Norman W. Rantanen

ULTRASOUND EXAMINATION OF DISTAL INTERPHALANGEAL JOINT, NAVICULAR BURSA, NAVICULAR BONE AND DEEP DIGITAL TENDON

Summary Techniques were devised for real-time ultrasound examination of the coffin joint, navicular bursa, navicular bone and deep digital flexor tendon of the forelimb of the horse, including their anatomical relationships and associated fluid spaces. Correlation was made between the echogram, positive contrast arthrograms, and freeze dried gross specimens. Anatomical structures were imaged in a midsagittal plane, of a standing, clinically normal horse.

Ultrasound appearance of the palmar metacarpal soft tissues of the horse

Summary Using real-time ultrasound imaging, the normal anatomy of the soft tissues of the palmar aspect of the equine forelimb was examined. Sections of frozen specimens were prepared which correlated well with the ultrasound images. The superficial and deep digital flexor tendons, tendon sheaths, inferior check ligament (accessory ligament of the deep digital flexor tendon), suspensory ligament, contours of the apices of the proximal sesamoids and the intersesamoidean ligament, were identified.

Diagnostic ultrasound examination of the dorsal aspect of the equine metacarpophalangeal joint

Summary Diagnostic ultrasonography was used to demonstrate villonodular synovitis of the equine metacarpophalangeal joint. The presence of the soft tissue, intracapsular mass was confirmed with conventional radiography and positive contrast arthrography. The mass was surgically excised and submitted for histopathologic identification.

Suspensory desmitis: Diagnosis using real-time ultrasound imaging

Summary The textural and dimensional characteristics of the appearance of the normal suspensory ligament lends itself well to diagnosis of clinical disease of this structure. Following injury to the suspensory ligament there are changes that involve inflammation, and structural compromise. These changes may be manifest in a spectrum of severity, and documentation may be provided using real- time ultrasound imaging. Ultrasound imaging of the soft tissues in the equine extremity is an important aid; in diagnosis of lameness, prognosis, monitoring of healing, and retrospectively, in determining the more efficacious therapeutic regimens. To illustrate pathologic change of the suspensory ligament, selected cases of suspensory desmitis with varying degrees of severity are discussed.

Spontaneous contrast and mass lesions in the hearts of race horses: Ultrasound diagnosis-preliminary data

Summary The association of cardiac changes and decreased performance indicates that many horses have occult, but significant cardiac abnormality that may be a limiting factor. Many of these horses had no outward signs of disease. It is interesting to speculate on the etiology of endothelial damage with subsequent platelet aggregation to produce visible echogenic contrast passing through the right heart and measurable mass lesions within the right atrium or attached to the tricuspid valve. The potential therapeutic valueof platelet inhibitors, such as aspirin, appears to be worthy of clinical investigations in the horse.

Jugular venous prosthesis on the horse: A preliminary report

Summary Woven dacron vascular prostheses a were implanted in 6 horses to replace segments of external jugular veins. Anticoagulant therapy using sodium heparin and coumadin was done postoperatively. Clotting profiles and red blood cell counts were determined by measuring activated partial thromboplastin time (APTT), one stage prothrombin time (OSPT), and packed cell volume (PCV). The horses were observed postoperatively for 4 to 38 days. Real time ultrasonography was used to monitor patency of the prostheses. All grafts remained patent during the observation period, although 3 cases of septic thrombosis were seen at necropsy.

Congenital internal hydrocephalus in a quarter horse foal

Summary Since the normal absorption of CSF occurs in the cerebral veins and venous sinuses, any obstruction to the normal flow and absorption of CSF will result in accumulation of CSF central to the site of obstruction. Such accumulation within the cranium is defined as hydrocephalus. A foal was presented with an enlarged and an abnormally-shaped skull, but with normal behavior. The fillys condition deteriorated. Radiographs showed a domeshaped cranial vault with compression of the frontal sinus region. Massive hydrocephalus with little normal cerebral tissue left was diagnosed with ultrasound. Surgery was attempted to relieve the pressure. Eventually the foal was euthanized. Post-mortem confirmed the radiographic and ultrasound diagnosis. Since there was a lack of demonstrable obstruction, the authors suspected the foal had suffered from the Arnold-Chiari syndrome.

Early pregnancy detection in the mare with ultrasonography

Ultrasound can be defined as the propagation of energy waves with a frequency greater than the upper limit of the hearing range, approximately 20,000 cycles per second (Hertz, Hz.). In medical diagnostic ultrasound, frequencies much greater than that, in the range of 1 to 10 Megahertz (MHz.), are commonly employed. Energy waves of these frequencies can be produced by a transducer utilizing the piezoelectric property of crystals. When an electric current is applied to these crystals, vibrations of a frequency unique to the physical properties of that crystal are produced, resulting in the propagation of sound waves. When sound waves are passed through soft tissues, a portion of their energy will be reflected back toward the transducer as a reflected wave or echo. The echo can impinge on the face of the crystal causing pressure changes which result in the production of an electrical current of a corresponding frequency.] The magnitude of the reflected energy waves will be directly proportional to the difference in density existing at the interface of two tissues. In general, the greater the difference in tissue such as muscle and bone, the greater the impedance to the propagation of sound waves, and the greater the strength of the echo produced. Water is an excellent medium for the transmission of ultrasound waves and provides little impedance for the production of an echo until the signal encounters an interface of the water with an adjacent tissue of a different density. Air or gas, however, is very poor in propagating ultrasound signals and results in severe attenuation of the energy waves when encountered. For this reason, close contact of the transducer and the tissue to be examined without any air interspersed between the two is essential.] As a rule, higher frequency waves result in better detail or resolution of the tissue being examined. However, more attenuation of the sound waves as they pass through tissues is associated with the higher frequencies. Conversely, lower ultrasound frequencies offer deeper tissue penetration with less attenuation but poorer resolution and detail. The returning echo signal can be electronically processed

Diagnosis of lung consolidation in horses using diagnostic ultrasound

The appearance of normal lung surfaces has been described in the literature. The characteristic concentric reverberation artifact is easily recognizable. Any disease process that changes the normally flat surface of the lung will alter the concentric line artifact. Lung consolidation, which eliminates the highly reflective air from the lung will produce a marked change in the appearance. The gas reverberation artifact will no longer originate from the surface of the lung. Sound will penetrate into the non-aerated lung until it encounters air, producing a gas reverberation artifact unlike the normal lung surface. The artifact will usually be uneven in outline and brightly echogenic as opposed to the normal lung which is smooth and brightly echogenic. The lung surface can still be visualized as it slides on the parietal pleura. If the lung lobe is totally consolidated, sound will penetrate to the medial surface of the lobe and mediastinal structures (or diaphragm) will be visualized. Lung consolidations in the horse are most commonly caused by bacterial or viral pneumonia. Atelectasis of the ventral lung lobe margin, however, can be found in moderate to severe pleural effusions. It is not uncommon to have consolidated lung concomitant with pleural effusion, but not always. With atelectasis, the ventral margin will be nonaerated and the sound will penetrate to the medial margin of the lobe. The entire surface of both lungs must be examined to preclude overlooking significant findings, although most infectious pneumonia will be found ventrally, most often at the border of the cardiac notches just caudal to the right and left ventricular walls. The caudodorsal surfaces of the lungs in racehorses should be examined carefully because of the prevalence of lesions in those areas associated with exerciseinduced pulmonary hemorrhage.

Ultrasonographic appearance of normal lung surfaces of the horse

Since the first report of the use of ultrasound for thoracic examination of the horse appeared in the literature in 1981, its use has become commonplaceJ,2, There are certain anatomic landmarks that must be recognized and physical principles that must be followed to successfully scan the equine thorax. The entire surface of both lungs must be examined to avoid missing significant pathology, although most active infectious processes will be ventral dependent by the time they are scanned. Occasionally, abscesses and consolidated pneumonia can be found in more dorsal locations. Usually, skin preparation is minimal for surveying the thorax of the horse especially if the animal has been reasonable groomed. Copious amounts of contact gel will usually allow adequate contact. Winter haircoats present special problems in some areas, but the lung surfaces can still be evaluated in most horses without dipping the hair. This makes the examination more palatable to most horse owners and trainers. Skin preparation can always be carried further if suspected abnormal areas are to be tapped or biopsied. Administration of a tranquilizer is usually not needed except for fractious horses. Frequencies of 5.0 MHz (or lower) on sector or linear array scanners are commonly used to scan the horse thorax. It is more difficult, however, to contact the skin through the hair with the linear arrays greater contact surface. Because the lung surface is only a few centimeters from the skin surface, there is usually little difficulty in recognizing it. There can be some confusion, however, about the actual information present on the image. Since air is a near perfect reflector of sound at the commonly used frequencies, the sound beam will not penetrate beyond the visceral pleural thickness in normal lung. z This creates a reverberation of sound Figure 1. The normal concentric parallel lines produced when scanning normal lung surfaces.