Pediatric solid tumors: evaluation by gallium-67 SPECT studies.

A retrospective review of 37 children with a variety of solid tumors who underwent 60 67Ga single-photon emission computed tomographic (SPECT) studies was performed. These studies were correlated with clinical and radiological findings and, where possible, histopathologic confirmation. In all studies, SPECT gave better definition and better anatomic localization of disease sites than obtained with planar views. SPECT detected more lesions in the head and neck (planar 16, SPECT 19), chest (planar 39, SPECT 45), and abdomen (planar 22, SPECT 24). In six of 20 patients scanned following chemotherapy, SPECT was useful in demonstrating that tracer accumulation in a normally located and shaped thymus indicated uptake resulting from thymic regeneration rather than tumor recurrence. It is concluded that 67Ga SPECT studies are very useful in the pediatric population, where perhaps because of their small size, interpretation of standard planar views may be difficult.

Optimization of the scintigraphic segmental anatomy of the lungs.

UNLABELLED: Accurate and reproducible reporting of lung scintigraphy is predicated on a sound knowledge of the segmental anatomy of the lungs. A limited amount of hard data exists about the true segmental anatomy of the lungs. A virtual model of human lungs was created using a CT-based dataset and a Monte Carlo simulation technique to examine the optimal projections for the visualization of each segment in the lungs. METHODS: Segmental anatomy of the lungs was modeled using CT, cadaveric lungs and standard anatomical texts. The emission, scatter and attenuation of photons was modeled within these virtual lungs and the surrounding tissues. Single segmental lesions were created in eight projections and submitted for blinded reporting to four experienced nuclear medicine physicians to obtain the best views for each segment. RESULTS: The anterior and posterior oblique projections yielded the best views for 10 of 18 segments, with the laterals contributing four views, the anterior contributing two views and the posterior contributing one view. The majority of basal segments (six of nine) were best seen in the anterior and posterior oblique projections. CONCLUSION: This model overcomes the major problems associated with experimentation in the normal human and has the potential to provide answers to the major problems of scatter, attenuation and "shine-through" in lung scintigraphy.

Enhanced accuracy and reproducibility in reporting of lung scintigrams by a segmental reference chart.

UNLABELLED: The diagnostic probability of pulmonary embolic disease is based on the recognition of unmatched segmental perfusion defects. Although interobserver and intraobserver reproducibility have been studied, accuracy has been an elusive goal due to the lack of a gold standard. We investigated the accuracy and reproducibility of reporting in a virtual scintigraphic model of the lungs, with and without the use of a lung segmental reference chart. METHODS: A Monte Carlo package was used to model lung scintigraphy from a digital phantom of the human lungs. An ideal lung segmental reference chart was created from the phantom. Five experienced nuclear medicine physicians reported a set of all possible defects involving 100% of a segment, without and with the chart. A further set of defects involving 45%-55% of a segment in the lower lobes was investigated using the chart. RESULTS: There was a significant improvement in accuracy (from 48% to 72%) and intraobserver agreement (from 61% to 77%) with the chart. The accuracy of reporting defects in the upper and middle lobes was consistently better than that in the lower lobes. There was no significant difference between the accuracy of reporting large defects and that of reporting moderate defects in the lower lobes. CONCLUSION: The lung segmental reference chart significantly improves both the accuracy and reproducibility of reporting lung scintigrams; however, although reporting in the lung bases is improved, absolute accuracy is substantially less than that in the upper and middle lobes. This emphasizes the need for caution because the lung bases are the most common site of embolic disease.

Variability of perceived defect size in virtual lung scintigraphy.

UNLABELLED: The diagnosis of pulmonary embolism is based on the presence of mismatched segmental or subsegmental defects. An important axiom is the classification of defect sizes into small, moderate and large. Little information about the recognition and classification of such defects has been published. We undertook a study of the perception of defect size using a model of the virtual scintigraphic anatomy of the lungs to address this issue. METHODS: Segmental anatomy of the lungs was modeled with CT, cadaveric lungs and standard anatomical tests. The emission, scatter and attenuation of photons were modeled within these virtual lungs and the surrounding tissues. Single segmental lesions, each 100% of a segment, were created in eight projections and submitted for blinded reporting by four experienced nuclear medicine physicians to obtain their assessment of the size of each defect on two occasions. RESULTS: Of the 144 defects submitted for reporting, 15% were reported as <25% of a segment, 35% were reported as 25%-75% and 50% were reported as 75%-100%. The accuracy of each reporter and the intraobserver agreement were calculated; the weighted kappa value ranged from 0.34 to 0.60. The segmental defects that were most likely to be underestimated in size were in the right lower lobe. CONCLUSION: It is clear that segmental defect sizes were underestimated, particularly in the right lower lobe. Although the intraobserver agreement in reporting was fair, the accuracy of estimation was only 50%. The variability and inaccuracy might be reduced by the use of a guide to segmental anatomy.

Regional left ventricular wall motion assessment: comparison of two-dimensional echocardiography and radionuclide angiography with contrast angiography in healed myocardial infarction.

The diagnostic ability of radionuclide angiography (RNA) and 2-dimensional echocardiography (2-D echo) to assess regional left ventricular (LV) wall motion was compared with contrast angiography in 52 patients with healed myocardial infarction. After 5 patients were excluded for inadequate 2-D echocardiographic studies, the LV images of 47 patients obtained by all 3 techniques were divided into 7 segments for analysis. Both 2-D echo and RNA showed close agreement with contrast angiography in assessing normal vs abnormal wall motion in the anterobasal (91%, 91%), anterolateral (87%, 79%) and posterolateral segments (77%, 79%). The sensitivity in detecting wall motion abnormalities was highest for 2-D echo and RNA in the anterolateral (83%, 77%) and apical (95%, 84%) segments and lowest for the inferior segment (48%, 48%). Specificity of 2-D echo and RNA was high, ranging from 94% in the anterolateral segment to 71% in the septal segment for 2-D echo, and from 91% in the inferior segment to 81% in the posterobasal and septal segments for RNA. Major discrepancies with contrast angiography occurred more often in the posterobasal, posterolateral, inferior and septal LV segments. Thus, in comparison with contrast angiography, 2-D echo and RNA are reliable for detecting anterior and apical wall motion abnormalities, but relatively less sensitive for detecting wall motion abnormalities involving the inferior, posterobasal and posterolateral LV segments.

Early and long-term results of coronary artery bypass grafting with severely depressed left ventricular performance.

The effects of coronary artery bypass grafting (CABG) on ventricular performance and long-term clinical status were studied in 18 consecutive patients with disabling angina pectoris and severely depressed left ventricular (LV) performance (ejection fraction [EF] 27 +/- 9%). All patients survived CABG, although 1 patient had a perioperative myocardial infarction. There was no change in LVEF at rest, 29 +/- 12%, in the other 17 patients. However, LVEF during peak exercise increased from 22 +/- 7% to 27 +/- 14% (p less than 0.05). The 17 patients were separated into 2 groups: those who increased their peak exercise LVEF by at least 10% (group A, 8 patients) and those who increased it by less than 10% (group B, 9 patients). Preoperatively, patients in group A had a higher LVEF at rest (p less than 0.001) and smaller end-systolic and end-diastolic volumes at rest (p less than 0.001) and during exercise (p less than 0.005). Preoperatively, the LVEF in group A decreased with exercise, from 36 +/- 4% to 27 +/- 5% (p less than 0.01), but was unchanged in group B (19 +/- 3% vs 17 +/- 4%, difference not significant). After CABG, patients in group A had a smaller increase in end-systolic volume with exercise than those in group B (13 +/- 7 vs 34 +/- 22 ml/m2, p less than 0.05), but the changes in end-diastolic volume with exercise were not significantly different. At 27 +/- 5 months after CABG, 5 of 8 patients in group A were asymptomatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Titration of PEEP by the arterial minus end-tidal carbon dioxide gradient.

It was shown in dogs that intrapulmonary physiologic shunt (Qsp/Qt), arterial oxygen tension (PaO2), total static respiratory compliance (CT), oxygen delivery (O2AV), cardiac output (Qt), and arterial minus end-tidal carbon dioxide gradient (PaCO2-PetCO2) undergo statistically significant deterioration when oleic acid is injected into the pulmonary artery. Positive end-expiratory pressure (PEEP) therapy reduced Qsp/Qt and PaCO2-PetCO2 gradient and increased PaO2. The CT did not show any consistent pattern of improvement with the application of PEEP. The Qt and the O2AV progressively decreased as PEEP was increased. The application of additional PEEP beyond that which minimized the PaCO2-PetCO2 gradient produced a statistically significant increase in the PaCO2-PetCO2 gradient, but this was not reflected by concomitant changes in Qsp/Qt or PaO2 in spite of a further decrease in Qt. Thus, the PaCO2-PetCO2 gradient may be a more sensitive indicator of excessive PEEP than is Qst/Qt or PaO2, since it should be smallest when there is maximal recruitment of perfused or functional gas units without overdistention of alveolar areas contributing to dead space. Also, the use of the PaCO2-PetCO2 gradient permits the rapid titration of PEEP without the need for a pulmonary artery catheter.

Cardiopulmonary bypass, profound hypothermia, and circulatory arrest for neurosurgery.

Six female and 4 male patients (age, 23 to 75 years) underwent operation for difficult intracranial lesions. Preoperative diagnoses included four giant intracranial aneurysms, three base of skull glomus jugulare tumors, two arteriovenous malformations, and one cerebellar hemangioblastoma. All lesions were inoperable or nearly so by standard neurosurgical techniques. All patients were placed on total bypass via groin cannulations. Bypass times ranged from 111 to 269 minutes (mean, 174 minutes) with cooling times of 26 to 83 minutes (mean, 48 minutes) and warming times of 68 to 110 minutes (mean, 83 minutes). Circulatory arrest times ranged from 1.25 to 60 minutes with 1 patient not requiring arrest. The lowest core temperatures recorded varied from 8.4 degrees to 13.7 degrees C. There was one postoperative death and one major complication, both in patients with arteriovenous malformations. Eight patients (80%) have achieved an excellent result. Profound hypothermia with the option of circulatory arrest and exsanguination has been an indispensable adjunct to the safe management of intracranial aneurysm, glomus jugulare tumor, and hemangioblastoma.

Quantitation of pulmonary gallium-67 uptake: comparison of computer-derived indices.

A variety of computer-derived indices of pulmonary gallium-67 were compared in 51 subjects with and without interstitial lung disorders. An index which quantitates lung uptake in relation to liver uptake, both being corrected for tissue background activity over the thigh, was the most reliable in differentiating between the two patient groups. The index is easily derived using standard computer techniques, so permitting further studies to assess its role in serial assessments of the progress of these disorders.

A ventilatory assistance device for use with Technegas.

The demand for high-quality ventilation imaging of the lungs has resulted in the advent of Technegas, which has proven its superiority to the more conventional agents in a number of clinical trials. Images of similar diagnostic quality have been difficult to obtain in patients who are uncooperative, intubated or very young. With this problem as the impetus, a ventilatory assistance device (VAD) was designed to exploit the superior imaging qualities of Technegas. The Technegas generator was interposed between the patient and the VAD, allowing the controlled movement of Technegas into the patient from the generator. Utilizing this device, the problems of increased dead space, turbulent gas flow and possible contamination were circumvented. Twenty patients, comprising nine children and eleven adults, were studied for various indications including assessment of pulmonary parenchymal disease, suspected pulmonary embolism and the lung clearance of modified Technegas. In all cases, images of diagnostic quality were obtained with ease, facilitating relevant clinical decision making. We conclude from this preliminary appraisal that the VAD is a simple, safe addition to the Technegas generator for imaging a group of patients in whom images of diagnostic quality have traditionally proven difficult to obtain.

Recognition of subsegmental scintigraphic defects in virtual lung scintigraphy.

A virtual model of the segmental scintigraphic anatomy of the lungs was used to investigate the threshold at which small defects are perceptible. A model of the segmental anatomy of the lungs was developed from a number of sources and counts generated within the phantom by Monte-Carlo simulation of photon emission. Multiple subsegmental defects were created in both lungs and submitted for blinded reporting to detect the presence of any defect. A total of 36 of the 47 (77%) defects were seen. Of those defects in the lower lobes, 16 of 22 (73%) were visible. All the defects in the left lung (n = 21) were visible, while 15 of 26 (58%) of the defects on the right were visible. In the lower lobe of the right lung, 4 of 10 defects were visible. The defects that were not visible were all in the right lung. We conclude that absolute size and location are critical in the perception of defects. The perception of defects was dependent on absolute defect size rather than the proportion of a segment involved. Defects less than 3% of the volume of a lung were not detected.

Simulation of the stripe sign in a scintigraphic model of the lungs.

Using a virtual model of the lungs, we investigated the nature of the 'stripe sign' which is sometimes encountered in pulmonary scintigraphy. A model of the segmental anatomy of the lungs was developed from a number of sources and counts generated within the phantom by Monte-Carlo simulation of photon emission. Multiple segmental and subsegmental defects were created in both lungs and submitted for blinded reporting of the 'stripe sign'. Images were resubmitted for reporting with the contralateral lung removed. The stripe sign was reported in 32 of the 117 studies performed. Nearly half of these were present in defects involving approximately 25% of a segment and the sign was most commonly seen in the lateral projection. Removal of activity from the contralateral lung abolished the sign in only 2 of 32 cases. We conclude that shine through of activity from the contralateral lung is a mechanism rarely responsible for the stripe sign. Most occurrences of the sign are due to interposition of activity from unaffected areas of the same lung between the defect and the periphery of the lung. Orientation of the segments, particularly in the lung bases, accounts for the lateral projection being the most common view in which the sign is present.

Rationalization of the optimal views in planar lung scintigraphy.

A knowledge of the segmental anatomy of the lungs is the cornerstone for interpreting lung scintigraphy. Many attempts have been made to determine the best views for the appreciation of segmental defects and various theories have been formulated to explain the mechanisms of this process. In earlier work, we hypothesized that the arrangements of the segments was the principal determinant of this process. However, data subsequently derived from work on a model of diffuse lung disease indicates that the external shape of the lobes and lungs may be the most significant contributor to the optimal views of the lungs.

A novel view for the scintigraphic assessment of the elbow.

Using any imaging modality, the elbow is a complex joint to evaluate. The use of scintigraphy in the evaluation of the effects of acute or chronic trauma has largely been confined to epicondylitis. We developed a skyline view of the elbow that minimized the effect of overlap and assessed its incremental value in the scintigraphic assessment of several pathological conditions. Thirty-four abnormalities were evaluated in 20 patients with a range of pathologies, including epicondylitis, ligamentous avulsion injury, articular injury, fractures and synovitis. The incremental value of addition of the skyline view to the standard views was assessed in addition to the overall accuracy of scintigraphy. Overall, scintigraphy detected 27 of 34 abnormalities, with the standard views of the elbow accurately identifying 15 and the skyline view 23 abnormalities. This gave the skyline view an incremental value of 24% over the standard views. In conclusion, scintigraphy has the potential to identify a greater range of pathologies in the elbow than previously reported, due to the addition of the skyline view to the standard views.

Pentavalent 99mTc DMSA: uptake into a variety of human rhabdomyosarcoma xenografts.

BACKGROUND: Rhabdomyosarcoma is a common soft tissue sarcoma of childhood. While Ga is currently the most accurate modality for imaging residual or recurrent tumour its dosimetry is unfavourable. Pentavalent 99mTc DMSA [99mTc (V) DMSA] has been shown to accumulate in this tumour in a limited number of clinical cases. METHODS: Biodistribution of 99mTc (V) DMSA was determined in non-tumour bearing BALB-C mice. Operative specimens from four clinically 67Ga avid tumours were xenografted into nude mice and allowed to reach a significant size. Biodistribution studies were performed after the injection of 99mTc (V) DMSA in all animals and 125I HSA and 67Ga in a limited number of animals. RESULTS: None of the tumours investigated demonstrated significant 99mTc (V) DMSA accumulation. Biodistribution was identical in tumour and non-tumour bearing animals. CONCLUSIONS: Rhabdomyo-sarcoma xenografts do not demonstrate significant uptake of 99mTc (V) DMSA.

Distribution of m-IBG in nude mice bearing LAN-5 neuroblastoma xenografts and in vitro cell culture.

BACKGROUND: Neuroblastoma is the commonest extra-cranial solid tumour of childhood and has a poor clinical outcome in patients with disseminated disease. Animal xenografts of this tumour offer a useful method of studying new diagnostic and therapeutic strategies for the tumour, prior to consideration of clinical trials. METHODS: 131I m-IBG was injected into nude mice bearing xenografts of the human neuroblastoma line LAN 5 in several sites. Animals were sacrificed at 24 (n = 6) and 48 hours (n = 5) and the biodistribution of the agent as well as uptake into the xenografted tumours was determined in a gamma well counter. In-vitro uptake of m-IBG into suspensions of LAN 5 cells was also determined in order to confirm the animal studies. RESULTS: There was no preferential accumulation of m-IBG in the xenografted tumours in any of the sites considered. Similarly, the in-vitro uptake of m-IBG showed the typical Michaelis-Menten kinetics of simple diffusion with no evidence of active uptake. CONCLUSIONS: The human neuroblastoma line LAN 5 failed to enrich m-IBG in either the xenograft or in-vitro situation. This may be related to the poor degree of differentiation of the tumour as evidenced by its unusual ease of growth in the sub-cutaneous site.

The role of SPECT in the evaluation of skeletal trauma.

Single photon emission computed tomography (SPECT) has, in the last decade, established a critical role in routine diagnosis. Skeletal scintigraphy exemplifies the impact in improving detection of lesions by delineation of their site and size. The advantage of minimizing the superimposed radioactivity from overlying and underlying structures is typified by the readiness with which avascular necrosis of the femoral head can be identified by removal of the surrounding hyperaemia which masks the classical photopaenia. However, the ability to achieve an accurate image at a plane at a prescribed depth is most characteristically shown by the study of a vertebra, a bone of irregular contour and subject to a variety of pathological disorders at different sites within it. The various focal abnormalities resulting from these can be localized exactly, readily distinguishing, for example, those in the body from those in the natural arch. In particular, the alterations resulting from trauma, such as pars interarticularis stress fracture, are readily seen. Consequently SPECT has an indispensable role in the investigation and management of low back pain. However, the ability of SPECT to delineate abnormal accumulation has provided a new approach to the evaluation of knee pain, especially when acute such as that resulting from athletic injury, since the identification of the presence or absence of focal abnormalities can be critical to patient management. The frequency of these various disorders in which SPECT is so useful explains why the procedure has become such a routine high-volume examination is so many departments.

Photopenia in skeletal scintigraphy of suspected bone and joint infection.

The results of skeletal scintigraphy with Tc-99m-medronate of five children, in whom bone or joint infection was suspected, are presented. They illustrate that the demonstration of areas of diminished radionuclide accumulation may be of considerable assistance in establishing a diagnosis.

Prominence of the C2 vertebra on SPECT. A normal variant.

Mild preferential focal uptake of Tc-99m HDP in the spinous process of C2 was identified with SPECT of the cervical spine performed in patients in whom the indication for bone scintigraphy was suspected of lesions in the limbs. Its presence in all 21 subjects indicates that such uptake is a normal finding.

Three-phase skeletal scintigraphy for suspected bone tumors.

The advantage of using three-phase skeletal scintigraphy rather than merely conventional delayed imaging in the investigation of suspected bone tumors is illustrated by two cases in which this procedure provided greater information on the site and extent of the lesion than other single modalities.