Model-based correction for scatter and tailing effects in simultaneous 99mTc and 123I imaging for a CdZnTe cardiac SPECT camera

An advantage of semiconductor-based dedicated cardiac single photon emission computed tomography (SPECT) cameras when compared to conventional Anger cameras is superior energy resolution. This provides the potential for improved separation of the photopeaks in dual radionuclide imaging, such as combined use of (99m)Tc and (123)I . There is, however, the added complexity of tailing effects in the detectors that must be accounted for. In this paper we present a model-based correction algorithm which extracts the useful primary counts of (99m)Tc and (123)I from projection data. Equations describing the in-patient scatter and tailing effects in the detectors are iteratively solved for both radionuclides simultaneously using a maximum a posteriori probability algorithm with one-step-late evaluation. Energy window-dependent parameters for the equations describing in-patient scatter are estimated using Monte Carlo simulations. Parameters for the equations describing tailing effects are estimated using virtually scatter-free experimental measurements on a dedicated cardiac SPECT camera with CdZnTe-detectors. When applied to a phantom study with both (99m)Tc and (123)I, results show that the estimated spatial distribution of events from (99m)Tc in the (99m)Tc photopeak energy window is very similar to that measured in a single (99m)Tc phantom study. The extracted images of primary events display increased cold lesion contrasts for both (99m)Tc and (123)I.

Can upright myocardial perfusion imaging be used alone with a solid-state dedicated cardiac camera?

AIM

The novel solid state dedicated cardiac cameras provide fast high resolution cardiac imaging. The D-SPECT camera enables semi-reclining (upright) positioning, increasing comfort and potentially reducing movement during myocardial perfusion imaging. Physicians are generally familiar with supine imaging and the different positioning in upright imaging could potentially cause diagnostic challenges. The aim of this study was to compare the upright and supine imaging for diagnostic ability to assess Physician confidence and determine any artefacts in upright imaging.

METHODS

Fifty-five patients underwent myocardial perfusion imaging on the D-SPECT camera in both upright and supine positions. Where both images showed the same defects the 2 techniques were regarded as equally diagnostic. Where only one set showed a defect this was regarded as artefact and was defined as non-diagnostic. The location and cause of the artefact was recorded.

RESULTS

In 13 /55 patients either form of imaging was regarded as equally diagnostic. In 24/55 the supine images revealed artefact affecting interpretation. The reasons for this were most frequently large BMI, motion and gut uptake. In 18/55 upright images were considered non-diagnostic. In 16/18 this was due to an infero-apical defect seen in female patients (14/16) with raised BMI and/or large breasts.

CONCLUSION

Upright myocardial perfusion imaging on D-SPECT shows a common artefact (in up to 1/3 of cases) in the infero-apical region mainly in overweight female patients. Getting acquainted with this artefact this may increase Physician confidence in reporting, similarly as to conventional supine imaging. Indeed, some of the artefacts seen on supine imaging appear less commonly with upright imaging. Thus, upright imaging can potentially be used alone for diagnosis with D-SPECT. Performance of both supine and upright imaging can be reserved for overweight patients thereby minimizing impact on scanning time and clinical throughput in busy departments.

PET/CT for atherosclerotic plaque imaging

Atherosclerosis is one of the leading causes of morbidity and mortality in the world. Rupture of atherosclerotic plaques and thrombi formation are the primary mechanisms of myocardial infarction or cerebrovascular accident. Angiography is considered to represent the gold standard technique for imaging of the arterial lumen. However, in recent years it has been realized that the primary determinant of the atherosclerotic plaque stability is the composition of the plaque and other imaging modalities have been suggested. The purpose of this review is to briefly summarize the knowledge accumulated to present date regarding the potential role of fluodeoxyglucose imaging in the assessment of atherosclerosis and to compare this modality to additional available imaging approaches for the detection of vulnerable plaques.

The Added Value of Spiral Computed Tomographic Angiography After Lung Scintigraphy for the Diagnosis of Pulmonary Embolism

OBJECTIVES

The objectives of this study were to evaluate the added clinical value of spiral computed tomographic angiography (CTA) after ventilation-perfusion lung scintigraphy (V/Q) for the management of patients with suspected pulmonary embolism (PE).

METHODS

Of 987 patients who had V/Q during 2001, 64 patients (6%) had CTA performed for further evaluation. V/Q and CTA findings were retrospectively analyzed by 2 clinicians who were blinded to the patients' outcome. Patient management was determined based on clinical and V/Q data and was reassessed after the addition of CTA data.

RESULTS

CTA was performed in 2 patients with normal V/Q, 16 patients with low probability, 28 patients with intermediate, 4 patients with high probability, and 14 patients with nonconclusive V/Q. Three patients (19%) with low probability, 9 (32%) with intermediate probability, 4 (29%) with nonconclusive, and 4 (100%) with high probability V/Q had PE diagnosed by CTA. CTA findings changed the management in 2 patients (13%) with low probability, 15 (54%) with intermediate probability, and 4 (29%) with nonconclusive V/Q.

CONCLUSION

In our institution, V/Q remains the main imaging modality for evaluation of patients with clinically suspected PE. CTA was performed after V/Q in 6% of patients. Patients with intermediate probability and those with nonconclusive V/Q, and to a much lesser extent, patients with low probability V/Q could benefit from the addition of CTA after V/Q. In patients with normal V/Q and those with high-probability V/Q, the addition of CTA does not seem to influence patient management.

Three-dimensional electromechanical mapping: imaging in the operating room of the future

BACKGROUND

Three-dimensional electromechanical mapping has previously been shown to be a clinically important tool for cardiac imaging and intervention. We hypothesized that this technology may be beneficial as an intraoperative modality for assessing cardiac hemodynamics and viability during cardiac surgery. We report here the use of this technology as an imaging modality for intraoperative cardiac surgery.

METHODS

The tip of a locatable catheter connected to an endocardial mapping and navigating system is accurately localized while simultaneously recording local electrical and mechanical functions. Thus the three-dimensional geometry of the beating cardiac chamber is reconstructed in real time. The system was tested on 6 goats that underwent acute dynamic cardiomyoplasty and on 5 dogs that underwent left anterior descending (LAD) coronary artery ligation.

RESULTS

The electromechanical mapping system provided an accurate three-dimensional reconstruction of the beating left ventricle during cardiomyoplasty. After the wrapping procedure, significant end-diastolic area reduction was noted in the base and mid parts of the heart (948 +/- 194 mm2 vs 1245 +/- 33 mm2, p = 0.021; and 779 +/- 200 mm2 vs 1011 +/- 80 mm2, p = 0.016). The area of the cross-section of the apex did not change during the operation. Acute infarcted tissue was characterized 3 days after LAD ligation by concomitant deterioration in both electrical and mechanical function.

CONCLUSIONS

By providing both a clear view of the anatomical changes that occur during cardiac surgery, and an accurate assessment of tissue viability, electroanatomic mapping may serve as an important adjunct tool for imaging and analysis of the heart during cardiac surgery

Novel magnetic technology for intraoperative intracranial frameless navigation: in vivo and in vitro results

OBJECTIVE

To characterize the accuracy of the Magellan electromagnetic navigation system (Biosense Webster, Tirat HaCarmel, Israel) and to demonstrate the feasibility of its use in image-guided neurosurgical applications.

DESCRIPTION OF INSTRUMENTATION

The Magellan system was developed to provide real-time tracking of the distal tips of flexible catheters, steerable endoscopes, and other surgical instruments, using ultra-low electromagnetic fields and a novel miniature position sensor for image-correlated intraoperative navigation and mapping applications.

METHODS

An image registration procedure was performed, and static and qualitative accuracies were assessed in a series of phantom, animal, and human neurosurgical studies.

EXPERIENCE AND RESULTS

During the human study phase, an accuracy error of up to 5 mm was deemed acceptable. Results demonstrated that this degree of accuracy was maintained throughout all procedures. All anatomic landmarks were reached with precision and were accurately viewed on the display screen. Navigation that relied on the system was also successful. No interference with operating room equipment was noted. The accuracy of the system was maintained during regular surgical procedures, using standard surgical tools.

CONCLUSION

The system provides precise lesion localization without limiting the line of vision, the mobility of the surgeon, or the flexibility of instruments. Electromagnetic navigation promises new advances in neuronavigation and frameless stereotactic surgery.

Kidney function after radical nephrectomy: assessment by quantitative SPECT of 99mTc-DMSA uptake by the kidneys

To determine the function of the remaining contralateral kidney after the removal of a functioning kidney, 30 consecutive patients (18 men, 12 women; average age, 67 y; age range, 34-87 y) who were undergoing unilateral radical nephrectomy were evaluated by sequential quantitative 99mTc-dimercaptosuccinic acid (DMSA) SPECT (QDMSA) studies.

METHODS

The 30 patients were undergoing radical nephrectomy for renal tumors. The first study was done before surgery. Follow-up studies were performed 2-23 mo after surgery. Clinical evaluations and determinations of serum creatinine level were performed at the same time as the QDMSA studies.

RESULTS

The relative contribution of the resected kidneys to the global renal function before surgery was 43.2% +/- 7.3%. After surgery the uptake of the remaining kidney increased from 13.4% +/- 4.0% to 18.3% +/- 5.8% (t = 5.7; P = 0.0000). The relative function of the remaining kidney increased from 56.8% +/- 7.1% to 79.1% +/- 23.6% (t = 4.9; P < 0.0001) of the global renal function before nephrectomy. Increases in the renal volume (from 211 +/- 62 cm3 to 229 +/- 68 cm3; t = 4.5; P = 0.0001) and in the percentage injected dose per cubic centimeter (%ID/cm3) of the remaining kidney (from 0.066 +/- 0.02 % ID/cm3 to 0.085 +/- 0.03 %ID/cm3; t = 4.6; P = 0.0001) were associated with this change. Nine patients had 2 follow-up studies performed 3-4 mo after surgery and 12-14 mo after surgery. The volume of the remaining kidney (209.22 +/- 46.20 cm3 versus 217.88 +/- 58.85 cm3; t = 0.962; P = 0.364), the %ID/cm3 (0.09 +/- 0.016 %ID/cm3 versus 0.093 +/- 0.025 %ID/cm3; t = 0.362; P = 0.726), and the percentage uptake (19.26% +/- 4.45% versus 20.11% +/- 7.01%) did not change significantly between these 2 QDMSA studies.

CONCLUSION

The results of this study suggest that adaptive changes causing hyperfunction of the remaining kidney may occur after nephrectomy of a functioning kidney in adults. These changes occur soon after surgery, persist for at least 1 y, and are evident on QDMSA studies.

False positive metaiodobenzylguanidine scan in a patient with a huge adrenocortical carcinoma

We report a case of a 17-cm cortisol-secreting adrenocortical carcinoma in which [123I] metaiodobenzylguanidine (MIBG) scan showed accumulation of the isotope in the area of the tumor. Catecholamine levels were normal, and no chromaffin cells were found in histological examination of the tumor. A literature review of previously described cases of false positive MIBG scans in the adrenal region is offered. We conclude that MIBG scans might not be as specific as previously thought in differentiating pheochromocytoma from adrenocortical carcinoma. They should be performed only when clinical suspicion and abnormalities in catecholamines advocate the need.

Response to repeated equal doses of epinephrine during cardiopulmonary resuscitation in dogs

STUDY OBJECTIVE

Advanced cardiac life support (ACLS) guidelines recommend a 3- to 5-minute interval between repeated doses of epinephrine. This recommendation does not take into account the dose of epinephrine used, and only very limited data exist regarding the hemodynamic responses to repeated "high" doses of epinephrine. The objective of this study was to analyze the hemodynamic responses to repeated, equal, high doses of epinephrine administered during cardiopulmonary resuscitation (CPR) in a canine model of ventricular fibrillation (VF).

METHODS

This study used a secondary analysis of data collected in a prospective, randomized study, primarily designed to assess the effects of acid buffers in a canine model of cardiac arrest. VF was electrically induced. After 10 minutes, CPR was initiated, including ventilation with FIO(2)=1.0, external chest compressions, administration of epinephrine (0.1 mg/kg repeated every 5 minutes) and defibrillation. Animals were randomized to receive either NaHCO(3), Carbicarb, tromethamine (THAM), or NaCl. The hemodynamic variables were sampled from each experiment's paper chart at 1-minute intervals, and the responses to the first 4 doses of epinephrine were compared.

RESULTS

Thirty-six animals (9 in each buffer group) were included in this analysis. Systolic, diastolic, and coronary perfusion pressures increased steeply (by 100%, 130%, and 190%, respectively) only after the first epinephrine dose. These pressures peaked at 2 to 3 minutes and decreased only slightly and insignificantly during the rest of the 5-minute interval, until the next epinephrine dose. No further significant increases in arterial pressures were observed in response to the next 3 doses of epinephrine, administered 5 minutes apart.

CONCLUSION

The hemodynamic effects of high-dose epinephrine (0.1 mg/kg) during CPR appear to last longer than 5 minutes. Therefore, longer intervals between doses may be justified with high doses of epinephrine.

Lower extremity scintigraphy: the foot and ankle

Disorders of the ankle and foot are common and may pose a significant clinical problem. Acute injuries of the ankle and foot are routinely evaluated by radiographs and, if inconclusive, by magnetic resonance imaging (MRI) or computed tomagraphy (CT). In subacute or chronic injuries, where prolonged pain is unexplained, bone scintigraphy may play a significant role. The bone scan may differentiate soft tissue from bone pathology, and, being a sensitive test, it may indicate the region that needs further specific radiologic examination. It may also indicate the clinical significance of a radiologic finding. Moreover, in some clinical settings bone scintigraphy can be specific in the diagnosis. Careful attention to the technique enhances the efficiency of bone scintigraphy and SPECT allows better investigation of the hindfoot. The importance of ankle and foot injuries in the orthopedic practice and the better understanding of subacute and chronic injuries in athletes and in the general population has led to an increased use of specific tests such as MRI, CT, and bone scintigraphy. With improved technique and instrumentation it is no longer sufficient to indicate a focal abnormality in the ankle or foot on bone scintigraphy. More precise information about perfusion, blood pool, and specific location of a lesion can be obtained by high resolution and tomographic images. The role of bone scintigraphy in the diagnosis of such disorders will be presented with a focus on subacute traumatic injuries and related disorders, as well as its role in systemic inflammatory disorders that often involve the ankle and foot.

Benign proliferative lesions mimicking recurrence of Hodgkin's disease

Salvage treatment in patients with recurrent Hodgkin's disease is more effective when tumor burden is minimal. That is why more intensive follow-up strategies, including frequent imaging tests, have been recently developed for the detection of early relapse. However, as screening procedures become more sensitive, there is an increasing risk of false-positive results, demonstrating nonmalignant proliferative disorders. We describe three young patients who had lymphocyte-predominant or mixed-cellularity Hodgkin's disease and were in clinical complete remission for 2.5-3 years after a combined treatment with chemotherapy and radiation. Imaging tests revealed new gallium-avid lymphadenopathy in the chest in two cases. Pathologically enlarged pelvic lymph nodes were identified in another case, after a diagnosis of recurrent disease in axilla. Those findings were interpreted as relapse, and the patients underwent thoracotomy and laparotomy, respectively, for histologic confirmation. The results showed progressively transformed germinal centers and sarcoid-like lesions, two benign proliferative disorders. When patients with Hodgkin's disease in remission show new lymphadenopathy, even with positive gallium scan, it seems mandatory to obtain tissue for histologic examination, even through invasive procedures such as laparotomy and thoracotomy, to avoid wrong diagnosis and unnecessary treatment.

Utility of gallium-67 scintigraphy in low-grade non-Hodgkin's lymphoma

PURPOSE

Low-grade non-Hodgkin's lymphoma (LGNHL) has traditionally been considered non-gallium-avid. The sensitivity of gallium 67 (67Ga) scintigraphy when using modern equipment and techniques in patients with LGNHL was investigated.

MATERIALS AND METHODS

Fifty-seven consecutive patients with LGNHL underwent 67Ga scintigraphy at initial presentation (n = 40), when tumor progression occurred during treatment (n = 3), and at suspected disease recurrence after continuous clinical remission (CCR) (n = 14). Planar and tomographic images were obtained with either a very large field-of-view or a dual-head digital camera. Of 45 patients with Ga-avid LGNHL, 30 underwent 93 follow-up scans (one to six studies per patient). Scan findings were correlated with clinical and computed tomographic (CT) findings and with patient outcomes.

RESULTS

67Ga scintigraphy was positive in 45 of 57 patients (sensitivity, 79%) and in 113 of 164 disease sites (sensitivity, 69%). The sensitivity was higher in the more common types of LGNHL: follicular, predominantly small cleaved cell (FSC), and follicular, mixed small cleaved and large cell (FM) (84% and 91% in patients and 72% and 71% in disease sites, respectively). Sensitivity was lower in patients with mucosa-associated lymphoid tissue lymphoma (MALT) and small lymphocytic lymphoma (SL). Among 28 patients with disease recurrence after CCR (14 with and 14 without baseline studies), 67Ga scan was positive in 25, for a sensitivity of 89% for detection of disease recurrence.

CONCLUSION

When modern technology is used, 67Ga scintigraphy has good sensitivity in patients with LGNHL. It therefore can be used to monitor response to therapy and to provide early detection of disease recurrence in these patients.

Diffuse lung uptake of Ga-67 after treatment of lymphoma: is it of clinical importance?

PURPOSE

To determine if diffuse lung uptake (DLU) of gallium-67 at scintigraphy in patients with lymphoma is indicative of lymphomatous involvement of the lungs.

MATERIALS AND METHODS

Thirty-eight patients (24 male, 14 female; aged 15-76 years) with DLU were examined. The relation between DLU and lymphoma was investigated. Radiographic and computed tomographic findings and the persistence of Ga-67 uptake were investigated to detect lymphomatous involvement of the lungs. The relations between chemotherapy and radiation therapy, previous lung or heart disease, and DLU were also examined.

RESULTS

DLU appeared only during or after chemotherapy. No clinical, radiologic, or follow-up evidence indicated that patients with DLU had active lymphomatous involvement of the lungs. The difference in survival between patients with persistent and patients with transient DLU was not statistically significant. No statistically significant correlation between DLU and any possible inductive factor was indicated at multivariate analysis.

CONCLUSION

DLU after treatment does not indicate lymphomatous involvement of the lungs.

Gallium-67 scintigraphy in lymphoma with bone involvement

Both Hodgkin's and non-Hodgkin's lymphoma (NHL) may involve bone. Traditionally, 99mTc-MDP bone scintigraphy has been used to detect such involvement. In recent years, 67Ga scintigraphy has shown to be useful in monitoring treatment response in lymphoma. Although 99mTc-MDP has not been found particularly useful for monitoring bone response to cancer treatment, we were interested in whether 67Ga scintigraphy and SPECT could be used to monitor bone involvement with lymphoma.

METHODS

Gallium-67 and 99mTc-MDP uptake were investigated in 20 patients with lymphoma involving the bone before treatment. Gallium-67 scans were done in 16 patients for monitoring response to treatment in the bone lesions.

RESULTS

Gallium-67 studies diagnosed bone lesions in 19 of the 20 patients. Technetium-99m-MDP detected bone lesions in all patients investigated. In four patients, uptake by Ga-67 was more intense than 99mTc-MDP and in another four patients 99mTc-MDP uptake was more evident. Gallium-67, however, was useful in detecting other regions of involvement in 18 of the 19 patients with soft-tissue lymphoma lesions. Gallium-67 scintigraphy also correctly monitored bone response to treatment in all but one of the 16 patients who had 67Ga scintigraphy after completing therapy.

CONCLUSION

Gallium-67 uptake by lymphoma involving the bone can be used to monitor osseous response to treatment.

Utility of Tc-99m mebrofenin scintigraphy in the assessment of infantile jaundice

Technetium-99m mebrofenin hepatobillary excretory patterns were assessed in 36 infants with hyperbilirubinemia. Phenobarbital was administered to 22 patients before imaging. Final diagnoses included: intrahepatic cholestasis (14 patients), neonatal hepatitis (nine patients), biliary atresia (eight patients), alpha-1-antitrypsin deficiency (two patients), Alagille's syndrome (two patients), and cystic fibrosis (one patient). No patient with biliary atresia showed bowel activity by 24 hours. Of the 28 infants without biliary atresia, 23 (82%) had bowel activity visualized by 6-8 hours and 26 (90%) had bowel activity by 24 hours. Two had no bowel activity at 24 hours: one had cystic fibrosis and one had neonatal hepatitis. Of the 26 patients with bowel visualization, the time to visualize bowel did not differ between patient groups with and without phenobarbital induction. All of the patients with hepatitis, including those with marked dysfunction, showed good hepatic uptake. Mebrofenin scintigraphy is an important imaging technique in the diagnostic evaluation of infants with hyperbilrubinemia. In addition to biliary atresia, intrahepatic cholestasis due to cystic fibrosis and severe neonatal hepatitis may also cause bowel nonvisualization up to 24 hours. The results of this study suggest phenobarbital induction may not be needed when Tc-99m mebrofenin scintigraphy is used for the assessment of infantile jaundice.

Theoretical analysis predicts that respiratory sinus arrhythmia does not accurately measure efferent vagal activity during anesthesia

The respiratory sinus arrhythmia (RSA) is an oscillation of cardiac cycle length (CCL) at the frequency of breathing. RSA is a non-invasive measure of efferent vagal activity, during controlled experimental conditions. Our goal is to assess whether existing theory predicts that RSA amplitude reliably measures efferent vagal activity during and after anesthesia. To do so we combine several existing mathematical models to predict the respiratory sinus arrhythmia. Computer simulation shows that for positive-pressure ventilation without spontaneous breathing efforts, increasing mean arterial pressure causes increase in efferent vagal activity, but not RSA amplitude. Therefore, for positive-pressure ventilation, RSA amplitude does not predict efferent vagal effects on CCL. In contrast, for spontaneous breathing, increasing mean arterial pressure causes increase in both efferent vagal activity and RSA amplitude. Therefore, during spontaneous breathing, RSA amplitude does predict efferent vagal activity. Nevertheless, RSA amplitude also depends on factors that have little effect on efferent vagal activity. For example, RSA amplitude is decreased by increasing respiratory rate or administering acetylcholinesterase and muscarinic antagonists. We conclude that current theory provides little or no justification for using RSA amplitude as a surrogate for efferent vagal activity during anesthesia.

Captopril-enhanced 99Tcm-MAG3 renal scintigraphy in subjects with suspected renovascular hypertension

This pilot study was undertaken to generate preliminary data on the accuracy of captopril-enhanced renal scintigraphy with a relatively new radiopharmaceutical, 99Tcm-mercaptoacetyltriglycine (99Tcm-MAG3) for detecting significant renal artery stenosis. Truth data was based either on arteriographic or outcome criteria (blood pressure response to therapy). Twenty-seven subjects with suspected renovascular hypertension were studied with baseline and captopril-enhanced 99Tcm-MAG3 renal scintigraphy and renal arteriography. Scan interpretations were expressed as a probability of a significant renal artery stenosis. Scan interpretations were compared with renal arteriographic results, renal vein renin levels, blood pressure values after renal artery repair, and blood pressure control after 4-26 months of clinical follow-up. Using > or = 50% luminal obstruction on arteriography as the reference standard for renal artery stenosis and a high probability scan representing a positive test, the test sensitivity and specificity were 33 and 97%, respectively (using high or indeterminate probability to represent a positive scan, the test sensitivity and specificity were 67 and 83%, respectively). The negative predictive value of a low probability scan for renal artery stenosis was 80%. However, including a measure of renovascular hypertension (blood pressure response to renal artery repair) as the reference standard, the accuracy of the scan improves, with the negative predictive value of a low probability scan for renovascular hypertension increasing to 97%. Scintigraphic results were also positively correlated with renal vein renin values in a statistically significant fashion (two-tailed Fisher exact test statistic = 6.43, P = 0.0219). Captopril-enhanced 99Tcm-MAG3 renal scintigraphy is a moderately accurate technique for detecting renal artery stenosis. More importantly, our preliminary findings suggest that the scintigraphic technique using 99Tcm-MAG3 appears to predict the blood pressure response to renal artery repair in subjects with suspected renovascular hypertension, thereby separating subjects with haemodynamically insignificant renal artery stenosis from those with renovascular hypertension.

SPECT quantitation of cobalt-57-bleomycin to predict treatment response and outcome of patients with lung cancer

Our hypothesis is that the concentration of 57Co-bleomycin (Co-bleo) in lung tumors reflects tumor cell kinetics and thus, prognosis. The relationship between the tumor concentration of Co-bleo measured in vivo by quantitative SPECT, response to chemotherapy and survival was investigated.

METHODS

Twenty patients with small-cell lung carcinoma (SCLC) and 49 patients with non-small-cell lung carcinoma (NSCLC) were studied. The concentration of Co-bleo was measured by SPECT in vivo in the tumor. The correlation between Co-bleo concentration in the tumor and the fraction of Co-bleo bound to DNA was investigated in an EMT6 murine tumor model and in samples of eight human tumors.

RESULTS

Tumors that did not respond to treatment showed a significantly higher Co-bleo concentration 8 hr after injection than tumors that responded (5.83% +/- 1.97% ID/cc * 10(-3) versus 2.55% +/- 1.23% ID/cc * 10(-3), p < 0.001). Values of Co-bleo concentration of 2.97% ID/cc * 10(-3) for SCLC and 2.72% ID/cc * 10(-3) for NSCLC were found to best separate patients into short- and long-term survival groups. In the EMT6 murine tumor model, a good correlation was found between the concentration of Co-bleo in the tumor and the fraction of Co-bleo bound to DNA (r = 0.75). In human tumor samples, a good correlation was found between DNA-bound Co-bleo measured in vitro and the concentration measured in vivo by SPECT (r = 0.85).

CONCLUSIONS

SPECT-measured Co-bleo concentration predicts the response to treatment and the outcome in patients with lung tumor by showing Co-bleo binding to DNA and tumor cell kinetics.

Positron emission tomographic measurement of bone marrow blood flow to the pelvis and lumbar vertebrae in young normal adults

Ten young normal adults had pelvic and lumbar vertebral body bone marrow blood flow examined using [15O]water and positron emission tomography (PET) in a study designed to assess the feasibility and reproducibility of the PET technique for measuring marrow blood flow to various marrow regions. The procedure was well tolerated. Repeated blood flow measurements obtained from two consecutive [15O]water exams on each individual subject were highly reproducible. In addition, there was minimal variation in marrow blood flow from individual to individual and no gender differences were noted. In contrast, mean +/- SD bone marrow blood flows (expressed as milliliters per minute per 100 g) at selected anatomical sites were significantly different and were as follows: lower lumbar vertebral bodies, 17.6 +/- 3.1; most posterior and superior pelvis (conventional site of percutaneous bone marrow biopsy), 14.3 +/- 3.1; and total superior pelvis, 11.1 +/- 2.0. We conclude that PET is a relatively noninvasive, simple, and reproducible technique for measuring bone marrow blood flow. Marrow blood flow is consistent between normal young subjects, but varies significantly between different anatomic regions of the marrow.

The safety and pharmacokinetics in adult subjects of an intravenously administered 99mTc-labeled 17 amino acid peptide (CYT-379)

A phase I study was designed to evaluate the safety and pharmacokinetics of a novel platelet reactive peptide, peptide acetyl-SYGRGDVRGDFKCTCCA-amide (CYT-379), which binds to the fibrinogen receptor of activated platelets and also binds to 99mTc. Eleven subjects with suspected deep venous thrombosis had 0.1, 0.5 or 1.0 mg of the peptide infused intravenously. Pharmacokinetics were determined by assaying blood samples in 6 of the 11 subjects and by urine sampling in 5 of these 6 subjects. Plasma and whole blood time-activity curves demonstrated an initial fast component with half-time clearance of 0.2 +/- 0.01 and 0.2 +/- 0.02 h and a slow component with half-time clearance of 2.8 +/- 0.3 and 2.7 +/- 0.2 h (mean +/- SEM for plasma and whole blood, respectively). Urine clearance was 22.6 +/- 3.3 and 10.8 +/- 1.6 mL/min when normalized to body surface area. The cumulative excretion of 99mTc-CYT-379 in the urine was 16.6 +/- 3.6, 45.6 +/- 16.9 and 45.6 +/- 1.8% of the administered dose over 0-2, 0-12 and 0-24 h after radiopharmaceutical injection, respectively. Images obtained in 11 subjects immediately, at 1-2, and 4-6 h after injection were evaluated for abnormalities and were compared with duplex Doppler ultrasonography. 99mTc-CYT-379 images were positive in only 3 of 7 subjects who had a positive duplex Doppler examination in at least one lower extremity. One subject with negative duplex Doppler had also negative 99mTc-CYT-379 scintigraphy. One subject with negative scintigraphy and two other subjects with positive scintigraphy had no other imaging studies of the deep venous system performed. No adverse reactions were observed during or after the infusion of 99mTc-CYT-379. 99mTc-CYT-379 appears to be a safe radiopharmaceutical and demonstrates rapid clearance from plasma in human subjects.

Cardiac function and responsiveness to beta-adrenoceptor agonists in rats with obstructive jaundice

The function and role of the heart and the contribution of cardiac beta-adrenoceptors in the pathogenesis of circulatory failure in obstructive jaundice were studied in the 3-day bile duct-ligated (BDL) rat using three different techniques to measure cardiac function and beta-adrenoceptor activity, number, and affinity. The techniques were the pithed rat preparation, the isolated working heart preparation, and a competitive radioligand binding assay for beta-adrenoceptors. The results of these experiments were compared with those obtained in 3-day bile duct-manipulated (sham operated; SO) rats. Impaired indexes of basal cardiac contractility were observed in the BDL pithed rats and isolated working hearts. In these two preparations, responsiveness to norepinephrine and the beta-adrenoceptor agonists, isoproterenol and dobutamine, was unaffected by bile duct ligation. The affinity and number of cardiac beta-adrenoceptors in membranes from the hearts of SO and BDL rats were not significantly different from each other. These experiments have established for the first time that the 3-day BDL rat has a cardiac myopathy associated with intact responsiveness to beta-adrenoceptor agonists, a normal unchanged affinity and number of cardiac beta-adrenoceptors.

Diuretic-enhanced I-131 clearance after ablation therapy for differentiated thyroid cancer

The authors assessed whether the whole-body radiation burden can be reduced with diuretic enhancement of iodine-131 excretion in patients with thyroid cancer and slow clearance. Whole-body imaging and quantitative I-131 clearance data obtained before and after ablation therapy were evaluated in 56 patients. Fourteen patients with slow pre-ablation therapy clearance (> 50% retention at 24 hours) received oral diuretics after I-131 therapy. Nine patients began taking furosemide 24 hours after I-131 treatment. Five patients had been receiving thiazide diuretics and were continued on the same dose after treatment. The mean half-time of I-131 clearance for the patients treated with furosemide decreased by 12 hours (P < .05) but was not significantly decreased for those who received thiazides or for the patients who did not receive diuretics. Administration of diuretics can improve I-131 clearance in patients with thyroid cancer and slow clearance, reducing the radiation burden and shortening the hospital stay.

Power spectrum analysis and heart rate variability in Stage 4 and REM sleep: evidence for state-specific changes in autonomic dominance

The present study investigated autonomic activity during NREM and REM sleep stages and wakefulness by spectral analysis of heart rate variability. The results demonstrated that NREM sleep in humans was characterized by a widely different autonomic activation pattern than REM sleep: high parasympathetic activity was found in NREM, while REM was characterized by attenuated vagal tone, and augmented sympathetic activity. The overall pattern during wakefulness showed an intermediate position between NREM and REM patterns; parasympathetic activity was lower than in NREM and higher than in REM, with an opposite trend for sympathetic activity.

Intraperitoneal bleeding demonstrated by Tc-99m labeled red blood cell scintigraphy

Tc-99m RBC scintigraphy is known to be useful for the evaluation of gastrointestinal bleeding. The authors describe a patient with a posttraumatic peritoneal tap in whom Tc-99m RBC imaging showed bleeding into the gastrointestinal wall and into the ascitic fluid.

Leukocyte scintigraphy in the diagnosis of mycotic aneurysm

Early diagnosis of a mycotic aneurysm is critical, but often unsuspected, due to the insidious onset of symptoms related to occult infection. This study was undertaken to assess the role of leukocyte scintigraphy in establishing the diagnosis of mycotic aneurysm. The records of all patients with possible mycotic aneurysm between 1985 and 1991 were reviewed. Seven patients had leukocyte scintigraphy and computed tomography (CT), three also had magnetic resonance imaging (MRI) and three had angiography as part of the diagnostic workup. CT and MRI detected aneurysms in five of the seven patients, but CT scans were misinterpreted in two patients as indicative of abscess only. In six patients, infection could not be differentiated from thrombosis, seroma or hemorrhage by CT or MRI. Leukocyte scintigraphy was positive in all four patients with infected aneurysms; it was negative in two of the three noninfected aneurysms and equivocal in the third. Leukocyte scintigraphy provided a useful early survey that demonstrated evidence of infected aneurysms in four patients and identified other sites of infection in two patients. Leukocyte uptake complemented CT, MRI and angiographic findings distinguishing between seroma/hematoma and adjacent infection to establish a preoperative diagnosis of infected aneurysms.

Dynamic properties of cardiovascular systems

A recently derived mathematical model of an isolated heart is extended here to a closed-loop cardiovascular system. Taking the end-diastolic volume as state variable, the authors show that the closed-loop cardiovascular system can be described by a one-dimensional nonlinear discrete dynamical system that depends on parameters describing the systolic and diastolic properties of the heart, heart rate, total peripheral resistance, and arterial capacitance. Studies of this model show that the system possesses a rich spectrum of dynamical behavior, from stable points through stable cycles to a "chaotic" behavior. It is shown that such an analysis of dynamic behavior yields those domains in the parameter space that correspond to a normal and abnormal beating heart, when the heart ejects time-invariant and time-variant (periodic or aperiodic) stable stroke volumes, respectively. Determination of such domains may lead to better understanding of the specific pathologic mechanism involved in the evolution of an abnormal beating heart.

Spectrum of scintigraphic appearance of liver hemangiomas

Two hundred and twenty five liver hemangiomas in 166 patients were studied with Tc-99m labeled RBC and are the basis for this atlas. All hemangiomas showed various presentations of the perfusion blood pool mismatch, which is the basis for diagnosis. The size of the hemangiomas was the factor that determined the mixing of the Tc-99m RBC with the blood and, hence, the sequence of visualization of the lesion. Hemangiomas may appear as multiple lesions on liver scan and imitate metastases. Ninety-five hemangiomas appeared in 36 patients as multiple focal abnormalities. Hemangiomas are extremely variable in size. They may be huge (31 hemangiomas) and sometimes occupy most of the abdomen. Or they can be very small and are then detected only by SPECT (two cases). Thrombosed large hemangiomas appear as focal defects on Tc-99m RBC.

Ga-67 uptake unsuppressed by leukopenia and intense antibiotic therapy

The authors describe a patient with myelofibrosis who showed intense Ga-67 uptake in spite of being severely leukopenic and receiving large amounts of antibiotics. They conclude that false-negative results associated with leukopenia or intensive antibiotic treatment may not always be correct.

Lymphoma: predictive value of Ga-67 scintigraphy after treatment

The negative predictive value (PV-) and positive predictive value (PV+) of gallium-67 scintigraphy and computed tomography (CT) were compared after treatment in 43 patients with Hodgkin disease and in 56 patients with non-Hodgkin lymphoma. The usefulness of these studies in predicting survival was also evaluated. In patients with Hodgkin disease, the PV- of Ga-67 scintigraphy was 0.84 and of CT was 0.88. The PV+ was 0.80 for Ga-67 studies and only 0.29 for CT. In patients with non-Hodgkin lymphoma, the PV- of Ga-67 scintigraphy was 0.84 and of CT was 0.80. The PV+ was 0.73 and 0.35, respectively. For both groups, the differences in disease-free survival between patients with negative and positive Ga-67 studies were significant (P less than .05 in Hodgkin disease and P less than .001 in non-Hodgkin lymphoma), but the differences were not significant for CT. These data show that, after treatment of patients with lymphoma, Ga-67 scintigraphy is a good predictor of clinical outcome and can be used beneficially in patient treatment.

[Adult respiratory distress syndrome complicating acute pyelonephritis in pregnancy]

On the fifth day of a course of antibiotic therapy for acute Klebsiella pyelonephritis, a 21-year-old pregnant woman developed adult respiratory distress syndrome. She improved rapidly on fluid restriction and intravenous furosemide and did not require mechanical ventilation. 17 weeks later, after 40 weeks of pregnancy, she spontaneously delivered a healthy male infant weighing 3280 g.

Stability analysis of one-dimensional dynamical systems applied to an isolated beating heart

In this paper we propose a new model of an isolated beating heart. The model is described by a one-dimensional non-linear discrete dynamical system which depends on several parameters. Applying stability analysis we investigate the dynamic properties of the non-linear system. We find those domains in the parameter space in which the equilibrium point of the system (the fixed point) and the periodic orbits are attractors and in which they are unstable. These domains correspond to a normal and abnormal beating heart, i.e. when the end diastolic volumes are stable time invariant and time variant, respectively. On transition between these domains there is a bifurcation which gives rise to a pair of attracting points of period 2. This case corresponds to the simplest type of period doubling behavior of an abnormal beating heart, called mechanical alternans. Our results provide qualitative and quantitative predictions which can be used for comprehensive experimental design.

Administered dose and tumor dose of bleomycin labeled with cobalt-57 in mice and men

Tumor concentrations of the chemotherapeutic drug, bleomycin, labeled with cobalt-57 (Co-bleo) were compared in mouse tumor models and in human lung tumors using quantitative single-photon emission computed tomography. Drug concentrations in histologically similar human tumors showed marked variability for the same injected dose (ID). Small cell carcinomas showed concentrations between 1.09 and 8.85 %ID/cc x 10(-3) while non-small cell lung tumors showed a concentration variation between 0.36 and 6.75 %ID/cc x 10(-3). In contrast to the situation in human tumors, uptake in mouse tumors showed only slight variability in animals with the same tumor model. EMT-6 tumors in mice showed at 6 hr significantly higher uptake of Co-bleo (p less than 0.001) and significantly higher tumor-to-lung ratio (p less than 0.001) when compared to murine fibrosarcomas. The EMT-6 tumors in contrast to the fibrosarcomas responded to bleomycin treatment in a dose dependent manner. The results indicate that while in mice the tumor dose closely follows the administered dose, in humans, the tumor dose and the tumor-to-lung ratio in the individual patient cannot be predicted from the administered dose.

Late Potentials and Ventricular Arrhythmias

A computerized method, signal-averaged electrocardiography, analyzes standard electrocardiography recordings, thereby identifying particular microvolt-level signals, called "late potentials". Correlated with clinical ventricular tachycardia, these data are predictive of ventricular tachycardia inducibility and arrhythmic events after myocardial infarction.

Normal and abnormal Ga-67 SPECT anatomy in patients with lymphoma

The appearance of normal Ga-67 SPECT images in the coronal, sagittal and transaxial planes is described. The normal tomographic appearance of bone, liver, spleen, and gut is shown and compared with disease involvement above and below the diaphragm.

Residual mass and negative gallium scintigraphy in treated lymphoma

Two patients with treated lymphoma demonstrated a residual mass on CT following treatment. In both cases gallium-67 (67Ga) scintigraphy demonstrated increased uptake in the original tumor mass and no uptake in the mass after treatment. In both cases the entire residual tumor mass was resected and found to contain no cancer tissue. This is further evidence of the role 67Ga scintigraphy may play in monitoring response of lymphoma patients to treatment. In contrast, other imaging modalities such as ultrasound, plain film x-rays, or CT only show the presence of a mass but not its nature.

The concentration of bleomycin labeled with Co-57 in primary and metastatic tumors

The concentration over time of bleomycin labeled with Co-57 was measured in 39 primary and metastatic tumor sites in 16 patients using a newly developed and validated single photon emission computed tomography (SPECT) method. There were nine primary tumors, 15 metastatic tumors, and five multifocal lymphomas. Co-bleomycin concentrations also were measured in primary and metastatic B-16 melanoma tumors in mice. In humans, metastases to lymph nodes (1.58 +/- 0.51 %ID/ml X minutes) showed significantly higher (P less than 0.01) tumor cumulative concentrations of Co-bleomycin than metastases to liver, bone, lung, and brain (0.76 +/- 0.20 %ID/ml X minutes). The cumulative concentrations of Co-bleomycin in human lymphomas (1.1 +/- 0.25 %ID/ml X minutes) also were significantly higher (P less than 0.01) than the concentrations in human metastases other than lymph nodes. The cumulative concentration in cerebral metastases (0.65 +/- 0.18 %ID/ml X minutes) was significantly lower (P less than 0.05) than in noncerebral metastases (1.22 +/- 0.53 %ID/ml X minutes). Primary tumors in humans showed higher concentrations of Co-bleomycin than metastases, except for lymph nodes. In contrast with humans, murine metastases showed higher concentrations of Co-bleomycin (6.20 +/- 2.65 %ID/g) than primary tumors (2.94 +/- 0.90 %ID/g) (P less than 0.001). The concentrations of Co-bleomycin in murine tumors that were affected by bleomycin were about three orders of magnitude higher than in human tumors. The results of this in vivo study document the differences in drug delivery of Co-57-labeled bleomycin to human primary and metastatic tumors and show differences in drug delivery between human and murine tumors.

A practical SPECT technique for quantitation of drug delivery to human tumors and organ absorbed radiation dose

A practical quantitative single photon emission computed tomographic (SPECT) technique based on an empirical threshold analysis permits accurate measurements in humans of drug delivery and absorbed radiation dose. The limits of the method have been explored using a wide range of phantom volumes, concentrations, and target-to-nontarget ratios. A threshold of 43% was found to give the best results using volumes of 30 to 3,800 cc. An excellent correlation (r = .99 with a standard error of estimate [SEE] of 41 cc) was found between SPECT measured volumes and actual phantom volumes. A similarly high correlation (r = .98, SEE = 260 counts/voxel) was found in 77 measurements of concentrations between 0.01 and 3.6 microCi/cc. There was a direct relationship between the target-to-nontarget ratio of phantoms and the accuracy of volume measurements. The technique has been validated by an excellent in vivo/in vitro correlation of uptake in human tumors. The tumor cumulative concentration and tumor-to-blood ratio were used for assessment of drug delivery. In vivo quantitative measurements of the pharmacokinetics of technetium-99m (99mTc) glucoheptonate, cobalt-57 (57Co) bleomycin and platinum-195m (195mPt) cisplatin in human tumors in vivo indicates that, in contrast with tumor models in animals, there is a marked variability in drug delivery even in tumors with the same histology. Future development of labeled drugs should make it possible to use quantitative SPECT for predicting tumor response to therapy and for tailoring chemotherapy for the individual patient under treatment. SPECT quantitation of organ concentration was used for Medical Internal Radiation Dose committee (MIRD) calculations of organ absorbed radiation dose from 99mTc-labeled RBCs. Excellent in vivo/in vitro correlations were obtained between SPECT measured concentrations of blood radioactivity in the heart and in vitro measurements of blood samples. The possibilities and limitations of this technique are discussed and its use for in vivo measurement in humans of absorbed radiation dose from radiopharmaceuticals is suggested.

Gallium 67 imaging in monitoring lymphoma response to treatment

The value of gallium 67 (Ga) imaging in monitoring lymphoma response to treatment was assessed in 25 patients with Ga-avid tumors and compared to body computed tomography (CT), chest radiographs, and palpation of tumor infiltrated peripheral lymph nodes. Ga imaging was negative in 95% (20/21) of the patients who were clinically considered to be in remission and in whom treatment was stopped. The disease did not recur during a follow-up of 12 to 26 months in 15 patients. Six patients developed recurrence of the disease 3 to 12 months after treatment was stopped. In all six patients Ga imaging became positive again at the time of the appearance of active disease. In the group of patients in remission, CT was negative in 57% (11/19), chest x-rays in 55% (6/11) and peripheral lymph nodes were palpated in none of the patients (13/13). In four patients that did not achieve remission after treatment, Ga scans were positive. Ga imaging appears useful in monitoring lymphoma response to treatment. This is probably because Ga imaging monitors tumor cell viability, whereas body CT and chest radiographs show the tumor mass, which may consist of fibrotic or necrotic tissue.