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.

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.

Short-term effects of axillary lymph node clearance surgery on lymphatic physiology of the arm in breast cancer.

It is not known why some women develop breast cancer-related lymphedema (BCRL) of the arm, whereas others having similar treatment do not. We speculated that increased uptake of protein into local blood may protect against BCRL. Sixteen women were given bilateral subcutaneous hand webspace injections of polyclonal immunoglobulin (HIgG), (99m)Tc-HIgG on one side and (111)In-HIgG on the other, before and 3 mo after axillary clearance surgery. The rates of clearance of activity from the depot (k) and accumulation in central blood (b(contra)) were measured using a scintillation probe and bilateral antecubital vein blood sampling, respectively. Activity accumulating in blood ipsilateral to the injected side, in excess of central blood activity (b(ipsi)) was also calculated as a measure of local vascular uptake. The k correlated with b(contra), but neither changed in response to surgery. However, b(ipsi) for injections of (99m)Tc-HIgG into the affected arm increased in all seven patients in whom data were available (0.018 +/- 0.006 to 0.038 +/- 0.007%/min; P < 0.05); indeed, in five of these seven, b(ipsi) paradoxically exceeded b(contra), and none developed BCRL at 3-yr follow-up. We conclude that uptake of protein into local blood and/or proteolysis increases after axillary surgery and may protect against BCRL.

Velocity boundary condition at solid walls in rarefied gas calculations.

Maxwell's famous slip boundary condition is often misapplied in current rarefied gas flow calculations (e.g., in hypersonics, microfluidics). For simulations of gas flows over curved or moving surfaces, this means crucial physics can be lost. We give examples of such cases. We also propose a higher-order boundary condition based on Maxwell's general equation and the constitutive relations derived by Burnett. Unlike many other higher-order slip conditions these are applicable to any form of surface geometry. It is shown that these "Maxwell-Burnett" boundary conditions are in reasonable agreement with the limited experimental data available for Poiseuille flow and can also predict Sone's thermal-stress slip flow-a phenomenon which cannot be captured by conventional slip boundary conditions.

Measurement of the extraction fractions of nanocolloid and polyclonal immunoglobulin by axillary lymph nodes in patients with breast cancer.

BACKGROUND: 99mTc nanocolloid (99mTc-NC) is the most widely used tracer for lymphoscintigraphy, although others have been proposed, including radiolabelled proteins such as human serum albumin and polyclonal human immunoglobulin G (HIG). The extraction fraction of such tracers by individual nodes is clearly important but has not previously been measured in humans. METHODS: Patients scheduled for axillary clearance surgery (three groups) received dual-labelled radiotracers 2-4 h before surgery: group 1 (3 patients) received 99mTc-NC (10 MBq) and 111In-HIG (2 MBq) as a mixture (0.2 ml) into the breast parenchyma above the primary tumour; group 2 (3 patients) received 99mTc-HIG (10 MBq) and 111In-HIG (2 MBq) as a mixture (0.2 ml) into the breast parenchyma above the primary tumour; and group 3 (4 patients) received 99mTc-HIG (10 MBq) and 111In-HIG (2 MBq) separately (both 0.2 ml) into the breast parenchyma above the tumour and the intradermal plane at the areola. All resected nodes were counted for Tc and In in a well-type scintillation counter. In group 1, nodes were ranked according to their Tc uptake. In groups 2 and 3, nodes were ranked separately according to their respective Tc and In uptakes. If nodes are arranged in linear order and each node extracts a constant fraction of incoming tracer, then the activity in the nodes would decrease exponentially with an individual nodal extraction fraction, E, equal to 1-e(-k), where k is the rate constant of decrease. RESULTS: In the first group, 99mTc-NC and 111In-HIG identified the same sentinel and second echelon nodes. The observed decrease in nodal activity was exponential in all groups, at least for the first five nodes. Average values for E, based on the first five nodes were 0.69 (range 0.57-0.89; n=3) for 99mTc-NC and 0.45 (0.15-0.70; n=17) for HIG (irrespective of label) (Wilcoxon rank sum, P=0.02). With respect to HIG, there was no significant difference in E between 99mTc and 111In or between deep and superficial injections in group 3. CONCLUSION: Although HIG has an extraction fraction less than 99mTc-NC, the value of E is still high enough to make HIG a useful tracer for lymphoscintigraphy, especially for identifying second echelon nodes in addition to sentinel nodes and for imaging lymphatic vessels as well as lymph nodes.

Local vascular access of radioprotein injected subcutaneously in healthy subjects and patients with breast cancer-related lymphedema.

UNLABELLED: The aim of the study was to use dual-isotope lymphoscintigraphy in healthy volunteers and women with breast cancer-related lymphedema (BCRL) to detect and quantify transport of radiolabeled protein from a subcutaneous injection depot to local blood vessels as a potential mechanism of protection against edema resulting from treatment to the axilla. METHODS: A total of 29 subjects and 18 women with a history of BCRL received bilateral subcutaneous injections of human IgG (HIgG) in the second dorsal web space of each hand, (99m)Tc-HIgG on one side and (111)In-HIgG on the other. In 8 further healthy subjects, epinephrine was administered with the labeled HIgG. Radioactivity at each depot was measured at regular intervals for a total of 3 h using a collimated sodium iodide scintillation detector, and radioactivity in venous blood sampled from both arms was measured using an automatic sample counter. Ipsilateral blood time-concentration curves were corrected for recirculating activity by subtraction of the simultaneous contralateral concentration, to define the component of ipsilateral blood resulting from local vascular access of radioprotein. Accumulation of activity in blood was expressed in relation to injected activity and activity that had left the depot and was calculated as a function of time-in systemic blood, by multiplying contralateral concentrations by an estimate of the subject's blood volume, and in ipsilateral blood, by using indicator dilution theory and an assumed forearm blood flow of 20 mL/min. RESULTS: (99m)Tc-HIgG and (111)In-HIgG behave almost identically with respect to depot clearance and accumulation in contralateral venous blood, with or without epinephrine, which reduced both depot clearance and blood accumulation rate. Moreover, a side-to-side correlation with respect to contralateral accumulation was present in healthy subjects, was not abolished by epinephrine, and was maintained in the face of asymmetric accumulation in BCRL. Contralateral accumulation of radioprotein was reduced in BCRL after injection into the affected side only when the hand was involved. In contrast to contralateral sampling, ipsilateral time-concentration and accumulation profiles were consistent with instability of (111)In-HIgG and rapid local vascular access of small amounts of protein-free (111)In. Experiments based on precipitation of protein with trichloroacetic acid confirmed relatively high levels of unbound ipsilateral (111)In, especially in samples obtained early after injection. Substantial accumulation of protein-bound (99m)Tc was observed in ipsilateral blood, with a time course similar to that of contralateral accumulation. Positive correlation between ipsilateral and contralateral blood (99m)Tc activity was observed at all time points, often significantly, in contrast to (111)In, for which it was negative at all time points. Ipsilateral accumulation of (99m)Tc adjusted for activity that had left the depot was unchanged with respect to the affected arm in BCRL patients. CONCLUSION: Whereas (111)In-HIgG and (99m)Tc-HigG are interchangeable for measurement of depot clearance and contralateral venous accumulation rates, ipsilateral sampling is much more sensitive to protein-free radionuclide and detects significant differences resulting from some instability of (111)In-HIgG. On the basis of (99m)Tc data, there appears to be substantial local vascular access of radioprotein within the arm, both in healthy subjects and in patients with BCRL, through either lymphaticovenous communications or direct transendothelial transport.

Finding an optimal method for imaging lymphatic vessels of the upper limb.

Lymphoscintigraphy involves interstitial injection of radiolabelled particulate materials or radioproteins. Although several variations in the technique have been described, their place in clinical practice remains controversial. Traditional diagnostic criteria are based primarily on lymph node appearances but in situations such as breast cancer, where lymph nodes may have been excised, these criteria are of limited use. In these circumstances, lymphatic vessel morphology takes on greater importance as a clinical endpoint, so a method that gives good definition of lymphatic vessels would be useful. In patients with breast cancer, for example, such a method, used before and after lymph node resection, may assist in predicting the development of breast cancer-related lymphoedema. The aim of this study was to optimise a method for the visualisation of lymphatic vessels. Subcutaneous (sc) and intradermal (id) injection sites were compared, and technetium-99m nanocolloid, a particulate material, was compared with (99m)Tc-human immunoglobulin (HIG), which is a soluble macromolecule. Twelve normal volunteers were each studied on two occasions. In three subjects, id (99m)Tc-HIG was compared with sc (99m)Tc-HIG, in three id (99m)Tc-nanocolloid was compared with sc (99m)Tc-nanocolloid, in three id (99m)Tc-HIG was compared with id (99m)Tc-nanocolloid and in three sc (99m)Tc-HIG was compared with sc (99m)Tc-nanocolloid. Endpoints were quality of lymphatic vessel definition, the time after injection at which vessels were most clearly visualised, the rate constant of depot disappearance ( k) and the systemic blood accumulation rate as measured by gamma camera imaging over the liver or cardiac blood pool. Excellent definition of lymphatic vessels was obtained following id injection of either radiopharmaceutical, an injection route that was clearly superior to sc. Differences between radiopharmaceuticals were less clear, although after id injection, (99m)Tc-HIG gave images that were marginally but significantly better than those given by (99m)Tc-nanocolloid. Image quality correlated inversely with time after injection at which the best image was obtained, consistent with the notion that good vessel definition was dependent on a "narrow" bolus width. k was approximately three times higher after id injection than after sc injection but it was not significantly different between radiopharmaceuticals for either injection route. Intradermal (99m)Tc-HIG gave a cardiac blood pool signal that, over the first 60 min, increased about five times faster than that with sc (99m)Tc-HIG, but no clear difference was observed in the rate of increase in hepatic activity between id (99m)Tc-nanocolloid and sc (99m)Tc-nanocolloid. We conclude that id injection provides rapid access of radiotracers to lymphatic vessels, which is ideal for imaging lymphatic vessel morphology. (99m)Tc-HIG is marginally superior to nanocolloid for this purpose and, in drainage basins from which lymph nodes have been excised, is not handicapped by a potentially inferior ability, compared with radiocolloid, to image lymph nodes.

Side-to-side symmetry of radioprotein transfer from tissue space to systemic vasculature following subcutaneous injection in normal subjects and patients with breast cancer.

Quantitative lymphoscintigraphy can be used for investigation of unilateral lymphatic disease of the limbs, such as breast cancer-related lymphoedema (BCRL). Previous studies have compared lymphatic function in the affected limb with that in the unaffected contralateral limb. This study aims to confirm that the assumption of pre-morbid symmetry, never previously demonstrated, is valid. A dual-isotope technique, with bilateral subcutaneous hand injection of polyclonal human immunoglobulin G (HIgG) labelled with either technetium-99m or indium-111, was performed on a total of 37 subjects. The use of two different labels, one for each limb, enabled comparison not only of the rate of clearance from the injection depot, but also of the rate of appearance in venous blood. Results demonstrate clear symmetry between the two arms with respect to both depot clearance and blood appearance rates, as well as the coupling between these two variables. In unilateral lymphatic disease, results of quantitative lymphoscintigraphy should be expressed in relation to the normal arm rather than to an independent control population.

Quantification of lymphatic function for investigation of lymphedema: depot clearance and rate of appearance of soluble macromolecules in blood.

UNLABELLED: The object of this study was to develop a new technique for the quantitative measurement of lymphatic function. The rate of clearance of radiolabeled protein from a subcutaneous depot is supplemented by measurement of the appearance of the protein in venous blood. This initial study was performed on normal arms, with a view to subsequent clinical application such as in the investigation of women with breast cancer--related lymphedema (BCRL). METHODS: Fourteen healthy volunteers (12 women, 2 men) and 8 women awaiting surgery for breast cancer were recruited for the study. Each received subcutaneous depot injection of protein solution in the second dorsal web space of each hand, labeled with (111)In on one side and with (99m)Tc on the other side. Human serum albumin (HSA) was the protein used in the first 8 subjects and human polyclonal immunoglobulin G (HIgG) was used thereafter. The activity at each depot was measured at regular intervals using a collimated sodium iodide scintillation detector, and the activity in venous blood sampled from both arms was measured in an automatic sample counter. RESULTS: (99m)Tc-HSA cleared from the depot consistently faster than (111)In-HSA (P = 0.001). The proportions of radionuclide remaining bound to protein in venous blood were higher for (99m)Tc than for (111)In. HIgG displayed improved labeling stability for both nuclides, reflected in equal rates of clearance. Blood activity rose steadily after an early latent phase and for HIgG correlated strongly with the rate of clearance from the depot (P < 0.001). Marked variation between individuals was observed. CONCLUSION: A dual-isotope technique relies on identical behavior of the 2 radiopharmaceuticals used. This study shows that this is the case with respect to HIgG but not HSA. (99m)Tc-HSA cleared faster than (111)In-HSA and yet displayed better in vivo labeling stability. We conclude that (111)In dissociates from HSA in the depot but then becomes locally bound. Using HIgG, a close correlation was observed between the rates of clearance from the depot and the appearance in venous blood. This finding suggests that HIgG would be a suitable marker for subsequent dual-isotope studies on women with BCRL.