Anatomical distribution of vertebral fractures: comparison of pediatric and adult spines.

SUMMARY: We compared the distribution of vertebral fractures in adults and children and found that fractures occurred in different locations in the two age groups. This likely relates to the different shape of the immature spine. INTRODUCTION: We hypothesized that the anatomical distribution of vertebral fractures (VF) would be different in children compared to adults. METHODS: We compared the distribution of VF defined using the Genant semi-quantitative method (GSQ method) in adults (N = 221; 545 fractures) and in children early in the course of glucocorticoid therapy (N = 44; 94 fractures). RESULTS: The average age in the adult cohort was 62.9 years (standard deviation (SD), 13.4 years), 26% was male, the mean lumbar spine Z-score was -1.0 (SD, 1.5), and the corresponding T-score was -2.4 (SD, 1.4). The pediatric cohort median age was 7.7 years (range, 2.1-16.6 years), the mean lumbar spine Z-score was -1.7 (SD, 1.5), 52% was male, and disease categories were acute lymphoblastic leukemia (66%), rheumatological conditions (21%), and nephrotic syndrome (14%). The VF distribution was biphasic in both populations, but the peaks differed in location. In adults, the peaks were at T7/T8 and at T12/L1. In children, the focus was higher in the thoracic spine, at T6/T7, and lower in the lumbar spine, at L1/L2. When children were assessed in two age-defined sub-groups, a biphasic VF distribution was seen in both, but the upward shift of the thoracic focus to T6 was observed only in the older group, with the highest rates of fracture present between ages 7 and 10 years. CONCLUSIONS: These results suggest that the anatomical distribution of VF differs between children and adults, perhaps relating to the different shape of the immature spine, notably the changing ratio of kyphosis to lordosis.

Periarticular cancellous bone changes following anterior cruciate ligament injury.

To understand more fully the early bone changes in an experimental model of osteoarthrosis, we quantified periarticular bone mineral density and bone mechanical properties in anterior cruciate ligament transected (ACLX) knee joints (4, 10, 32, and 39 wk post-ACLX) compared with contralateral joints and unoperated normal joints of skeletally mature animals. Maximal stress and energy were significantly reduced in ACLX cancellous bone from the medial femoral condyles at 4 wk postinjury. All mechanical properties (e.g., yield stress and elastic modulus) declined after 4 wk and were significantly reduced at 10 wk. ACLX bone mineral density was significantly reduced at all measured time points. Ash content was significantly reduced at 10 and 32 wk. Changes in the lateral condyles were similar but less pronounced than in the medial condyles. These bony changes accompanied the earliest articular cartilage molecular changes and preceded changes in the articular cartilage gross morphology. We suggest that these early changes in bone mechanical behavior contribute to the progression of osteoarthrosis and pathogenic changes in the joint.

Automatic three-dimensional multimodality registration using radionuclide transmission CT attenuation maps: a phantom study.

UNLABELLED: Coregistration of images from a single subject, acquired by different modalities, is important in clinical diagnosis, surgery and therapy planning. The purpose of this study was to evaluate, using a physical torso phantom, a novel, fully automated method for three-dimensional image registration of CT and SPECT, using radionuclide transmission (RNT) attenuation maps. METHODS: We obtained CT scans and SPECT scans paired with RNT maps of an anthropomorphic cardiac phantom. RNT attenuation maps were acquired using an uncollimated 99mTc-filled flood source. RNT and SPECT scans were acquired in the same spatial orientation (usual clinical practice in nonuniform attenuation correction). In addition, CT attenuation maps (CTMAPs) for 99mTc SPECT were generated from CT by linear energy scaling. RNT maps were registered to CT and CTMAPs by iterative simplex minimization of count difference and uniformity index (sum of RNT map intensity variances corresponding to each intensity level in the CT volume). In each iteration, three shifts and three angles were adjusted. To register SPECT to CT, we applied the RNT transformation parameters to SPECT. RESULTS: RNT maps could be registered to CT and CTMAP images using both criteria. The average three-dimensional distance between landmark and automated registration was 2.5 +/- 1.2 mm for count difference and 3.3 +/- 1.3 mm for uniformity index. The three-dimensional reproducibility errors were 1.2 +/- 0.7 mm for count difference, 2.1 +/- 0.5 mm for uniformity index and 2.3 +/- 1.0 mm for manual marker registration. The minimization of uniformity index was robust when up to 50% CT or RNT slices were missing and was not affected significantly (<2 mm) by realistic variation in CT values (+/- 12 Hounsfield units). CONCLUSION: In addition to typical use in nonuniform attenuation correction, RNT maps can be used for fully automated three-dimensional registration of SPECT to CT. Such registration is not affected by features and quality of SPECT images and avoids difficulties associated with fiducial markers. Our method can be applied to SPECT-CT registration of various organs, such as brain, heart, lungs, breasts and abdomen, including oncological scans.

Comparison of ordered subsets expectation maximization and Chang's attenuation correction method in quantitative cardiac SPET: a phantom study.

Photon attenuation is one of the primary causes of artifacts in cardiac single photon emission tomography (SPET). Several attenuation correction algorithms have been proposed. The aim of this study was to compare the effect of using the ordered subsets expectation maximization (OSEM) reconstruction algorithm and Chang's non-uniform attenuation correction method on quantitative cardiac SPET. We performed SPET scans of an anthropomorphic phantom simulating normal and abnormal myocardial studies. Attenuation maps of the phantom were obtained from computed tomographic images. The SPET projection data were corrected for attenuation using OSEM reconstruction, as well as Chang's method. For each defect scan and attenuation correction method, we calculated three quantitative parameters: average radial maximum (ARM) ratio of the defect-to-normal area, maximum defect contrast (MDC) and defect volume, using automated three-dimensional quantitation. The differences between the two methods were less than 4% for defect-to-normal ARM ratio, 19% for MDC and 13% for defect volume. These differences are within the range of estimated statistical variation of SPET. The calculation times of the two methods were comparable. For all SPET studies, OSEM attenuation correction gave a more correct activity distribution, with respect to both the homogeneity of the radiotracer and the shape of the cardiac insert. The difference in uniformity between OSEM and Chang's method was quantified by segmental analysis and found to be less than 8% for the normal study. In conclusion, OSEM and Chang's attenuation correction are quantitatively equivalent, with comparable calculation times. OSEM reconstruction gives a more correct activity distribution and is therefore preferred.

Pulmonary edema during IL-2 therapy: combined effect of increased permeability and hydrostatic pressure.

Systemic administration of recombinant interleukin-2 (rIL-2) has been shown to be promising against certain metastatic cancers. However, major side effects, such as pulmonary edema, have limited its widespread use. Although this pulmonary edema has been attributed to a vascular leak syndrome, this hypothesis has not been verified in humans. The purpose of our study was to determine both the severity and mechanism of pulmonary edema in seven patients treated with rIL-2. The severity of edema was assessed by daily evaluation of chest radiographs, using a semiquantitative scale, as well as by repeated measurements of the alveolar-to-arterial oxygen gradient (A-aDO2) in each patient. To determine the mechanism of pulmonary edema, we serially measured in each patient the lung clearance of technetium 99m-diethylenetriamine pentaacetic acid (DTPA) 99mTc-DTPA), the plasma levels of Von Willebrand factor antigen, and the pulmonary capillary wedge pressure (PCWP). Our results show that there was a gradual increase in the chest radiography edema score that was paralleled by a significant increase in A-aDO2 over its baseline value. During rIL-2 treatment, 99mTc-DTPA clearance was augmented, and the plasma concentration of Von Willebrand factor antigen was elevated. PCWP climbed from 7 to 14 mm Hg and serum total protein fell from 66.1 to 42.1 gm/L. The results obtained indicate that although pulmonary edema associated with rIL-2 treatment is partially dependent on increased permeability of the lung, changes in hydrostatic and oncotic forces may be the principal determinants of edema development.

Two-dimensional restoration of single photon emission computed tomography images using the Kalman filter.

The discrete filtered backprojection (DFBP) algorithm used for the reconstruction of single photon emission computed tomography (SPECT) images affects image quality because of the operations of filtering and discretization. The discretization of the filtered backprojection process can cause the modulation transfer function (MTF) of the SPECT imaging system to be anisotropic and nonstationary, especially near the edges of the camera's field of view. The use of shift-invariant restoration techniques fails to restore large images because these techniques do not account for such variations in the MTF. This study presents the application of a two-dimensional (2D) shift-variant Kalman filter for post-reconstruction restoration of SPECT slices. This filter was applied to SPECT images of a hollow cylinder phantom; a resolution phantom; and a large, truncated cone phantom containing two types of cold spots, a sphere, and a triangular prism. The images were acquired on an ADAC GENESYS camera. A comparison was performed between results obtained by the Kalman filter and those obtained by shift-invariant filters. Quantitative analysis of the restored images performed through measurement of root mean squared errors shows a considerable reduction in error of Kalman-filtered images over images restored using shift-invariant methods.

Hydroxyapatite orbital implants. Scanning with technetium-99m MDP.

Porous hydroxyapatite spheres are an ideal prosthetic device for orbital implantation because they are incorporated into soft tissues. Once vascularized, an eye prosthesis can be coupled to the sphere by a peg placed within a central motility hole. This hole should not be drilled while the sphere is avascular because of the risk of infection. Radionuclide scanning with Tc-99m methylene diphosphonate has been used to assess implant vascular ingrowth because radiophosphonate deposition within the sphere parallels vascularization. Using this technique, the authors examined the hydroxyapatite implants of 15 patients 6 months following insertion. Results showed that complete vascularization is best defined by planar imaging rather than SPECT. While the relative intensity of implant activity may be an important feature, uniformity of activity is probably more significant.

Chronic biliary-type pain in the absence of gallstones: the value of cholecystokinin cholescintigraphy.

Radiologic criteria for the diagnosis of gallbladder disease largely rest on the detection of calculi. Surgeons are reluctant to do a cholecystectomy in patients with symptoms of gallbladder disease if the results of sonography or cholecystography are normal. Consequently these patients are often left with no satisfactory treatment. Such patients may have chronic acalculous cholecystitis, partial obstruction of the cystic duct, or gallbladder dyskinesia. Increasing evidence indicates that at least some of these patients have decreased gallbladder emptying in response to a stimulus such as a test meal or cholecystokinin. Impaired emptying shown by cholecystokinin cholescintigraphy may be useful for predicting which patients with typical biliary-type pain but no evidence of calculi will be cured by cholecystectomy.

Iliopelvic lymphoscintigraphy as a predictor of early metastatic disease in patients with prostate carcinoma.

Fifty-one patients had iliopelvic lymphoscintigraphy (IPL) as part of the initial assessment of newly diagnosed prostate carcinoma over a 3-year period. Investigations other than IPL showed that all patients had disease confined to the prostate, and they received radiotherapy to the prostate and regional pelvic lymph nodes. Patients with complete absence of activity in an iliac chain on IPL were excluded from the analysis because that finding could have resulted from tumor replacement or a failed injection. Of the remaining 41 patients, 12 had abnormal scintigrams, and 6 (50%) had recurrence within a mean 15-month follow-up period. Of 29 patients with normal scintigrams, 26 (90%) remain disease free over an average 27-month follow-up period.

Preconstruction restoration of myocardial single photon emission computed tomography images.

A restoration scheme for single photon emission computed tomography (SPECT) images that performs restoration before reconstruction (preconstruction restoration) from planar (projection) images is presented. A comparison is performed between results obtained in this study and those obtained by a method reported previously where the restoration is performed after reconstruction (postreconstruction restoration). The filters investigated are the Wiener and power spectrum equalization filters. These filters are applied to SPECT images of a hollow cylinder phantom and a cardiac phantom acquired on a Siemens Rota camera. Quantitative analyses of the results are performed through measurements of contrast ratios and root mean squared errors. The preconstruction restored images show a significant decrease in the root mean squared error and an increase in contrast over the postconstruction restored images.

Whole-body imaging of the distribution of mercury released from dental fillings into monkey tissues.

The fate of mercury (Hg) released from dental "silver" amalgam tooth fillings into human mouth air is uncertain. A previous report about sheep revealed uptake routes and distribution of amalgam Hg among body tissues. The present investigation demonstrates the bodily distribution of amalgam Hg in a monkey whose dentition, diet, feeding regimen, and chewing pattern closely resemble those of humans. When amalgam fillings, which normally contain 50% Hg, are made with a tracer of radioactive 203Hg and then placed into monkey teeth, the isotope appears in high concentration in various organs and tissues within 4 wk. Whole-body images of the monkey revealed that the highest levels of Hg were located in the kidney, gastrointestinal tract, and jaw. The dental profession's advocacy of silver amalgam as a stable tooth restorative material is not supported by these findings.

Chronic right upper quadrant pain without gallstones: does HIDA scan predict outcome after cholecystectomy?

Patients with chronic right upper quadrant pain who do not have gallstones on ultrasound or cholecystography are often referred for surgery for presumed acalculous chronic cholecystitis. We followed 26 patients who had cholecystokinin (CCK) cholescintigraphy for evaluation of chronic right upper quadrant pain without demonstrable gallstones on ultrasound who underwent cholecystectomy so that it could be determined whether there was any relation between a low ejection fraction (EF), morphological features of chronic cholecystitis, and clinical outcome. Eighteen patients (69%) were considered therapeutic successes, whereas eight (31%) were failures after an average 2-yr follow-up. Both patient groups had significantly reduced EF: the successful group at 0.39 and the failures at 0.25. Thus, a low EF did not predict clinical outcome, since the failure group had an even lower EF than the success group. Seven gallbladders demonstrated chronic acalculous cholecystitis; the average EF of this group was 0.35. The remaining 19 gallbladders were normal, yet also had an EF of 0.35. Thus, decreased EF does not predict the histologic features of chronic cholecystitis without gallstones. The diagnostic value of cholescintigraphy in patients with acalculous right upper quadrant pain is low, probably because this entity represents a variety of processes, including inflammation, gallbladder dysmotility, and the irritable bowel syndrome.

Dental "silver" tooth fillings: a source of mercury exposure revealed by whole-body image scan and tissue analysis.

Mercury (Hg) vapor is released from dental "silver" tooth fillings into human mouth air after chewing, but its possible uptake routes and distribution among body tissues are unknown. This investigation demonstrates that when radioactive 203Hg is mixed with dental Hg/silver fillings (amalgam) and placed in teeth of adult sheep, the isotope will appear in various organs and tissues within 29 days. Evidence of Hg uptake, as determined by whole-body scanning and measurement of isotope in specific tissues, revealed three uptake sites: lung, gastrointestinal, and jaw tissue absorption. Once absorbed, high concentrations of dental amalgam Hg rapidly localize in kidneys and liver. Results are discussed in view of potential health consequences from long-term exposure to Hg from this dental material.

The complementary role of plain radiographs and radionuclide shuntography in evaluating CSF-VP shunts.

Cerebrospinal fluid-ventriculoperitoneal shunts are often used in the treatment of hydrocephalus in children. Many complications can arise that may lead to shunt malfunction, including detachment of the distal limb of the shunt. A case is presented where such a complication occurred with distal migration of the detached tubing into the abdomen, which resulted in a patent subcutaneous tract through which cerebrospinal fluid could drain. The need for radiographic correlation at the time of radionuclide shuntography is stressed.

Restoration of gamma camera-based nuclear medicine images.

Experiments were conducted using a Siemens Rota camera to study the applicability of two linear shift-invariant (LSI) filters, namely, the Wiener and power spectrum equalization filters, for restoration of planar projections and single-photon-emission computed tomography (SPECT) images. In the restoration scheme, the system transfer function, computed from a line source image, is modeled by a 2-D Gaussian function. The noise power spectrum is modeled as a constant for planar images and as a ramp for SPECT images. The filters have been applied to restore computer-simulated 1-D and 2-D projections and SPECT images of two simple phantoms, 2-D projections of two phantoms obtained from the Siemens Rota camera, and SPECT images of a cardiac phantom obtained from the Siemens Rota camera. The filters are shown to perform partial restoration. Considerable noise suppression and detail enhancement have been observed in the restored images. quantitative measurements such as root-mean-squared error and contrast ratio have been used for objective analysis of the results, which are encouraging.

Biliary obstruction after cholecystectomy: diagnosis with quantitative cholescintigraphy.

Fifty patients with recurrent post-cholecystectomy pain underwent hepatobiliary scintigraphy. Time-activity curves were generated from regions of interest over the liver, bile duct, duodenum, and bowel. Patients were divided into obstructed and unobstructed groups with endoscopic retrograde cholangiopancreatography criteria. Measurements from the liver, duodenum, and bowel curves contributed little to the analysis. The washout phase of the bile duct curve showed intermittent emptying in both obstructed and unobstructed groups. Less than one-third of peak activity remained in both groups at 90 minutes. Retention fell more rapidly in the later portion of the sequence in patients with obstruction. Quantification was essential, since differences were subtle and could not be appreciated visually. In the absence of hepatocellular disease, the most reliable criterion was the time at which maximal bile duct activity occurred. A cutoff level of 29 minutes or more was used in the diagnosis of obstruction. A sensitivity of 93% with an adequate specificity of 64% and an overall accuracy of 80% was achieved in the prediction of obstruction.

Usefulness of early positive technetium-99m stannous pyrophosphate scan in predicting reperfusion after thrombolytic therapy for acute myocardial infarction.

To test the hypothesis that scans with technetium-99m pyrophosphate (Tc-99m-PPi) are positive when performed early after successful thrombolytic therapy for acute myocardial infarction (AMI), 16 consecutive patients with AMI who received thrombolytic therapy within 5 hours after the onset of chest pain were studied. Patients were included if chest pain lasted for greater than 30 minutes, was unresponsive to sublingual nitroglycerin and was associated with at least 0.2 mV ST-segment elevation in at least 2 contiguous electrocardiographic leads. All patients received 1.5 million IU of streptokinase intravenously, a mean of 195 +/- 99 minutes after onset of chest pain. Tc-99m-PPi scans and coronary cineangiograms were recorded 491 +/- 156 minutes and 518 +/- 202 minutes, respectively, after the onset of symptoms. Effective reperfusion was present in 10 patients, 6 of whom had positive Tc-99m-PPi scans (sensitivity of 60% to detect reperfusion). Of the 6 patients without effective reperfusion, 3 had positive Tc-99m-PPi scans (specificity of 50%, p greater than 0.05). Analysis of the data using various definitions of effective reperfusion or artery patency yielded similar results. Thus, our findings indicate that early AMI scanning with Tc-99m-PPi does not accurately detect the presence or absence of reperfusion in patients with AMI after treatment with intravenous streptokinase. At this time, coronary cineangiography is the only reliable method to detect reperfusion promptly after thrombolytic therapy.

The scintigraphic and radiographic appearance of the ischiopubic synchondroses in normal children and in osteomyelitis.

Five cases of hematogenous osteomyelitis of the ischiopubic synchondrosis (IPS) were encountered among 180 patients with osteomyelitis treated over a 5-year period. Symptoms were poorly localized in all these IPS osteomyelitis patients. The IPS can normally show expansion and irregular mineralization radiographically and focal hyperconcentration of radiophosphates on scintigrams. Findings are frequently asymmetrical negating comparison with the contralateral side. In the cases of osteomyelitis, radiographs were abnormal at the time of presentation in only one of these five cases. In two of the four patients who had radionuclide bone scans, activity at the IPS exceeded that seen in a normal control population, but all showed loss of definition of the IPS and regional increased uptake permitting an early diagnosis.