Direct in vivo evidence of activated macrophages in human osteoarthritis.

OBJECTIVE: Through binding to folate receptor-ß (FR-ß), the new (99m)Tc-EC20 (Etarfolatide) imaging technique detects activated but not resting macrophages in vivo. The goal of this study was to investigate macrophage-related inflammation in osteoarthritis (OA). METHODS: Twenty-five individuals (50 knees) with symptomatic OA of at least one knee underwent SPECT-CT imaging of both knees and planar imaging of the whole body after injection of Etarfolatide. Scans and knee radiographs were scored blinded to clinical information including knee and other joint site pain severity. Measures of association controlled for age, gender, body mass index (BMI) and employed repeated measures to adjust for correlation between knees. DESIGN: Activated macrophages were present in the majority (76%) of knees. The quantity of knee-related macrophages was significantly associated with knee pain severity (R = 0.60, P < 0.0001) and radiographic knee OA severity including joint space narrowing (R = 0.68, P = 0.007), and osteophyte (R = 0.66, P = 0.001). Macrophages were also localized to joints commonly affected by OA including hand finger joints (12%), thumb bases (28%), shoulders (26%), great toes (18%) and ankles (12%). The presence of joint pain at fingers, wrists, ankles and great toes was significantly positively associated with presence of activated macrophages at these sites (P < 0.0001-0.04). CONCLUSIONS: This study provides the first direct in vivo evidence for macrophage involvement in OA in a substantial proportion of human knees. The association of quantity of activated macrophages with radiographic knee OA severity and joint symptoms suggests that drugs targeting macrophages and macrophage-associated inflammatory pathways may have the potential to be both symptom and structure modifying.

Comparison of technetium-99m sestamibi and thallium-201 retention characteristics in canine myocardium.

OBJECTIVES: The aim of this study was to compare the myocardial retention of technetium-99m (Tc-99m) sestamibi and thallium-201 over a wide range of blood flow at different time points after tracer injection. BACKGROUND: Technetium-99m sestamibi has been proposed as a new perfusion tracer with better physical characteristics than those of thallium-201 for scintigraphic imaging. However, no studies have simultaneously compared the ability of both tracers to assess myocardial blood flow during pharmacologic vasodilation. METHODS: The myocardial retention of Tc-99m sestamibi and thallium-201 were compared over a wide range of blood flow induced by regional coronary occlusion and dipyridamole infusion in an open chest dog model. Myocardial retention of both tracers was determined by in vitro tissue counting at 2, 5, and 20 min after tracer injection and was correlated with microsphere-determined blood flow. RESULTS: Thallium-201 demonstrated greater absolute tissue retention than did Tc-99m sestamibi. At 2 min after tracer injection, there was an almost linear relation between the retention of both tracers and myocardial blood flow over a wide flow range. However, this relation was not maintained over time. At 20 min after injection, the retention of both tracers underestimated myocardial blood flow at higher flow rates. At 2, 5 and 20 min after injection, increments of relative tracer retention between the different levels of flow were always greater for thallium-201 than for Tc-99m sestamibi. CONCLUSIONS: Thallium-201 displays more suitable physiologic characteristics as a flow tracer and may allow better differentiation of myocardial regions with different levels of coronary flow reserve. For both tracers, early cardiac imaging may minimize underestimation of blood flow at higher flow rates.

Blood flow imaging of a posterior circulation stroke. Use of technetium Tc 99m hexamethylpropyleneamine oxime and single photon emission computed tomography.

Regional cerebellar perfusion was imaged using technetium Tc 99m hexamethylpropylene amine oxime and single photon emission computed tomography (HM-PAO-SPECT) in a patient with chronic left lateral medullary syndrome with contralateral weakness due to traumatically induced thrombosis of the left vertebral artery. Despite continued neurologic deficits, x-ray transmission computed tomography was normal. However, HM-PAO-SPECT demonstrated that blood flow to the left cerebellar hemisphere was significantly impaired. This abnormality was still apparent after correction for atrophy as estimated by magnetic resonance imaging. Technetium Tc 99m hexamethyl-propyleneamine oxime and single photon emission computed tomography effectively imaged regional blood flow in the vertebrobasilar circulation and appears to more clearly reflect the nature and extent of the neurologic deficit than either x-ray transmission computed tomography or magnetic resonance scanning.

Metastatic angiosarcoma with thrombocytopenia and intratumoral indium-111-platelet deposition.

A 66-yr-old woman with cutaneous angiosarcoma of the face presented with thrombocytopenia and metastases to the skeleton. Scintigraphic imaging with 111In-oxine-labeled autologous platelets demonstrated localization of radiolabeled platelets at sites of metastatic tumor. This imaging study suggests intratumoral destruction of platelets by the metastases of the malignant vascular tumor as the cause of the patient's thrombocytopenia.

Prognostication of recovery following stroke using the comparison of CT and technetium-99m HM-PAO SPECT.

This study investigated the possibility that a relationship between the anatomic defects observed on computed tomography (CT) and the functional defects observed on single photon emission computed tomography (SPECT) might be used as an outcome measure to predict clinical recovery from the neurologic deficits induced by stroke. Twenty-seven patients with stroke location limited primarily to cerebral cortex were included in the study: each patient underwent a cranial CT scan, 99mTc hexamethylpropyleneamineoxime SPECT cerebral perfusion scan, and an initial and 1-yr follow-up neurologic examination. A strongly positive correlation between the ratio of the SPECT to CT volume defect sizes (SPECT divided by CT) and recovery following stroke was found, such that the greater the SPECT to CT ratio, the better the subsequent recovery of neurological deficits. Discriminant function analysis revealed that the best predictor of clinical outcome following stroke was the log-transformation of SPECT divided by CT. The results suggest that the relationship between the perfusion defects and tissue loss measured by SPECT and CT imaging may have prognostic utility following stroke limited primarily to cerebral cortex.

Diagnostic accuracy and pitfalls of [iodine-131]6-beta-iodomethyl-19-norcholesterol (NP-59) imaging.

NP-59 concentrates in steroid hormone synthesizing tissues, enabling scintigraphic localization and characterization of endocrine dysfunction in the adrenal cortex and ovary. Studying 108 consecutive cases from 1982 to 1985 and using clinical, biochemical, radiographic, and pathologic data, we performed a rigorous assessment of the accuracy and pitfalls of NP-59 scintigraphy. The evaluation was divided into categories of abnormal hormone secretion: Cushing's syndrome, primary aldosteronism, and hyperandrogenism. Additional categories included euadrenal tumors (without detectable hormone dysfunction) and sites of residual adrenal cortical tissue. The accuracy of NP-59 scintigraphy ranged from 71% in primary aldosteronism and 75% in euadrenal tumors, to 100% for Cushing's syndrome and hyperandrogenism. However, more than in most nuclear medicine studies, NP-59 imaging requires well-defined indications to be met for it to be efficacious, including the fulfillment of clear clinical, biochemical, and radiographic criteria. The high reproducibility of NP-59 scintigraphic interpretation was demonstrated when 40 random cases underwent interinstitutional exchange and through interobserver evaluation at the University of Michigan. Responses of 85/126 medical centers to questionnaires revealed the high level of NP-59 safety.

Myocardial clearance kinetics of technetium-99m-SQ30217: a marker of regional myocardial blood flow.

SQ30217 is a new, technetium-99m-(99mTc) labeled perfusion agent introduced for cardiac imaging. To evaluate the myocardial tracer kinetics, 99mTc-SQ30217, was injected intracoronarily in open-chested dogs under baseline conditions and after administration of intravenous (i.v.) dipyridamole. Myocardial first-pass retention fraction averaged 0.90 +/- 0.04. Clearance of the tracer occurred in a biexponential manner. Sixty-seven percent of retained activity cleared with a half-time of 2.3 +/- 0.6 min, while the residual activity demonstrated slow clearance. The clearance rate of the rapid phase correlated with myocardial blood flow (r = 0.72, p less than 0.001). Myocardial SQ30217 clearance rate following i.v. injection as determined by dynamic imaging with tomography (SPRINT) averaged 21 +/- 4 min and increased to 13 +/- 4 min following dipyridamole. Thus, 99mTc-SQ30217 is a promising flow tracer with high initial myocardial retention and rapid tissue clearance, which allow repeated flow determinations within short time intervals using advanced SPECT technology.

Determination of extent and location of coronary artery disease in patients without prior myocardial infarction by thallium-201 tomography with pharmacologic stress.

Seventy-six patients undergoing pharmacologic stress 201TI tomography and coronary angiography within 14 +/- 12 days were studied to determine how well coronary artery disease extent and location could be determined by this scintigraphic technique. No patient had prior myocardial infarction or revascularization. Scintigrams were scored visually and quantitatively. Angiographic lesions > or = 50% were considered significant. Receiver operating characteristic curves were generated for the scintigrams against the angiographic gold standard. Predictive accuracies were determined and compared with the quantitative results. Predictive accuracy was 0.49 for visual and 0.58 for computer identification of single-vessel disease, 0.52 for both visual and computer identification of multivessel disease, 0.64 for both in correctly localizing left anterior descending artery disease, 0.78 versus 0.70 for the right coronary artery and 0.72 versus 0.68 for the left circumflex artery. For the overall detection of disease, the predictive accuracies were 0.79 and 0.80. Although high diagnostic accuracy for detection of coronary artery disease by this approach has been previously documented, the assessment of extent of disease in patients without prior myocardial infarction appears limited.

Iodine-123-4-amino-3-iodobenzylguanidine, a new sympathoadrenal imaging agent: comparison with iodine-123 metaiodobenzylguanidine.

Iodine-123-4-amino-3-iodobenzylguanidine ([123I]AIBG), an analog of 123I metaiodobenzylguanidine ([123I]MIBG), has an advantage in having a more rapid and simple synthesis. This, combined with animal data that suggested a greater affinity of the new radiopharmaceutical for the autonomic innervation of the myocardium led us to study the biodistribution of [123I]AIBG in three men with metastatic pheochromocytoma. In all instances, [123I]AIBG revealed the same metastatic deposits shown by [123I]MIBG. Iodine-123 AIBG uptake, however, was greater than [123I]MIBG in lung, gut, and spleen. These higher backgrounds may pose diagnostic problems in some cases.

Synthesis, rodent biodistribution, dosimetry, metabolism, and monkey images of carbon-11-labeled (+)-2 alpha-tropanyl benzilate: a central muscarinic receptor imaging agent.

Muscarinic cholinergic receptors (mAChR) are abundant in the brain, and the mAChR system mediates many aspects of brain function. There is evidence of alterations in muscarinic binding in degenerative brain disorders. A muscarinic receptor radioligand, carbon-11-(+)-2 alpha-tropanyl benzilate ([11C]TRB), has been prepared through N-[11C]methylation of N-desmethyl TRB, and evaluated in rodents and primates. Full body biodistribution in rats has been determined and the expected human dosimetry calculated. Comparisons with [11C]scopolamine in rats showed 2-6 times greater brain uptake of [11C] TRB. Highly specific and saturable binding of [11C]TRB in the striatum and cortex was demonstrated by greater than 85% blockade of uptake following QNB or scopolamine pretreatment. Striatum/cerebellum ratios in mice at 60 min exceeded 12.6. TLC analysis of rat tissues showed the absence of 11C-metabolites in brain and heart, and a rapid solid phase C-18 Sep-Pak method found that unmetabolized plasma [11C]TRB in monkeys fell from 81% at 5 min to 48% at 80 min. Finally, brains of living primates have been imaged using PET and [11C]TRB; regional localization was consistent with muscarinic receptor distribution. These results represent intermediate steps in the development of [11C]TRB for quantification of central muscarinic receptors in man.

Technetium-99m-N1-(2-mercapto-2-methylpropyl)-N2-(2-propargylthio-2- methylpropyl)-1,2-benzenediamine (T691): preclinical studies of a potential new tracer of regional cerebral perfusion.

We report in vitro and in vivo preclinical studies of a new cerebral blood flow tracer, [99mTc]N1-(2-mercapto-2-methyl-propyl)-N2-(2- propargylthio-2-methylpropyl)-1,2-benzenediamine (T691). The tracer demonstrates excellent in vitro chemical stability and accumulates regionally in the brain in a pattern consistent with that of cerebral blood flow. First-pass cerebral extraction determined with the use of the brain uptake index method in the rat was 0.76. Bolus intracarotid injection in monkeys indicated a cerebral extraction of 68% and prolonged retention of 67% of the initially extracted activity. Autoradiographic studies in rats revealed a pattern characteristic of cerebral blood flow at both 1 and 60 min after systemic injection. Dynamic tomographic imaging following systemic injection in the monkey revealed peak brain activity 1 to 2 min postinjection, without significant decline over 60 min. Chromatographic studies of brain as long as 60 min following systemic injection of [99mTc]T691 showed no evidence of tracer metabolism to account for its retention. Overall, [99mTc]T691 demonstrates promise as a potential new clinical tracer of cerebral perfusion.

Treatment of established prosthetic vascular graft infection with antibiotics preferentially concentrated in leukocytes.

The efficacy of treating established vascular graft infections with rifampin and clindamycin (preferentially concentrated in leukocytes) and cefazolin (not concentrated in leukocytes) was studied in a canine model. Infrarenal aortic, 6 mm by 6 cm knitted Dacron double velour grafts were implanted and infected with 10(8) colony-forming units (CFU) of coagulase-positive Staphyloccus aureus organisms injected intravenously immediately after graft placement. Antibiotic therapy was instituted at 3 months postimplantation. Three groups were studied: (I) untreated controls (n = 3); (II) therapy with intravenous cefazolin 15 mg/kg/8 hr for 28 days (n = 7); and (III) combined therapy with intravenous rifampin 13 mg/kg/24 hr and intravenous clindamycin 13 mg/kg/8 hr for 28 days (n = 7). Grafts were removed for quantitative bacteriologic studies after the 28-day course of therapy. Two group I control grafts remained patent with 6.4 X 10(6) and 8.1 X 10(3) CFU S. aureus/gm of graft. The third control graft was thrombosed. Two group II animals demonstrated 1.6 X 10(7) and 2.3 X 10(5) CFU S. aureus organisms/gram of graft, respectively; the remaining five group II grafts were free of organisms. All group III grafts were sterile--a significant difference (p less than 0.05) from group I grafts. In this experimental model, established prosthetic graft infections were eradicated by intensive treatment with antibiotics preferentially concentrated in leukocytes.

Radiolabeled antibodies, albumin and antimony sulfide colloid: a comparison as lymphoscintigraphic agents.

The kinetics of lymph node and systemic uptake of members of three different classes of lymphoscintigraphic agents were studied in normal laboratory rats. 99mTc antimony trisulfide colloid (TcSbC), 99mTc human serum albumin (TcHSA), 125I 5G6.4 (a murine IgG2ak monoclonal antibody), 125I 763.24T (a murine IgG1), and 125I FT166 ( a murine IgM monoclonal) all current or potential lymphoscintigraphic agents, were injected subcutaneously into the hind foot pads of healthy rats. Ipsilateral and contralateral popliteal lymph nodes were sampled up to 4 h post-injection. Subcutaneous injection resulted in far higher nodal uptake for all agents than i.v. delivery with ipsilateral popliteal node/blood ratios 1 h postsubcutaneous injection of: for TcSbC (1900) greater than 125I IgM (497) greater than TcHSA (72) greater than 125I Intact IgG2a or 125I IgG1 at approximately 10. Thus, while all agents achieve popliteal node/blood ratios far greater than unity, TcSbc has the greatest absolute and relative nodal accumulation, greater than the 125I IgM monoclonal antibody and TcHSA. Uptake of the intact 125I IgG antibodies is lowest. These data suggest that TcSbC in particular, as well as TcHSA and IgM may be most useful as non-specific nodel imaging agents, while the lower background activity of the IgGs may make targeting specific antigen in nodes more feasible.

SPECT imaging of moyamoya disease using 99mTc-HM-PAO. Comparison with computed tomography findings.

99mTc-HM-PAO was used to evaluate regional cerebral blood flow in a 26-year-old woman with Moyamoya disease. This patient had an 18-month history of recurrent neurologic deficits and had angiographic evidence of Moyamoya disease. She had used oral contraceptives and cigarettes, but had no other risk factors for stroke. Single photon emission computed tomographic images showed bilateral and asymmetric reductions in blood flow to anterior and lateral brain regions. These findings correlated better with clinical symptomatology and suggested more extensive brain involvement than did computed tomography.

Platelet reactivity in human aortic grafts: a prospective, randomized midterm study of platelet adherence and release products in Dacron and polytetrafluoroethylene conduits.

Platelet-related phenomena at the blood-surface interface of randomly placed knitted Dacron (n = 6) and polytetrafluoroethylene (ePTFE) (n = 6) interposition aortic grafts were studied in patients undergoing abdominal aortic aneurysmectomy. Luminal accumulation of platelets was assessed by infusing indium-111-oxine (400 microCi) labeled autologous platelets and imaging grafts at 1 week, 3 months, and 6 months after surgery. Image analysis included an indium ratio technique (comparing aortic graft radioactivity to that of an iliac artery) and a red blood cell technetium subtraction technique (excluding blood pool radioactivity from graft radioactivity, with the heart or iliac artery serving as reference regions). Plasma levels of beta-thromboglobulin and platelet factor 4 were correlated with platelet accumulations on the aortic prostheses. Differences in graft radioactivity or platelet-release products were not evident 1 week after surgery. Three months after implantation, Dacron and ePTFE conduits exhibited 87% and 47% (p less than 0.05) more radioactivity with the indium ratio technique than the iliac artery. Similarly, increased Dacron compared with ePTFE graft radioactivity was noted using technetium subtraction techniques: 71% vs 30% with a heart reference and 26% vs 11% with an iliac artery reference, respectively. Increases in graft radioactivity correlated with increases in both plasma beta-thromboglobulin and platelet factor 4 at 3 months (r = 0.6 to 0.9; p less than 0.05 to 0.001 depending on the imaging technique used). At 6 months, differences did not persist. In fact, technetium subtraction techniques suggested less Dacron conduit reactivity. It is speculated that differences in platelet accumulation and activation associated with different graft substrates may prove clinically important.

Clinical experience with Tc-99m labeled (N2S2) anti-melanoma antibody fragments and single photon emission computed tomography.

We evaluated the imaging capability of murine Tc-99m-labeled antimelanoma Fab fragments in 12 patients with clinical stage II and III melanoma. Tc-99m-NRX118.7 antimelanoma Fab fragment, 10.0 to 27.2 mCi (370-1, 006 MBq), was injected IV 30 min after irrelevant nonspecific intact antibody and 5 min after intact specific antibody were given. In all patients, whole-body scans and spot views were obtained. Single photon emission computed tomography (SPECT) was additionally performed in eight of the patients. The procedure was well tolerated, and 31 of 38 known foci of melanoma were detected (sensitivity, 82%). SPECT aided in detecting and better localizing lesions in the head, neck, and chest. The specificity of the technique was satisfactory when interpretation was performed with a knowledge of normal sites of accretion and excretion of technetium-99m activity such as the kidneys and gut. In several instances, lesions were discovered by means of the antibody scan before detection by other methods, and in two instances, the lack of visualization on antibody scan of a palpable mass correctly indicated that no melanoma was present in the mass. Scan results in three patients led to alterations in patient care; including preventing aggressive surgical and nonsurgical treatments. Although these data are encouraging, evaluation in additional patients will be essential to determine the clinical utility of this antibody scan in the management of patients with melanoma.

Nuclide imaging of vascular graft-platelet interactions: comparison of indium excess and technetium subtraction techniques.

Indium-111-labeled platelet adherence to ePTFE thoracoabdominal vascular prostheses in a canine model (n = 10) was quantitated by (1) an indium-111 excess technique, contrasting graft radioactivity to that in a reference region, and (2) a technetium-99m subtraction technique, with radioactivity of circulating platelets eliminated by discounting background blood activity. Variation in graft thrombogenicity was provided by seeding six prostheses with enzymatically derived autologous endothelial cells, and implanting four prostheses without seeding. Grafts were imaged at 1, 4, and 6 weeks postimplantation, with platelet labeling using indium-111-oxine and red blood cell labeling using technetium-99m. At 7 weeks grafts were excised and gamma activity was measured in proximal, middle, and distal segments. Luminal generation of TxB2 and 6-keto-PGF1 alpha from midportions of grafts was assayed. Indium-111 excess ratios at 6 weeks correlated with actual gamma activity of excised grafts (proximal r = 0.80, P less than 0.01; middle r = 0.73, P less than 0.05; distal r = 0.48, ns) but such a correlation did not exist for the technetium-99m subtraction technique (r = -0.05, -0.25, and 0.16, in the three segments, respectively, all ns). The ratio of graft to aortic TxB2 production revealed a positive correlation with graft gamma activity (r = 0.87, P less than 0.01), and the ratio of graft 6-keto-PGF1 alpha to TxB2 production also correlated with gamma counts (r = -0.64, P = 0.05). In this experimental setting technetium-99m subtraction analysis was an imprecise method of detecting graft platelet accumulation, whereas indium-111 excess ratios proved to be a more accurate method of quantitating vascular prosthetic thrombogenicity.

Radioimmunotherapy of B-cell lymphoma with [131I]anti-B1 (anti-CD20) antibody.

BACKGROUND: Many patients with non-Hodgkin's lymphomas are not cured by current therapies, and new approaches to treatment are needed. As part of an ongoing phase 1 study, we examined the effect of radioimmunotherapy with 131I-labeled B-cell-specific anti-CD20 monoclonal antibody in 10 patients with CD20-positive B-cell lymphomas in whom primary chemotherapy had failed. METHODS AND RESULTS: Anti-B1 (anti-CD20) mouse monoclonal antibody trace-labeled with 131I (15 mg containing 5 mCi) was given intravenously at approximately one-week intervals: first, without pretreatment with unlabeled anti-B1 antibody, to all 10 patients; then, with pretreatment with 135 mg of unlabeled antibody, to 8 patients; and then, with pretreatment with 685 mg, to 2 patients. Serial quantitative gamma-camera images and measures of whole-body radioactivity were obtained after each tracer dose. All known disease sites larger than 2 cm could be imaged. The effect of a pretreatment dose of unlabeled anti-B1 antibody on targeting of the tumor with the radiolabeled antibody was variable. The pretreatment dose of unlabeled antibody that produced the highest ratio of the tumor dose to the whole-body dose in tracer studies was then used to deliver higher doses of radioactivity for radioimmunotherapy in nine patients. Three patients received doses designed to deliver 25 cGy to the whole body (two patients treated twice, six to eight weeks apart), four patients received 35 cGy (one patient treated twice), and two patients received 45 cGy (one patient treated twice); each dose contained 34 to 66 mCi of activity. Six of the nine treated patients had tumor responses, including patients with bulky or chemotherapy-resistant disease: four patients had complete remissions, and two had partial responses. Three patients had objective responses to tracer infusions before they received radioimmunotherapeutic doses. Of the four patients with complete remissions, one remained in remission for eight months and the other three continue to have no disease progression (for 11, 9, and 8 months). There was mild or no myelosuppression. CONCLUSIONS: Radioimmunotherapy with [131I]anti-B1 antibody is a promising new treatment for lymphoma.