Axillary reverse mapping with indocyanine green or isosulfan blue demonstrate similar crossover rates to radiotracer identified sentinel nodes.

BACKGROUND: Sentinel lymph node (SLN) resection is imperative for breast cancer staging. Axillary reverse mapping (ARM) can preserve arm draining nodes and lymphatics during surgery. ARM is generally performed with isosulfan blue (ISB), restricting its use for concurrent SLN biopsy. Indocyanine green (ICG) could serve as an alternative to ISB for ARM procedures. METHODS: SLN mapping and biopsy was performed via periareolar injection of 99 technetium-sulfur colloid (99m TcSc, TSC). ISB and ICG were injected in the upper arm. Blue-stained lymphatics or nodes were visualized in the axilla; ICG was identified using the SPY Elite® system. RESULTS: Twenty-three patients underwent SLN biopsy with or without axillary node dissection and ARM procedures. Twenty of these patients had at least one hot node; 12 patients had SLNs that were only hot, 6 hot/blue/fluorescent, and 2 hot/fluorescent. Overall, crossover of ARM agents with SLNs occurred in 8 cases. Inspection of the axillary cavity after SLN biopsy revealed fluorescent lymphatics and nodes remaining in 14 and 7 patients, respectively. Blue lymphatics and blue nodes were detected in fewer cases. CONCLUSION: Nearly one-third of patients showed crossover between breast and arm draining nodes, which provides insight as to why some patients develop lymphedema symptoms after SLN biopsy. ICG and ISB identify similar numbers of SLNs. As such ICG could substitute for ISB in ARM procedures.

In house development of (99m)Tc-Rhenium sulfide colloidal nanoparticles for sentinel lymph node detection.

In this study, rhenium sulfide colloidal nanoparticles were developed as radiopharmaceutical for sentinel lymph node detection. We directly used rhenium sulfide as a starting material for the preparation of colloidal nanoparticles. UV-visible spectrophotometry was used for characterization of in house developed colloidal particles. The size distribution of radioactive particles was studied by using membrane filtration method. The percentage of radiolabeled colloidal nanoparticles was determined by paper chromatography (PC). The study also includes in vitro stability, protein binding in human blood and bioevaluation in a rabbit model. The results indicate that 77.27 ± 3.26 % particles of size less than 20nm (suitable for lymphoscintigraphy) were radiolabeled. (99m)Tc labeled rhenium sulfide labeling efficacy with the radiometal is 98.5 ± 0.5%, which remains considerably stable beyond 5h at room temperature. Furthermore, it was observed that 70.2 ± 1.3% radiolabeled colloid complex showed binding with the blood protein. Bioevaluation results show the remarkable achievement of our radiopharmaceutical. The in house prepared (99m)Tc labeled rhenium sulfide colloidal nanoparticles reached the sentinel node within 15 min of post injection. These results indicate that (99m)Tc labeled rhenium sulfide colloid nanoparticles kit produced by a novel procedure seems of significant potential as a feasible candidate for further development to be used in clinical practice.

Quantification of the spatial distribution of rectally applied surrogates for microbicide and semen in colon with SPECT and magnetic resonance imaging.

AIMS: We sought to describe quantitatively the distribution of rectally administered gels and seminal fluid surrogates using novel concentration-distance parameters that could be repeated over time. These methods are needed to develop rationally rectal microbicides to target and prevent HIV infection. METHODS: Eight subjects were dosed rectally with radiolabelled and gadolinium-labelled gels to simulate microbicide gel and seminal fluid. Rectal doses were given with and without simulated receptive anal intercourse. Twenty-four hour distribution was assessed with indirect single photon emission computed tomography (SPECT)/computed tomography (CT) and magnetic resonance imaging (MRI), and direct assessment via sigmoidoscopic brushes. Concentration-distance curves were generated using an algorithm for fitting SPECT data in three dimensions. Three novel concentration-distance parameters were defined to describe quantitatively the distribution of radiolabels: maximal distance (D(max) ), distance at maximal concentration (D(Cmax) ) and mean residence distance (D(ave) ). RESULTS: The SPECT/CT distribution of microbicide and semen surrogates was similar. Between 1 h and 24 h post dose, the surrogates migrated retrograde in all three parameters (relative to coccygeal level; geometric mean [95% confidence interval]): maximal distance (D(max) ), 10 cm (8.6-12) to 18 cm (13-26), distance at maximal concentration (D(Cmax) ), 3.8 cm (2.7-5.3) to 4.2 cm (2.8-6.3) and mean residence distance (D(ave) ), 4.3 cm (3.5-5.1) to 7.6 cm (5.3-11). Sigmoidoscopy and MRI correlated only roughly with SPECT/CT. CONCLUSIONS: Rectal microbicide surrogates migrated retrograde during the 24 h following dosing. Spatial kinetic parameters estimated using three dimensional curve fitting of distribution data should prove useful for evaluating rectal formulations of drugs for HIV prevention and other indications.

(99m)Tc sulfur colloid and (99m)Tc mebrofenin hepatobiliary functional liver imaging in normal and diabetic rats.

OBJECTIVES: To use (99m)Tc sulfur colloid ((99m)Tc-SC) and (99m)Tc mebrofenin ((99m)Tc-BrIDA) to study liver function in normal and diabetic rats. MATERIALS AND METHODS: Radionuclide imaging was performed on 2 groups of rats, using (99m)Tc-SC for one group and (99m)Tc-BrIDA for the other (20 rats per group) before and after induction of diabetes mellitus (DM) using streptozotocin administration (55 mg/kg i.p.). Dynamic acquisition was obtained for 1 h after the injection of 37 MBq of radiotracer. For the (99m)Tc-SC group, organ/tissue uptake was determined by drawing regions of interest (ROI) over the heart, liver, spleen and also the whole body (WB). The ratio of the ROI of each organ to the WB ROI was calculated. For (99m)Tc-BrIDA, ratios of cumulative count rates in liver, liver parenchyma, biliary tree and abdomen ROI to a WB ROI were also calculated. Statistical analysis was performed to compare the ratios of organ/tissue uptake to WB uptake before and after DM induction using the paired t test. RESULTS: (99m)Tc-SC uptake ratios (means ±SD) showed a lower liver-to-WB uptake ratio (0.75 ± 0.05) in the rats after DM induction compared to baseline (0.81 ± 0.06), while the cardiac blood pool showed higher uptake ratios in the rats after DM induction (p = 0.026). For (99m)Tc-BrIDA, there was no significant difference in radiotracer uptake ratios obtained from the rats before and after DM induction (p = 0.41). CONCLUSION: Using functional liver imaging, there was a statistically significant decrease in the liver phagocytic/reticuloendothelial system function after DM induction, as evidenced by decreased (99m)Tc-SC liver uptake and increased blood pool compared to prediabetes, while the hepatobiliary function remained unchanged after DM induction using (99m)Tc-BrIDA imaging.

Inadvertent Injection of a Breast Implant During Lymphoscintigraphy.

A 34-year-old woman with history of bilateral saline implants, invasive ductal carcinoma of the right breast, and suspicious left breast calcifications was referred for left breast lymphoscintigraphy before bilateral mastectomy. A total of 3.2 mCi of Tc-filtered sulfur colloid was administered with 3 subdermal injections in the superior, lateral, and inferior periareolar left breast in the late afternoon preceding the day of surgery. Imaging identified radiotracer uptake within a dense, circular area deep to the injection sites within the left breast, compatible with implant puncture and radiotracer administration within the indwelling breast implant.

Colonic transit studies with 99mTc-rhenium sulfide colloid in live rats. A preliminary study.

Abnormal colonic motility is associated with clinical relevant conditions such as irritable bowel syndrome or constipation. Accurate assessment of colonic transit in an animal model would be useful in studying these conditions and screen potential drug candidates. The aim of this study was to assess if scintigraphic analyses could reliably evaluate total and segmental colonic transit as a measure of colonic motility of a non-absorbable radiotracer in rats. Normal Lewis rats (250-300 g) were given oral technetium-99m-rhenium sulfide colloid (15-20 MBq; 0.5 mL; n=4) followed by a rinse with water for injection (1.0 mL). Rats were fed and hydrated ad libitum. After 30 min, each rat was contained inside an 'imaging' tube then placed on a g-camera collimator. Whole body 5 min static images were acquired every 30 min up to 9 h, and then finally at 25 hours. Region of interest analyses were applied to the caecum/proximal colon, sigmoidal loop and distal colon/rectum. The tracer entered into the colon at approximately 4 hours, and the rats remained static to permit 'live' imaging. At 4 hours the % whole body activity was: 51% caecum/proximal colon, 39% sigmoidal loop, 6% distal colon/rectum; at 8 hours, 30% caecum/proximal colon, 13% sigmoidal loop, 7% distal colon/rectum. In the whole colon there was < or =1% of total activity present at 25 hours, and the half clearance time was determined as 4.0 hours. These results suggest this is a reliable technique of measuring regional colonic transit as a measure of colonic motility in normal rats. This methodology might be well suited to screen potential motility effects of drug candidates.

Quantitative simultaneous In-111/Tc-99m planar imaging in a long-bone infection phantom.

In-111-white-blood-cell and Tc-99m-sulfur-colloid dual-radionuclide imaging are frequently utilized in the evaluation of patients with suspected osteomyelitis. We have developed a quantitative planar imaging method in which Tc-99m and In-111 scans are acquired simultaneously in accurate spatial registration. Long, thin tubes containing only In-111 or Tc-99m were first imaged in a list mode within a water bath inclined with respect to the water surface; from these, 12 energy spectra corresponding to different Tc/In ratios were synthesized. Triple-energy-window (TEW) parameters for scatter and radionuclide crosstalk correction, including scatter windows and weights, were optimized using 100 noise realizations of each of the spectra (1200 total). A long-bone phantom containing a simulated infection site was then imaged in water with five In/Tc ratios; 100 noise realizations of two conjugate-view images were generated from each acquisition (500 total). Two regions of interest (ROIs) were defined, and the ratio of In/Tc count ratios in these two ROIs was evaluated with and without the TEW scatter correction and geometric mean attenuation compensation. The average bias improved from 17.2% to 5.3%, with comparable precision. TEW corrections with non-optimized but practical energy windows also improved the bias to 6.4%. Compared with subjective visual assessment, quantitation of In-111/Tc-99m ratios may improve diagnostic accuracy and could eventually permit grading of osteomyelitis.

Assessment of functional liver reserve: old and new in 99mTc-sulfur colloid scintigraphy.

PURPOSE: A semiquantitative assessment of hepatic reticuloendothelial system function using colloidal particles scintigraphy has been proposed previously as a surrogate for liver function evaluation. In this article, we present an updated method for the overall assessment of technetium-99m (Tc)-sulfur colloid (SC) biodistribution that combines information from planar and attenuation-corrected Tc-SC single-photon emission computed tomography (SPECT) images. The imaging protocol described here was developed as an easy-to-implement method to assess overall and regional liver function changes associated with chronic liver disease. PATIENTS AND METHODS: Thirty patients with chronic liver disease and primary liver cancers underwent Tc-SC whole-body planar imaging and upper-abdomen SPECT/computed tomography (CT) imaging before external beam radiation therapy. Liver plus spleen and bone marrow counts as a fraction of whole-body total counts were calculated from SC planar imaging. Attenuation correction Tc-SC images were rigidly coregistered with treatment planning CT images that contained liver and spleen regions-of-interest. Ratios of total liver counts to total spleen counts were obtained from the aligned Tc-SC SPECT and CT images, and were subsequently used to separate liver plus spleen counts obtained on the planar images. This hybrid SPECT/CT and planar scintigraphy approach yielded an updated estimation of whole-body SC distribution. These biodistribution estimates were compared with historical data for reference. Statistical associations of Tc-SC biodistribution to liver function parameters and liver disease scoring systems (Child-Pugh) were evaluated by Spearman rank correlation. RESULTS: Percentages of Tc-SC uptake ranged from 19.3 to 77.3% for the liver; 3.4 to 40.7% for the spleen; and 19.0 to 56.7% for the bone marrow. Spearman's correlation coefficient showed a significant statistical association between Child-Pugh score and bone marrow uptake at 0.55 (P≤0.05), liver uptake at 0.71 (P≤0.001), spleen uptake at 0.56 (P≤0.05), and spleen plus bone marrow uptake at 0.71 (P≤0.001). There was also a good correlation of SC uptake percentages with individual quantitative liver function components such as albumin and total bilirubin, and qualitative liver function components (varices, portal hypertension, ascites). For albumin: r=0.64 (P<0.001) compared with liver uptake percentage from the whole-body counts, r=0.49 (P<0.001) compared with splenic uptake percentage, and r=0.45 (P≤0.05) compared with bone marrow uptake percentage. CONCLUSION: We describe a novel liver function quantitative assessment method that combines whole-body planar images and SPECT/CT attenuation-corrected images of Tc-SC distribution. Attenuation-corrected SC images provide valuable regional liver function information, which is a unique feature compared with other imaging methods available. The results of our study indicate that the Tc-SC uptake by the liver, spleen, and bone marrow correlates with liver function parameters in patients with diffuse liver disease and the correlation with liver disease severity is slightly better for liver uptake percentages than for individual values of bone marrow and spleen uptake percentages.

Regional Ventilation Is the Main Determinant of Alveolar Deposition of Coarse Particles in the Supine Healthy Human Lung During Tidal Breathing.

BACKGROUND: To quantify the relationship between regional lung ventilation and coarse aerosol deposition in the supine healthy human lung, we used oxygen-enhanced magnetic resonance imaging and planar gamma scintigraphy in seven subjects. METHODS: Regional ventilation was measured in the supine posture in a 15 mm sagittal slice of the right lung. Deposition was measured by using planar gamma scintigraphy (coronal scans, 40 cm FOV) immediately postdeposition, 1 hour 30 minutes and 22 hours after deposition of 99mTc-labeled particles (4.9 µm MMAD, GSD 2.5), inhaled in the supine posture (flow 0.5 L/s, 15 breaths/min). The distribution of retained particles at different times was used to infer deposition in different airway regions, with 22 hours representing alveolar deposition. The fraction of total slice ventilation per quartile of lung height from the lung apex to the dome of the diaphragm at functional residual capacity was computed, and co-registered with deposition data-apices aligned-using a transmission scan as reference. The ratio of fractional alveolar deposition to fractional ventilation of each quartile (r) was used to evaluate ventilation and deposition matching (r > 1, regional aerosol deposition fraction larger than regional ventilation fraction). RESULTS: r was not significantly different from 1 for all regions (1.04 ± 0.25, 1.08 ± 0.22, 1.03 ± 0.17, 0.92 ± 0.13, apex to diaphragm, p > 0.40) at the alveolar level (r22h). For retention times r0h and r1h30, only the diaphragmatic region at r1h30 differed significantly from 1. CONCLUSIONS: These results support the hypothesis that alveolar deposition is directly proportional to ventilation for ∼5 µm particles that are inhaled in the supine posture and are consistent with previous simulation predictions that show that convective flow is the main determinant of aerosol transport to the lung periphery.

Intratissular lymphaticovenous anastomoses demonstrated by perioperative intramuscular injection of 99mTC-colloids.

BACKGROUND: The existence of intratissular lymphaticovenous anastomoses has often been suggested, but it has never been demonstrated. This study aims at demonstrating the presence of such anastomoses. METHODS AND RESULTS: The free flap model was used to investigate the drainage of radiolabeled colloid particles whose size prevents direct passage to the blood vessels. The tracer was injected into the muscle or the skin during the surgical procedure. Blood samples were sequentially drawn from the venous pedicle over the 30 minutes that followed the tracer injection. The blood samples were counted using a gamma well-counter. In all 14 patients, the venous blood radioactivity steadily increased over time. Radiochemical analyses performed on the blood samples demonstrated that the radioactivity is related to the labeled colloids and not to free pertechnetate. Planar imaging performed 24 hours after the surgical procedure showed a significant liver uptake, and no accumulation in the area of normal lymphatic relays. CONCLUSIONS: As, in the free flap model, there is no lymphatic drainage through the classical pathways whatsoever, and since the size of the radiolabeled particles prevents them from directly entering the blood stream, the results strongly suggest the presence of functional intratissular lymphovenous anastomoses.

Cervical hibernoma demonstrating uptake on Tc-99m lymphoscintigraphy.

A hibernoma is an uncommon, benign tumor composed of brown adipose tissue. It is a rare but documented cause of neck masses. Hibernomas may be first diagnosed not by clinical examination, but incidentally through radiologic tests assessing the metabolic activity of certain tissues. These tumors are by definition benign entities but, given their propensity for growth over time, they require complete extirpation to prevent recurrence. Different radiologic modalities have been used to evaluate hibernomas, including computed tomography scan, magnetic resonance imaging, fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography, and angiography. It is rare for a hibernoma to be discovered through Tc-99m lymphoscintigraphy.

[Analysis of gastric emptying dynamics in relationship to qualitative composition of intake. Comparison between normal-weight and obese subjects]. / Análisis de la dinámica de vaciamiento gástrico en relación con la composición cualitativa de la ingesta. Comparación entre sujetos con normopeso y obesos.

AIMS: To analyze whether the gastric emptying profile could define obesity and to study the impact of macronutrients diet composition on gastric emptying in obese and non obese people. MATERIAL AND METHODS: 47 subjects were selected (12 non obese and 35 obese). The study was organized in 4 visits. In each visit the subject was given isocaloric breakfast differing in macronutrient composition, (either equilibrated, or lipid, protein or carbohydrate rich) quantitative gastric emptying assay was done realized, every 15 minutes for two hours using a radionuclide technique. The week prior to the visit, the subject followed a standard 1,800 cal/day diet. RESULT: A significant interaction between time and diet composition is shown regardless of the group (obese or non-obese) the subject belongs to. The different macronutrient composition differentially affected gastric emptying only in the obese group. Post hoc analysis of the results showed significant differences after 45 min post breakfast between protein and carbohydrate rich breakfast. CONCLUSIONS: Gastric emptying in obese but not in non obese subjects, was significantly modified depending on the intake qualitative composition. These differences are clear when protein rich (significantly slower emptying) is compared versus hydrocarbon enriched diet (significantly faster emptying). A significant difference in gastric emptying between obese and non-obese subjects cannot be established.

Renal allograft accumulation of technetium-99m sulfur colloid as a predictor of graft rejection.

Differentiation between rejection (the most common cause) and many other possibilities for detrimental effects on graft function represents a difficult issue to diagnose the cause of renal allograft dysfunction. This study was designed to determine whether technetium-99m sulfur colloid (TSC) accumulation predicted graft rejection. We prospectively studied 54 episodes of allograft dysfunction in 53 kidney transplant recipients who underwent TSC scintiscanning and graft biopsy. Visual analysis of TSC uptake compared uptake, in the allograft with that in the marrow of the fifth lumbar vertebra (L5). A 3+ result meant that allograft uptake was greater than L5 marrow uptake; 2+, the same; 1+, less and finally 0, no allograft uptake. Transplant accumulation of 2+ or more was considered consistent with rejection (P = .01). Allograft biopsies interpreted based on the Banff Working Classification showed rejection in 45 of 54 renal biopsies with 42 the biopsy-proven rejection episodes showing at least 2+ graft uptake. Furthermore, this nuclear medicine technique had a sensitivity of 93.3%, a specificity of 44.4%, a positive predictive value of 89.3%, a negative value of 57.1% and an efficiency of 83.3% for the diagnosis of renal allograft rejection.

Rim sign in Tc-99m sulfur colloid hepatic scintigraphy.

A case of pericholecystic hyperperfusion on Tc-99m sulfur colloid (SC) flow images with a pericholecystic rim of increased activity (PCHA) on delayed planar and single-photon emission computed tomography images of the liver was seen in a patient with a history of multiple renal transplants admitted with cramping right lower quadrant abdominal pain. Laparotomy performed 5 days after the scan revealed an acutely perforated gangrenous gallbladder and occluded cystic duct. The secondary findings of gallbladder hyperperfusion and PCHA or "rim sign" have been frequently reported with Tc-99m IDA hepatobiliary imaging. These secondary findings in conjunction with a nonvisualized gallbladder on an IDA scan suggest a complicated or advanced stage of acute cholecystitis and usually require urgent surgical intervention. The rim sign on Tc-99m SC scintigraphy also likely indicates the same grave diagnosis.

Heterogeneous patterns of lymphatic drainage to sentinel lymph nodes by primary melanoma from different anatomic sites.

UNLABELLED: We want to define the patterns of lymphatic drainage for primary melanoma to sentinel lymph nodes (SLNs) based on a large lymphoscintigraphic database. Preoperative lymphoscintigraphy was used to identify and classify SLN drainage basins and patterns of drainage. METHODS: Lymphoscintigraphy using intradermally administered technetium-99m labeled sulfur colloid was performed on 400 consecutive patients with malignant melanoma to define lymphatic drainage channels and draining SLN basins before surgery. Primary tumor sites consisted of head and neck, upper extremity, trunk, and lower extremity. Different types of drainage patterns were classified and correlated with different anatomic sites. RESULTS: SLN(s) were identified in over 98% of the patients, whereas lymphatic drainage channels were successfully identified in 90% of the patients. Drainage from the primary site to a single SLN through a single lymphatic channel (type IA) was seen in 186 of 400 patients (47%) as the most common type. In patients with a single SLN within a single basin (type I-V), the percentage of patients with primary lesions in the head and neck, upper extremity, trunk, and lower extremity regions were 61%, 79%, 55%, and 78%, respectively. In cases of multiple lymphatic channels (type VI-VII), the percentages of patients with primary lesions in the head and neck, upper extremity, trunk, and lower extremity regions were 24%, 8%, 36%, and 19%, respectively. CONCLUSION: Various drainage patterns were noted from primary melanomas in different anatomic sites. Preoperative lymphoscintigraphy is important in establishing the SLN basins for harvesting the SLN(s).

Lymphatic drainage patterns on early versus delayed breast lymphoscintigraphy performed after injection of filtered Tc-99m sulfur colloid in breast cancer patients undergoing sentinel lymph node biopsy.

The axillary lymph node status is the most important predictor of prognosis and aids in breast cancer treatment planning. Patients with breast cancer now frequently undergo sentinel lymph node (SLN) biopsy rather than axillary lymph node dissection to determine the status of the regional lymph nodes. However, the optimal timing of radionuclide injection relative to the timing of SLN biopsy remains controversial. The objective of this study was to compare the lymphatic drainage patterns on lymphoscintigraphy performed at 15 minutes to 4 hours and at 18 to 24 hours after injection of filtered Tc-99m sulfur colloid, and to determine whether, over time, radiocolloid migrates to second-echelon nodes that are not the SLNs. Fifteen women with breast cancer (mean age, 55 years; range, 38-78 years) were scheduled to undergo SLN biopsy after each received an injection of 18.5 MBq (0.5 mCi) filtered Tc-99m sulfur colloid into the breast parenchyma surrounding the tumor or biopsy cavity. Both early (15 minutes to 4 hours after radionuclide injection) and delayed (18-24 hours after radionuclide injection) lymphoscintigraphy was performed in each patient. SLN biopsy was performed, followed by completion axillary lymph node dissection and planned breast surgery. In each patient the patterns of distribution of the radionuclide in the lymph nodes were the same on early and delayed lymphoscintigrams. These findings, that the distributions of radionuclide in lymph nodes are identical on early and delayed images obtained after injection of filtered Tc-99m sulfur colloid, suggest that performing SLN biopsy on the day after injection does not diminish the accuracy of the technique in predicting the potential site of metastasis in the regional lymph nodes in patients undergoing this procedure for breast cancer.

Effect of Posture on Regional Deposition of Coarse Particles in the Healthy Human Lung.

BACKGROUND: Understanding the regional partition of deposition of inhaled particles within the lung is important for improving targeted delivery of inhaled aerosolized drugs. One factor affecting regional deposition is gravity. As the lung deforms under its own weight, changes in lung volume, in airway geometries, and in spatial patterns of ventilation distribution between postures have the potential to alter the regional distribution of deposited particles. METHODS: Using gamma-scintigraphy, we measured regional deposition and clearance of (99m)Tc labeled particles (5 µm) in 6 healthy subjects, with aerosol inhalation occurring both in the supine and seated postures at constant flow (0.5 L/sec) and breathing rate (15 breaths/min). After aerosol deposition, mucociliary clearance data were collected in the seated posture, immediately post-particle administration, 1 h 30 min, 4 h, and 22 h post-inhalation. Relative regional deposition was computed using retention (R) at the different time points, with (1-R(1h30min)), (R(1h30min)- R(4h)), and (R(4h)- R(22h)) corresponding to deposition in the large, intermediate, and small airways, respectively. Alveolar deposition was estimated as the relative retention at 22 h (R(22h)). RESULTS: Relative deposition of coarse particles in the alveolar region decreased from 60±8% seated to 34±16% supine (p=0.04). This change was accompanied by an increase in relative deposition in the intermediate (7±3% seated to 16±17% supine, P=0.09) and small airways (19±6% seated to 34±13% supine, p=0.06) when inhalation occurred in the supine posture. No change was observed in central to peripheral deposition (C/P ratio), the skew of the deposition distribution, or the apex-to-base ratio of deposition between seated and supine postures. CONCLUSIONS: Inhalation of coarse particles in the supine posture shifts relative deposition from the alveolar to the bronchial airways, when compared to the seated posture, likely driven by changes in functional residual capacity, and airway size, as well as changes in the regional distribution of ventilation between postures.

Microautoradiographic study of technetium-99m colloid uptake by the rat liver.

A new microautoradiographic technique was developed to study the distribution of 99mTc-labeled radiopharmaceuticals. Using a thick emulsion, it is possible to get microscopically visible tracks of internal conversion and Auger electrons. The liver uptake of microscopic particles has been thought to occur in Kupffer cells but no direct evidence has been provided for technetium colloids. Using this method, 99mTc-labeled colloids were clearly identified in Kupffer cells in the sinusoidal areas of liver. "Track" microautoradiography using a thick emulsion layer may be used on any frozen tissue sections and may provide an important tool to assess the biodistribution of 99mTc radiopharmaceuticals.

Technetium-99m-sulfur colloid for lymphoscintigraphy: effects of preparation parameters.

UNLABELLED: There has been a resurgence in the use of lymphoscintigraphy for the external detection of lymph nodes for metastatic melanoma and breast tumors. Technetium-99m-antimony trisulfide colloid was the radiopharmaceutical developed for this procedure and was found to have a narrow distribution of small particles, 0.003-0.03 microns, but it was never approved by the FDA. Technetium-99m-sulfur colloid also forms particles and this article reports on the effects different preparation parameters have on its particle size distribution and stability. METHODS: Four groups of kits were evaluated, kits which utilized: (a) a reduced heating protocol with a new 99mTc-elution, (b) a reduced heating protocol with an old 99mTc-elution, (c) a prolonged heating protocol with a new 99mTc-elution and (d) a prolonged heating protocol with an old 99mTc-elution. The particle size distribution and the stability of the different 99mTc-sulfur colloid kit preparations were evaluated over 6 hr utilizing polycarbonate filters ranging from 0.03 to 10 microns. RESULTS: In vitro studies demonstrated no significant change in the particle size distribution over a 6-hr period and all 99mTc-sulfur colloid preparations had a bimodal particle size distribution pattern. Importantly, heating the kit for shorter periods of times utilizing [99mTc]pertechnetate, which had a longer ingrowth of [99mTc]pertechnetate, produced a formulation which had the largest percentage of particles smaller than 0.03 microns. CONCLUSION: In our clinical setting, 99mTc-sulfur colloid prepared with the reduced heating protocol and utilizing [99mTc]pertechnetate, which has the highest ingrowth of [99mTc]pertechnetate has proved to be an excellent agent for lymphoscintigraphy studies. This preparation has demonstrated rapid movement of the particles from the primary site to the lymph nodes in over 97% (106/109) of the patients we have studied.

Dosimetry at the cellular level of Kupffer cells after technetium-99m-sulphur colloid injection.

The radiation dose to Kupffer cells was estimated at the cellular level after intravenous injection of 99mTc labeled sulphur colloids in rats. The results were then compared with those obtained using macroscopic dosimetry. From the microscopy appearance observed using a "track" microautoradiographic method (MAR), it was shown that only 0.2% of the Kupffer cells were actually involved in the pinocytosis of radioactive colloids. For each electronic emission from 99mTc (Auger and internal conversion), the fraction of the emitted energy actually absorbed within the Kupffer cell was calculated using the values provided by Berger. About 15% of the total energy emitted by electrons was absorbed in 0.2% of the Kupffer cells. If these results are extrapolated to humans, the dose absorbed by the labeled cells can be estimated to be between 0.5 and 0.9 Gy/MBq. This represents about 15,000 times the average electron dose to the liver as estimated from macrodosimetric methods. In cases such as this one where an important distribution heterogeneity is expected, dosimetric estimations at a cellular level may be particularly useful.