Faculty Bibliography

OBJECTIVE: The aim of this study was to demonstrate the use of ultrasound guidance in confirming intralesional injection of corticosteroids and local anesthetic into symptomatic ganglia, and to propose potential advantages of this technique. DESIGN AND PATIENTS: Ten patients (five men, five women) underwent ultrasound-guided injection of a ganglion. Seven ganglia were near the wrist, one was adjacent to a finger interphalangeal joint and two were adjacent to the talus. All were injected with a 1:1 mixture of long-acting corticosteroid and local anesthetic, the actual volume being dependent on the size of the ganglion. Three patients had a second injection 9-18 months following the initial injection. RESULTS: In four patients the ganglia resolved completely. In five patients there was significant improvement, with a reduction in size of the ganglion and symptomatic relief. CONCLUSION: Ultrasound-guided injection insures intralesional deposition of corticosteroids and may provide an alternative to surgery in the management of ganglia.

OBJECTIVE: Power Doppler sonography is a relatively new technique that has been shown to depict hyperemia associated with musculoskeletal inflammatory disease. We performed this study to evaluate the ability of power Doppler sonography to differentiate musculoskeletal fluid collections of varying etiologies. SUBJECTS AND METHODS: Gray-scale and power Doppler sonography were performed on 39 patients with joint effusions or appendicular fluid collections. Blood flow (hyperemia) in the soft tissues adjacent to the fluid collections was subjectively analyzed and graded on a scale of 1 to 4 (1, normal flow; 2-4, increasing degrees of hyperemia). All fluid collections were aspirated within 24 hr of the sonographic examination. We found 31 joint effusions and 12 periarticular collections with appropriate imaging and pathologic correlation. RESULTS: Adjacent to 36 effusions and fluid collections, we saw moderate or marked hyperemia. Thirty-five of the 36 had an inflammatory or neoplastic cause, including 15 infected collections. One fluid collection had a degenerative etiology (subdeltoid bursitis secondary to supraspinatus tendon tear). Adjacent to the seven remaining effusions and fluid collections, we saw normal or mildly increased hyperemia; none of these collections had an inflammatory etiology. CONCLUSION: Power Doppler sonography helps distinguish inflammatory and infectious musculoskeletal fluid collections from those that are noninflammatory, and it may help guide the decision to perform diagnostic aspiration. Power Doppler sonography does not reliably differentiate between inflammatory collections of infectious and noninfectious origin because collections of either origin may significantly increase adjacent soft-tissue perfusion.

Magnetic resonance imaging of the knee was performed in 28 patients (ages 15-72 years), using a 1.5-T unit. Volume gradient echo (3D GRASS) acquisition with and without presaturation off-resonance RF pulse was used to evaluate magnetization transfer (MT) effects, determined by placing regions of interest on muscle, fat, hyaline, and fibrocartilage; the percent change in signal intensity was calculated and compared using a paired two-sample t test. An in vitro study of the normal meniscus from a cadaver containing a scalpel cut extending to an articular surface was performed to observe the relative improvement in contrast in the presence of a small meniscal defect. MR imaging of the specimen was performed using an Omega CSI 2.0-T system (General Electric Medical Systems, Fremont, CA). Analysis of clinical images resulted in signal loss, compared to that of the identically timed and tuned non-MT images of 47 +/- 5, 8 +/- 5, 49 +/- 5, and 57 +/- 7% for muscle, fat, articular cartilage and fibrocartilage, respectively. Application of MT improved the depiction of the artificially introduced meniscal defect. Meniscal fibrocartilage demonstrates significant MT effect after application of off-resonance RF presaturation, which may improve visualization of meniscal defects.

A method for quantitative imaging of internal tissue motion based on speckle tracking is described. Tissue displacement images from eight patients with sonographically apparent breast masses are used to illustrate the technique. The local displacement response of tissues surrounding malignant and benign breast masses is compared, testing the hypothesis that altered mechanical properties may result in motion signatures for many soft tissue tumors relative to their host tissue. In addition, the potential or anticipated influence of various biological and physical factors on tissue motion response is discussed.

Imaging of blood flow perfusion is an area of significant medical interest. Recently, the advantages of using the total integrated Doppler power spectrum as the parameter that is encoded in color has been shown to result in an approximately threefold increase in flow sensitivity, a relative insensitivity to acquisition angle and lack of aliasing. We have taken this mode a step further and demonstrated the potential for quantifying blood flow using correlation-based algorithms applied to the power signal. We show that phi(tau) = phi(0)e-VT, where phi(tau) is the two-time correlation of the fluctuation in the power signal, and v is the specific flow (reciprocal of mean transit time). Scans of a dog's blood, pumped at a constant rate through gum rubber tubing, were obtained using a Diasonics Spectra 10-MHz linear array transducer at standard range-gated spectral mode (PRF = 1400 Hz, wall filter = 50 Hz, sample gate = 1.5 mm). A fixed Doppler angle of 68 degrees was used. Five different flow rates were tested, and the velocities determined by power decorrelation were compared to the mean velocities calculated from the Doppler shifts by linear regression (R2 = 0.987). We believe the results are very encouraging for using power decorrelation in perfusion evaluation.

The relative success of manual palpation in the detection of breast cancer would suggest that a method for remote palpation resulting in a measurement of tissue elasticity could provide a diagnostic tool for detecting cancerous lesions deeper within the breast. This presumption is based in part on the excellent contrast between neoplastic and normal tissue due to the large (orders of magnitude) relative variation in the shear elastic modulus. By comparison, the bulk deformational modulus maintains the same value to within 20% for most soft tissues. A specific method of magnetic-resonance imaging (MRI) which measures tissue displacements has been used in experiments with a phantom containing regions of increased Young's modulus as a demonstration. The spatial modulation of magnetization technique uses the displacement of a spatial grid pattern caused by spin saturation to track regional motion. Mathematical reconstruction of the distribution of elastic moduli is shown for select examples. Any modality, e.g., MRI, ultrasound, etc., which can detect local tissue motion with sufficient spatial resolution can be used and therefore the results presented here should give an indication of the utility of such motion tracking techniques to future measurement of tissue elasticity.

RATIONALE AND OBJECTIVES: We tested whether testicular torsion could completely damp distal arterial pulsatility, resulting in venous-appearing arterial waveforms. METHODS: Progressively increasing testicular torsion was unilaterally produced in five rats. Doppler waveforms of the testicular artery distal to the torsion were obtained as soon as possible after each level of torsion until a complete absence of pulsatility was noted. RESULTS: One animal was not studied further after the first 180 degrees of torsion occluded flow. In three of the remaining four animals, the testicular artery resistive index (RI) at baseline (0.51, 0.58, 0.64) was within the range of the normal human intratesticular RI and decreased with increasing torsion, culminating in nonpulsatile, venous-appearing waveforms at high degrees of torsion. CONCLUSIONS: Testicular torsion can completely damp arterial pulsatility, resulting in nonpulsatile, venous-appearing arterial Doppler waveforms.

PURPOSE: To estimate the fraction of moving blood in tissue with power Doppler ultrasound (US). MATERIALS AND METHODS: Power Doppler US measurements of moving scatterers in a flow tube were made as a function of successive dilutions of the perfusate. Measurements were normalized relative to the maximum Doppler power in the center of the flow tube at the highest concentration and were used to calculate the fractional dilution of the perfusate for each run with each dilution used to represent increasing amounts of non-moving soft tissue in the sample volume. The technique was also applied to two clinical examples. RESULTS: Successive dilutions of the perfusate in the flow experiment showed a monotonic, linear decrease in the Doppler power as a function of dilution. CONCLUSION: The power Doppler US technique has the potential to more accurately estimate alterations in blood flow and has the advantage of being a continuous parameter that can be depth normalized.