Intrinsic dual-energy processing of myocardial perfusion images

We have developed a software-based method for processing dual-energy 201TI SPECT emission projection data with the goal of calculating a spatially dependent index of the local impact of gamma-ray attenuation. We refer to this method as intrinsic dual-energy processing (IDEP).

METHODS

IDEP exploits the differential attenuation of lower energy emissions (69-83 keV) and higher energy emissions (167 keV) resulting from the decay of 201TI to characterize the relative degree of low-energy gamma-ray attenuation throughout the myocardium. In particular, IDEP can be used to estimate the relative probability that a low-energy gamma-ray emitted from a particular region of the myocardium is detected during the acquisition of SPECT projection data. Studies on phantoms and healthy human volunteers were performed to determine whether the IDEP method yielded detection probability images with systematic structure visible above the noise of these images and whether the systematic structure in the detection probability images could be rationalized physically. In patient studies, the relative regional detection probabilities were applied qualitatively to determine the likely effects of attenuation on the distribution of mapped photon emissions.

RESULTS

Measurements of the detection probability in uniform phantoms showed excellent agreement with those obtained from computer simulations for both 180 degrees and 360 degrees acquisitions. Additional simulations with digital phantoms showed good correlation between IDEP-estimated detection probabilities and calculated detection probabilities. In patient studies, the IDEP-derived detection probability maps showed qualitative agreement with known nonuniform attenuation characteristics of the human thorax. When IDEP data were integrated with the findings on the emission scan, the correlation with coronary anatomy (known in 6 patients and hypothesized on the basis of clinical and electrocardiographic parameters in 5 patients) was improved compared with evaluating the mapped emission image alone.

CONCLUSION

The IDEP method has the potential to characterize the attenuation properties of an object without use of a separate transmission scan. Coupled with the emission data, it may aid coronary diagnosis.

Phase I dose escalation of 131I-metaiodobenzylguanidine with autologous bone marrow support in refractory neuroblastoma

PURPOSE

The analogue 131I-metaiodobenzylguanidine (MIBG), which is specifically targeted to neuroblastoma cells, may provide more effective and less toxic treatment for neuroblastoma than conventional external-beam radiotherapy. We report a dose escalation study of 131I-MIBG to define dose-limiting toxicity without and with autologous bone marrow support.

PATIENTS AND METHODS

Thirty patients with relapsed neuroblastoma were treated in groups of six with escalating doses of 3 to 18 mCi/kg of 131I-MIBG. After rapid escalation in the first three patients treated at 3 to 6 mCi/kg, treatment was escalated in 3-mCi/kg increments from 9 to 18 mCi/kg. Autologous tumor-free bone marrow was cryopreserved in all patients receiving 12 mCi/kg and more. Toxicity and response were assessed.

RESULTS

Eighty percent of patients who received 12 mC/kg or more experienced grade 4 thrombocytopenia and/or neutropenia. Dose-limiting hematologic toxicity was reached at 15 mCi/kg, at which level two of five assessable patients required bone marrow reinfusion for absolute neutrophil count (ANC) of less than 200/microL for more than 2 weeks, and four of nine at the 18-mCi/kg level. Prolonged thrombocytopenia was common, with failure to become platelet-transfusion independent in nine patients. One patient with extensive prior treatment developed secondary leukemia and three became hypothyroid. Responses were seen in 37% of patients, with one complete response (CR), 10 partial response (PR), three mixed response, 10 stable disease, and six progressive disease. The minimum dose of 131I-MIBG for 10 of the 11 responders was 12 mCi/kg.

CONCLUSION

Treatment with 131I-MIBG has mainly hematologic toxicity, which can be abrogated with bone marrow rescue. The high response rate in refractory disease suggests that this agent may be useful in combination with myeloablative chemotherapy and autologous stem-cell rescue to improve outcome in advanced neuroblastoma.

Contradictory renal function measured with mercaptoacetyltriglycine diuretic renography in unilateral hydronephrosis

PURPOSE

We studied apparently supranormal renal function in hydronephrotic kidneys, as measured by 99mtechnetium mercaptoacetyltriglycine renography.

MATERIALS AND METHODS

We retrospectively reviewed the clinical history, ultrasonography and renography of 29 children.

RESULTS

Of the 29 children 7 had greater than 50% relative function in the hydronephrotic kidney. This finding was independent of patient age, gender, degree of hydronephrosis or obstructive pattern. Of these 7 cases 6 occurred on the right side (p < 0.05 versus a large registry).

CONCLUSIONS

In most cases supranormal renal function is caused by a technical problem, likely the inadequate background subtraction of mercaptoacetyltriglycine in the liver.

The effect of newer generation lithotripsy upon renal function assessed by nuclear scintigraphy

PURPOSE

We studied the effect of second generation lithotripsy on renal function.

MATERIALS AND METHODS

We evaluated 42 patients with unilateral renal calculi by nuclear renography, serum creatinine levels, renal ultrasonography and plain radiographs.

RESULTS

There was no significant change in glomerular filtration rate at 1 or 3 months. Split function of the treated kidneys was lower at 1 month (mean 47.2%, p = 0.01) and 3 months (47.3%, p = 0.01) than before treatment (49.1%). A greater than 5% decrease in split function of the treated kidney occurred at 1 month in 6 patients (16.2%) and at 3 months in 3. Of the patients 23 (62.2%) were stone-free and 11 had residual fragments less than 4 mm., with a 19% retreatment rate for an overall success rate of 91.9%.

CONCLUSIONS

Newer generation lithotriptors may limit renal damage while permitting satisfactory treatment of renal calculi.

Normal cerebellar MIBG localization. Implications in the interpretation of delayed scans

In the I-131 MIBG scans of 14 patients with neuroblastoma (86%) or pheochromocytoma/paraganglioma (14%) that were studied more than 48 hours after administration of the radiopharmaceutical, 12 (86%) had discernible cerebellar MIBG localization. A few had midbrain or diffuse cerebral uptake as well. None of the patients had cerebellar or other central nervous system signs or symptoms, and the localization is consistent with the known distribution density of central nervous system catecholamine receptors. This suggests that cerebellar MIBG localization is normal in delayed scans and that it should not be confused with neuraxial metastasis of adrenergic neuronal neoplasms.

Normal cholescintigram in In-111 WBC positive acute acalculous cholecystitis. The converse photopenic 'rim' sign

The authors report a case of a patient with acute acalculous cholecystitis whose cholescintigram was negative, but showed a pericholecystic photopenic halo. The diagnosis was confirmed by an In-111 WBC scan and histopathology.

Urolithoscintigraphy: preliminary report of a new imaging modality for urolithiasis

We investigated the use of bisphosphonates, analogs of pyrophosphate that bind to mineralized tissue, to image renal calculi in vivo. Twenty stone-bearing kidneys in 15 patients without urinary obstruction were studied. 99mTechnetium-methylene diphosphonate was injected intravenously followed by 20 mg of furosemide 4 hours later, and images were obtained by gamma counter for 30 minutes. Areas of increased uptake corresponded with the sites of calculi, and even small or radiolucent calculi were easily seen. Counts in the region of each kidney, the L4 vertebral body, and a background area were combined to calculate a scintigram index (SI) for each kidney. The mean SI of the stone-bearing kidneys was 4.8 +/- 3.5 v 1.3 +/- 0.4 for the normal kidneys. There was correlation of the SI with stone composition and size but not with radiographic density. After correction for size, the SI of stone-bearing kidneys remained significantly higher than the SI of normal kidneys, but the differences between calculi of different compositions were diminished. Nonetheless, high SI values were associated with soft types of calculi and low values with hard types. Future investigations will reveal if this association is constant and if there is any relation between bisphosphonate uptake and response to lithotripsy. The sensitivity of urolithoscintigraphy to image small or radiolucent calculi may make it an effective technique for the assessment of residual fragments after lithotripsy.

Clinical utility of bone scan features of pleural effusion: sensitivity and specificity for malignancy based on pleural fluid cytopathology

Asymmetric chest activity with malignant and benign pleural effusions has been described in bone scans. However, the clinical utility of this finding is not elucible from the literature. We developed specific scintigraphic criteria for malignant pleural effusion and retrospectively assessed their sensitivity and specificity in a group of patient scans.

METHODS

Pleural fluid was submitted for cytopathology from 850 patients over a 5-yr period. Bone scans were done within 2 mo of the thoracentesis in 74 patients. As a consensus panel, we reread the scans and reviewed the cytology.

RESULTS

The effusions were cytologically malignant in 25/74 patients (34%), indeterminate in 9/74 (12%) and benign in 40/74 (54%). Based on cytopathology, malignant pleural effusions were detected by bone scans with a sensitivity of 34%-50% and a specificity of 78%-89%; true sensitivity and specificity was somewhere in between averaging 42% (95% confidence interval 24%-60%) and 84% (95% confidence interval 73%-95%), respectively.

CONCLUSIONS

The bone scan is frequently the first examination suggesting pleural metastasis, and when it is detected it should be pursued beyond pleural fluid cytology, if negative or indeterminate.

Optimized diagnostic strategy for neuroblastoma in opsoclonus-myoclonus

Infantile myoclonic encephalopathy (opsoclonus-myoclonus or IME) is a rare clinical syndrome associated with occult neuroblastoma in 20%-50% of all cases. IME is the initial presentation of neuroblastoma in 1%-3% of children. Imaging approaches including chest radiography and abdominal computed tomography (CT) have been proposed to detect neuroblastoma in IME. Metaiodobenzylguanidine (MIBG) is highly effective in the detection of neuroblastoma. These scans can identify both soft-tissue and skeletal lesions anywhere in the body. Our purpose was to attempt to determine the best screening method for detection of occult neuroblastoma in patients with IME. Records of all neuroblastoma patients from 1983 to May 1991 were reviewed. Four cases of IME with neuroblastoma were identified in which imaging studies included an MIBG scan. All four patients had positive MIBG scans (100%) while only two had masses on initial CT (50%). In the three patients initially evaluated by traditional methods, the mean time to diagnosis and the mean number of advanced radiologic studies were 7.5 mo and 7.3 studies respectively. The patient screened with MIBG had only cranial and abdominal CT prior to surgery. Although based on a limited number of patients, results suggest that MIBG may prove to be a useful screening procedure in patients with IME. Traditional imaging modalities can then be directed to evaluate sites of disease identified by MIBG scans.

Practical considerations in the scintigraphic evaluation of endocrine hypertension. The adrenal cortex and medulla

A nuclear scan maps the distribution of a radiopharmaceutical that is specific for a physiologic property of a targeted tissue. As such, it is not limited by the anatomic changes necessary for CT and MR scans. It is just because of this that maps of specific metabolic precursors of adrenal medullary and cortical hormones offer information crucial to the therapeutic strategy of endocrine hypertension. NP-59 and MIBG scans can specify the nature of abnormalities revealed by anatomic images and because of the ease of surveying the whole body can give transcendent information about lesions remote from the adrenals. In instances when the origin of endocrine hypertension is not forthcoming from CT or MR imaging or when the anatomic and biochemical findings are in conflict, NP-59 or MIBG can almost always provide the answer.

Efficacy of metaiodobenzylguanidine as a scintigraphic agent for the detection of neuroblastoma

RATIONALE AND OBJECTIVES

Metaiodobenzylguanidine (MIBG) has been shown to be both sensitive and highly specific for the detection of neuroblastoma. However, controversy surrounds its sensitivity in detecting neuroblastoma when compared with radionuclide (technetium 99m-methylene diphosphonate [99mTc]-MDP) bone scans. Because a diagnostic test ideally should be easy to interpret in addition to being sensitive and specific, this study aims to determine the most efficacious scintigraphic agent for diagnostic use in neuroblastoma.

METHODS

Twenty patients with neuroblastoma had a total of 26 paired MIBG and 99mTc-MDP bone scans obtained less than 4 weeks apart. Each study was evaluated independently of its counterpart by six separate observers (3 experienced and 3 inexperienced in MIBG scintigraphy) to determine the presence or absence of disease and the tumor burden.

RESULTS

Inexperienced observers reported more confidence in their interpretations of 99mTc-MDP bone scans; however, seven false-positive bone scans were reported. Using MIBG, all true-positive and true-negative scans, as well as significantly more sites of both primary and metastatic disease, were identified by all observers.

CONCLUSION

This study suggests that MIBG is the more efficacious agent for the scintigraphic evaluation of neuroblastoma.

Bilateral testicular neuroblastoma. Scintigraphic depiction and therapy with I-131 MIBG

The authors describe a 29-year-old man who had a 16-year history of neuroblastoma and uncommon manifestations. At age 13, he was diagnosed with stage III retroperitoneal ganglioneuroblastoma that was resected. Ten years later, bilateral testicular enlargement and a pelvic mass from infiltration of the neuroblastoma became palpable. Metastatic involvement was depicted with MIBG, a radiotracer that concentrates in tissues of the sympathetic nervous system. Using I-131 MIBG, the tumors were treated with therapeutic doses of radiation and a partial response was obtained. This case is unique because of the massive degree of bilateral testicular infiltration and its occurrence as a late manifestation of neuroblastoma in early adulthood.

Scintigraphic assessment of MIBG uptake in globally denervated human and canine hearts--implications for clinical studies

To further characterize the behavior of metaiodobenzylguanidine (MIBG) in the myocardium and to test the hypothesis that the denervated heart would show normal early uptake on MIBG due to non-neuronal localization, we examined the early and late distribution of 123I-labeled MIBG in normal and globally denervated canine and human hearts. Canine hearts were denervated by intravenous injections of 6-hydroxydopamine, while patients were studied a mean of 4.3 mo following cardiac transplantation. Results in denervated hearts were compared to normal controls. Normal hearts showed prominent MIBG uptake on initial 5-min and 3-hr delayed images. Globally denervated canine hearts showed prominent uptake on initial images and absence of localization on delayed images, indicating complete washout of non-neuronally bound radionuclide. The transplanted human hearts showed no localization of MIBG on either early or delayed images. These results suggest that the non-neuronal uptake mechanism (uptake 2) is not significant in human myocardium. This finding has significant implications for interpreting the myocardial behavior of MIBG in various pathologic situations such as dilated cardiomyopathy.

Neuroblastoma: dose-related sensitivity of MIBG scanning in detection

Iodine-131 metaiodobenzylguanidine (MIBG) has shown effectiveness as a systemic radiotherapeutic agent in neuroblastoma. The authors postulated a likely dose-related relationship of MIBG sensitivity when it was administered for neuroblastoma detection. They studied this relationship in neuroblastoma patients who underwent scanning after receiving diagnostic and therapeutic doses of MIBG in temporal proximity. Seven patients with stage IV disease received a total of 14 therapeutic administrations of I-131 MIBG (150-350 mCi [5,550-12,950 MBq]/m2 per treatment). Posttherapy scans were obtained at 3 and at 5-7 days. Diagnostic MIBG scans had been obtained no more than 4 weeks before the start of therapy. Use of diagnostic MIBG scanning led to underestimation of the tumor burden by 50% compared with use of posttherapy scanning. This difference may be an important consideration in selecting therapeutic strategies for individual patients. It further suggests that use of much larger diagnostic doses of MIBG is a rational strategy in histologically confirmed cases of advanced disease.

Unique scintigraphic findings of bile extravasation in the presence of ascites: a complication of hepatic transplantation

A 99mTc-HIDA scan was performed on a 4-mo-old female, six days after hepatic transplantation. Gradually, a diffuse increase in activity was seen over the peritoneal region, consistent with a slow bile leak into ascitic fluid. Although the scintigraphic appearance of a bile leak has been previously described, it is usually seen as a focal area of extrabiliary activity. In this case, we report a pattern identified when the leak occurs in conjunction with ascites.

Asymmetry of salivary gland I123 metaiodobenzylguanidine (MIBG) uptake in a patient with cervical neuroblastoma and Horner's syndrome--possible etiologic mechanisms

Horner's syndrome may be due to a variety of serious underlying disorders including cervical neuroblastoma. Horner's syndrome results from a unilateral disruption of the sympathetic innervation to the head and neck. We report a patient with cervical neuroblastoma in whom post operative metaiodobenzylguanidine (MIBG) scans showed a striking decrease in uptake in the ipsilateral salivary glands. Since the bio-distribution of I123 metaiodobenzylguanidine in the salivary glands in also dependent on sympathetic innervation, the presence of Horner's syndrome can be reflected in the MIBG scan.

Duration of etidronate effect demonstrated by serial bone scintigraphy

There have been several reports of etidronate disodium (EHDP) interference upon the biodistribution of 99mTc-methylene diphosphonate (MDP). With the increasing use of etidronate for the treatment of Paget's disease, hypercalcemia, and osteoporosis, nuclear physicians can expect to encounter increasing numbers of cases in which EHDP-induced artifacts impair the diagnostic utility of bone scans. The temporal duration of this effect is unknown yet obviously important. We report serial bone scintigraphy in a patient who received a single dose of EHDP for hypercalcemia. Normal biodistribution of 99mTc-MDP was noted at 15 days, suggesting that 2 wk are sufficient before performing a bone scan after a single intravenous dose of etidronate.

Gallium-67/stable gadolinium antagonism: MRI contrast agent markedly alters the normal biodistribution of gallium-67

An 11-yr-old patient was scanned 96 hr after the administration of gallium-67 (67Ga). The scan emulated the biodistribution of a typical bone-seeking radipharmaceutical-rather than that of 67Ga. None of the factors previously identified with alteration of the biodistribution of 67Ga were found. However, the patient had been injected with gadopentetate in conjunction with magnetic resonance imaging 4 hr before receiving the 67Ga. Gadolinium appears to cause a strong carrier-like effect in 67Ga scans.

Scintigraphic assessment of regional cardiac adrenergic innervation

To assess the feasibility of noninvasively imaging the regional distribution of myocardial sympathetic innervation, we evaluated the distribution of sympathetic nerve endings, using 123I metaiodobenzylguanidine (MIBG), and compared this with the distribution of myocardial perfusion, using 201Tl. Twenty dogs were studied: 11 after regional denervation, and nine as controls. Regional denervation was done by left stellate ganglion removal, right stellate ganglion removal, and application of phenol to the epicardial surface. Computer-processed functional maps displayed the relative distribution of MIBG and thallium in multiple projections in vivo and excised heart slices in all animals. In six animals, dual isotope emission computed tomograms were acquired in vivo. Tissue samples taken from innervated and denervated regions of the MIBG images were analyzed for norepinephrine content to validate image findings. Normal controls showed homogeneous and parallel distributions of MIBG and thallium in the major left ventricular mass. In the left stellectomized hearts, MIBG was reduced relative to thallium in the posterior left ventricle; whereas in right stellectomized hearts, reduced MIBG was in the anterior left ventricle. Phenol-painted hearts showed a broad area of decreased MIBG extending beyond the area of phenol application. In both stellectomized and phenol-painted hearts, thallium distribution remained homogeneous and normal. Norepinephrine content was greater in regions showing normal MIBG (550 +/- 223 ng/g) compared with regions showing reduced MIBG (39 +/- 44 ng/g) (p less than 0.001), confirming regional denervation. Combined MIBG-thallium functional maps display the regional distribution of sympathetic innervation. This new ability to noninvasively map the distribution of sympathetic nerves with simultaneous comparison to regional perfusion may provide important new insights into mechanisms, whereby an imbalance in sympathetic activity may relate to clinical disorders.

Bayesean-deblurred Planar and SPECT nuclear bone imaging for the demonstration of facial anatomy and craniomandibular disorders

Ambiguities in diagnoses can often be resolved when images from different imaging modalities are compared, and when images are processed with algorithms that improve resolution and contrast. Bayesean deblurring algorithms were developed and applied to Planar and SPECT images of the maxillofacial and temporomandibular joint regions. The combined use of Planar and SPECT imaging with Bayesean deblurring were complementary and provided more diagnostic information than either modality individually. A facial imaging protocol using Planar and SPECT imaging and Bayesean deblurring is described. SPECT maxillofacial anatomy is presented, as well as the application of the imaging protocol of craniomandibular dysfunction. Although not recommended for all patients with craniomandibular disorders, combined use of Planar and SPECT images and Bayesean deblurring techniques appears to be useful in diagnostically difficult or refractory cases.

Dumping in infancy diagnosed by radionuclide gastric emptying technique

Two infants were diagnosed with dumping syndrome by a radionuclide gastric emptying method. Both patients presented with anorexia, weight loss, agitation and diaphoresis following bolus feeding by gastrostomy tube. One had documented hyperglycemia and glycosuria. Symptoms and signs of dumping in one patient were due to a gastrostomy placed in the antrum, whereby bolus tube feedings were inadvertently introduced directly into the duodenum. The second patient developed dumping symptoms after a Waterston colonic interposition was performed to correct a long gap esophageal atresia. Gastric emptying, measured by administering 99mTc-sulfur colloid-labeled formula, demonstrated an initial extremely rapid appearance of isotope in the small intestine, with greater than one-third of the formula leaving the stomach in less than 2 min. The gastric emptying pattern in both patients appeared biphasic; after the initial "dumping" phase, the remaining formula emptied slowly, with monoexponential decay kinetics.

Nuclear medicine: metaiodobenzylguanidine in the diagnosis of pheochromocytoma and neuroblastoma

The Scientific Board of the California Medical Association presents the following inventory of items of progress in nuclear medicine. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, research workers, or scholars to stay abreast of these items of progress in nuclear medicine that have recently achieved a substantial degree of authoritative acceptance, whether in their own field of special interest or another.The items of progress listed below were selected by the Advisory Panel to the Section on Nuclear Medicine of the California Medical Association and the summaries were prepared under its direction.

Analysis of thallium-201 "washout" from parametric color coded images

We developed a parametric washout image which color codes regional washout, and blindly compared enhanced perfusion images in multiple projections with regional washout graphs and images in 25 patients. Washout images permitted true spatial and anatomic assessment of regions viewed en face as well as those seen in tangent, making possible the exclusion of non-coronary irregularities and permitting evaluation of washout over the apparent cavity. "Cavitary" washout was abnormal in 10 of 12 patients with apparent cavitary dilation on the post stress image, but in none without this finding. The distribution and rotation of washout abnormalities seen over the cavity when viewed en face, and the long delay between the termination of stress and post-exercise image acquisition, suggest that apparent cavitary dilation is often related to improved visibility of the 201T1 deficient blood pool due to relative ischemia of the overlying myocardial wall.

Emission imaging of patients with craniomandibular dysfunction

Signs and symptoms of craniomandibular dysfunction in 37 patients were compared with the results of corrected cephalometric tomography and an emission imaging protocol consisting of both planar and single photon emission computed tomography (SPECT) (7500 ZLC Orbiter) images. The planar images and the single photon emission computed tomography projection views were processed with a bayesian deblurring algorithm to improve image quality. The correlation of emission imaging with craniomandibular dysfunction, as indicated by temporomandibular joint pain and joint noise, showed a high sensitivity (93%) and a high specificity (86%), whereas the correlation of corrected cephalometric tomography with temporomandibular joint pain and joint noise showed a relatively high sensitivity (89%) but a low specificity (27%). These results indicate that emission imaging is a sensitive and accurate indicator of craniomandibular dysfunction.

No gravity-independent gradient of blood flow distribution in dog lung

The existence of a major gravity-independent gradient of blood flow in lungs has recently been described based on single photon emission computed tomography after intravenous injection of radioactively labeled macroaggregates. We wanted to test this hypothesis of a major gravity-independent gradient in lung blood flow in experiments with direct measurement of macroaggregate distribution in the dog lung. In six anesthetized (4 prone spontaneously breathing, 2 mechanically ventilated) dogs we injected 111In-labeled albumin macroaggregates intravenously. We killed the dogs, removed, inflated, and froze the lower lobes. We sliced the lobes 1 cm thick and made gamma camera images of the slices. We then cut three or four slices in each lobe into two or three concentric layers and measured the radioactivity per gram of tissue in a well-type gamma counter. In three of the dogs we also labeled the red cells (99mTc) so that blood volume in each sample could be determined. The gamma camera images were acquired on a 64 X 64 matrix with 4 X 4 mm pixels. On the numeric printouts from the individual slices we made two or three concentric layers and calculated activity per pixel in each layer. Neither by the well counting nor by the pixel analysis of the gamma scans did we detect any gravity-independent distribution of blood flow. With the well counting the distribution was the same whether macroaggregate activity was expressed per gram of tissue or per gram of blood-free tissue. We conclude that by direct measurements no major gravity-independent gradient of pulmonary blood flow can be detected in dog lungs.

Improved immune-specificity in monoclonal radioimmunoimaging using dual radionuclide color functional maps

Diagnostic radioimmunoimaging is potentially limited by tissue localization of radiolabeled antibody products through mechanisms other than antigen binding. Comparing the distributions of reactive and nonreactive products can distinguish tracer in targeted and nontargeted tissues. To achieve this in a single imaging procedure, dual photopeak scintigraphy was performed using 111In and 67Ga products. Melanoma-bearing athymic mice were coadministered intravenously subtype-matched 111In melanoma-reactive and 67Ga melanoma-nonreactive murine monoclonal antibodies. Paired images from 245 and 93 keV windows were processed with a unique dual parameter color display program. The display algorithm expresses pixel counts from paired photo-peak images in polar coordinates and color-encodes angle as hue and magnitude as intensity. The color functional maps permitted ready distinction of immune from nonimmune uptake. Compared with single tracer imaging methods, this technique better depicts antigen distribution.

The effects of coronary angioplasty and reperfusion on distribution of myocardial flow

To assess the effects of angioplasty (PTCA) and intracoronary streptokinase (ICSK) on relative myocardial perfusion, we administered 99mTc-macroaggregated albumin (MAA) to the uninvolved coronary artery before successful PTCA in 33 patients and before successful infusion of ICSK in eight patients and of 111In-MAA into the same vessel after the intervention. In 10 patients who underwent PTCA, MAA was injected into the involved, instrumented coronary artery. Computer-processed images were acquired in registry and compared. Similar scintigraphic studies were performed in six control patients and in 11 in whom planned interventions were not performed or were unsuccessful. Distribution of MAA was also compared with angiographic results and with the distribution of 201Tl on images obtained in patients at rest or on redistribution images obtained before and soon after intervention in 22 patients. In control patients and those studied after aborted or unsuccessful intervention, scintigraphic results showed excellent correlation with the angiographic anatomy and were without serial change. When MAA was injected into the uninvolved vessel, the scintigram revealed evidence of collateral perfusion with retraction of the perfusion zone from that of the involved coronary in 19 of 33 patients undergoing PTCA and in three of eight of those receiving ICSK. When MAA was injected into the involved artery, a relative increase in perfusion was seen in eight of 10 patients after PTCA. Although 30 patients demonstrated scintigraphic evidence of collateral vessels, only 10 patients had angiographic evidence of collateral circulation before intervention. The distribution of 201Tl demonstrated little change in its global pattern and regions previously supplied by collaterals were generally well perfused after intervention. Coronary collateral perfusion may be inapparent angiographically and regress rapidly after angioplasty or reperfusion. Native perfusion is generally and quickly restored after successful PTCA or ICSK infusion, which obviates the need for collaterals. After intervention, the distribution of total perfusion may not change, but its regional source may demonstrate beneficial alterations, shifting from collateral to native circulation.

Multinuclide digital subtraction imaging in symptomatic prosthetic joints

One hundred eleven patients with symptomatic prosthetic joints (86 hips, 23 knees, and two shoulders) were evaluated for prosthetic loosening and infection by combined technetium-99m-MDP/gallium-67 digital subtraction imaging. Clinical correlation was based on the assessment of loosening and bacterial cultures obtained at the time of surgery in 54 patients, joint aspiration cultures obtained in 37 patients, and long-term clinical follow-up for greater than 1.5 years in an additional 15 patients. Results revealed an 80%-90% predictive value of a positive test for loosening, and a 95% predictive value of a negative test for infection. However, because of the low sensitivities and specificities observed, this approach to the evaluation of symptomatic prosthetic joints does not seem cost effective.

Correlation between gallium lung scans and fiberoptic bronchoscopy in patients with suspected Pneumocystis carinii pneumonia and the acquired immune deficiency syndrome

We retrospectively examined the sensitivity and specificity of gallium lung scans for detecting Pneumocystis carinii pneumonia in 22 patients with known or suspected acquired immune deficiency syndrome. Correlations were made between bronchoscopic results and gallium scan findings interpreted using a simple system (normal or abnormal) and a graded score (1 to 4). All 12 patients with Pneumocystis had abnormal scans by both interpretations (sensitivity, 100%). Five of these 12 patients had normal arterial PO2 values, chest roentgenograms, or both. In the 10 patients without Pneumocystis, scans were read as abnormal in 8 using the simple system (specificity, 20%) but were abnormal in only 1 using the grading system (specificity, 90%). Five patients with Pneumocystis pneumonia had scans and bronchoscopy after treatment; neither method of interpretation correlated with the presence of organisms. We conclude: (1) gallium scanning is a sensitive initial diagnostic test in patients with suspected Pneumocystis pneumonia; (2) a graded scoring system improves specificity; (3) an abnormal gallium scan (3 or greater) in patients with suspected Pneumocystis pneumonia is an indication for biopsy, even when the PO2 and/or chest roentgenogram are normal.

Osteoid osteoma: radionuclide diagnosis

The double-density sign, seen on radionuclide bone scans, is described for diagnosing osteoid osteomas and for localizing the nidus. Its use in differentiating the nidus of an osteoid osteoma from osteomyelitis is also described. The utility of computed tomography in localization of the nidus is also illustrated. The double-density sign was helpful in diagnosing seven cases of surgically confirmed osteoid osteoma.

The effect of secretin on colonic mucin secretion rate in the dog

A method of quantitation of mucin using chondroitin sulfate A as a standard has been modified and applied to timed mucin collections from surgically created isolated colonic fistulas in 8 dogs. 25 experiments were conducted in which the effect of secretin was tested in 5. The mucin assay is precise and showed increased colonic mucin secretin in response to secretin. This model appears suitable for pharmacologic assessment of potential drugs for augmenting colonic mucin secretin in states of impaired colonic motility.

Radionuclide bone scanning in neuroblastoma: skeletal metastases and primary tumor localization of 99mTc-MDP

Of 42 radionuclide bone scans in 35 children with neuroblastoma, 21 were abnormal for the presence of skeletal metastases. Of the 21 abnormal scans, 16 were corroborated by positive bone-marrow biopsy or clinical data. The false-negative and false-positive rates for bone scanning were 4.8% and 9.5%, respectively. Calcification of the primary tumor was seen on pretreatment computed tomographic (CT) scans in 24 (89%) of 27 cases, while only 13 (48%) of 27 were detectable by plain radiographs. Uptake of technetium-99m methylene diphosphate (99mTc-MDP) by the primary tumor occurred in 20 of 27 cases, but correlation between tumor uptake and calcification was not statistically significant. All children with markedly elevated urinary vanillylmandelic acid exhibited primary tumor uptake. Survival was not affected independently by primary tumor uptake.

The functional vascular anatomy of rib

The adequacy of nutrient blood supply to ribs based on the intercostal-periosteal system versus the medullary nutrient artery was investigated in six dogs containing ribs of each type. Free grafts with periosteum and without periosteum were also included. Vascularity was monitored by bone scanning and tetracycline double labeling. A preliminary study with RES scanning using sulfur colloid was also preformed. The results of this study showed (1) that no demonstrable difference in blood supply exists between rib supplied by the anterior intercostal-periosteal system versus the nutrient artery (this was seen with bone scans, tetracycline double labels, and RES scans); (2) that bone scans can differentiate between vascularized rib grafts and free rib grafts for at least the first 7 days (after 7 days, some free grafts begin to take up label); and (3) that by using bone scan, no difference in the rate of revascularization is detected between free grafts with the periosteum stripped or the periosteum intact (RES scans and tetracycline labeling were not given late enough after surgery to be incorporated in either type of nonvascularized graft).

Characterization of radiation-induced photopenic abnormalities on bone scans

Photopenic abnormalities induced by radiation therapy are important to recognize on bone scans, since they often affect longitudinal or lateral symmetry. This phenomenon was studied in 43 patients treated through 67 ports (including the axial skeleton). Bone doses spanned 450-6,700 R (mean +/- S.D. = 3,600 +/- 1,700 R), and the interval from the midpoint of therapy to the time of the scan was 1-19 months. Photopenic defects appeared between 4 and 6 months after therapy. Of 20 patients (31 ports) studied more than 4 months after therapy, 14 (45%) had such defects. None was detected in regions receiving less than 2,000 R. The authors conclude that knowledge of a patient's radiotherapy history is an important prerequisite to interpretation of subsequent bone scans.

Altered 67Ga citrate distribution in patients with multiple red blood cell transfusions

Gallium-67 citrate studies from four patients who received multiple red blood cell transfusions were reviewed. Increased kidney, bladder, or bone localization was associated with decreased liver and colon activity. The findings suggest altered distribution due to competition with iron for receptor binding. Identification of inflammatory disease in two patients was possible. However, the effect of transfusions on detection of inflammatory or neoplastic diseases requires further evaluation.