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  | l Imaging Techniques l Light Scanning l Sonogram l Duplex Doppler l Color & Power Doppler l References l |
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 Image1: Spinal cord model. |
Multimodality Imaging Techniques in the Spinal Soft Tissue Injuries The skyrocketing costs of diagnosing soft tissue injuries from automobile accidents and job related trauma have led to an extravagant increase in medical expenditure. The author proposes that most personal injury/soft tissue injury may be adequately detected and documented by the non invasive, cost effective medical technologies of transillumination, ultra high resolution sonography and color Doppler ultrasound. The purpose of this article is to re-introduce these proven imaging procedures to detect soft tissue trauma. The above cited simple exams are not meant to replace more sophisticated radiologic procedures, but rather to remind the physician that they are readily available and often diagnostic. Improvements in both imaging technology and physician's interpretive skills merit further consideration of these studies. | ||
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The oldest, fastest and certainly the least expensive study used for centuries is light scanning. The non invasive procedure of transillumination, clinically used for breast disease evaluation and scrotal pathology, shows great promise in evaluating injuries. Potentially important is the role of light scanning, the current term for transillumination, in the diagnosis of the nature and extent of muscle rupture. Although light scanning has been used for breast cancer detection for over fifty years and scrotal hydrocele analysis for many years, its usage in muscle injury is relatively new while seemingly quite logical. Light absorption of the transilluminated area is compared with the contralateral side or with adjacent normal tissue architecture and adjusted for differences in depth. Early usage called the test "diaphanography" and required photographic picture acquisition and visual observation. Today's interpretation is often made with a radiographic sensitometer or a low light level closed circuit television monitor. This technique is the primary screening modality for the Chinese people. While not widely appreciated, it may be used to narrow the focus of other imaging modalities to a specific region. Minor trauma to a muscle belly may be accompanied by serous fluid extravasation. If this process is localized, light scanning will be unremarkable. If the leakage is larger, accompanied by hemorrhage and more distant from the capsule, light absorption will be noted since the deoxygenated hemoglobin in the hematoma dramatically blocks light transmission due to absorption in proportion to the hematoma's size and borders and is compared with the unaffected normal contralateral side. It is important to realize that calcification or bone do not affect the absorption of the optical transmission in the way that x rays are absorbed by calcium. A long standing serous leakage may become secondarily infected, thus producing unilateral light absorption. Thus, trauma, blunt or penetrating, may be associated with bleeding or products of tissue inflammation that absorb light rays. Thus, normal symmetric transillumination may suggest the probability of structural intactness of the muscle. Medium degrees of transmission blockage are associated with structural failure of the muscle and massive light absorption loss accompanies hemorrhage and/or infection in the muscle or its associated traumatic seroma. 
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Sonography was originally introduced to map ocean topography and detect submarines in World War II (sonar). Since then military and civilian technology has developed ultra high frequency systems designed for detecting microscopic flaws in the ceramic tiles used to surface spacecraft. High resolution real time sonography using the newer 20 Mhz transducers permits fluid detection as small as 0.1 mm. This means that cystic areas of fluid or blood within tendons, ligaments or muscle may be imaged definitively and their regression or expansion followed. Muscle imaging with ultrasound shows simple cysts as echo free regions. Seromas with necrotic internal debris and hematomas in certain stages of organization demonstrate internal particulate echogenicity in proportion to the degree of solid component. Indeed, resolution of the bleeding with scar formation shows up as a discrete echogenic complex within the echo poor muscle with disruption of the stepladder pattern of the internal perimysial septa. Additionally, disruption of fascial planes is easily demonstrated. Myositis in the paraspinal region is best imaged with a linear array transducer and presents with increased echogenicity in the affected areas. Tendons and ligaments may now be well imaged by sonography. Not only can sonograms detect hematomas with or without muscle rupture, but associated posttraumatic and inflammatory lesions in the subcutaneous soft tissues, adjoining musculature and adjacent tendons may be identified. Tendons appear slightly more echogenic than muscle. Hypoechoic areas are demonstrative of early injury and are associated with enlargement of the structure (Fig 3) Chronic trauma produces hyperechoic areas as scarring progresses. Sonography reliably differentiates lesions that respond to conservative or surgical therapies. Fluid around the tendon occurs with tendinitis. Indeed, definitive diagnosis of ligamentous laxity as a cause of chronic pain syndrome is possible. The type of injury of ligaments, such as partial tear with thickening (Fig 4) and decreased echogenicity or complete rupture with discontinuity of the structure with the ends separated by a hematoma is documented and the evolution of the healing process may be observed. Injury to the posterior spinal ligaments may show partial tearing or complete rupture of the supraspinous ligament during longitudinal scanning. Tears of the interspinous ligament may be seen longitudinally as well as transversely with the transducer angled to traverse the soft tissues by avoiding the bony spinous processes. The transverse plane is similarly best for imaging the flaval ligaments and posterior longitudinal ligaments. These ligaments have been grouped together to be called the posterior ligament complex (PLC). Injuries to this area may result in kyphosis deformity leading to permanent disability if not surgically treated. It is now well known that standard radiographs in two planes miss fractures of the curved bony surfaces. Spinal laminar fractures may also be imaged by ultrasound. The degree of injury within the structure may be immediately assessed at or near the site of trauma due to the compact nature of the new scanners, such as an athletic facility, an emergency room or a stadium so that triage may be performed and the injury classified as minor with a week of therapy for a young athlete or major with loss of a season for a professional player. The advantage of ultrasound over arthroscopy is that capsular ligaments may be evaluated. Arthrography on visualizes intraarticular structures. CT lacks the fine resolution to see ligaments. Ultrasound and MRI provide multiplanar imaging and sonograms have the advantage with short exam time, capability of dynamic exam, potential availability and moderate cost. In extreme injury, myositis ossificans, true bone formation within the muscle, and not uncommon in supracondylar fractures of the humerus and femur, will be radiologically visible after several months as bone tissue on a plain x ray. This entity shows up earlier on a sonogram initially as very high amplitude echoes of the pre-bony calcification with blockage of the sound beam transmission resulting in a "sonic shadow" sign. 
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Duplex Doppler is the combined application of high resolution real time ultrasound and simultaneous Doppler flow analysis (blood or other fluids in motion) of the area under investigation. Duplex Doppler sonogram uses the regular images and adds the capacity of blood flow analysis to see if flow is present, normal in direction and adequate in velocity. Trauma may produce arterial and venous thrombosis. Blunt craniocervical trauma that does not cause loss of consciousness may yet be severe enough to produce dissection and thrombosis of a vertebral artery. Occlusion of one of the paired vertebral arteries that supplies the base of the brain results in blood supply from the other member of the pair of arteries. Depending upon the- site of the occlusion, blood flow in the paired vessels may show different flow and velocity measurements. This may affect the brain causing a variety of symptoms including local pain, dizziness, double vision and other eye symptoms, facial numbness, headaches and various degrees of paralysis. Routine diagnostic tests including MRI, CT scan, EEG, x rays of the skull, orbits, facial bones, internal auditory canals and brain stem evoked auditory potentials may all be normal. Cerebral angiography is an accurate test but one that is inherently dangerous. Sonogram of the arteries has proven to be as accurate and in some cases more accurate the angiography in various arteries in the head and neck. Duplex Doppler sonogram uses the regular images and adds the capacity of blood flow analysis to see if the flow is present, in normal in direction and adequate in velocity. Doppler sonogram may show the actual site of occlusion and the effect of altered brain circulation due to collateral arterial supply. Since the blood clot may spread, anti coagulation immediately is needed to prevent the catastrophic entity called basilar artery thrombosis, which is the artery to which the vertebrals pair up in side the skull. Sonogram
may be used as a baseline screening test for this disorder as well as a follow up during treatment since it is simple, safe, non x-ray and can pin point the problem with a similar degree of accuracy to the more invasive x ray cerebral angiogram. Since a blood clot may spread, anticoagulation immediately is needed to prevent the catastrophic entity called basilar artery thrombosis. Sonogram may be used as a baseline screening test for this disorder as well as a follow up during treatment since it is simple, safe, non x-ray and can pin point the problem with a similar degree of accuracy to the more invasive x ray cerebral angiogram. Doppler sonogram may show the actual site of occlusion and the effect of altered brain circulation due to collateral arterial supply. Hematoma that compresses veins producing venous congestion or arterial ischemia may be documented instantaneously. Also, duplex Doppler may show linear fluid filled structures to be arteries or veins as contrasted to centrally displaced ligaments or fibrous membranes. This ultrasonic "angiography" is of critical importance to the trauma surgeon since fasciotomy for decompression of compartment syndrome will avert muscle necrosis or nerve damage. The state of the art introduction of color in the Doppler image makes interpretation faster and easier. At the 1996 meeting of the 6th Annual Musculoskeletal Ultrasound Society it was shown that inflammation in the tissues has increased blood flow which is captured by the power Doppler image. Additionally, combined use of light scanning, sonogram and duplex Doppler ultrasound in addition to radiography (called multimodality imaging) may detect pathology adjacent to and hidden by the hematoma. Thus, non radio-opaque foreign objects, such as glass and wood, only radiographically visible 15% of the time, are depicted by sonograms. Inflamed bursae or cancerous lymph nodes may be imaged near and adjoining hemorrhage. Spinal facet inflammation presents as increased echogenicity in the focal site. Nerve root area inflammation is demonstrated by the appearance of a linear echo corresponding to the ventral wall of the spinal nerve as it exits from the foramen. Disc herniation in the lumbar area may be diagnosed with 78% accuracy with sonography alone. The Most important, the evaluation of low back pain by MRI examination has proven to be non specific. Nerve root pain etiology is not purely mechanical. Pain requires edema, inflammation or fibrosis.  |
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Conventional pulsed and continuous wave Doppler exams are
used to demonstrate blood flow. However, these are time consuming and relatively insensitive. Color Doppler uses computer coding to demonstrate directional blood flows in a clinically useful manner. Power Doppler is a new feature of blood flow analysis that is proportional to the total number of moving scatterers. This allows low flow states and minute vascular structures to be imaged. Potential clinical applications are the neovascular regions found in healing fractures, resolving hematomas, inflammatory
tenosynovitis, acute gouty inflammation, and distinguishing synovial fluid from vascular synovium. Gouty arthritis demonstrates the highest vascular power Doppler response and active rheumatoid synovitis is next in line closely followed by the new callus of fracture healing. Evaluation of arterial and venous malformations is possible by power Doppler's high sensitivity. Abnormal pulsatility may be noted in a non vascular region during routine scanning. Arterial occlusive disease is best examined by color Doppler and pulsed wave ultrasound since power Doppler is non directional. Venous insufficiency is best studied with color Doppler and pulsed wave sonography as well for similar reasons.
MRI, the so called "Gold Standard" apparently underestimates the degree of tendon damage and nerve root inflammation when compared to high resolution ultrasound with power doppler.
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