Thallium-201 brain SPECT of lymphoma in AIDS patients: pitfalls and technique optimization.

PURPOSE: Our aim was to examine the 201Tl-SPECT scans in AIDS patients with focal CNS lesions to identify those studies with a false-positive or false-negative result to determine any potential pitfalls in interpretation as well as to suggest methods for technique optimization. METHODS: We retrospectively reviewed the charts of 162 AIDS patients with cerebral mass lesions on 201Tl-SPECT studies. One hundred sixty-one patients had CT examinations, of which 50 also had MR studies. One patient had MR imaging without CT. Those patients in whom the diagnosis by 201Tl-SPECT did not correspond with the known pathologic or clinically proved diagnosis were then singled out and their CT, MR, and 201Tl-SPECT studies were reviewed, including blinded interpretation of the 201Tl-SPECT scans alone and alongside the corresponding CT and MR examinations. Studies were examined for lesion morphology, size, location, enhancement pattern, and presence of necrosis. The review of the 201Tl-SPECT studies included both a qualitative approach (subjective analysis of the scans for areas of abnormally increased uptake) and a quantitative approach (comparison of lesion activity versus activity within a reference standard, such as the scalp). RESULTS: Sensitivity and specificity of 201Tl-SPECT in depicting lymphoma were 100% and 93%, respectively, based on the initial qualitative analysis. Fifty-one patients had positive 201Tl-SPECT results, of whom 43 were determined to have lymphoma (four by biopsy/autopsy, 39 by clinical and radiologic findings). Upon reevaluation with both a quantitative and qualitative approach, those studies initially interpreted as positive in patients without lymphoma (false positives) were found to be negative. CONCLUSION: Brain 201Tl-SPECT is an effective study in the diagnosis of CNS lymphoma in AIDS patients. Specificity can be increased by routinely performing a quantitative analysis of all lesions.

Nuclear medicine applications to the neuroimaging of AIDS. A neuroradiologist's perspective.

The human immunodeficiency virus (HIV) responsible for AIDS is reaching epidemic proportions in the United States and Europe. As new therapeutic modalities against HIV are uncovered and applied to treat prophylactically asymptomatic and therapeutically symptomatic HIV positive patients, imaging studies are no longer used just to characterize the organic-morphologic effects of HIV and opportunistic infections and neoplasms. This article discusses the current applications and contribution of nuclear medicine to the management of neurologically symptomatic HIV-positive patients.

Primary central nervous system lymphoma in patients with AIDS.

Primary central nervous system lymphoma (PCNSL), once considered a rare brain neoplasm, has been steadily increasing in incidence mainly due to an enlarging population of immunosuppressed patients. PCNSL has become the second most common brain space occupying lesion in patients with the acquired immunodeficiency syndrome. A rapid diagnosis of this entity may represent weeks to months of survival to immunosuppressed HIV-positive patients. The radiologist now plays an important role in the noninvasive diagnosis and management of this condition through the accurate interpretation of imaging findings provided by CT, MR, and brain SPECT studies. This article focuses on the pathogenesis, clinical manifestations, neuropathology, and imaging characteristics of this brain neoplasm. New accurate imaging algorithms combining the diagnostic information provided by CT, MR, and T1-201 brain SPECT are discussed.

Review of tests for monitoring doxorubicin-induced cardiomyopathy.

The objective of this review is to make physicians aware of new radionuclide methods to detect cardiac effects of chemotherapeutic drugs. This knowledge is important because of the limitations of the physical examination and the electrocardiogram for detecting early reversible cardiac damage. Presently left ventricular ejection fraction (LVEF) is routinely used to screen for cardiotoxicity. Since LVEF obtained by radionuclide angiocardiography is more accurate than the LVEF estimated by echocardiography, serial radionuclide LVEF monitoring is most commonly used to monitor cardiotoxicity. Diastolic measurements of left ventricular function (such as peak filling rate) are now being added to routine LVEF measurements to enhance standard radionuclide evaluation. This screening test should be done prior to beginning therapy and at appropriate points based on the baseline study, therapy scheme and the patient's clinical status. At some centers, exercise LVEF methods are being used to determine if cardiac reserve is adequate for the patient to tolerate additional chemotherapy when cardiac injury may be present. Previously, endomyocardial biopsy was needed to detect and confirm early anthracycline cardiotoxicity. This invasive test may be replaced by a new noninvasive in vivo method using radioactive monoclonal antibodies against cardiac muscle (indium-111-antimyosin). Because cardiac failure has been associated with adrenergic neuron injury, it has been proposed that radioactive methyliodobenzylguanine may detect the adrenergic abnormality which may predict future development of congestive heart failure or sudden death months after therapy is discontinued. Advantages and disadvantages of these methods in evaluating cardiotoxicity, and an algorithm to optimally monitor antitumor therapy-induced cardiomyopathy are discussed.

Reduction of neutrophil margination by L-arginine during hypothermic cardiopulmonary bypass in a pig model.

Nitric oxide generation by L-arginine (2 mg/kg/min) infusion during cardiopulmonary bypass (CPB) increases blood flow to all organs and reduces cytokine induced organ damage by reducing the level of marginating neutrophils (Ns). The N-trapping in the oxygenator (OX), arterial filter (AF), cardiotomy reservoir (CR), and N-margination were quantified with indium 111 labeled autologous neutrophils (INN) in nine groups of 40 Yorkshire pigs (30-35 kg). Cardiopulmonary bypass (180 min or 90 min CPB, 90 min reperfusion) was carried out at 2.5-3.5 L/min and at two temperatures (18 degrees C, 28 degrees C). The INN (650-780 microCi) was administered intravenously 15 mins before CPB. All pigs received heparin systemically (activated coagulation time > 400 secs); CPB was instituted with a roller pump, OX (Univox 1.8 m2), AF (0.25 m2), and CR (BCR-3500, Bentley Lab, Irvine, CA). The INN distribution in the device (OX, AF, CR) and organs was imaged with a gamma camera and measured with an ion chamber and a gamma counter. The LA infusion decreased N-trapping, estimated as the percent of injected INN (mean +/- standard deviation), in OX from control (2.7 +/- 2.02)% to (0.94 +/- 0.29)%, and margination in lung from control (48 +/- 4)% to minimal levels (23 +/- 2)% (p < 0.01). In the CPB reperfusion group, a beneficial effect was observed at LA low dose and toxicity of higher N-margination at 15 mg/ kg/min. Neither CPB temperature nor Leumedin affected N-margination significantly.

Role of nuclear medicine and AIDS: overview and perspective for the future.

The Human Immunodeficiency Virus (HIV) is the causative agent for the expanding epidemic of the Acquired Immunodeficiency Syndrome (AIDS). Sixteen million individuals were estimated to be infected worldwide with HIV by the World Health Organization in 1995, with over 10 million in Africa and one million in the USA. As the HIV cost in dollars and lives continues to rise it will become more important to understand AIDS and to foresee the potential role of nuclear medicine in HIV diseases. Nuclear medicine may have a role in the assessment of immune function, including the ability to predict if individuals can avoid progression to HIV+status, if pre-AIDS to AIDS conversion can be prevented, and if an individual's immune status requires addition of prophylaxis. Also it can be used for disease detection at an early stage and determination of the extent of disease. It is especially useful to assist clinicians in optimizing therapy and assessing its efficacy. In the future new radiopharmaceuticals for detecting a specific infections and tumors will be needed. This will require collaborative efforts with basic scientists and clinicians working hand in hand to address specific issues related to AIDS.

Inflammatory and infectious processes of the cervical spine.

This article discusses infectious and inflammatory processes of the cervical spine. Major emphasis is placed on infectious discitis/osteomyelitis and epidural abscess, particularly the epidemiologic, bacteriologic, pathophysiologic, and clinical aspects, as well as the major role played by magnetic resonance imaging and other imaging modalities used in the detection and diagnosis of these processes.

Use of thallium-201 brain SPECT to differentiate cerebral lymphoma from toxoplasma encephalitis in AIDS patients.

PURPOSE: To determine whether thallium-201 brain single-photon emission CT could be used to make the distinction between central nervous system lymphoma and toxoplasma encephalitis, which may not be possible by routine MR and CT. METHODS: A total of 37 patients with acquired immunodeficiency syndrome who had intracranial mass lesions found during a 9-month prospective study by either MR or CT underwent further evaluation with Tl-201 brain single-photon emission CT. RESULTS: Twelve patients had increased intense focal Tl-201 uptake. All of these patients had either biopsy- or autopsy-proven lymphoma. Twenty-five of the patients studied had no Tl-201 brain uptake in the lesion(s); 24 of these patients had toxoplasma encephalitis on clinical follow-up. One patient with no Tl-201 uptake was found by cerebrospinal fluid analysis to have mycobacterium tuberculosis abscess. CONCLUSION: Patients with acquired immunodeficiency syndrome who have intracranial mass lesions on MR or CT may benefit from Tl-201 brain single-photon emission CT because it can help distinguish between lymphoma and infectious lesions such as toxoplasma encephalitis.

Detection of early anthracycline cardiotoxicity by monitoring the peak filling rate.

Three patients developed clinical congestive heart failure after cumulative doxorubicin doses of 264, 440, and 450 mg/m2, respectively, despite serial monitoring of systolic cardiac function by resting gated radionuclide scanning. All three patients had depressed diastolic function, as shown by a decreased peak filling rate preceding a change in systolic function, which was assessed by left ventricular ejection fraction prior to the development of clinical congestive heart failure. We recommend serial monitoring of the peak filling rate, in addition to left ventricular ejection fraction. If broader experience confirms our impression that the peak filling rate is more sensitive than the current standard assessment of left ventricular ejection fraction, new guidelines may need to be drawn to monitor cardiotoxicity of anthracyclines and anthraquinones.

Indium 111-labeled leukocyte scintigraphy in evaluating head and neck infections.

This retrospective study looked at the role of indium 111-labeled white blood cell (111In WBC) scintigraphy in head and neck infections. The efficacy of 111In WBCs was compared to gallium 67 citrate (67Ga) and technetium Tc99m methylene diphosphonate (99mTc MDP) scintigraphy in detecting and monitoring the resolution of infection. For 22 active infections, the sensitivities for 111In WBC, 67Ga, and 99mTc MDP scintigraphy were 94%, 56%, and 86%, respectively, and the specificities for 111In WBC, 67Ga, and 99mTc MDP scintigraphy were 100%, 43%, and 0%, respectively. For 8 successfully treated infections, all seven 111In WBC studies became negative after therapy, in as short an interval as 1 month. In contrast, all seven 99mTc MDP images remained positive for as long as 6 months after therapy. The seven 67Ga studies had variable results, with four (57%) remaining positive, including two (28%) positive at 6 months after therapy. These results suggest that 111In WBC scintigraphy should be the initial radionuclide imaging tool in detecting active head and neck infections because of its greater accuracy, and its ability to revert to normal much sooner than 67Ga or 99mTc MDP scintigraphs when applied to a subset of patients with resolved infections.

Clinical comparison of technetium-99m-teboroxime and thallium-201 utilizing a continuous SPECT imaging protocol.

To examine the advantages of a 99mTc-labeled cardiac perfusion agent, teboroxime or SQ30,217 (Squibb Diagnostics), a prospective study was undertaken comparing it to 201Tl stress testing in 17 patients suspected or known of having coronary artery disease (CAD). All patients were studied utilizing a single-detector SPECT camera with a continuous acquisition imaging protocol. Testing was performed on a treadmill to comparable levels with both agents within a 2-wk period. Concordance between the two studies on a patient by patient basis was seen in 16/17 (94%) patients, and discordance was seen in 1/17 (6%) patients. Comparison of findings between 201Tl and 99mTc-teboroxime on a segment by segment basis showed concordance in 107/119 (90%) segments, and 12/119 (10%) were discordant. Both examinations independently detected an equal number of normal (77) and abnormal (42) segments. There was no significant difference between the two agents in classifying lesions as ischemic, although there were significant differences between thallium and teboroxime in classifying infarct and infarct/ischemia. Technetium-99m-teboroxime SPECT imaging is a clinically useful method for detecting CAD, with a major advantage being the shorter examination time per individual patient study. The mean total examination time for completion of the 99mTc-teboroxime study was 2.5 hr versus 4.0 hr for 201Tl.

Diagnostic uses of nuclear medicine in AIDS.

Radionuclide imaging, if applied with an organ system approach, is useful in the diagnosis of the AIDS (acquired immunodeficiency syndrome)-related complex. Specific pathologic processes can be suspected on the basis of uptake patterns. The intensity and pattern of pulmonary uptake and concomitant nonpulmonary uptake of gallium provide guidelines for distinguishing among various opportunistic pulmonary pathogens. Gastrointestinal and extra-gastrointestinal tract uptake of gallium aids distinction among fungal, mycobacterial, and viral infections and neoplasms. Patterns of spleen uptake of technetium-99m sulfur colloid and gallium allow differentiation between neoplasm (Kaposi sarcoma) and infection (with mycobacteria). Skeletal and soft-tissue abnormalities can be characterized and differentiated on the basis of bone scan and other radionuclide scan findings. Thallium uptake in brain tumors (and not in areas of infection) allows brain lesion discrimination. In the proper clinical setting, AIDS nephropathy has a characteristic gallium uptake pattern. Cardiac abnormalities (including functional) can also be assessed with scintigraphy. With knowledge of these organ-specific patterns and with correlative imaging studies, the manifestations of AIDS can be differentiated and appropriate treatment instituted.

Technetium-99m-labeled platelets: comparison of labeling with a new lipid-soluble Sn(II)-mercaptopyridine-N-oxide and 99mTc-HMPAO.

Platelets pretinned with a neutral Sn(II)-2-mercaptopyridine-N-oxide (SN-MPO) were labeled with 99mTc and compared to those labeled with 99mTc-HMPAO. The conditions of labeling platelets, e.g. concentrations of platelets and Sn(II)-MPO, 99mTc in ACD-saline or ACD-plasma media, pH and incubation time, were optimized using canine platelets. Moderate labeling efficiency was obtained with 20 micrograms of tin(II) chloride and 30 min incubation with Sn-MPO and pertechnetate. The viability of labeled platelets was determined by platelet recovery and platelet survival times in Beagle dogs. The labeling efficiency with platelets from 43 mL of blood was 62.8 +/- 7.6%. The platelet recovery was 35.7 +/- 5.0% and exponential survival time was 34.6 +/- 3.1 h compared to 43.3 +2- 12.0% and 29.5 +/- 3.3 h for 99mTc-HMPAO-labeled platelets. These values were significantly (P less than 0.01) lower than 111In-labeled platelets. Biodistribution in dogs indicates lower retention in blood, spleen and liver after some initial 99mTc excretion in urine. The platelet deposition with 99mTc platelets (Sn-MPO method) on polyurethane angio-catheters was similar to 99mTc-HMPAO-labeled platelets. This study indicates that the platelets could be successfully labeled with pertechnetate in a cost-effective manner for the evaluation of thromboembolic complications.

The diagnostic role of nuclear medicine in the acquired immunodeficiency syndrome.

This paper is a review of (a) the pathophysiology of the autoimmune deficiency syndrome (AIDS), and (b) the diagnostic procedures nuclear medicine has to evaluate human immunodeficiency virus related disorders. This article is organized in an organ system approach to AIDS pathology. The application of [67Ga]citrate, 111In-labeled white blood cells, [201Tl]chloride, single photon emission computed tomographic, and positron emission tomographic brain agents, [99mTc]sulfur colloid and [99mTc]methylene diphosphonate to the pulmonary, nervous, gastrointestinal, dermatologic, musculoskeletal, and renal systems is discussed. These radioisotopes allow earlier diagnosis than routine radiographic studies, and can monitor the effect of therapy on disease activity. In this review an attempt is made to provide clinically useful algorithms to suggest a specific pathogen based on the pattern of radionuclidic uptake.

Magnetic resonance imaging of the normal and ischemic femoral head.

The femoral heads of 38 normal and 20 abnormal patients were evaluated using magnetic resonance imaging (MRI). The normal femoral head is surrounded by a thin, sharply defined, low-intensity cortex. The medullary cavity has a strong signal intensity in all imaging sequences due to the large content of marrow fat and hematopoietic cells. Crossing the high-intensity marrow is a thin, curvilinear, transverse, low-intensity line representing the physis and a broad, vertically oriented, low-intensity band resulting from the prominent central weight-bearing trabeculae. Anatomic structures can be identified on all scanning sequences if the examinations are technically satisfactory, although images with the best clarity and detail are obtained by using short echo times. MRI of patients with ischemic necrosis revealed areas of low intensity in the femoral heads. The abnormal areas may take the form of homogeneous regions of decreased signal intensity, inhomogeneous areas of low intensity, bands of low intensity, or rings of low intensity with higher signal intensity centrally. No correlation was found among the specific MRI patterns, the stage of the disease, the radiographic appearance, or the radionuclide bone scan findings. MRI was abnormal in all cases where the radiographs or the scintigraphs (or both) were abnormal. MRI also was abnormal in several cases where either radiographs or scintigraphs produced false-negative results.