Vertebral fluid collection associated with vertebral collapse

OBJECTIVE

Three elderly women with osteoporotic compression fractures of a vertebral body underwent MR imaging because of neurologic signs and symptoms. Atypical fluid collections were shown by MR imaging in all three patients. For histologic characterization of these vertebral fluid collections, CT-guided biopsies and aspirations were done for all three patients.

CONCLUSION

After studying the clinical, histologic, and imaging features of these fluid collections associated with vertebral fracture, we suggest that they are most likely associated with underlying avascular necrosis.

Increase in bone density and lean body mass during testosterone administration in men with acquired hypogonadism

Acquired hypogonadism is being increasingly recognized in adult men. However, the effects of long term testosterone replacement on bone density and body composition are largely unknown. We investigated 36 adult men with acquired hypogonadism (age, 22-69 yr; median, 58 yr), including 29 men with central hypogonadism and 7 men with primary hypogonadism, and 44 age-matched eugonadal controls. Baseline evaluation included body composition analysis by bioimpedance, determination of site-specific adipose area by dual energy quantitative computed tomography scan (QCT) of the lumbar spine, and measurements of spinal bone mineral density (BMD) using dual energy x-ray absortiometry, spinal trabecular BMD with QCT, and radial BMD with single photon absorptiometry. Percent body fat was significantly greater in the hypogonadal men compared to eugonadal men (mean +/- SEM, 26.4 +/- 1.1% vs. 19.2 +/- 0.8%; P < 0.01). The mean trabecular BMD determined by QCT for the hypogonadal men was 115 +/- 6 mg K2HPO4/cc. Spinal BMD was significantly lower than that in eugonadal controls (1.006 +/- 0.024 vs. 1.109 +/- 0.028 g/cm2; P = 0.02, respectively). Radial BMD was similar in both groups. Testosterone enanthate therapy was initiated in 29 hypogonadal men at a dose of 100 mg/week, and the subjects were evaluated at 6-month intervals for 18 months. During testosterone therapy, the percent body fat decreased 14 +/- 4% (P < 0.001). There was a 13 +/- 4% decrease in subcutaneous fat (P < 0.01) and a 7 +/- 2% increase in lean muscle mass (P = 0.01) during testosterone therapy. Spinal BMD and trabecular BMD increased by 5 +/- 1% (P < 0.001) and 14 +/- 3% (P < 0.001), respectively. Radial BMD did not change. Serum bone-specific alkaline phosphatase and urinary deoxypyridinoline excretion, markers of bone formation and resorption, respectively, decreased significantly over the 18 months (P = 0.003 and P = 0.04, respectively). We conclude that testosterone therapy given to adult men with acquired hypogonadism decreases sc fat and increases lean muscle mass. In addition, testosterone therapy reduces bone remodeling and increases trabecular bone density. The beneficial effects of androgen administration on body composition and bone density may provide additional indications for testosterone therapy in hypogonadal men.

Vertebral morphometry derived from digital images

OBJECTIVE

We describe a method for capturing measurement data directly from digitized images using specialized software and high-resolution workstations. We have evaluated the reliability, accuracy, and reproducibility of this method in an international clinical trial involving vertebral morphometry.

MATERIALS AND METHODS

Accuracy was determined using clinical radiographs measured with vernier calipers and a film phantom. Intra- and interobserver variabilities were assessed, and longitudinal reproducibility was evaluated. As part of the trial, spinal radiographs were collected from more than 200 international health care facilities and digitized at four screening centers. Digitized images were stored and sent to our central facility for morphometry and archiving. Timeliness and variability of the process were tracked.

RESULTS

Relative accuracy was nearly 100%. Correlation with clinical measurements was high (r = .96; p < .05). The mean coefficient of variation for interobserver variability was 2%. Intraobserver variation was 3-5%. The coefficient of variation for longitudinal reproducibility ranged from 4% to 6%. After 9 months of operation, our trial included 9494 patients. Of approximately 36,000 radiographs, 98% passed quality review. Only 1% of vertebral levels were not measurable. Hardware and software problems were minimal.

CONCLUSION

The use of digitized images for morphometry is accurate, reproducible, and convenient. When applied to a large-scale clinical trial, it offers unique advantages that may justify the cost and complexity that exceed those of conventional radiographs.

Quantification of articular cartilage in the knee with three-dimensional MR imaging

RATIONALE AND OBJECTIVES

To determine the volume of articular cartilage in cadavers, patients, and healthy volunteers by using a volumetric, fat-suppressed spoiled gradient-recalled signal acquisition in the steady state (SPGR) magnetic resonance (MR) sequence.

METHODS

Sagittal MR images were obtained with a fat-suppressed SPGR sequence (repetition time, 52 msec; echo time, 10 msec; 60 degrees flip angle; 3.0-3.5-mm partitions, 256 x 192 matrix, two signals acquired). The cartilaginous surfaces of the tibia, femur, and patella were planimetrically defined with a three-dimensional workstation. A three-dimensional model volume was created by threshold segmenting the cartilage from the adjacent tissues. The volume as calculated by using MR imaging was compared with the actual volume of the cartilage specimens.

RESULTS

Observed measurements correlated with actual weight and volume displacement measurements with an accuracy of 82%-99% and linear correlation coefficients of 0.99 (P = 2.5e-15) and 0.99 (P = 4.4e-15). Precision of segmentation in healthy volunteers yielded a coefficient of variation of 0.4% for interobserver variability and 0.3% for intraobserver variability.

CONCLUSION

This pilot study suggests that accurate volumetric calculations of knee articular cartilage are possible with currently available MR imaging pulse sequences and a commercially available work station.

Magnetic resonance imaging of rheumatoid arthritis

MR imaging is able to demonstrate both the structural changes that occur in rheumatoid arthritis and the inflammatory changes, including synovial proliferation and joint effusion. MR imaging can demonstrate erosion before it is visible on radiographs. Although MR imaging appears to be very helpful in assessing the severity of rheumatoid arthritis and its response to therapy, the optimal technique for this assessment and the ultimate clinical value of MR imaging have yet to be determined.

Radiofrequency tissue ablation: importance of local temperature along the electrode tip exposure in determining lesion shape and size

RATIONALE AND OBJECTIVES

We determined whether heat distribution along a radiofrequency (RF) electrode would be uniform when longer tip exposures are used and whether local temperature effects would influence the shape of induced tissue coagulation.

METHODS

Thermistors were embedded within 18-gauge RF electrodes at both ends and in the middle of the exposed tip. The length of tip exposure varied from 1 to 7 cm. RF was applied in vitro to pig liver for 6 min using a constant tip temperature, which was varied in 10 degrees C increments from 60 degrees C to 110 degrees C. Experiments were performed in triplicate. The 3- and 5-cm probes were used at a 90 degrees C tip temperature to create lesions in live pig liver and muscle using similar parameters. Temperature was measured throughout the procedure. Observable coagulation necrosis was measured at the end of the treatment. Regression analysis was used to evaluate the local temperature-lesion diameter relationship.

RESULTS

Temperatures were not uniform along the tip exposure for any given trial. Temperature variation increased with higher tip temperatures and longer tip exposures. The diameter of local coagulation necrosis was a function of the local mean temperature. For in vitro trials, no coagulation was seen when the local temperature was less than 50 degrees C. Temperatures above this threshold resulted in progressively greater lesion diameter, with a minimum of 1 cm of necrosis occurring at 71 degrees C. Additional increases in lesion diameter (1.4-1.6 cm) were observed at approximately 90 degrees C. Mathematical modeling demonstrated a best-fit curve: lesion diameter (in cm) = ¿1.4 + 0.03 (tip exposure)¿ ¿1 - e [-0.067(local temp - 49.5 degrees C)]¿, r2 = .986, SD = 0.14 cm for each curve. In living tissue, less uniformity in the shape of coagulation necrosis was seen around the electrodes. Local temperature-lesion diameter data fit the same logarithmic relation, but the threshold for coagulation necrosis was 8.5 degrees C higher than for in vitro specimens.

CONCLUSION

Using a single-probe technique for RF-induced tissue necrosis, the diameter of tissue coagulation may be predicted by the local temperature along the exposed electrode. The uniformity of temperature decreases with increased tip exposures. This effect may be partially corrected by creating lesions at higher tip temperatures, where necrosis diameter is increased. Because effects are more pronounced in vivo, uniform volumes of tissue necrosis are limited to tip exposures of 3 cm or less.

Osteoid osteoma: percutaneous radio-frequency ablation

PURPOSE

To evaluate a percutaneous technique for in situ destruction of osteoid osteoma.

MATERIALS AND METHODS

Radio-frequency ablation was performed in 18 patients with osteoid osteoma (17 male, one female; age range, 8-42 years). Diagnosis was established by means of clinical and radiographic features and confirmed by means of needle biopsy findings. No attempt was made to remove the lesion. A small radio-frequency electrode introduced into the lesion through the biopsy track was used to produce thermal necrosis of a 1-cm sphere of tissue.

RESULTS

Symptoms were completely relieved in 16 (89%) of 18 patients. In one patient, a second procedure was required for pain relief. All but two patients underwent treatment as outpatients: These two were hospitalized for 1 night only. All patients resumed normal daily activities immediately. No casts or external supports were required; there were no complications. Twelve patients were followed up for more than 1 year. There were no recurrences

CONCLUSION

Radio-frequency ablation of osteoid osteoma is a promising alternative to surgery in selected patients.

Enzyme replacement therapy for Gaucher disease: skeletal responses to macrophage-targeted glucocerebrosidase

OBJECTIVES

Reversal of the hematologic and visceral abnormalities characteristic of Gaucher disease, the most common lipid storage disorder, with biweekly infusions of macrophage-targeted glucocerebrosidase (glucosylceramidase) is well documented. The extent to which the skeleton responds to enzyme replacement therapy has not been systematically investigated.

METHODS

To assess the skeletal response to enzyme replacement therapy, we treated 12 patients with type 1 Gaucher disease, who had intact spleens, with macrophage-targeted glucocerebrosidase. The initial dose of enzyme was 60 U/kg body weight every 2 weeks for 24 months, followed by reduction in dosage to 30 and then 15 U/kg body weight every 2 weeks, each for 9 months.

RESULTS

The lipid composition of bone marrow, determined by direct chemical analysis, began to improve after 6 months of treatment at a time when noninvasive imaging studies showed no significant changes. By 42 months, improvement in marrow composition was demonstrable on all noninvasive, quantitative imaging modalities (magnetic resonance score, quantitative xenon scintigraphy, and quantitative chemical shift imaging) used in this study. Quantitative chemical shift imaging, the most sensitive technique, demonstrated a dramatic normalization of the marrow fat content in all patients. Net increases in either cortical or trabecular bone mass, as assessed by combined cortical thickness measurements and dual-energy quantitative computed tomography, respectively, occurred in 10 patients.

CONCLUSIONS

Prolonged treatment over 3 1/2 years with macrophage-targeted glucocerebrosidase produces objective reversal of disease in both the axial and appendicular skeleton in patients with Gaucher disease. Marked improvement occurs in marrow composition and bone mass in both children and adults.

Quantification of inflammation in the wrist with gadolinium-enhanced MR imaging and PET with 2-[F-18]-fluoro-2-deoxy-D-glucose

PURPOSE

To quantify the activity of joint inflammation with magnetic resonance (MR) imaging and positron emission tomography (PET).

MATERIALS AND METHODS

Gadolinium-enhanced MR imaging and 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) PET of the wrist were performed prospectively in 12 patients receiving antiinflammatory therapy. Patients were studied three times: off medications for 2 weeks, after 2 weeks of treatment with prednisone or nonsteroid antiinflammatory drugs, and after 12 weeks of treatment with methotrexate. Volume of enhancing pannus (VEP) was determined from fat-suppressed MR images (12 patients). FDG uptake was calculated from PET images (11 patients).

RESULTS

VEP and FDG uptake were closely correlated (r > .86, P < .0001), as were changes in VEP and standardized uptake volume (r > .91, P < .0002). VEP and FDG uptake were strongly associated with clinical findings in wrists (P < .002) but not with treatment outcomes (P > .05).

CONCLUSION

Contrast material-enhanced MR imaging and PET allow quantification of volumetric and metabolic changes in joint inflammation and comparison of efficacies of antiinflammatory drugs.

Dynamic evaluation of exercising leg muscle in healthy subjects with echo planar MR imaging: work rate and total work determine rate of T2 change

Echo planar MR imaging of the leg was performed in nine healthy volunteers to better understand the dynamic relationship between exercise and changes in muscle T2. Imaging and T2 calculation was performed before, during, and after ankle dorsiflexion exercises using a TR of 9 seconds and a TE of 60 msec. Performing 9-second duty cycles, six of the subjects exercised for sets of 12 duty cycles, three with a graded series of weights and pulleys and three with an isometric orthotic device graded in varying percentages of maximum voluntary contraction. The other three volunteers performed duty cycles to fatigue. Gastrocnemius and soleus muscle T2 relaxation times were unchanged before, during, and after exercise. The tibialis anterior muscle showed an initial brief 1.7-6.2% decrease in T2 values after starting exercise, followed by a linear increase. Maximum T2 values and percent changes were higher for higher work rates (P < .05), and the rate of T2 change increased in a linear fashion with increasing work rates. By using rapid serial MR imaging, we show that the rate of muscle T2 change bears a simple linear relationship to muscle work. This technique may be exploited in both diagnostic and rehabilitation procedures.

Tissue ablation with radiofrequency using multiprobe arrays

RATIONALE AND OBJECTIVES

We studied the feasibility of increasing the volume of tissue destroyed by radiofrequency tissue coagulation using multiprobe arrays and defined parameters that determine lesion size and shape.

METHODS

Radiofrequency was applied to ex vivo calf liver using arrays of two to five 18-gauge probes for 6 min at 70-90 degrees C. Probe spacing (1-3 cm) and arrangement, as well as the method of radiofrequency application (simultaneous or sequential), were varied. The resulting areas of tissue coagulation were measured and compared.

RESULTS

Uniform tissue necrosis was observed with simultaneous radiofrequency application for probes 1.5 cm or less apart. At 1.5 cm, arrays of three equidistant probes produced spheroid lesions approximately 3.0 +/- 0.2 cm in diameter. Arrays of four equidistant probes produced cuboid lesions of 3.2 +/- 0.1 cm per side. However, probes placed 2 cm or more apart produced independent lesions 1.4 cm in diameter, with incomplete necrosis between probes. In the trials using five-probe arrays, a central region 4mm in diameter showed no visible evidence of tissue necrosis. With each array, lesion size varied less than 3 mm in any direction. Greater necrosis was accomplished when radiofrequency was applied simultaneously rather than sequentially.

CONCLUSION

Multiprobe radiofrequency arrays permit the destruction of more tissue in a single treatment session than is possible with multiple individual probes operating alone. Probes spaced 1.5 cm or less apart act synergistically, producing a total volume of coagulated tissue that is greater than when the individual probes are operated sequentially.

Phase I studies of continuous-infusion paclitaxel given with standard aggressive radiation therapy for locally advanced solid tumors

Currently available therapies are unsatisfactory for locally advanced solid tumors of the lung, head and neck, and brain. Laboratory data suggest that the addition of paclitaxel (Taxol; Bristol-Myers Squibb Oncology, Princeton, NJ), a microtubule-stabilizing drug, to radiation therapy may result in significant radiation sensitization, perhaps because paclitaxel induces cell cycle arrest at G2/M. Relatively low concentrations, 1 to 10 nmol/L, appear to be optimal for direct cytotoxicity and radiosensitization in vitro. Within this dose range, more prolonged exposure seems to result in higher response rates. We are conducting phase I trials designed to test continuous infusion (24 hours per day, 7 days per week) intravenous paclitaxel combined with standard curative-intent radiation therapy. To date, 22 patients are evaluable, and the maximum tolerated dose of paclitaxel has not been reached at up to 2.5 mg/m2/d. Observed toxicities include anemia, lymphopenia, mucositis, and cutaneous erythema/desquamation.

Generalized periarticular myositis ossificans as a complication of pharmacologically induced paralysis

To our knowledge, no previous direct associations have been made between generalized myositis ossificans and pharmacological therapy. We report a case of generalized periarticular myositis ossificans associated with the use of curare and diazepam. The previously reported associations of myositis ossificans with tetanus and burns may be misleading. It is possible that it is not the disease process itself (e.g., tetanus, severe burn) that precipitates heterotopic ossification, but the treatment of these ailments. These observations suggest the importance of early mobilization and restrained use of immobilizing drugs. Further investigation is warranted with regard to the predisposing factors of generalized myositis ossificans and to its prevention.

Tissue ablation with radiofrequency: effect of probe size, gauge, duration, and temperature on lesion volume

RATIONALE AND OBJECTIVES

We evaluated the parameters affecting the size and distribution of thermal tissue damage produced by radiofrequency electrodes.

METHODS

Thermal lesions were produced by electrodes connected to a radiofrequency generator in specimens of liver (n = 143) and muscle (n = 20). Various combinations of probe tip exposure (0.5-8 cm), gauge (12-24 gauge), duration of treatment (0.5-12 min), and temperature (80-90 degrees C) were studied. The resulting volumes of tissue coagulation were measured and compared.

RESULTS

Lesions equal to or less than 1.6 cm in diameter were symmetrically distributed around the electrode. Lesion diameter (but not length) increased with probe gauge and duration of treatment to a maximum of 6 min. However, lesions with mean diameters larger than 1.6 cm could not be produced using a single probe with any technique. Lesion length correlated with probe tip exposure from 1 to 8 cm (r2 = .996). Over the limited range investigated, increased temperature had minimal effects, except for tip exposures greater than 5 cm, in which larger and more uniform lesions resulted. Lesions varied equal to or less than 3 mm in diameter and equal to or less than 5 mm in length for each combination of variables.

CONCLUSION

Radiofrequency ablation can accurately and reproducibly cause coagulative tissue necrosis. Necrosed tissue volume increases with length of exposed probe tip, larger probes, and sessions lasting at least 6 min.

Skeletal repair by in situ formation of the mineral phase of bone

A process has been developed for the in situ formation of the mineral phase of bone. Inorganic calcium and phosphate sources are combined to form a paste that is surgically implanted by injection. Under physiological conditions, the material hardens in minutes concurrent with the formation of dahllite. After 12 hours, dahllite formation was nearly complete, and an ultimate compressive strength of 55 megapascals was achieved. The composition and crystal morphology of the dahllite formed are similar to those of bone. Animal studies provide evidence that the material is remodeled in vivo. A novel approach to skeletal repair is being tested in human trials for various applications; in one of the trials the new biomaterial is being percutaneously placed into acute fractures. After hardening, it serves as internal fixation to maintain proper alignment while healing occurs.

Making global telemedicine practical and affordable: demonstrations from the Middle East

OBJECTIVE

The purpose of this study was to demonstrate the first use of voice-grade telephone lines for the international transmission of both high-resolution digital images (radiology and pathology) and video in near real-time.

MATERIALS AND METHODS

Eight live demonstrations were performed from the United Arab Emirates and the Kingdom of Saudi Arabia at the invitation of the respective ministries of health. Thirty radiologic studies (CT, MR, and radiographs) were digitized, compressed, and transmitted to Cambridge, MA, where they were interpreted on diagnostic workstations (1792 x 2252 display matrix) by a team of subspecialist radiologists. Near real-time image transmission was achieved by combining wavelet-based image compression (average compression ratio of 23:1) and multiplexing technology that used four phone lines simultaneously. During each demonstration, one pathology image was transmitted from Cambridge to the demonstration site, where it was interpreted by a visiting pathologist. Video-conferencing was implemented with a 64-kilobits-per-sec leased line from the United Arab Emirates and with four multiplexed telephone lines from Saudi Arabia.

RESULTS

For teleradiology and telepathology, transmission times ranged from 2-5 min per image. Image fidelity was judged to be of diagnostic quality in all transmitted cases. The video link to the United Arab Emirates was highly reliable. Bandwidth for videoconferencing from Saudi Arabia was marginal on four voice-grade telephone lines, resulting in some downtime (10-20%). Live consultations provided by subspecialists in Cambridge assisted in the management of patients at both venues. The system was well received by both the referring physicians in the Middle East and the participants in the United States.

CONCLUSION

Image compression and multiplexing technologies enabled high-resolution teleradiology and telepathology as well as real-time video consultations over international telephone lines. While telecommunications systems are advancing rapidly in many parts of the world, those areas most in need of telemedicine services are likely to be the last to upgrade their telecommunications infrastructures. This "proof of concept" article outlines a practical and affordable approach that makes telemedicine more accessible to underserved areas worldwide.

Clinical applications of photodynamic therapy

This is a review of photodynamic therapy, which is a classic binary system involving the use of a photosensitizer and light of very specific wavelength, consistent with the absorption characteristics of that sensitizer. As a binary system, its effects are almost entirely limited to tumour cells, but the major drawback is its limited penetration because it utilizes physical light within the visible spectrum. For Photofrin II, which is the only approved sensitizer for clinical use in this country, the effects are limited to approximately 0.5 cm or less, depending on the tissue and the amount of blood, etc. Newer sensitizers offer more penetration and the opportunity to repeat treatments, because the newer sensitizers do not have the very long (up to 10 weeks) period of enhanced skin sensitivity to sunlight. A summary of the results of photodynamic therapy by individual sites is included. The use of newer sensitizers, which represent much purer substances than Photofrin II, should give an opportunity for repeated treatments, which should eventually make this form of treatment far more important than it has been up to now.

Accuracy of volume measurements of computed tomography and magnetic resonance imaging phantoms by three-dimensional reconstruction and preliminary clinical application

RATIONALE AND OBJECTIVES

Using an independent three-dimensional workstation, the accuracy of volume measurements of phantoms was assessed using three-dimensional reconstruction of two-dimensional computed tomography (CT) and magnetic resonance (MR) images.

METHODS

Round, cylindrical, and irregularly shaped high-contrast phantoms of known volume were imaged in a water bath. The effect of object contrast on volume estimation was tested using phantoms of known volume diluted serially with a contrast agent. The effect of changing field of view and slice thickness was assessed. A clinical application was performed, in which nine shoulders were injected with a known quantity of contrast material, to test the accuracy of the technique in vivo.

RESULTS

A strong paired correlation (r = .99) between estimated and true volumes was obtained for high-contrast phantoms ranging from 17 to 128 mL. The weighted average absolute error was 1.42 mL (MR) and 3.50 mL (CT). Accuracy of the serially diluted 27-mL phantoms was essentially unaffected by contrast differences greater than 133 units (MR) and 102 units (CT). The weighted average absolute error was 1.33 mL (MR) and 1.56 mL (CT). Changing field of view had no effect on accuracy, but increasing the slice thickness resulted in over-estimation of volume. The mean error for the clinical application was 4.4% (range: 1.7%-8.3%).

CONCLUSION

Under certain circumstances, three-dimensional reconstructive volume estimation can be a convenient and accurate method for volume determination.

Labral-ligamentous complex of the shoulder: evaluation with MR arthrography

PURPOSE

To determine the usefulness of magnetic resonance (MR) arthrography in assessment of the labral-ligamentous complex and test the hypothesis that the inferior glenohumeral ligament (IGHL) is an important anatomic feature of clinical instability.

MATERIALS AND METHODS

Forty-eight shoulders with labral diagnoses proved with arthroscopy or open surgery were prospectively examined with MR arthrography after intraarticular injection of gadopentetate dimeglumine.

RESULTS

Surgical findings showed that 14 labra were normal, 29 were torn, and six were deficient. (One labrum was torn and deficient in separate locations.) MR arthrographic findings had a diagnostic sensitivity of 91% and specificity of 93%. In 32 patients with proved labral abnormalities, 30 lesions involved the labral-bicipital junction, origins of the glenohumeral ligaments, or both. In 22 of 23 shoulders considered clinically unstable, a labral abnormality involved the origin of the IGHL.

CONCLUSION

MR arthrography accurately shows the relationship of labral lesions to the origins of the glenohumeral ligaments and helps in distinction between stable and unstable lesions.