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.

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.

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.

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.

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.

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.

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.

Double peak attenuation method for estimating organ location.

Radioactive sources of finite volume containing 133Xe, 67Ga, 99Tcm and 111In were used to measure the attenuation coefficient, mu, in water at six different energies in the range 80-296 keV using an Anger camera. The experimental accuracy was about 7% for the volume range from 40-225 ml when corrections were made for background. The same radioactive sources were used to measure zero attenuation count rates per unit of activity. The theoretical basis was also derived, which confirms our experimental findings, i.e. the measurement of the thickness of the attenuator using a dual energy method. The determination of the linear attenuation coefficient in the broad-beam geometry situation is possible by accounting for cross-talk, scatter and out-of-target activity. By correcting for the broad-beam geometry, agreement with the narrow-beam geometry linear attenuation coefficient was obtained. We also demonstrate the use of the technique to accurately determine the depth of the organ using two separate energies. This methodology is independent of the organ volume for determination of the depth. It is hoped that our findings will provide a better understanding of the photon interactions when extended sources are used. Such a knowledge can also be applied to organ volume measurements.

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.

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.

Combined superior vena cava and pulmonary artery obstruction by an ascending aortic aneurysm.

A case report is presented on the use of intravenous radioisotope angiocardiography in the diagnosis of an atherosclerotic aneurysm of the ascending aorta in a 44-year-old man who presented with mild superior vena cava obstruction. In addition to outlining the site and extent of the aneurysm, intravenous Tc-99m-albumin radioisotope angiocardiography and blood pool imaging permitted demonstration of the site of obstruction of the cava, indicated the presence of venous collateral channels bringing about delayed filling of the right heart, and also detected obstruction of the right pulmonary artery by the aneurysm. The procedure is simple, rapid, and entirely noninvasive and permits both anatomic and hemodynamic evaluation of the abnormality.

A crossover study comparing the effect of particle size on the distribution of radiocolloid in patients.

Two radiocolloid preparations, differing in particle size by a factor of 5 to 20, were compared in each of 15 patients. The smaller colloid, measuring less than 80 nm, showed a relative decrease in the calculated target to background ratios for the liver and spleen and an increase for the bone marrow. The increased uptake of the smaller particle in the bone marrow, as measured by the bone marrow to soft-tissue background ratio, was about 50% higher than that of the larger colloidal particles. Comparable marrow images can be obtained in a half to a third of the time with the smaller particle size for a given administered dose.

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.

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.

Selection of renal background for quantitative 131I-hippurate relative renal function studies.

In a series of 100 patients with a full range of normal to poor renal function it was found, using 99mTC--albumin, that the zone between the superior poles of the kidneys best approximates the vascular pool in the renal areas. It is therefore possible to perform sufficiently accurate background-corrected relative renal function studies with 131I-hippurate alone. It is most valid in monitoring renal function in follow-up examinations. Both the accumulated 1- to 2-min count and 0- to 3-min count of the estimated net 131I-hippurate renogram were compared to a standard 99mTc-albumin corrected 131I-hippurate renogram for relative renal function measurements and they correlated very well (r = 0.91). The integrated 0- to 3-min count is preferred to the integrated 1- to 2-min count as the former yields better counting statistics, particularly in renal failure.

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.

Sr-89 therapy for metastatic bone disease: scintigraphic and radiographic follow-up.

Ten patients with disseminated bone metastases, nine from prostatic and one from renal cell carcinoma, were treated with intravenous strontium-89. Half the patients experienced significant improvement in pain control and increased general well-being for an average of 14 weeks. Sequential radiophosphate bone scanning showed decreased activity in lesions present at the time of therapy, with subsequent remineralization of the metastases on radiographs. Some patients showed simultaneous reduction in alkaline and acid phosphatase levels. These objective findings prove a physiologic basis for the clinical improvement. Treatments, however, did not prevent progression at initially uninvolved sites, particularly in the extremities.

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.

Sequential thallium-201 myocardial perfusion studies after successful percutaneous transluminal coronary artery angioplasty: delayed resolution of exercise-induced scintigraphic abnormalities.

To characterize the sequential changes of myocardial perfusion scintigraphy in patients with coronary artery disease (CAD) after complete revascularization, 43 patients underwent exercise thallium-201 (201Tl) myocardial perfusion scintigraphy before and at 9 +/- 5 days, 3.3 +/- 0.6, and 6.8 +/- 1.2 months after percutaneous transluminal coronary angioplasty (PTCA). Only patients with single-vessel CAD, without previous myocardial infarction, and without evidence of restenosis at 6 to 9 months after PTCA were included. Perfusion scans were analyzed blindly with the use of a new quantitative method to define regional myocardial perfusion in the topographic distribution of each coronary artery, which was shown to be reproducible (r = .94 or higher and SEE of 7% or less, between repeated measures by one and two operators). At 4 to 18 days after PTCA, the mean treadmill walking time increased by 123 +/- 42 sec, mean exercise-induced ST segment depression decreased by 0.6 +/- 0.3 mm, group maximal heart rate increased by 20 +/- 9 beats/min, and group systolic blood pressure at peak exercise increased by 24 +/- 10 mm Hg, compared with pre-PTCA values (p less than .001). However, no group differences were noted in these variables between the three post-PTCA stages. Myocardial perfusion in the distribution of the affected (dilated) coronary artery, on the other hand, improved progressively. In the 45 degree left anterior oblique view for instance, myocardial perfusion increased at 9 days after PTCA (from 68 +/- 24% before PTCA to 91 +/- 9%, p less than .001) and at 3.3 months after PTCA (101 +/- 8%, p less than .05 vs 9 days after PTCA), but no further significant changes were seen at 6.8 months after PTCA (102 +/- 8%). Similar changes were noted in the other two views. No relationship between minor complications during PTCA and delayed improvement on the 201Tl was observed. Myocardial ischemia was diagnosed in 12 of the 43 scans recorded a few days after PTCA, but in none recorded at later stages. We conclude that 201Tl scans after PTCA often show delayed improvement and therefore, an abnormal myocardial perfusion scan soon after PTCA does not necessarily reflect residual coronary stenosis or recurrence.