroporation. Also, (99m)Tc PYP washout from electroporated muscle differed between poloxamer-188 treatment and saline treatment. Finally, 10-kDa dextran treatment of electroporated muscle altered (99m)Tc PYP washout less than poloxamer-188 treatment.

CONCLUSIONS

Behavior of (99m)Tc PYP in electroporated muscle appears to be an indicator of the amount of electroporation injury. Compared to saline, intravenous polaxamer-188 treatment reduced the amount of (99m)Tc PYP uptake. Coupled to results showing poloxamer-188 seals ruptured cellular membranes, lessens the extent of electroporation injury and improves cell viability, (99m)Tc PYP imaging appears to be a useful in vivo monitoring tool for the extent of electroporation injury.

Muscular injury in a child diagnosed by 99mTc-MDP bone scan

An 11-year-old boy had bone scanning to rule out an osseous lesion of the right arm. He presented progressive pain and hard swelling of the right arm. His past medical history and general physical examination were unremarkable. He trained for karate. The scan demonstrated considerable muscular uptake in both arms. CPK and CPK MB levels were both abnormally high, suggesting muscle injury. After a 10-day rest period the bone scan returned to normal.

Basic principles of nuclear medicine techniques for detection and evaluation of trauma and sports medicine injuries

Nuclear medicine skeletal imaging is a very sensitive technique for evaluating bone and muscle abnormalities because it can detect minor changes in metabolism and blood flow. The specificity of bone imaging, however, depends on the ability of the nuclear medicine physician to make a differential diagnosis. To aid in making a specific diagnosis, this article describes the various patterns of abnormality in stress fractures, tibial stress syndrome (shin splints), compartment syndrome, enthesopathy, and traumatic fractures. The characteristic scintigraphic appearance of joint injuries, muscle injuries (rhabdomyolysis), and radionuclide arthrography is discussed and the way the scan patterns change with time in these various disorders is described. A brief summary of the basic anatomy and physiology of bone and muscle in normal and injured tissue is presented and the basic mechanisms which cause the various abnormal scan patterns is postulated. In addition, a staging system for stress fractures is presented to help direct the referring physician toward the proper management of the injured patient. In most cases, nuclear medicine skeletal imaging can be used to differentiate between acute muscle injury, tibial stress syndrome, skeletal injury (periosteal reaction, stress fracture, and traumatic fracture) or an abnormality that is entirely associated with the joint or connective tissue. This differential diagnosis is easier if the nuclear medicine procedure is performed within a few days after the onset of injury.

Quantitation of postischemic skeletal muscle necrosis: histochemical and radioisotope techniques

Skeletal muscle necrosis will result from prolonged periods of ischemia. The purpose of this study was to develop a method to estimate the extent of necrosis using nitroblue tetrazolium staining and technetium scanning. The bilateral canine gracilis muscle preparation with total vascular isolation was exposed to 4 hr of complete normothermic ischemia followed by reperfusion. After 45 hr of reperfusion 99mTc pyrophosphate (PYP) was injected and 3 hr later the muscles were harvested, cut into six slices, and stained with nitroblue tetrazolium. Biopsies were taken from tetrazolium-positive and -negative areas for electron microscopy to confirm the ability of the stain to distinguish viable from necrotic muscle. Computerized planimetry of the staining pattern was used to estimate the extent of necrosis as a percentage of the total muscle. Electron microscopy confirmed the validity of nitroblue tetrazolium to discriminate between viable and necrotic skeletal muscle in this experimental model. After 4 hr of ischemia the percentage necrosis was 30.2 +/- 6.1% (mean +/- SEM, n = 12), there was no difference in the extent of necrosis in left vs right paired muscles, using tetrazolium staining or technetium PYP uptake. There was a statistically significant correlation between the percentage necrosis and the density of 99mTc PYP uptake per muscle (r = 0.83, P less than 0.001) and per slice (r = 0.94, P less than 0.001). This study demonstrates the ability of tetrazolium staining to accurately differentiate between viable and necrotic skeletal muscle and provides a reproducible method for estimating the extent of necrosis in the gracilis muscle model.