Preclinical PET Imaging of Tumor Cell Death following Therapy Using Gallium-68-Labeled C2Am.

There is an unmet clinical need for imaging agents capable of detecting early evidence of tumor cell death, since the timing, extent, and distribution of cell death in tumors following treatment can give an indication of treatment outcome. We describe here 68Ga-labeled C2Am, which is a phosphatidylserine-binding protein, for imaging tumor cell death in vivo using positron emission tomography (PET). A one-pot synthesis of 68Ga-C2Am (20 min, 25 °C, >95% radiochemical purity) has been developed, using a NODAGA-maleimide chelator. The binding of 68Ga-C2Am to apoptotic and necrotic tumor cells was assessed in vitro using human breast and colorectal cancer cell lines, and in vivo, using dynamic PET measurements in mice implanted subcutaneously with the colorectal tumor cells and treated with a TRAIL-R2 agonist. 68Ga-C2Am showed predominantly renal clearance and low retention in the liver, spleen, small intestine, and bone and generated a tumor-to-muscle (T/m) ratio of 2.3 ± 0.4, at 2 h post probe administration and at 24 h following treatment. 68Ga-C2Am has the potential to be used in the clinic as a PET tracer for assessing early treatment response in tumors.

Use of autologous 99mTechnetium-labelled neutrophils to quantify lung neutrophil clearance in COPD.

RATIONALE: There is a need to develop imaging protocols which assess neutrophilic inflammation in the lung. AIM: To quantify whole lung neutrophil accumulation in (1) healthy volunteers (HV) following inhaled lipopolysaccharide (LPS) or saline and (2) patients with COPD using radiolabelled autologous neutrophils and single-photon emission computed tomography/CT (SPECT/CT). METHODS: 20 patients with COPD (Global initiative for chronic obstructive lung disease (GOLD) stages 2-3) and 18 HVs were studied. HVs received inhaled saline (n=6) or LPS (50 µg, n=12) prior to the injection of radiolabelled cells. Neutrophils were isolated using dextran sedimentation and Percoll plasma gradients and labelled with 99mTechnetium (Tc)-hexamethylpropyleneamine oxime. SPECT was performed over the thorax/upper abdomen at 45 min, 2 hours, 4 hours and 6 hours. Circulating biomarkers were measured prechallenge and post challenge. Blood neutrophil clearance in the lung was determined using Patlak-Rutland graphical analysis. RESULTS: There was increased accumulation of 99mTc-neutrophils in the lungs of patients with COPD and LPS-challenged subjects compared with saline-challenged subjects (saline: 0.0006±0.0003 mL/min/mL lung blood distribution volume [mean ±1 SD]; COPD: 0.0022±0.0010 mL/min/mL [p<0.001]; LPS: 0.0025±0.0008 mL/min/mL [p<0.001]). The accumulation of labelled neutrophils in 10 patients with COPD who underwent repeat radiolabelling/imaging 7-10 days later was highly reproducible (0.0022±0.0010 mL/min/mL vs 0.0023±0.0009 mL/min/mL). Baseline interleukin (IL)-6 levels in patients with COPD were elevated compared with HVs (1.5±1.06 pg/mL [mean ±1 SD] vs 0.4±0.24 pg/mL). LPS challenge increased the circulating IL-6 levels (7.5±2.72 pg/mL) 9 hours post challenge. CONCLUSIONS: This study shows the ability to quantify 'whole lung' neutrophil accumulation in HVs following LPS inhalation and in subjects with COPD using autologous radiolabelled neutrophils and SPECT/CT imaging. Moreover, the reproducibility observed supports the feasibility of using this approach to determine the efficacy of therapeutic agents aimed at altering neutrophil migration to the lungs.

Radiolabelled leucocytes in human pulmonary disease.

Introduction: Radionuclides for leucocyte kinetic studies have progressed from non-gamma emitting cell-labelling radionuclides through gamma emitting nuclides that allow imaging of leucocyte kinetics, to the next goal of positron emission tomography (PET). Sources of data: Mostly the authors' own studies, following on from studies of the early pioneers. Areas of controversy: From early imaging studies, it appeared that the majority of the marginated granulocyte pool was located in the lungs. However, later work disputed this by demonstrating the exquisite sensitivity of granulocytes to ex vivo isolation and labelling, and that excessive lung activity is artefactual. Areas of agreement: Following refinement of labelling techniques, it was shown that the majority of marginated granulocytes are located in the spleen and bone marrow. The majority of leucocytes have a pulmonary vascular transit time only a few seconds longer than erythrocytes. The minority showing slow transit, ~5% in healthy persons, is increased in systemic inflammatory disorders that cause neutrophil priming and loss of deformability. Using a range of imaging techniques, including gamma camera imaging, whole-body counting and single photon-emission computerized tomography, labelled granulocytes were subsequently used to image pulmonary trafficking in lobar pneumonia, bronchiectasis, chronic obstructive pulmonary disease and adult respiratory distress syndrome. Growing points: More recently, eosinophils have been separated in pure form using magnetic bead technology for the study of eosinophil trafficking in asthma. Areas timely for developing research: These include advancement of eosinophil imaging, development of monocyte labelling, development of cell labelling with PET tracers and the tracking of lymphocytes.

Effects of tocilizumab on neutrophil function and kinetics.

BACKGROUND: Decreases in circulating neutrophils (polymorphonuclear leucocytes, PMNs) have been reported in patients treated with the anti-interleukin-6 receptor (IL-6R) antibody tocilizumab (TCZ); the mechanism for this is unclear. We hypothesize that TCZ reduces circulating neutrophils by affecting margination and/or bone marrow trafficking without affecting neutrophil function or apoptosis. MATERIALS AND METHODS: Eighteen healthy subjects were randomized to single intravenous dose of TCZ 8 mg/kg (n = 12) or placebo (n = 6) on day 0. On day 4, each subject had autologous indium-111-labelled neutrophils re-injected, and their kinetics quantified with longitudinal profiling in a whole body gamma-counter. TCZ-treated subjects were divided into two groups according to the extent of reduction in neutrophil count. RESULTS: Mean day 4 neutrophil counts, as % baseline, were 101·9%, 68·3% and 44·2% in the placebo, TCZ-PMN-'high' and TCZ-PMN-'low' groups, respectively (P < 0·001). Following TCZ, neutrophil function, activation and apoptosis ex vivo were all unaffected. In vivo, there were no differences in early blood recovery or margination to liver/spleen and bone marrow; however, later neutrophil re-distribution to bone marrow was markedly reduced in the TCZ-PMN-low group (peak pelvic count as % day 4 count on: day 5, 188% placebo vs. 127% TCZ-PMN-low, P < 0·001; day 10, 180% placebo vs. 132% TCZ-PMN-low, P < 0·01), with a trend towards higher liver/spleen neutrophil retention. CONCLUSIONS: We have demonstrated for the first time in humans that IL-6R blockade affects neutrophil trafficking to the bone marrow without influencing neutrophil functional capacity.

Clinical application of autologous technetium-99m-labelled eosinophils to detect focal eosinophilic inflammation in the lung.

The detection of focal eosinophilic inflammation by non-invasive means may aid the diagnosis and follow-up of a variety of pulmonary pathologies. All current methods of detection involve invasive sampling, which may be contraindicated or too high-risk to be performed safely. The use of injected autologous technetium-99m (Tc-99m)-labelled eosinophils coupled to single-photon emission computed tomography (SPECT) has been demonstrated to localise eosinophilic inflammation in the lungs of a patient with antineutrophil cytoplasmic antibody-positive vasculitis. Here, we report on the utility of this technique to detect active eosinophilic inflammation in a patient with focal lung inflammation where a biopsy was contraindicated.

Pulmonary retention of primed neutrophils: a novel protective host response, which is impaired in the acute respiratory distress syndrome.

RATIONALE: Acute respiratory distress syndrome (ARDS) affects over 200000 people annually in the USA. Despite causing severe, and often refractory, hypoxaemia, the high mortality and long-term morbidity of ARDS results mainly from extra-pulmonary organ failure; however the mechanism for this organ crosstalk has not been determined. METHODS: Using autologous radiolabelled neutrophils we investigated the pulmonary transit of primed and unprimed neutrophils in humans. Flow cytometry of whole blood samples was used to assess transpulmonary neutrophil priming gradients in patients with ARDS, sepsis and perioperative controls. MAIN RESULTS: Unprimed neutrophils passed through the lungs with a transit time of 14.2 s, only 2.3 s slower than erythrocytes, and with <5% first-pass retention. Over 97% of neutrophils primed ex vivo with granulocyte macrophage colony-stimulating factor were retained on first pass, with 48% still remaining in the lungs at 40 min. Neutrophils exposed to platelet-activating factor were initially retained but subsequently released such that only 14% remained in the lungs at 40 min. Significant transpulmonary gradients of neutrophil CD62L cell surface expression were observed in ARDS compared with perioperative controls and patients with sepsis. CONCLUSIONS: We demonstrated minimal delay and retention of unprimed neutrophils transiting the healthy human pulmonary vasculature, but marked retention of primed neutrophils; these latter cells then 'deprime' and are re-released into the systemic circulation. Further, we show that this physiological depriming mechanism may fail in patients with ARDS, resulting in increased numbers of primed neutrophils within the systemic circulation. This identifies a potential mechanism for the remote organ damage observed in patients with ARDS.

Use of 111-Indium-labeled autologous eosinophils to establish the in vivo kinetics of human eosinophils in healthy subjects.

Eosinophils are the major cellular effectors of allergic inflammation and represent an important therapeutic target. Although the genesis and activation of eosinophils have been extensively explored, little is known about their intravascular kinetics or physiological fate. This study was designed to determine the intravascular life span of eosinophils, their partitioning between circulating and marginated pools, and sites of disposal in healthy persons. Using autologous, minimally manipulated 111-Indium-labeled leukocytes with blood sampling, we measured the eosinophil intravascular residence time as 25.2 hours (compared with 10.3 hours for neutrophils) and demonstrated a substantial marginated eosinophil pool. γ camera imaging studies using purified eosinophils demonstrated initial retention in the lungs, with early redistribution to the liver and spleen, and evidence of recirculation from a hepatic pool. This work provides the first in vivo measurements of eosinophil kinetics in healthy volunteers and shows that 111-Indium-labeled eosinophils can be used to monitor the fate of eosinophils noninvasively.

Clinical significance of scintigraphic rapid gastric emptying.

OBJECTIVES: To analyse our results of gastric-emptying scintigraphy in relation to presenting symptoms, and examine in detail the clinical significance of rapid gastric emptying (RGE). MATERIALS AND METHODS: Results of 642 consecutive patients who underwent a solid gastric-emptying scintigraphy in our department over an 11-year period were retrospectively reviewed with particular emphasis to the presenting symptoms and the clinical profile of patients, especially of those who showed an accelerated pattern of emptying. RESULTS: Seventy (11%) patients were clinically suspected to have a RGE and 572 (89%) patients had presumed gastroparesis. Gastric emptying was found to be normal in 290 (45%), rapid in 182 (28%) and delayed in 170 (27%) patients. Normal, rapid and delayed gastric emptying were seen, respectively, in 17 (24%), 48 (69%) and five (7%) patients with the clinical suspicion of dumping and 273 (48%), 134 (23%) and 165 (29%) patients with suspected gastroparesis. The positive predictive value of clinical suspicion for RGE was 62%, whereas the positive predictive value of delayed gastric emptying was 29%. Of the 182 patients with RGE, 144 (79%) were found to have no obvious explanation for this result; reactive hypoglycaemia was present in a quarter of these patients, but diarrhoea was seen only in 3%. CONCLUSION: Upper gastrointestinal symptoms have a poor clinical specificity to the actual rate of gastric emptying on scintigraphy. Diarrhoea as a symptom does not appear to be associated frequently with RGE, but our results confirm its relationship with hypoglycaemia. The majority of patients with a rapid emptying on gastric-emptying scintigraphy have no identifiable cause for an accelerated motility. Scintigraphic gastric-emptying studies provide a reliable and noninvasive method of investigation in patients where conventional investigations have failed to establish the cause of upper gastrointestinal dysfunction.

Quantification of neutrophil migration into the lungs of patients with chronic obstructive pulmonary disease.

OBJECTIVE: To quantify neutrophil migration into the lungs of patients with chronic pulmonary obstructive disease (COPD). METHODS: Neutrophil loss via airways was assessed by dedicated whole-body counting 45 min, 24 h and 2, 4, 7 and 10 days after injection of very small activities of (111)In-labelled neutrophils in 12 healthy nonsmokers, 5 healthy smokers, 16 patients with COPD (of whom 7 were ex-smokers) and 10 patients with bronchiectasis. Lung accumulation of (99m)Tc-labelled neutrophils was assessed by sequential SPECT and Patlak analysis in six COPD patients and three healthy nonsmoking subjects. RESULTS: Whole body (111)In counts, expressed as percentages of 24 h counts, decreased in all subjects. Losses at 7 days (mean ± SD) were similar in healthy nonsmoking subjects (5.5 ± 1.5%), smoking subjects (6.5 ± 4.4%) and ex-smoking COPD patients (5.8 ± 1.5%). In contrast, currently smoking COPD patients showed higher losses (8.0 ± 3.0%) than healthy nonsmokers (p = 0.03). Two bronchiectatic patients lost 25% and 26%, indicating active disease; mean loss in the remaining eight was 6.9 ± 2.5%. The rate of accumulation of (99m)Tc-neutrophils in the lungs, determined by sequential SPECT, was increased in COPD patients (0.030-0.073 min(-1)) compared with healthy nonsmokers (0-0.002 min(-1); p = 0.02). CONCLUSION: In patients with COPD, sequential SPECT showed increased lung accumulation of (99m)Tc-labelled neutrophils, while whole-body counting demonstrated subsequent higher losses of (111)In-labelled neutrophils in patients who continued to smoke. Sequential SPECT as a means of quantifying neutrophil migration deserves further evaluation.

Measuring whole-body neutrophil redistribution using a dedicated whole-body counter and ultra-low doses of 111Indium.

BACKGROUND: There is increasing interest in the 'homing' of neutrophils to bone marrow. The aim of this study was to measure the whole-body redistribution of (111) In using a whole-body counter following the administration of ultra-small activities of (111) In-labelled neutrophils. METHODS: The detectors of a dedicated whole-body counter were fitted with lead collimators. Whole-body (111) In distribution was recorded at 45 min, 24 h, and 2, 4, 7 and 10 days after administration of (111) In-labelled neutrophils (0·29-0·74 MBq) in eight healthy non-smokers, five healthy smokers, eight patients with inactive bronchiectasis, three with asthma and nine with chronic obstructive pulmonary disease (COPD). RESULTS: Intravascular 45-min (111) In-labelled neutrophil recovery was not significantly different between groups, ranging from 33 (SD 8%) in healthy smokers to 45 (14%) in healthy non-smokers (P > 0·05). Peaks were identified on the whole body count profile corresponding to the chest, upper abdomen (liver/spleen) and pelvis (bone marrow). (111) In distribution changed between 45 min and 24 h and then remained stable thereafter. Peak chest counts increased ∼ 1·5-fold between 45 min and 24 h, whereas upper abdominal peak counts decreased by ∼ 25% with no significant inter-group differences. The increment in pelvic counts (∼ 2·7-fold) was similar between groups, except COPD patients, in whom it was 2·04 (0·35; P < 0·02 vs. healthy participants). CONCLUSIONS: Assuming neutrophils are distributed only between blood, liver, spleen and bone marrow, the data suggest that marrow pools 25% and destroys 67% of circulating neutrophils, rising in COPD to 40% and 80%, respectively, possibly as a result of the effects on marrow of chronic hypoxaemia.

Measurement of lymph node function from the extraction of immunoglobulin in lymph.

BACKGROUND: We aimed to measure the extraction fraction of human immunoglobulin G (HIG) by the 1st echelon lymph node (sentinel node) following intradermal injection in patients with breast cancer undergoing axillary lymph node dissection (ALND) and examine its association with node size and presence and extent of nodal metastatic disease. MATERIALS AND METHODS: HIG labelled with either In-111 (n = 21) or Tc-99m (n = 9) was injected intradermally at the areolar. ALND was performed 2-4 h later. All lymph nodes were isolated and individually counted in a well-counter. The counts in the 'hottest' (1st echelon) node were expressed as a fraction of total counts in all the resected nodes. Since counts in the least hot nodes barely exceeded background, this fraction represents extraction fraction for the 1st echelon node. Presence of disease was noted in each 1st echelon node and the extent quantified as percentage replacement with disease. RESULTS: Median extraction fraction in 1st echelon nodes with no or low (<1%) disease burden (n = 21) was 68 (range 23-93)%, significantly higher (p < 0.05) than in diseased 1st echelon nodes (n = 9), in which it was 44 (21-66)%. There was, however, no association between extraction fraction in diseased nodes and disease extent. In nodes with no/low disease, extraction fraction was similar for the two radiolabels. There was no association between extraction fraction and node size. CONCLUSION: Nodal extraction fraction of HIG is a novel physiological measurement. It is reduced as a result of metastatic invasion. In the absence of disease, it shows no correlation with node size.

Delivery of radiolabelled blood cells to lymphatic vessels by intradermal injection: a means of investigating lymphovenous communications in the upper limb.

OBJECTIVE: To identify peripheral lymphovenous communications (LVCs) using labelled erythrocytes and intradermal injection. Intradermal injection delivers macromolecules to loco-regional lymph nodes faster than subcutaneous injection, suggesting easier lymphatic vessel access. METHODS: Autologous erythrocytes labelled with 111In and 99mTc were injected into opposite hands. In four normal volunteers, the differentially labelled cells were given by intradermal injection on one side and subcutaneous injection on the other while in four breast cancer patients they were given by intradermal injection bilaterally 3 months after axillary lymph node clearance surgery. The axillae were imaged and blood samples obtained bilaterally at approximately 15, 30, 60, 120 and 180 min post-injection. Plasma activity was subtracted from whole blood activity to obtain erythrocyte-bound activity and contralateral concentrations were subtracted from ipsilateral concentrations to correct for ipsilateral recirculation. From estimated blood volume, erythrocyte and plasma activities contralateral to the injected side were calculated as percentage administered activity. Tracer concentrations in ipsilateral samples (%/l) were integrated to give total percentage administered activity, assuming a forearm blood flow of 20 ml/min. RESULTS: Kinetics of plasma activity were consistent with small diffusible 99mTc complexes and protein-bound 111In. With both radionuclides, axillary nodes were visualized after intradermal but not subcutaneous injection, suggesting that nodal activity arises from erythrocytes. In one patient, 99mTc and 111In labelled erythrocytes accumulated in similar amounts ipsilaterally and contralaterally, suggesting bilateral LVCs distal to the ipsilateral sampling point. There was no evidence of LVCs in the other seven volunteers. CONCLUSION: Intradermally injected erythrocytes are able to detect and potentially quantify peripheral LVCs.

Axillary lymph node drainage pathways from intradermal and intraparenchymal breast planes.

BACKGROUND: To compare functional anatomy of breast peri-areolar and peri-tumoral lymphatic drainage basins. METHODS: Fifteen breast cancer patients received simultaneous peri-areolar (intradermal) and peri-tumoral (intraparenchymal) injections of human polyclonal immunoglobulin (HIG) labeled with (99m)Tc and (111)In 2 to 4 h before axillary lymph node clearance surgery. Resected nodes (range 5-20; median 16) were individually counted for (99m)Tc and (111)In in a well-counter and ranked according to activity content (echelon). Activity in distal nodes was negligible so extraction efficiency (E) of HIG in the first echelon node was calculated as counts divided by total counts in the chain. RESULTS: Five- to 10-fold more activity was recovered after intradermal injection. The injection planes identified the same first echelon node in 10 patients (group 1) but different in five (group 2). In group 1, intradermal E correlated with intra-parenchymal E (r = 0.82; P < 0.01). E of intradermal first echelon nodes in group 2 was 51 (SD 13)%, similar to intradermal E in group 1 (58 [23]%). E of intraparenchymal first echelon nodes in group 2, however, was 28 (6)%, lower than intraparenchymal E in group 1 (54 [20]%; P < 0.02). CONCLUSIONS: Lymph nodes extract approximately 50% of HIG. Extracted HIG does not cascade to distal nodes, validating HIG for sentinel node lymphoscintigraphy. HIG injected intradermally at the areola drains via a single route to the axilla. In two-thirds of patients, peri-tumoral HIG follows a similar route, but in one-third of patients drainage from the parenchymal plane is more complex, with more than one route to the axilla.

Functional variation in lymph node arrangements within the axilla.

The aim of the project was to identify how lymphatic pathways are functionally arranged within the axilla (i.e., single linear chains, branching chains, and networks). We used ex vivo dual isotope radioassay of individual nodes resected at axillary lymphatic clearance surgery in breast cancer patients given simultaneous intradermal breast and intradermal hand injections (n = 15) or simultaneous intradermal breast and parenchymal breast injections (n = 15) of differentially labelled human immunoglobulin (Tc-99m-HIG and In-111-HIG). Nodes were ranked according to isotope content and activity-rank profiles constructed for each of the two injection sites. The majority of profiles following intradermal breast injection (17/30) were mono-exponential, consistent with a simple linear chain of nodes, with each node extracting a constant fraction of incoming HIG. In 15/17 of these, the accompanying profile from the alternative injection site was also mono-exponential and, in 11/15, essentially parallel. The profile appeared biphasic in 12/30 intradermal breast injections and of these 9/12 were accompanied by a biphasic profile (7/9 parallel) from the alternative injection site. In one patient, both profiles were polyphasic and parallel. Considering the respective shapes of paired profiles and whether the two injection sites shared the same first echelon nodes, functional lymph node arrangements are proposed. The commonest is a single linear chain, then a chain branching into two linear chains, and, least common, a network.

Lymphatic drainage pathways of the breast and the upper limb.

OBJECTIVE: To determine how often the sentinel lymph node (SLN) draining the breast is the same node as the SLN draining the upper limb. A common SLN might increase the risk of upper limb breast cancer-related lymphoedema after SLN biopsy. METHODS: Patients with invasive breast cancer, identified as being suitable for axillary lymph node dissection, were injected preoperatively with 40 MBq of technetium-99m (Tc)-human polyclonal immunoglobulin G intradermally into the ipsilateral breast and 3 MBq of indium-111 (In)-human polyclonal immunoglobulin G intradermally into the ipsilateral hand, or vice versa. Axillary lymph nodes were removed, separated and assayed in a well counter for Tc and In. RESULTS: Fifteen patients entered the study. In 13 of 15 patients, the 'hottest' lymph node for Tc was separate from the 'hottest' lymph node for In. In two of 15 patients the 'hottest' lymph node for Tc was also the 'hottest' lymph node for In, suggesting a common drainage pathway from the ipsilateral breast and upper limb. CONCLUSION: Although the majority of patients has different pathways of lymphatic drainage from the ipsilateral breast and upper limb, in a small minority of patients the drainage pathway is through a common SLN. Such patients may be at increased risk of developing upper limb breast cancer-related lymphoedema after SLN biopsy.

Utility of 111In-labelled leucocyte scintigraphy in patients with fever of unknown origin in an era of changing disease spectrum and investigational techniques.

BACKGROUND: (111)In-labelled leucocyte, imaging is often used to investigate patients with fever of unknown origin (FUO). Its diagnostic performance, however, has been variable and a broad range of sensitivities and specificities have been reported. The purpose of this investigation was to evaluate the usefulness of (111)In-labelled leucocytes scintigraphy in the detection of a cause of FUO in the light of a changing spectrum of diseases causing it and advances in investigational techniques. MATERIALS AND METHODS: Sixty-one patients with a clinical diagnosis of FUO underwent whole-body (111)In-troponolate-labelled leucocyte scintigraphy in our department over a 2-year period between February 2004 and February 2006. Of these, 54 patients were retrospectively reviewed to identify a cause of FUO. Other parameters such as C-reactive protein (CRP), leucocyte count and radiological findings were also evaluated. RESULTS: Leucocyte scintigraphy was found to be true positive in 12 patients, true negative in 24 patients, false positive in 10 patients and false negative in eight patients. The overall sensitivity of scintigraphy was 60%, specificity 71%, positive predictive value 55%, and negative predictive value 75%. There was no difference in the scintigraphic sensitivity between patients with spontaneous FUO and those with post-operative FUO although the latter showed a higher specificity and PPV. CRP and leucocyte count did not differ significantly between patients with true positive and true negative scintigrams. Overall, 83% of patients with abnormal radiological examinations had positive findings on scintigraphy and 87% of patients with negative findings on radiology had normal scintigraphy. CONCLUSION: Despite changes in disease spectrum and advances in investigational techniques, our results suggest that (111)In-leucocyte scintigraphy is still a useful technique in establishing the cause of FUO. A higher PPV of this test in post-operative situations makes it especially applicable in this category of patients. Equally, the higher NPV in patients with spontaneous FUO virtually excludes infection/inflammation. Finally, a higher pre-test probability based on the radiological tests seems to be important in the optimal use of leucocyte imaging.

Dual-isotope lymphoscintigraphy using albumin nanocolloid differentially labeled with 111In and 99mTc.

The aim of this study was to develop and evaluate 111In- and 99mTc-labeled derivatives of albumin nanocolloid (NC) for dual-label lymphoscintigraphy to allow simultaneous comparison of lymphatic flow from different tissue planes draining a tumour bed for accurate identification of sentinel lymph nodes (SLN). Using the chelator, p-isothiocyanatobenzyl-1,4,7, 10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), 111In-DOTA-NC and 99mTc-DOTA-NC were compared in vitro with respect to stability of labeling, colloidal status and particle size, then in vivo by measuring their clearance rates from a subcutaneous injection depot. 111In-DOTA-NC and 99mTc-DOTA-NC were indistinguishable on the basis of in vitro criteria. Their in vivo clearance rates, however, were disparate (0.0015 to 0.075 min(-1) for 111In and 0.0072 to 0.067 min(-1) for 99mTc), 111In being faster in three studies and markedly slower in three. This demonstrates that even when dual-labeled radiotracers behave identically in vitro, they will not necessarily do so in vivo. Further work is needed to develop dual-labeled NC.

Imaging of lymphatic vessels in breast cancer-related lymphedema: intradermal versus subcutaneous injection of 99mTc-immunoglobulin.

OBJECTIVE: The disordered physiology that results from axillary lymph node clearance surgery for breast cancer and that leads to breast cancer-related lymphedema is poorly understood. Rerouting of lymph around the axilla or through new pathways in the axilla may protect women from breast cancer-related lymphedema. The aim of the study was to compare intradermal with subcutaneous injection of technetium-99m ((99m)Tc)-labeled human polyclonal IgG (HIG) with respect to lymphatic vessel imaging. MATERIALS AND METHODS: Six women with breast cancer-related lymphedema underwent unilateral upper limb lymphoscintigraphy, using a web space injection of (99m)Tc-labeled HIG, after intradermal and subcutaneous injections on separate occasions. Multiple sequential images were obtained of the affected upper limb and torso over 3 hr on each occasion. Accumulation of activity in blood was quantified from venous blood samples taken from the opposite arm. RESULTS: Imaging after intradermal injection clearly showed discrete lymphatic vessels in five of six patients, in contrast to imaging after subcutaneous injection, which did not show any discrete vessels in any patient. Intradermal injection resulted in more rapid visualization of cutaneous lymph rerouting than subcutaneous injection in six of six patients. Recovery of injected (99m)Tc-labeled HIG in venous blood was greater after intradermal injection in six of six patients. CONCLUSION: In patients with breast cancer-related lymphedema, lymphatic vessels are more clearly depicted after intradermal than subcutaneous injection as a result of direct access of radiotracer to dermal lymphatics. This finding has implications for imaging lymphatic vessel regeneration and lymph rerouting.