Assessing the limping child with skeletal scintigraphy.

Skeletal scintigraphy is frequently used in the clinical investigation of young children who present with limping as their only or predominant symptom. This article reviews techniques used for pediatric skeletal scintigraphy, skeletal tracer distribution in the immature skeleton and scintigraphic manifestations of relatively common conditions that can produce limping in children 1-6 yr old. Acute osteomyelitis, vertebral infections, transient synovitis, septic arthritis, Legg-Calvé-Perthes disease, lower extremity injuries in toddlers and osteoid osteoma are emphasized.

Technetium-99m-HMPAO SPECT in Sturge-Weber syndrome.

UNLABELLED: Technetium-99m-HMPAO interictal SPECT was performed on three pediatric patients with Sturge-Weber syndrome (SWS). RESULTS: Brain SPECT of all three patients demonstrated markedly diminished tracer localization in the affected hemisphere. In one patient, the SPECT abnormality was more extensive than the associated abnormalities on CT and MRI. CONCLUSION: Technetium-99m-HMPAO brain SPECT can detect cerebral perfusion abnormalities associated with SWS and deserves consideration in the imaging evaluation of SWS patients.

Effect of early emptying on quantitation and interpretation of liquid gastric emptying studies of infants and young children.

UNLABELLED: This study assesses the effect of emptying that occurs during feeding on quantitation and interpretation of liquid gastric emptying studies of infants and young children. METHODS: Forty-nine 99mTc-sulfur colloid liquid gastric emptying studies of 44 children (22 boys, 22 girls; mean age, 20 mo; age range, 2-46 mo) fed orally or by gastrostomy tubes were evaluated. Gastric residuals quantitated by 2 commonly used methods, the first of which does not account for early emptying and the second of which does, were compared. With the first method, residual relative to activity in the stomach at the start of imaging (Rg) was quantified by comparing activity in a region of interest (ROI) drawn about the stomach on the final image to activity in an ROI drawn about only the stomach at the start of imaging. With the second method, residual relative to total dose (Rt) was quantified by comparing activity in the same final ROI to activity in an ROI that included stomach and small bowel at the start of imaging. Studies were interpreted independently for Rg and Rt considering a value >70% as evidence of delayed emptying. RESULTS: Rt was lower than Rg by 15%-16% for the entire population, for patients fed orally, and for patients fed by gastrostomy tube. These differences reached statistical significance (P < 0.0001). In 31 of 49 studies, R1 was lower than Rg by > or =10%. In 8 studies, emptying classified as delayed on the basis of Rg was classified as nondelayed on the basis of Rt. Clinical decisions based on Rt did not require later management changes that would have indicated that treatment of gastric dysmotility had been postponed in any patient. CONCLUSION: Emptying that occurs during feeding should be factored into quantitation of liquid gastric emptying in infants and young children. Not recognizing and accounting for early emptying results in overestimated gastric residuals and can lead to classification of emptying as delayed in children whose residuals of the total administered dose are within a recognized range of normal.

Assessment of the clinical significance of asymptomatic lower extremity uptake abnormality in young athletes.

UNLABELLED: This study was undertaken to evaluate our hypothesis that most asymptomatic lower extremity uptake abnormalities are of no clinical consequence and to assess whether these findings should affect patient care. METHODS: One hundred consecutive young athletes referred for bone scintigraphy by a sports medicine clinic because of low back pain were evaluated for the presence of asymptomatic bone scan abnormalities in the lower extremities. The patients were then reexamined by the referring sports medicine physician, who had full knowledge of the bone scan results. Scintigraphic findings were correlated with the clinical evaluation at the time of scintigraphy and on follow-up evaluations ranging from 8 to 14 mo later. RESULTS: Asymptomatic lower extremity abnormalities were present in 34% of patients. There were abnormalities of the feet in 30 patients (focal uptake in 26 patients, diffuse uptake in 10 patients), the tibia in 13 patients (2 focal uptake, 11 diffuse uptake), and the femur in 2 patients (both with diffuse uptake). None of the regions of abnormal lower extremity uptake was symptomatic at the time of initial evaluation. There was no change in the clinical management of any patient because of the scan findings. None of the patients was advised to restrict the activity level because of the asymptomatic scan findings. None of the regions of scan abnormality became symptomatic on follow-up evaluation. CONCLUSION: This study shows that asymptomatic bone scintigraphic abnormalities of the feet, as well as diffuse abnormalities of the tibia, are common in young athletes. These findings are most likely of no clinical consequence and do not require a change in the activity level. Focal abnormalities of the femur or tibia are not commonly seen in asymptomatic young athletes.

Meckel's diverticulum: demonstration of heterotopic gastric mucosa with technetium-99m-pertechnetate SPECT.

Demonstration of functioning heterotopic gastric mucosa with 99mTc-pertechnetate SPECT is reported. Abnormal tracer uptake was shown conclusively with SPECT but not with planar imaging. When a Meckel's diverticulum is suspected, we suggest SPECT be performed if the results of planar scintigraphy are equivocal and that it be considered if there is a high clinical suspicion and planar imaging is normal.

Pediatric applications of pinhole magnification imaging.

Pinhole magnification imaging is an important technique for practitioners of pediatric nuclear medicine. This article reviews basic principles of pinhole magnification imaging and ways for optimizing image acquisition with this technique. Applications to skeletal scintigraphy, scrotal scintigraphy and renal cortical scintigraphy are discussed and illustrated.

Reproducibility of renal length measurements with 99mTc-DMSA SPECT.

UNLABELLED: Renal length measurements are used in evaluating several abnormalities of the pediatric genitourinary tract. This study assesses reproducibility of renal length measurements obtained with 99mTc-dimercaptosuccinic acid (DMSA) SPECT. METHODS: The lengths of 98 kidneys of 51 children (age range, 1-16 y; mean age, 5.4 y) who underwent 99mTc-DMSA SPECT were measured independently by 2 observers. Renal length was calculated by converting pixels between points at the superior and inferior renal margins on a summated coronal image to centimeters. Lengths were measured for kidneys as they appeared in situ and after realignment along their long axes. SPECT reconstruction, choice of display parameters, positioning of points used for measuring, and alignment were performed independently by each observer. Interobserver variability, interobserver correlation, and mean differences between observers' measurements (expressed as measurement of observer 2 - measurement of observer 1) were calculated. RESULTS: Correlation between the observers' measurements was highly significant for both nonaligned and aligned studies (r = 0.95 and 0.97, respectively; both, P < 0.0001). Interobserver variability expressed as 1 SD was 3.6 mm for nonaligned studies and 2.8 mm for aligned studies. The mean difference between the 2 observers' measurements for nonaligned studies was 2.0 +/- 4.8 mm (P < 0.0001) with a range of -11 to 14 mm. For aligned studies the mean difference between the 2 observers' measurements was -0.1 +/- 4.0 mm (P = 0.88) with a range of -20 to 10 mm. Differences between observers were not dependent on absolute renal length (P = 0.68 for nonaligned studies; P = 0.40 for aligned studies). CONCLUSION: The variability in renal length measurements determined by 99mTc-DMSA SPECT is similar to that reported previously using sonography. Because the interobserver differences in renal length are similar to annual renal growth rates during childhood, caution should be applied when incorporating renal length measurements determined by 99mTc-DMSA SPECT into management algorithms. Additional studies are required to further establish interobserver variability, to assess intraobserver variability, and to evaluate means of improving standardization.

Hypoplastic dysplastic kidney with a vaginal ectopic ureter identified by technetium-99m-DMSA scintigraphy.

Ectopic insertion of a ureter draining a hypoplastic dysplastic kidney is a significant cause of urinary incontinence in girls. In this case, such a kidney was detected with 99mTc-DMSA scintigraphy but not by intravenous pyelography. Scintigraphy facilitated further delineation of the anatomy with CT prior to nephrectomy. Based on this case and a literature review, we suggest that 99mTc-DMSA scintigraphy be performed early when evaluating girls with urinary incontinence.

Imaging of sports injuries in children and adolescents.

Imaging plays an important role in the diagnosis and management of sports injuries of childhood and adolescence. The injuries discussed are typical of those seen in the skeletally immature athlete. Imaging specialists must be able to apply the full range of imaging modalities when evaluating the injured young athlete.

Single-photon emission computed tomography (SPECT) in pediatric epilepsy.

Single Photon Emission Computerized Tomography (SPECT) is a valuable tool in the assessment of epileptic patients. Radiotracers that distribute according to regional cerebral blood flow permit the identification of altered perfusion to an epileptogenic zone both ictally and interictally. This technique has proven especially useful in temporal lobe epilepsy.

Differentiation of anterior tibial stress fracture from osteoid osteoma.

The authors present a case in which skeletal scintigraphy helped them to differentiate an anterior tibial stress fracture from a possible osteoid osteoma. Important scintigraphic clues to the correct diagnosis included a linear rather than a round to oval configuration to the focus of intense uptake shown by pinhole imaging, absence of focally increased tracer localization on the angiographic and tissue phases, and a symmetrically positioned, less-conspicuous contralateral abnormality.

Registration of three-dimensional magnetic resonance and radionuclide skeletal images.

PURPOSE: To apply postprocessing techniques to register three-dimensional TI-201 bone SPECT datasets with MRI. This may provide more accurate anatomic-functional correlation when localizing active tumors. MATERIALS AND METHODS: Three-dimensional datasets were constructed from previously acquired MRIs using routine imaging protocols. Registration software was used to coregister the TI-201 SPECT studies and the MRIs in three dimensions. RESULTS: Adequate TI-201 uptake in muscles and soft tissues along with relatively low accumulation in tendons and joint spaces provided adequate landmarks for visually aligning SPECT and MRI datasets. MR abnormalities were more extensive because of surrounding reactive tissue, and more focal TI-201 uptake could be demonstrated within the region of MR signal abnormality, allowing the focal metabolically active tissue to be distinguished from adjacent edema. CONCLUSIONS: Image registration of SPECT and anatomic imaging (CT or MRI) is used routinely to evaluate functional abnormalities within the brain. This technique has now been applied to the combination of TI-201 SPECT and MR data for evaluating bone lesions and may provide additional anatomic information for localizing functional abnormalities. This may be valuable for defining targets for biopsy, planning surgical treatment, and using minimally invasive therapies.

Discordance of dual-isotope (hybrid) myocardial perfusion imaging results in patients who have undergone revascularization procedures.

Three hundred twenty-one separate acquisition dual-isotope myocardial perfusion scans were reviewed retrospectively. Studies performed in six patients demonstrated a relative improvement in Tc-99m sestamibi uptake during stress in segments that appeared abnormal on rest injected Tl-201 images. All patients who demonstrated this pattern had a prior history of myocardial infarction and interventional revascularization. While many factors may contribute to this appearance, the authors favor the presence of a patent infarct-related artery as being the most significant.

Scintigraphy of lower extremity cadaveric bone allografts in osteosarcoma patients.

PURPOSE: To describe scintigraphic characteristics of bone allografts used in limb salvage reconstruction after resection of lower extremity osteosarcoma. MATERIALS AND METHODS: The authors reviewed 85 skeletal scintigrams of 20 pediatric patients followed up for 0.5-5.7 years after resection of lower extremity osteosarcoma and allograft reconstruction. Uptake in the allograft and adjacent host tissues was assessed visually. RESULTS: Lack of tracer uptake in the allografts was seen in 99% of the studies and a faint rim of tracer localization outlining the allograft's periphery was seen in 95% of the studies. Increased uptake was noted at the allograft-host bone junction in 78% of the studies. Uptake was increased in the joint surfaces of native bones articulating with allografts (97% of studies), including the patella (93% of studies) when the knee was involved. These findings were stabilized as time passed. CONCLUSION: Cadaveric bone allografts have a characteristic scintigraphic appearance in this selected patient group that reflects the physiology of their incorporation process.

A prospective comparison of high-resolution planar, pinhole, and triple-detector SPECT for the detection of renal cortical defects.

To compare the detection rate of renal cortical defects with Tc-99m dimercaptosuccinic acid (DMSA) using triple-detector SPECT, pinhole, and planar cortical scintigraphy, the authors prospectively studied 80 kidneys in 40 patients (26 males, 14 females) who ranged in age from 3 months to 26 years (mean: 7.5 years). They found single or multiple definite defects in 30 kidneys using SPECT, 23 using pinhole imaging, and 17 using planar imaging (McNemar's test, two-tailed, P < 0.001 and P = 0.03, respectively). SPECT was significantly better than pinhole imaging at demonstrating definite defects (P = 0.008). This study indicates that SPECT, and to a lesser extent pinhole, are superior to planar imaging for conclusively demonstrating renal cortical defects.

Localization of Tc-99m MDP in neuroblastoma metastases to the liver and lung.

Localization of skeletal tracer in a neuroblastoma primary is common but localization in extraskeletal metastatic sites has not received recognition. Tc-99m MDP concentration in hepatic or pulmonary metastases was noted in three of ten patients with such metastases. Lesion size appears to be important for demonstrating these metastases with Tc-99m MDP. This was particularly true for hepatic metastases, which were identified only when they were 5 cm or greater in diameter.

Tc-99m MIBI to evaluate children with Ewing's sarcoma.

PURPOSE: Tc-99m MIBI has been used increasingly to evaluate benign and malignant tumors because of its tumor-seeking properties and ability to provide an imaging assessment of multiple-drug resistance. This study investigated the clinical utility of Tc-99m MIBI in the management of Ewing's sarcoma in children. METHODS: Thirteen Tc-99m MIBI studies in nine (six male, three female) patients ages 6.5 to 20 years (mean, 13.4 years) with Ewing's sarcoma were reviewed. All patients had imaging studies at diagnosis, and four had follow-up studies during or after therapy. Scintigraphy was evaluated for Tc-99m MIBI uptake within the tumor and in metastases, which other imaging modalities had shown to be present in four patients. Scintigraphic results were correlated with the clinical course in all patients and with tumor P-glycoprotein status in six patients. RESULTS: Tc-99m MIBI accumulated in 6 of 9 primary tumors and did not accumulate in one recurrent tumor. No metastases showed Tc-99m MIBI uptake. The presence or absence of Tc-99m MIBI uptake at diagnosis or after therapy carried no prognostic significance. Tc-99m MIBI was present in the two tumors that were P-glycoprotein positive and in only one of four tumors that were P-glycoprotein negative. CONCLUSION: Tc-99m MIBI imaging does not appear to be useful in Ewing's sarcoma.