One-step, kit-based radiopharmaceuticals for molecular SPECT imaging: a versatile diphosphine chelator for 99mTc radiolabelling of peptides

Radiotracers labelled with technetium-99m (99mTc) enable accessible diagnostic imaging of disease, provided that radiotracer preparation is simple. Whilst 99mTc radiopharmaceuticals for imaging perfusion are routinely prepared from kits, and regularly used in healthcare, there are no 99mTc-labelled receptor-targeted radiopharmaceuticals in widespread clinical use. This is in part due to the multistep radiosyntheses required for the latter. We demonstrate that the diphosphine, 2,3-bis(diphenylphosphino)maleic anhydride (BMA), is an excellent platform for preparation of kit-based, receptor-targeted 99mTc-labelled radiotracers: its conjugates are simple to prepare and can be easily labelled with 99mTc using one-step, kit-based protocols. Here, reaction of BMA with the αvβ3-integrin receptor targeted cyclic peptide, Arg-Gly-Asp-DPhe-Lys (RGD), provided the first diphosphine-peptide conjugate, DP-RGD. DP-RGD was incorporated into a "kit", and addition of a saline solution containing 99mTcO4- to this kit, followed by heating, furnished the radiotracer [99mTcO2(DP-RGD)2]+ in consistently high radiochemical yields (>90%). The analogous [ReO2(DP-RGD)2]+ compound was prepared and characterised, revealing that both [99mTcO2(DP-RGD)2]+ and [ReO2(DP-RGD)2]+ consist of a mixture of cis and trans geometric isomers. Finally, [99mTcO2(DP-RGD)2]+ exhibited high metabolic stability, and selectively targeted αvβ3-integrin receptors, enabling in vivo SPECT imaging of αvβ3-integrin receptor expression in mice.

Effect of the CXCR4 antagonist plerixafor on endogenous neutrophil dynamics in the bone marrow, lung and spleen

Treatment with the CXCR4 antagonist, plerixafor (AMD3100), has been proposed for clinical use in patients with WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome and in pulmonary fibrosis. However, there is controversy with respect to the impact of plerixafor on neutrophil dynamics in the lung, which may affect its safety profile. In this study, we investigated the kinetics of endogenous neutrophils by direct imaging, using confocal intravital microscopy in mouse bone marrow, spleen, and lungs. Neutrophils are observed increasing their velocity and exiting the bone marrow following plerixafor administration, with a concomitant increase in neutrophil numbers in the blood and spleen, while the marginated pool of neutrophils in the lung microvasculature remained unchanged in terms of numbers and cell velocity. Use of autologous radiolabeled neutrophils and SPECT/CT imaging in healthy volunteers showed that plerixafor did not affect GM-CSF-primed neutrophil entrapment or release in the lungs. Taken together, these data suggest that plerixafor causes neutrophil mobilization from the bone marrow but does not impact on lung marginated neutrophil dynamics and thus is unlikely to compromise respiratory host defense both in humans and mice.

Preparation, radiolabeling with 99mTc and 67Ga and biodistribution studies of albumin nanoparticles covered with polymers

OBJECTIVE

To optimize radiolabeling with ^99mTc and ⁶⁷Ga of albumin nanoparticles coated with 4 differents synthetic polymers and to evaluate their stability in vivo and in vitro, as well as their biodistribution in vivo after intravenous administration.

MATERIAL AND METHODS

The nanoparticles were prepared using albumin and NOTA-modified albumin by the desolvation method and coated with 4 different polymers; HPMC, GMN2, GPM2 and GTM2. They were purified, lyophilized and characterized. Radiolabelling with ^99mTc was perfomed with 74 MBq of ^99mTc sodium pertechnetate, previously reduced with and acid solution of tin chloride at different concentrations (0.003, 0.005, 0.007, 0.01, 0.05 and 0.1mg/ml) and at different times (5, 10, 15, 30 and 60minutes) and temperatures (room temperature, 40°C and 60°C). Radiolabelling with ⁶⁷Ga was perfomed by incubation of the nanoparticles with 37 MBq of ⁶⁷Gallium chloride (obtained from commercial gallium-⁶⁷ citrate) at different times (10 and 30minutes) and temperatures (room temperature, 30°C and 60°C), and posterior purification with microconcentrators. The radiochemical purity was evaluated by TLC. Stability studies of radiolabeled nanoparticles in physiological serum and blood plasma were perfomed. Biodistribution studies of nanoparticles coated with GPM2 polymer were carried out in Wistar rats after intravenous administration of the nanoparticles. Control animals were carried out with ^99mTc sodium pertechnetate and ⁶⁷Ga chloride. To do so, the animals were killed and activity in organs was measured in a gamma counter.

RESULTS

^99mTc labeling was carried out optimally with a tin concentration of 0.007mg/ ml for the GPM2 nanoparticles and 0.005mg / ml for the rest of the formulations, with a radiolabelling time of 10minutes at room temperature. In the case of ⁶⁷Ga the label was optimized at 30° C temperature and 30minutes of incubation. In both cases the radiochemical purity obtained was greater than 97%. The nanoparticles showed high stability in vitro after 48hours of labeling (70% nanoparticles labeled with ^99mTc and 90% those labeled with ⁶⁷Ga). Biodistribution studies of nanoparticles ^99mTc -GPM2 and ⁶⁷Ga -NOTA-GPM2 showed a high accumulation of activity in the liver at 2 and 24hours after intravenous administration.

CONCLUSION

The labeling procedure with ^99mTc and ⁶⁷Ga of albumin and albumin modified with NOTA nanoparticles allows obtaining nanoparticles with high labeling yields and adequate in vitro stability, allowing their use for in vivo studies.

A feasibility study of sentinel lymph node mapping by cervical injection of a tracer in Japanese women with early stage endometrial cancer

OBJECTIVE

The aim of this study was to investigate the feasibility of sentinel lymph node mapping characterized by a cervical tracer injection in endometrial cancer.

MATERIALS AND METHODS

This retrospective study was carried out using data for 57 patients with endometrial carcinoma who had undergone intraoperative sentinel lymph node mapping and subsequent surgical staging. Technetium colloid and/or indocyanine green was injected into the uterine cervix and a gamma-detecting probe and/or photodynamic eye camera system was used intraoperatively to locate hot spots.

RESULTS

Of the 57 patients, 52 (91.2%) had FIGO Stage I disease. Successful unilateral or bilateral mapping occurred in 54 patients (94.7%) and 46 (80.7%), respectively. The median number of sentinel lymph nodes detected was two (range, 0-5). Following sentinel lymph node mapping, 41 patients (71.9%) underwent pelvic lymphadenectomy alone and 16 (28.1%) full lymphadenectomy. The median number of lymph nodes resected was 17 (range, 8-110). Sentinel lymph nodes were involved in four patients (7.0%), two with macrometastases and two with low-volume metastases. The sensitivity and negative predictive value for detecting lymph node metastasis were both 100%.

CONCLUSION

Sentinel lymph node mapping with the use of cervical tracer injection is highly feasible in Japanese women with early stage endometrial cancer.

Evaluation of 99mTc-sulfadiazine as Bacillus microorganisms infection imaging agent using animal model

Bacterial infection is one of the vital sources of morbidity and mortality. The development of single photon emission computed tomography (SPECT) radiotracer agents using antibiotics, for targeting in-vivo bacteria, helps in antibiotic dose calibration, targeted infection therapy and reduction in mortality rate. The aim of this study was to appraised ^99mTc-labeling sulfadiazine as a radiopharmaceutical for bacillus infections imaging. Radiolabeling of sulfadiazine with technetium-99m was carried out by subsequent addition of 1.5 mL aqueous solution of sulfadiazine (1mg/mL), 120µg stannous tartrate, gentistic acid as stabilizing agent and 185 MBq normal saline solution of ^99mTcO₄-¹ (pertechnetate) at pH = 5. The reaction mixture was incubated for 40 min at room temperature with light stirring. The quality control analysis (ITLC-SG and paper chromatography analysis) revealed ~ 98% labeling yield. Biodistribution and scintigraphic study was carried using bacillus bacterial infection induced New Zealand white rabbits. Due to the ease of ^99mTc-sulfadiazine conjugation method, high labeling efficiency, shelf stability (>95% up to 6h), blood serum stability (~90% up to 6h) and high uptake in the infected muscle (T/NT =2.21 at ¹H), ^99mTc-SDZ could be used as radiopharmaceutical of choice for further pre-clinical and clinical studies.

Nuclear Cardiology: Are We Using the Right Protocols and Tracers the Right Way?

The field of nuclear cardiology has changed considerably over recent years, with greater attention paid to safety and radiation protection issues. The wider usage of technetium-99m (Tc-99m)-labeled radiopharmaceuticals for single-photon emission computed tomography (SPECT) imaging using gamma cameras has contributed to better quality studies and lower radiation exposure to patients. Increased availability of tracers and scanners for positron emission tomography (PET) will help further improve the quality of studies and quantify myocardial blood flow and myocardial flow reserve, thus enhancing the contribution of non-invasive imaging to the management of coronary artery disease. The introduction of new instrumentation such as solid state cameras and new software will help reduce further radiation exposure to patients undergoing nuclear cardiology studies. Results from recent studies, focused on assessing the relationship between best practices and radiation risk, provide useful insights on simple measures to improve the safety of nuclear cardiology studies without compromising the quality of results.

Paclitaxel-loaded folate-coated long circulating and pH-sensitive liposomes as a potential drug delivery system: A biodistribution study

A range of antitumor agents for cancer treatment is available; however, they show low specificity, which often limit their use. Recently, we have reported the preparation of folate-coated long-circulating and pH-sensitive liposomes (SpHL-folate-PTX) loaded with paclitaxel (PTX), an effective drug for the treatment of solid tumors, including breast cancer. The purpose of this study was to prepare and characterize SpHL-PTX and SpHL-folate-PTX radiolabeled with technetium-99m (^99mTc). Biodistribution studies and scintigraphic images were performed after intravenous administration of ^99mTc-PTX, ^99mTc-SpHL-PTX and ^99mTc-SpHL-folate-PTX into healthy and tumor-bearing mice. High radiochemical purity (>98%) and in vitro stability (>90%) were achieved for both liposome formulations. The pharmacokinetic properties of ^99mTc-SpHL-DTPA-PTX and ^99mTc-SpHL-folate-DTPA-PTX decreased in a monophasic manner showing half-life of 400.1 and 541.8min, respectively. Scintigraphic images and biodistribution studies showed a significant uptake in liver, spleen and kidneys, demonstrating these routes as way for excretion. At 8h post-injection, the liposomal tumor uptake was higher than ^99mTc-PTX. Interesting, 4h after administration, the liposome folate coated showed higher tumor-to-muscle ratio than ^99mTc-SpHL-DTPA-PTX and ^99mTc-PTX. In conclusion, the liposomal systems, showed high tumor uptake by scintigraphic images, especially the ^99mTc-SpHL-folate-DTPA-PTX that showed a sustained and higher tumor-to-muscle ratio than non-functionalized liposome, which indicate its feasibility as a PTX delivery system to folate positive tumors.

Diagnostic sensitivity of Tc-99m HYNIC PSMA SPECT/CT in prostate carcinoma: A comparative analysis with Ga-68 PSMA PET/CT

BACKGROUND

Emerging data from published studies are demonstrating the superiority of Ga-68 PSMA PET/CT imaging in prostate cancer. However, the low yield of the Ge-68/Ga-68 from which Gallium-68 is obtained and fewer installed PET/CT systems compared to the SPECT imaging systems may limit its availability. We, therefore, evaluated in a head-to-head comparison, the diagnostic sensitivity of Ga-68 PSMA PET/CT and Tc-99m PSMA SPECT/CT in patients with prostate cancer.

METHODS

A total of 14 patients with histologically confirmed prostate cancer were prospectively recruited to undergo Ga-68 PSMA PET/CT and Tc-99m HYNIC PSMA SPECT/CT. The mean age of patients was 67.21 ± 8.15 years and the median PSA level was 45.18 ng/mL (range = 1.51-687 ng/mL). SUVmax of all lesions and the size of lymph nodes with PSMA avidity on Ga-68 PSMA PET/CT were determined. Proportions of these lesions detected on Tc-99m HYNIC PSMA SPECT/CT read independent of PET/CT findings were determined.

RESULTS

A total of 46 lesions were seen on Ga-68 PSMA PET/CT localized to the prostate (n = 10), lymph nodes (n = 24), and bones (n = 12). Of these, Tc-99m HYNIC PSMA SPECT/CT detected 36 lesions: Prostate = 10/10 (100%), lymph nodes = 15/24 (62.5%), and bones = 11/12 (91.7%) with an overall sensitivity of 78.3%. Lesions detected on Tc-99m HYNIC PSMA SPECT/CT were bigger in size (P < 0.001) and had higher SUVmax (P < 0.001) as measured on Ga-68 PSMA PET/CT compared to those lesions that were not detected. All lymph nodes greater than 10 mm in size were detected while only 28% of nodes less than 10 mm were detected by Tc-99m HYNIC PSMA SPECT/CT. In a univariate analysis, Lymph node size (P = 0.033) and the SUVmax of all lesions (P = 0.007) were significant predictors of lesion detection on Tc-99m HYNIC PSMA SPECT/CT.

CONCLUSION

Tc-99m HYNIC PSMA may be a useful in imaging of prostate cancer although with a lower sensitivity for lesion detection compared to Ga-68 PSMA PET/CT. Its use is recommended when Ga-68 PSMA is not readily available, in planning radio-guided surgery or the patient is being considered for radio-ligand therapy with Lu-177 PSMA. It performs poorly in detecting small-sized lesions hence its use is not recommended in patients with small volume disease.

Improved Targeting of Photosensitizers by Intratumoral Administration of Immunoconjugates

Biodistribution of technetium (99m Tc) labeled hematoporphyrin derivative (HpD, Photosan-3) conjugated to a monoclonal antibody to carcinoembryonic antigen (anti-CEA) was compared following intravenous ( i.v.) and intratumoral ( i.t.) administration in solid Ehrlich ascites tumor bearing mice. Images of mice at different time intervals were acquired after injection of radiolabeled PS-3 in either conjugated or unconjugated forms. Quantitative estimation of the radiolabel in different tissues was performed by selecting the different region of interests (ROIs). Maximum accumulation of both free and antibody conjugated PS-3 following i.v. administration was observed in liver followed by tumor. Tumor/muscle (T/N) ratio was more with free PS-3 compared to conjugated PS-3. Pharmacokinetics of free and conjugated PS-3 was also different with faster accumulation of conjugated PS-3 in the tumor. With intratumoral administration of anti-CEA-PS-3-99m Tc, specific accumulation and retention of the sensitizer was observed in the tumor tissue. Since, direct injection of antibody conjugated photosensitizer into the tumor resulted in longer retention of the dye in the tumor with no accumulation in the normal tissues, the present results imply that the toxicity to normal tissues could be reduced significantly with selective destruction of the tumor following photodynamic treatment with the use of i.t. administration of specific antibodies conjugated to photosensitizers.

Simplified quantification method for in vivo SPECT/CT imaging of asialoglycoprotein receptor with (99m)Tc-p(VLA-co-VNI) to assess and stage hepatic fibrosis in mice

The goal of this study is to develop a noninvasive method of SPECT imaging to quantify and stage liver fibrosis with an Asialoglycoprotein receptor (ASGP-R) targeting tracer-(99m)Tc-p(VLA-co-VNI). ASGP-Rs are well known to specifically express in the mammalian liver. Here, we demonstrated ASGP-R expression decreased in carbon tetrachloride (CCl4)-induced mouse model. ASGP-R expression correlated with liver fibrosis progression. ASGP-R could be a useful marker in the stage of liver fibrosis. Liver uptake value (LUV) derived by SPECT imaging was used to assess liver fibrosis in the CCl4-induced mouse model. LUV = [radioactivity (liver uptake)/radioactivity (injected)] × 100/liver volume. The LUV decreased along with the disease progression. The relationships between LUV and liver hydroxyproline (i.e. collagen), as well as Sirius Red were established and verified. A strong negative linear correlation was found between LUV and hydroxyproline levels (r = -0.83) as well as LUV and Sirius Red quantification (r = -0.83). In conclusion, SPECT imaging with (99m)Tc-p(VLA-co-VNI) is useful in evaluating and staging liver fibrosis in vivo.

[Use of SPECT-CT for visualization of sentinel lymph nodes in breast cancer patients]

This study was performed in order to determine individual variability of axillary sentinel lymph nodes (SLN) localization in patient with breast cancer (BC). Individual topography of axillary SLN was determined in 182 patients with early BC. All women were candidates for conservative surgical treatment with postoperative radiotherapy. SPECT-CT visualization of SLN started 120-240 min after intratumoral injection of 74-150MBq of 99mTc-radiocolloids. Distribution of axillary SLN was allocated to following subregions: central (C), pectoral (P), apical (AP), lateral (L), subscapular (SSc). SLN visualization by SPECT-CT was successful in 153 cases (84%). AP nodes were detected in 7 patients (5%). SLN were localized on thoracic wall in 34 cases (22%), in the intrapectoral region--in 3 (2%) women. According to axillary levels they were detected on level I--in 149 (97%), level II--15 (10%), level III-- (7.5%) cases.

Comparative biological evaluation of two [99mTc(CO)3]-dextran pyrazolyl mannose conjugates developed for use in sentinel lymph node detection

AIM

This work aims to develop receptor based alternatives to the conventional colloidal tracers in sentinel lymph node (SLN) detection. In this study, we report the detailed biological evaluation of two dextran pyrazolyl mannose derivatives towards this purpose.

METHODS

The dextran pyrazolyl mannose derivatives (DAPM4 and DAPM8) were labeled with the [99mTc(CO)3(H2O)3]+ core. In vitro saturation binding studies for the ligands were performed in mannose receptor-bearing RAW 264.7 macrophage precursor cells. Localization and pharmacokinetics studies of the tracers were conducted in normal Wistar rats with different ligand concentrations using in vivo activity distribution and scintigraphic imaging techniques.

RESULTS

The ligands were labeled with the [99mTc(CO)3)]+ core in high yield and radiochemical purity (>90%). DAPM4 and DAPM8 showed specific uptake in RAW 264.7 cells. In vivo localization studies showed concentration-dependent uptake and selective retention of the [99mTc]-labeled complexes of DAPM4 and DAPM8 in the sentinel node with highly favorable values of popliteal extraction [PE] (%PEDAPM4=92.94%,%PEDAPM8=91.80% at 180 min p.i.) and rapid clearance from the site of injection when administered at 50 µg/mL ligand concentration.

CONCLUSION

[99mTc(CO)3]-complexes of DAPM4 and DAPM8 show good in vivo potential to undergo further testing as agents for SLN detection in the clinic and their biological efficacy varies depending upon the concentration of ligands used for the procedure.

Targeted novel surface-modified nanoparticles for interferon delivery for the treatment of hepatitis B

The purpose of the present work was to develop hepatitis B surface antigen (HBsAg) surface-adsorbed cationic poly (d,l-lactic-co-glycolic acid) PLGA nanoparticles for interferon alpha (IFNα) delivery targeted to hepatocytes. Cationic PLGA nanoparticles loaded with IFNα were prepared using the double emulsification technique. Delipidated HBsAg was passively adsorbed on the surface of nanoparticles by using the simple dipping and drying method. Surface morphology and size distribution of nanoparticles were analyzed by scanning electron microscopy and dynamic light-scattering method, respectively. The biodistribution behavior of plain and HBsAg-coated (99m)Tc-tagged PLGA nanoparticles was also examined followed by intravenous injection. The results revealed that ∼75% of the radioactivity was recovered in the liver after 4 h of injection that was nearly 3-fold greater in magnitude than the plain PLGA nanoparticles. These data demonstrated that the novel formulation of nanoparticles has potential application in hepatic-targeted drug delivery.

Tumor pretargeting in mice using MORF conjugated CC49 antibody and radiolabeled complimentary cMORF effector

AIM

Using the antiCEA antibody MN14, a LS174T mouse tumor model has been successfully targeted with (⁹⁹m)Tc for imaging and ¹⁸⁸Re for radiotherapy by phosphorodiamidate morpholino oligomers (MORF)/complementary MORF (cMORF) pretargeting strategy. This investigation evaluated the antiTAG-72 antibody CC49 as an alternative to MN14 for this application.

METHODS

Both CC49 and MN14 were labeled with ¹¹¹In via SCN-benzyl-DTPA and their biodistributions were compared to that of MN14 labeled via DTPA anhydride. Since the accessibility of the antibody to the effector is required for optimization of pretargeting, the internalization of both MORF-CC49 and MORF-MN14 antibodies in LS174T cells were evaluated in culture. In addition, the accessible concentration of MORF-CC49 antibody in tumor was determined in a series of pretargeting studies with escalating dosages of the [(⁹⁹m)Tc]cMORF effector. Finally, using these results and our semi-empirical model, an imaging study was performed under optimal pretargeting conditions.

RESULTS

The biodistribution of ¹¹¹In to trace the MN14 antibody depended significantly on the labeling method. Furthermore, both MORF-CC49 and MORF-MN14 antibodies showed rapid internalization in culture. Fortunately, the accessibility in tumor was found to be less seriously reduced in vivo. In a pretargeting study under optimal conditions, both by imaging and by necropsy, the [(⁹⁹m)Tc]cMORF effector accumulated predominantly in the tumor of pretargeted mice. Normal tissue accumulations were minimal except in kidneys, liver, and a segment of intestines.

CONCLUSION

MORF pretargeting with CC49 was equally successful in the LS174T tumor model to the MORF pretargeting with MN14. The MORF-CC49 antibody may therefore be considered for future investigations toward early clinical trials.

Comparative performance of two inhaler systems to assess distribution of convective ventilation by 99mTc-labeled aerosol scintigraphy in patients with airway obstruction

AIM

Redistribution of convective ventilation, the leading disorder in airway obstruction, is a target of pharmacological and mechanical ventilation treatments for patients with chronic obstructive pulmonary disease (COPD). Convective ventilation is visualized by ventilation scintigraphy using radiolabeled aerosol particles that should ideally deposit in the terminal airspaces, but not in the conducting airways, and have no Brownian motion (which characterizes diffusive ventilation). Currently available commercial systems do not meet these requirements as they do not ensure an optimal size of aerosol droplets delivered at the mouthpiece.

METHODS

A new inhaling system (FAI) was developed and designed so as to yield radioaerosol droplets with smaller particle size and to ensure more efficient aerosol delivery to the terminal airways than that obtained with a widely available commercial system (MMI). A cascade impactor was employed to measure the size of the radioactive droplets at the mouthpiece. Preliminary comparative validation was based on ventilation scintigraphy using the two systems (both followed by a standard lung perfusion scan) in control subjects and in patients with airway obstruction. The time required to reach a certain count rate in the lung fields (1 kc/s) was recorded by means of dynamic g camera acquisition during breathing. Subsequent static images allowed assessment of intrapulmonary distribution of ventilation (by both visual and quantitative evaluation) and of the ventilation/perfusion (V/Q) ratios relative to the upper, middle, and lower thirds of the lung fields. RESULTS. FAI yielded 99mTc-labeled droplets with a count median diameter of 1.4 microm and a geometric standard deviation of 2 microm , versus 3 microm and 2, respectively, produced by the commercial inhaler (MMI). The mean time to reach the 1 kc/s count rate was significantly shorter with the FAI than with the MMI both in control subjects (4.7+/-1.7 min versus 8.2+/-2 min, P<0.04) and in airway-obstructed patients (3.4+/-0.8 min versus 8.4+/-2 min, P<0.001). With the MMI, appreciable radioaerosol deposition in the large bronchi prevented reliable quantitative assessment of ventilation, even in the control subjects. With the FAI, radioaerosol deposition in the central large airways was never observed in the controls and was only sporadically or occasionally observed in patients with COPD or asthma, respectively. This feature allowed quantitative ventilation assessment. The FAI-generated radioaerosol particles reached the peripheral respiratory spaces more efficiently than those generated by MMI; on the ventilation scans, the FAI allowed better discrimination than the MMI of the different pathophysiologic conditions.

CONCLUSION

These findings consistently indicate that the smaller-sized radiolabeled droplets generated by FAI, combined with the better breathing dynamics of the inhaler device, result in better overall performance as compared to the commercial system. This makes scintigraphic images obtained with the new device especially suitable for assessing convective ventilation in COPD patients, a particularly helpful feature for analytically describing the distribution patterns observed in airway-obstructed patients and for evaluating the effects of drugs, mechanical ventilation, and other interventions in such patients.

Ionic strength-sensitive pullulan acetate nanoparticles (PAN) for intratumoral administration of radioisotope: Ionic strength-dependent aggregation behavior and 99mTechnetium retention property

In order to design an effective intratumoral radioisotope carrier, a self-assembled nanoparticle evidencing ionic strength (IS)-sensitivity from a polysaccharide derivative (pullulan acetate nanoparticle (PAN)) was prepared via dialysis. The PAN had a spherical shape in a range of size of 50-130 nm and a low critical aggregation concentration (CAC) (<8 microg/mL). With increases in the IS of the dialysis media (IS(dia)), the CAC of PAN was reduced gradually and the rigidity of the hydrophobic core in PAN was increased. This suggests that the property of PAN was altered more hydrophobically at high IS values. The stabilities of PANs prepared from various IS(dia) were also monitored with changes in the turbidity and particle size in different IS solutions. In the case of PAN prepared at an IS(dia)=0.0, the turbidity was dramatically reduced with increasing IS due to the facilitation of aggregation between the particles, whereas in the other cases, these changes were negligible. This finding indicates that PAN prepared in distilled water (IS=0.0) can be readily injected as the consequence of its nano-size, and accumulates quickly, then remains in the tumor site for a considerable period (IS=0.15). In order to closely estimate the potential of PAN as a radioisotope carrier, the radioisotope labeling efficiency of PAN with no chelating agents was evaluated. PAN evidenced a high degree of (99m)Technetium ((99m)Tc) labeling efficiency (approximately 98%). The percentage retention rate (%RR) of the (99m)Tc-labeled PAN was significantly longer than that of the free (99m)Tc (p<0.05), due largely to PAN's IS-sensitivity. In conclusion, PAN may constitute a new approach to the achievement of maximal radioisotope efficiency with regard to intratumoral administration.

Facemasks and aerosol delivery in vivo

It has been shown in vitro that even a small air leak in the facemask can drastically reduce the efficiency of drug delivery. In addition, it has been shown that drug deposition on the face does significantly add to overall drug loss and has the potential of local side effects. The aim of this study is therefore to verify these findings in vivo. Eight asymptomatic recurrently wheezy children, aged 18-36 months, inhaled a radiolabeled salbutamol formulation either from a pressurized metered-dose inhaler through a spacer with attached facemask or from a nebulizer with attached facemask. Drug deposition of radiolabeled salbutamol was assessed with a gamma camera and expressed as a percentage of the total dose. Lung deposition expressed as a percentage of the total dose (metered dose and nebulizer fill, respectively) was 0.2% and 0.3% in children who inhaled with a non-tightly fitted facemask. Lung deposition was 0.6% and 1.4% in screaming children with a tightly fitted facemask and between 4.8% and 8.2% in patients breathing normally. Overall mask deposition was between 0.8% and 5.2%. Overall face deposition was between 2.6% and 8.4%. The results from this pilot study support the results found in in vitro studies, where a facemask leak greatly reduces drug delivery to the patient.

[Technetium-99m labeled synaptotagmin I C2A detection of paclitaxel-induced apoptosis in non-small cell lung cancer]

Objective To evaluate the efficacy of 99mTc-labeled C2A probe in detection of apoptosis of non-small cell lung cancer (NSCLC) cells after chemotherapy.

METHODS

Imaging studies were performed in NSCLC H460-bearing mice. The mice were divided into 2 groups: the paclitaxel-treated group and control group. 99mTc-C2A was injected intravenously at 12, 24, 48 and 72 h after chemotherapy. Images were acquired at 3 h and 6 h after injection using a pinhole collimator. The regions of interest (ROI) were drawn in tumor area and contralateral nomal tissue, and the ratio of T/NT were caculated. The tumor sections were stained by HE and TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-nick-end labeling) staining to confirm the presence of apoptosis. Activated caspase-3 was also analyzed with flow cytometry.

RESULTS

Little uptake of 99mTc-C2A was found in baseline images, but tumor uptake increased very much after chemotherapy, the T/NT ratio was 1.79 +/- 0.34, 2.23 +/- 0.33 and 2.78 +/- 0.34, respectively. The T/NT ratio of control was 1.48 +/- 0.23. Tumor uptake (% ID/g) of 99mTc-C2A in chemotherapy groups were 2.82 +/- 0.90, 3.13 +/- 0.48 and 3.52 +/- 1.18, respectively. Tumor uptake (% ID/g) in the control group was 1.21 +/- 0.51. It in paclitaxel-treatment groups were 2.82 +/- 0.90, 3.13 +/- 0.48 and 3.51 +/- 1.18, respectively, significantly higher than that in untreated mice. Furthermore, the uptake of 99mTc-C2A correlated well with apoptotic index (r = 0.56, P < 0.01), and activated caspase-3 (r = 0.59, P < 0.01).

CONCLUSION

Our preliminary results demonstrated that 99mTc-C2A imaging in vivo for detection of cell death in solid tumors is feasible and well correlated with TUNEL staining and activated caspase-3. The C2A holds promise and warrants further development as a molecular probe to early predict cancer treatment efficacy.

Lanthanide-loaded liposomes for multimodality imaging and therapy

Many advanced molecular imaging agents are currently being investigated preclinically. Especially, liposomes, have proven to be very promising carrier systems for diagnostic agents for use in single-photon emission computed tomography (SPECT) or magnetic resonance imaging (MRI), as well as for therapeutic agents to treat diseases such as cancer. In this study, nanosized liposomes were designed and labeled with the radionuclides, holmium-166 (both a beta- and gamma-emitter and also highly paramagnetic) or technetium-99m, and coloaded with paramagnetic gadolinium allowing multimodality SPECT and MR imaging and radionuclide therapy with one single agent.

METHODS

Diethylenetriaminepentaacetic acid bisoctadecylamide (an amphiphilic molecule with a chelating group suitable for labeling with radionuclides) and gadoliniumacetylacetonate (GdAcAc) (a small lipophilic paramagnetic molecule) were incorporated in liposomes. The liposomes were characterized by measuring their mean size and size distribution, gadolinium content, and radiochemical stability after incubation in human serum at 37 degrees C. The MRI properties (in vitro) were determined by use of relaxivity measurements at 1.5 and 3.0 Tesla in order to evaluate their potency as imaging agents.

RESULTS

The liposomes were successfully labeled with holmium-166, resulting in a high labeling efficiency (95% +/- 1%) and radiochemical stability (> 98% after 48 hours of incubation), and coloaded with GdAcAc. Labeling of liposomes with technetium-99m was somewhat less efficient (85% +/- 2%), although their radiochemical stability was sufficient (95% +/- 1% after 6 hours of incubation). MRI measurements showed that the incorporation of GdAcAc had a strong effect on the MRI relaxivity.

CONCLUSIONS

The synthesized liposomes allow for multimodality imaging and therapy, which makes these new agents highly attractive for future applications.

Evaluation of biodistribution by local versus systemic administration of 99mTc-labeled pamidronate

BACKGROUND

There is an emerging interest in utilizing local and systemic administration of bisphosphonates in orthopedics. The primary objective of this study was to use (99m)Tc-pamidronate ((99m)Tc-PAM) as a tool and compare bone and tissue uptake by local versus systemic administration.

METHODS

(99m)Tc-PAM was administered intravenously (i.v.), subcutaneously (s.c.) and by direct application (d.a.) on a surgically exposed and fractured femur (d.a.#f). The animals were imaged at 2 h and 24 h after administration and then killed. Organs were harvested, and their radioactivity was estimated. Specific uptake in the right femur was compared between groups, as was systemic exposure to (99m)Tc PAM.

RESULTS

Bone uptake of (99m)Tc-PAM in the i.v. and s.c. groups was 2.2 +/- 0.15 and 0.65 +/- 0.07% ID/g, respectively, at the 2 h time point. Uptake by surgically exposed right femur (d.a) was 5.15 +/- 0.26% ID/g, 134% higher than the femoral uptake by the i.v. method (P < 0.05). In the presence of exposed bone when the femur was fractured (d.a.#f), the uptake was 7.89 +/- 0.46% ID/g, a further 50% increase (P < 0.05). The uptake of (99m)Tc-PAM increased after 24 h of application to 2.4 +/- 0.15, 1.53 +/- 0.09, 7.94 +/- 0.99, and 13.2 +/- 0.80% ID/g) for i.v., s.c., d.a., and d.a.#f methods, respectively. The increases in uptake for the d.a. methods were significantly higher than for the local methods at the 24-h time point (P < 0.05). Although renal uptake was comparable with the i.v. and s.c. methods (0.22 +/- 0.03 and 0.22 +/- 0.04% ID/g), it was significantly lower with the d.a. methods (0.05 +/- 0.07 and 0.16 +/- 0.07% ID/g) (P < 0.05). The corresponding urinary excretion was 55%, 45%, 36%, and 35% of the injected dose at 24 h.

CONCLUSIONS

The results indicate that the bone uptake of (99m)Tc-PAM was significantly higher (P = 0.001) and the kidney uptake significantly lower (P = 0.004) with the d.a. methods than with the i.v. or s.c. method. The findings indicate the need for further study into the potential of local administration of bisphosphonates in the presence of orthopedic indications.

Negligible clearance of ultrafine particles retained in healthy and affected human lungs

Ambient particles are believed to be a specific health hazard, although the underlying mechanisms are not fully understood. There are data in the literature indicating fast and substantial systemic uptake of particles from the lung. The present authors have developed an improved method to produce ultrafine particles with more stable radiolabelling and defined particle size range. Fifteen subjects inhaled technetium 99m (99mTc)-labelled carbonaceous particles of 100 nm in size. Radioactivity over the lung was followed for 70 h. The clearance of these ultrafine particles from the lungs and specifically translocation to the circulation was tested. Lung retention for all subjects at 46 h was mean+/-sd 99+/-4.6%. Cumulative leaching of 99mTc activity from the particles was 2.6+/-0.96% at 70 h. The 24-h activity leaching in urine was 1.0+/-0.55%. No evidence of a quantitatively important translocation of 100-nm particles to the systemic circulation from the lungs was found. More research is needed to establish if the approximately 1% cleared activity originates from leached activity or insoluble translocated particles, and whether a few per cent of translocated particles is sufficient to cause harmful effects.

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.

Annexin V SPECT imaging of phosphatidylserine expression in patients with dementia

The authors sought to use radiolabeled annexin V, a marker of phosphatidylserine expression, to image Alzheimer dementia (AD). Four of five patients with AD had multifocal cortical annexin V uptake, whereas all seven non-AD and six control patients had normal SPECT. The mean cortex/cerebellar activity in patients with AD (1.4 +/- 0.6) was higher than that of non-AD dementia patients (0.7 +/- 0.2; p = 0.02). Radiolabeled annexin V may be useful for imaging AD.

Phytate technetium-99m versus dextran 500 technetium-99m in the sentinel lymph node biopsy

PURPOSE

To study which of the two most used radiopharmaceutical drugs for the sentinel lymph node (SLN) biopsy procedure (dextran 500 99mTc and phytate 99mTc) best defines the SLN and migrates less to other lymph nodes.

MATERIAL AND METHODS

Thirty-two rats, separated into two groups, underwent lymphoscintigraphy examination with either dextran or phytate followed by sentinel (popliteal), lumbar, and inguinal lymph node biopsy. Radiation was detected with a gamma probe.

RESULTS

The statistical study indicated count rates significantly higher in the SLN than in the other basins for both the dextran (P<0.01) and phytate groups (P<0.001). There was no statistically significant difference concerning SLN absorption in either group (P=0.2981). In the dextran group, migration occurred to 1.5 lymphatic basins with counting higher than 10% of that found in the SLN versus 0.8 in the phytate group (P=0.0023). Migration was thus higher in the dextran group (P=0.0207).

CONCLUSION

There was no statistically significant difference between dextran and phytate in the SLN identification, but the phytate migrated to fewer lymphatic basins beyond the SLN and with less intensity.

Clinical evidences of GM3 (NeuGc) ganglioside expression in human breast cancer using the 14F7 monoclonal antibody labelled with (99m)Tc

The relevance of certain gangliosides in tumour growth and metastatic dissemination has been well documented, reasons for considering these molecules as potential targets for cancer immunotherapy and diagnosis. GM3(NeuGc) ganglioside is particularly interesting due to its restrictive expression in normal human tissues according to immunohistochemical studies, using either polyclonal or monoclonal antibodies. But both immunohistochemical and biochemical methods have strongly suggested its over-expression in human breast tumours. Nevertheless, the lack of a direct evidence of this antigenic display in human breast cancer has kept the subject controversial. For the first time, we described herein the "in vivo" detection of GM3(NeuGc) ganglioside in human breast primary tumours using a radioimmunoscintigraphic technique with 14F7, a highly specific anti-GM3(NeuGc) ganglioside monoclonal antibody, labelled with (99m)Tc. In an open, prospective Phase I/II clinical trial, including women diagnosed in stage II breast cancer, the 14F7 monoclonal antibody accumulation in tumours at doses of 0.3 (n=5), 1 (n=5) and 3 mg (n=4) was evaluated. Noteworthy, the immunoscintigraphic study showed antibody accumulation in 100% of patients' tumours for the 1 mg dose group. In turn, the radioimmunoconjugate injected at doses of 0.3 mg or 3 mg of the antibody, was uptaken by 60 and 33.3% of breast tumours, respectively. "In vivo" immune recognition of GM3(NeuGc) in breast tumours reinforces the value of this peculiar target for cancer immunotherapy.

High lung deposition of 99mTc-labeled ciclesonide administered via HFA-MDI to patients with asthma

OBJECTIVE

To examine the deposition and pharmacokinetics of ciclesonide administered via hydrofluoroalkane-metered dose inhaler (HFA-MDI) in patients with asthma.

METHODS

Twelve patients with mild asthma (FEV1, 95% predicted) inhaled a single dose of 99mtechnetium (Tc)-ciclesonide 320 microg ex-actuator (400 microg ex-valve). Deposition of ciclesonide in the lung and oropharynx was quantified using two-dimensional (2D)-gamma scintigraphy. Three-dimensional single photon emission computed tomography (3D SPECT) was used to assess the regional distribution of ciclesonide in the lung. The pharmacokinetics of ciclesonide and its active metabolite, desisobutyryl-ciclesonide (des-CIC), were determined by liquid chromatography-tandem mass spectrometry. Ciclesonide and des-CIC concentrations were determined in mouth-rinsing solutions.

RESULTS

2D-gamma scintigraphy indicated that ciclesonide deposition was higher in the whole lung (52%) than in the oropharynx (32.9%). Furthermore, 3D SPECT revealed that ciclesonide deposition within the lungs was highest in the peripheral regions that contain the small airways and alveoli. The pharmacokinetic profile of Tc-labeled ciclesonide and des-CIC was similar to that obtained after inhalation of non-labeled formulations in previous studies. Des-CIC accounted for 14.9% of the total molar concentration of ciclesonide/des-CIC in mouth-rinsing solutions obtained between 7 and 12min after inhalation.

CONCLUSION

Inhalation of ciclesonide via HFA-MDI results in high pulmonary deposition, especially in the peripheral regions of the lung. High pulmonary deposition contributes to ciclesonide's ability to maintain lung function and control symptoms in patients with asthma. Deposition and activation of ciclesonide in the oropharynx is low, consistent with previous reports of low oropharyngeal deposition and a reduced incidence of local side effects in patients receiving ciclesonide therapy.

(99m)Tc-labeled murine ior C5 monoclonal antibody in colorectal carcinoma patients: pharmacokinetics, biodistribution, absorbed radiation doses to normal organs and tissues and tumor localization

Monoclonal Antibody (mAb) ior C5 is a murine IgG(1) that recognizes the tumor associated antigen (TAA) ior C2, a cell surface O-linked glycoprotein carbohydrate chain not present in most normal tissues and homogeneously expressed in the cytoplasm of normal colon epithelium and heterogeneously expressed in more than 83% of primary colorectal carcinomas. This study was designed to investigate the pharmacokinetics, biodistribution and the absorbed radiation doses of (99m)Tc-labeled mAb ior C5 antibody in colorectal tumor patients. Ten patients were administered 3 mg of anti-O-linked glycoprotein carbohydrate chain TAA ior C2 murine monoclonal antibody ior C5 radiolabeled with (99m)Tc activity of 1435.0 +/- 123 MBq by intravenous (i.v.) bolus infusion. Blood and urine samples were collected from 4 out of 10 patients at timed intervals from 10 min and up to 24 h after injection of the (99m)Tc-labeled mAb ior C5 for pharmacokinetic studies. Whole body images were taken in 5 out of 10 patients for quantitative normal organ biodistribution and dosimetry studies and planar anterior and posterior and SPECT images were taken in 5 out of 10 patients for tumor localization. Mean absorbed doses were estimated using the methods developed by the Medical Internal Radiation Dose (MIRD) committee. The effective dose equivalent (EDE) and effective dose (ED) were calculated as prescribed in International Commission on Radiological Protection (ICRP) publications 30 and 60. Plasma disappearance curves of (99m)Tc-labeled murine antibody ior C5 were best fit by a two-compartment model in all patients with (t(1/2alpha)) of 4.32 +/- 2.18 h and (t(1/2beta) of 32.6 +/- 3.82 h. Among the main target organs, accumulation of the radiolabeled antibody was found in liver (9.38 +/- 0.80%), heart (8.92 +/- 0.94%) and spleen (1.37 +/- 0.30%) at 5 min post-administration. These values were reduced at 24 h to (5.91 +/- 0.73%) and (0.62 +/- 0.22%), respectively, for the heart and spleen and increased to (9.78 +/- 1.99%) for liver. Estimates of radiation absorbed dose to normal organs in rad/mCi administered were: whole body, 0.0181 +/- 0.0017; heart wall, 0.0768 +/- 0.0090; kidneys, 0.0530 +/- 0.0260; liver, 0.0565 +/- 0.0109 and spleen, 0.0540 +/- 0.0128. The effective dose equivalent and effective dose estimates for adults were 0.0314 +/- 0.0031 and 0.0249 +/- 0.0027 rem/mCi administered. This feasibility study indicates that the O-linked glycoprotein carbohydrate chain TAA ior C2 is expressed in primary and metastatic colorectal carcinomas and shows very limited expression in normal adult tissues. The very good pattern of biodistribution of (99m)Tc-labeled mAb ior C5 in patients will allow imaging of colorectal carcinoma lesions.

Oral therapy with dipyridamole limits ischemia-reperfusion injury in humans

BACKGROUND

Adenosine receptor stimulation induces several effects that could limit ischemia-reperfusion injury. We hypothesize that treatment with the nucleoside uptake inhibitor dipyridamole increases endogenous adenosine and limits ischemia-reperfusion injury in humans.

METHODS

Ischemia-reperfusion injury was studied in forearm skeletal muscle by technetium Tc 99m-labeled annexin A5 scintigraphy. Ischemia-reperfusion injury was induced by unilateral forearm ischemic exercise. Immediately on reperfusion, annexin A5 labeled with technetium Tc 99m was administered intravenously, and ischemia-reperfusion injury was expressed as the percentage difference in radioactivity between the experimental arm and the control arm 1 and 4 hours after reperfusion. Targeting was quantified in the region of the thenar muscle and forearm flexor muscles. This approach was used in 9 healthy male volunteers after a 1-week treatment with dipyridamole (200 mg, slow release, twice daily) and in 23 control subjects.

RESULTS

Dipyridamole treatment significantly reduced annexin A5 targeting in skeletal muscle compared with the control group (thenar region, 13% +/- 7% versus 22% +/- 15% at 1 hour after reperfusion and 9% +/- 6% versus 27% +/- 13% at 4 hours for dipyridamole and control groups, respectively [P = .01]; flexor region, 4% +/- 8% versus 7% +/- 6% at 1 hour after reperfusion and 1% +/- 4% versus 10% +/- 9% at 4 hours for dipyridamole and control groups, respectively [P = .01]).

CONCLUSIONS

One week of oral treatment with the nucleoside uptake inhibitor dipyridamole (200 mg, slow release, twice daily) significantly limits ischemia-reperfusion injury in humans in vivo, as assessed by technetium Tc 99m-labeled annexin A5 scintigraphy of forearm skeletal muscle.

Evidence of antisense tumor targeting in mice

Even though increased accumulations of radiolabeled antisense DNAs compared to control DNAs are becoming a routine observation in cultured tumor cells, trustworthy evidence of tumor targeting in vivo by an antisense mechanism remains elusive. The goal of this study was to obtain convincing evidence of antisense tumor targeting in nude mice by using two different tumors and both intratumoral (i.t.) and intravenous (i.v.) administration of radiolabeled antisense and control sense DNAs. Both the MDR++ cell line KB-G2 and its parent MDR+ cell line KB-31 were used in this study. The antisense (AS) DNA was directed against the AUG start codon of the MDR1 mRNA and, along with the sense (S) control DNA, was a uniform phosphorothioate administered naked. In previous cell culture studies from our laboratories, the accumulation of this AS DNA was strikingly high in KB-G2 cells and only average in KB-31 cells, a fact we attribute to the 1000-fold higher expression by RT-PCR of MDR1 mRNA in the former cell line. In this study, both DNAs were radiolabeled with (99m)Tc via MAG3 and administered i.t. or i.v. at 1 microg (100 microCi) per animal 24 h prior to sacrifice and dissection in mice bearing thigh tumors of about 1 g. Following i.t. administration, no statistically significant differences (Student's t test, p < 0.05, N = 4) between the AS and S DNA biodistributions in normal tissues were observed except in the KB-G2 mice in which muscle levels were lower for the S control. In contrast, tumor levels in the KB-G2 animals were significantly higher for the AS DNA vs S DNA (14.7 vs 8.5% ID/g) while this difference (8.6 vs 4.3% ID/g) was insignificant in the KB-31 animals. The whole body images obtained just prior to sacrifice clearly show improved targeting of AS DNA vs S DNA in the KB-G2 but not the KB-31 animals. Calculations based on these results show that about 60 000 AS DNAs accumulated specifically (i.e. AS DNA - S DNA) per KB-G2 tumor cell following i.t. administration. When administered i.v. rather than i.t., higher tumor levels in KB-G2 animals compared to KB-31 were not observed, most likely because of the lower dosage reaching the tumors. When the KB-G2 and KB-31 results are combined, no statistically significant differences between the AS and S DNA biodistributions in normal tissues were observed except in blood in which S DNA levels were higher and in spleen in which they were lower. In contrast, tumor levels were significantly higher for the AS DNA vs S DNA (0.100 vs 0.063% ID/g). Calculations based on these results show that about 400 AS DNAs accumulated specifically per tumor cell following i.v. administration. Therefore evidence for tumor targeting in vivo by an antisense mechanism has been obtained in that statistically higher tumor accumulations of the (99m)Tc-AS DNA were observed compared to the control (99m)Tc-S DNA both following i.t. and i.v. administrations. The successful localization of AS DNA in tumor demonstrates that in vivo AS targeting of tumor is feasible although improvements in tumor delivery and normal tissue clearance are needed for practical antisense imaging.

[Evaluation of the influence of patient age and spacer device volume on aerosol lung deposition]

OBJECTIVE

To evaluate the efficacy of three frequently used spacer devices to deliver aerosol to the lung, and to compare radioaerosol deposition with each device in different age groups.

METHODS

Nine healthy, non-smoking volunteers were recruited: three adults and six children, including three toddlers and three school age children. Qualitative and semi-quantitative analysis of radioaerosol deposition in the lung were carried out. Yet, two small-volume devices (Aerochamber and Inal-Air) and one large-volume device (Flumax) were compared. Each patient inhaled 99mtechnetium-phytate. The device was filled during 30 seconds with radioaerosol. Oxygen was used as the driving gas. During 10 seconds, the patients inhaled the radioaerosol. The radiation emitted at the front and back of the chest was measured. The radiation inside the device was also measured.

RESULTS

The quantitative evaluation of lung deposition revealed that the younger the patient, the less aerosol was deposited in the lung with the large-volume spacer device (Flumax). The difference between small-volume devices (Aerochamber and Inal-Air) was not significant.

CONCLUSION

Small-volume spacers are the most appropriate for children. Large-volume devices should only be used by adolescents and adults.

A low-dose radioisotope procedure for assessment of subcutaneous drug delivery systems used for slow intrathecal infusion of antispasmodic agents

STUDY DESIGN

Retrospective single centre study.

OBJECTIVES

To evaluate a low-dose radioisotope imaging procedure for assessment of implanted intrathecal drug delivery and to compare the radiation dose and diagnostic value of these studies with other reported studies using higher administered radiation dose.

SETTING

National Spinal Injuries Centre, Stoke Mandeville Hospital, UK.

METHOD

A total of 11 spinally injured patients with subcutaneous drug delivery systems and uncontrolled spasm were investigated for catheter failure using a low-dose radioisotope procedure with an administered dose of radioactivity of 40 MBq Technetium-99m.

RESULTS

Loss of catheter patency was demonstrated in six patients, enabling identification of the site of blockage. Catheter patency and subsequent perfusion of CSF (ie normal result) was demonstrated in five patients. Radiation effective dose was estimated at 1.3 mSv per patient study, with a low associated risk of deleterious effect of one in 13,000.

CONCLUSION

Radioisotope investigation using a reduced administered dose of 40 MBq Technetium-99m DTPA, formulated according to a strict radiopharmaceutical protocol, provides a safe test for assessment of intrathecal drug delivery systems.

Sentinel lymph node biopsy in breast cancer: results of intradermal periareolar tracer injection and follow-up of sentinel lymph node-negative patients

Several methods are in use for identification of the sentinel lymph node (SLN) in breast cancer. We set up the hypothesis that intradermal (i.d.) infra-areolar injection of technetium-99m in combination with i.d. injection of patent blue dye lateral to the areola can identify the same lymph node as peritumoral injection, regardless of the location of the tumour. Each of 50 patients with breast cancer (group I) received an i.d. injection of technetium-99m 1cm caudal to the areola. After induction, blue dye was injected intradermally 1cm lateral to the areola. These patients underwent axillary dissection regardless of their lymph node status. The SLN was identified in 96% of these patients. One of them had axillary lymph node metastases even though the SLN was negative (6%). Further 82 patients (group II) underwent SLN identification and removal without further axillary dissection. The duration of mean follow-up for these patients was 28 months (16-39 months). One patient developed axillary recurrence (1%) 24 months after the initial operation. Intradermal periareolar tracer injection is an accurate method of locating the sentinel node. Long-term follow-up of patients who had negative sentinel nodes and did not undergo axillary dissection revealed a low axillary recurrence rate.

Subareolar injection of radioactive colloid for sentinel lymph node identification in breast cancer patients

Sentinel lymph node biopsy (SLNB) is becoming the standard for staging the axilla in breast cancer patients in many institutions. The best method of injection is still questionable. The purpose of this study was to compare the results of SLNB using the peritumoral or the subareolar injection site. Between December 1997 and March 2000, we performed 100 SLNBs. Technecium-labeled colloidal human serum albumin was injected peritumorally (Group A, 31 patients; Group B, 31 patients) or subareolarly (Group C, 38 patients). Patent blue dye was given periareolarly (Group A) or peritumorally (Groups B and C). Preoperative lymphoscintigraphy was performed in all patients. SLNB was successful in 94 patients (94%). The identification rate improved from 80 per cent (first 25 patients) to 99 per cent (last 75). The subareolar injection of the colloid did not adversely influence the results of SLNB compared with the peritumoral injection (identification rate, 100% vs 97%; false negative rate, 6% vs 14%). The subareolar injection of colloid is a simple and at least as accurate technique as the peritumoral one. This technique can also improve the identification rate of SLNB for breast cancer patients.

Amplification targeting: a modified pretargeting approach with potential for signal amplification-proof of a concept

Conventional nuclear medicine imaging with large radiolabeled molecules such as antitumor antibodies suffers from slow localization and clearance. Pretargeting is under active investigation as an alternative using either (strept)avidin/biotin, bispecific antibodies, or oligomers. However, only the use of oligomers such as phosphorodiamidate morpholinos (MORFs) in pretargeting offers the potential of signal amplification at the target. Amplification targeting is a multistep procedure with the potential to greatly improve target localization of radioactivity (and eventually drugs) through the intermediate use of polymers conjugated with multiple copies of oligomers.

OBJECTIVE

This study was conducted to prove the concept in vivo in tumored mice of amplfication targeting.

METHODS

Nude mice bearing LS174T tumors received in order: the anti-CEA antibody MN14 conjugated with MORF, a polymer conjugated with multiple copies of complementary MORFs (cMORFs), and, finally, (99m)Tc-MORF.

RESULTS

In tumored animals, dual radiolabels ((99m)Tc and (111)In) were used to demonstrate that, after 18 h, about 25% of antibody MORFs in tumor were targeted with polymeric cMORFs and, after 3 h, about 12% of the polymeric cMORFs in tumor were targeted with (99m)Tc-MORF. Therefore, hybridization in tumor in both cases (i.e., polymeric cMORF to antibody MORF and radiolabeled MORF to polymeric cMORF) was surprisingly efficient given the barriers to targeting in vivo and the competition between targeting and clearance. Moles of radiolabeled MORF accumulating in tumor were more than tripled for study animals receiving all 3 injections compared with control animals not receiving the antibody or the polymer. Furthermore, MORF expression (on antibody) and cMORF expression (on polymer) were rapidly lost in normal organs such as liver, spleen, and kidneys but not in tumor, thus improving the target-to-nontarget ratios.

CONCLUSION

Although signal amplification has not yet been convincingly demonstrated and amplification targeting will require further studies for optimization, the concept has now been shown to be feasible.

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.

99mTc labelled model drug carriers - labeling, stability and organ distribution in rats

The surface characteristics of intravenously administered particulate drug carriers decisively influence the protein adsorption that is regarded as a key factor for the in vivo fate of the carriers. We labeled surface-modified polymer particles with the gamma-emitting radioisotope 99mTc in order to test their properties in blood and follow their in vivo fate. The biodistribution was different in various types of polymer particles. As expected, labeled particles were found in the mononuclear phagocyte system in a large scale but markedly different biodistribution for some particles were also shown.

Pharmacokinetics and biodistribution of [111In]-avidin and [99mTc]-biotin-liposomes injected in the pleural space for the targeting of mediastinal nodes

Pharmacokinetics and mediastinal node uptake of [111In]-avidin and [99mTc]-biotin-liposomes following either intrapleural (pleural) or intraperitoneal (ip) injection were determined using scintigraphic imaging. Biodistribution results of [111In]-avidin at 44 h showed 3.3% uptake in mediastinal nodes by pleural injection vs 1.3% with ip injection. Mediastinal node accumulation with [99mTc]-biotin-liposomes was not different between injections (0.6% ip vs 0.5% pleural). This study demonstrates the potential of the pleural route as a technique for mediastinal node targeting using the avidin/biotin-liposome system.

Characterization of the generation of radiolabeled monodisperse albuterol particles using the spinning-top aerosol generator

Inhaled radiolabeled aerosols provide invaluable information about in vivo drug deposition. Here, we report our methodology for radiolabeling and imaging monodisperse pharmacologic aerosols in order to study basic aerosol science concepts of drug delivery within the human airways.

METHODS

We used a spinning-top aerosol generator to produce (99m)Tc-labeled monodisperse albuterol sulfate aerosols of 1.5-, 3-, and 6- micro m mass median aerodynamic diameter.

RESULTS

In vitro Andersen cascade validation data showed that technetium and albuterol were coassociated on each impactor stage for all 3 aerosols, and the radiolabeling process itself did not affect their particle size distributions. Good-quality gamma-camera scintigraphic images of lung and extrathoracic deposition were obtained within an asthmatic patient.

CONCLUSION

We have successfully radiolabeled and imaged monodisperse albuterol aerosols within the human lungs. This novel technique provides an important tool to relate fundamental concepts of aerosol particle behavior, in vivo deposition, and therapeutic clinical response.

Prostate lymphoscintigraphy for sentinel lymph node identification in canines: reproducibility, uptake, and biokinetics depending on different injection strategies

At present there are neither clinical nor experimental data available on the influence of technical details on the quality and reproducibility of prostate lymphoscintigraphy. Six adult fox hounds received repeated transrectal ultrasound guided intraprostatic injections of a technetium 99m labeled nanocolloid to prove the influence of different techniques of injection (one central injection in both prostate lobes vs two peripheral injections in both lobes) on tracer accumulation in sentinel lymph nodes (SLN) and other organs. The reproducibility of the favored technique was examined and in a last step it was subject to scrutiny following a reduction of the injected volume to 1% of the prostate volume. The number of scintigraphically visualized SLN varied between four and seven. They were located in the region of the internal and external iliac vessels, presacrally, paravesically, and directly paraprostatically. In five of six cases, the localization was reproducible both with the central application of an identical volume as well as with the volume reduced central injection. Tracer accumulation of SLNs and other organs varied enormously. We expect that with the combination of both injection techniques, even with the reduced injection volume, an optimized prostate lymphoscintigraphy will be the outcome.

Radioactivity in cervical mucus after intraperitoneal deposition of Tc-99m labelled albumin particles before and after sterilisation

OBJECTIVE

To study the transport of radiolabelled albumin particles from the pouch of Douglas to cervical mucus.

STUDY DESIGN

A prospective randomised study, including 10 healthy women, undergoing laparoscopic sterilization. A solution of human serum albumin particles, labelled with Technetium 99(m) (Tc-99(m)) was injected into the pouch of Douglas, either before or after sterilisation.

RESULTS

Gamma camera images showed gradual spread to the entire peritoneal cavity. Blood samples, showed increasing levels of radioactivity. Measurement of radioactivity in cervical mucus showed significant activity both in women sterilized before and after the deposition.

CONCLUSION

The study showed evidence of transport of radioactivity from the pouch of Douglas to cervical mucus. The transport seemed to consist of free activity since no radionuclide labelled particles could be detected in cervical mucus. The transport was probably haematogenous or lymphatic and not intraluminal through the fallopian tube. Further studies utilizing particles comparable in size to fertilized ova are required to design methods for evaluating the transport from the fallopian tube to the uterine cavity.

Distribution of technetium-99m-labelled QVAR delivered using an Autohaler device in children

QVAR, an extrafine hydrofluoroalkane/beclomethasone dipropionate formulation, has been shown to double lung deposition in adults. The aim of the present study was to assess the total body deposition and distribution of technetium-99m-labelled (99mTc) QVAR in children after inhalation via an Autohaler. Sixteen male asthmatic children (5-14 yrs) inhaled labelled drug (<4 MBq 99mTc; 100 microg beclomethasone dipropionate) via an Autohaler within 30 min after salbutamol (200 microg) administration. Simultaneous anterior and posterior planar scintigraphic scans (120 s acquisition time) were collected after inhalation of labelled drug. Mean+/-SD lung deposition of labelled drug (attenuation-corrected; percentage of ex-actuator dose) was 36.9+/-9.2, 46.5+/-11.6 and 54.1+/-10.7% in children aged 5-7, 8-10 and 11-14 yrs, respectively. Combined oropharyngeal and gastrointestinal deposition was 59.7+/-8.2, 48.9+/-12.3 and 40.3+/-11.8%. Lung deposition positively correlated with the forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). Gastrointestinal dose negatively correlated with the FEV1, FVC, height and age. In older children (11-14 yrs), lung deposition was almost identical to that reported in adults using QVAR. In children aged 5-10 yrs, lung deposition using QVAR was greater than the levels measured using other commercial aerosol delivery systems. Oropharygeal and gastrointestinal deposition was inversely related to age.

[Method of penile scintigraphy]

A method of phalloscintigraphy, based on the gamma camera and computerized data processing, is offered. The results of examination of patients are described.

Novel oxorhenium and oxotechnetium MO(NS)(S)2 complexes in the development of 5-HT1A receptor imaging agents

The [NS][S](2) mixed-ligand system was applied to synthesize oxorhenium and oxotechnetium complexes of the general formula MO(o-CH(3)OC(6)H(4)N(CH(2)CH(2))(2)NCH(2)CH(2)S)(p-CH(3)C(6)H(4)S)(2) (M=Re in 1, M=(99)Tc in 2, and M=(99m)Tc in 3). The bidentate [NS] ligand includes the 1-(2-methoxyphenyl)piperazine moiety which is a fragment of the true 5-HT(1A) antagonist WAY 100635. The oxorhenium complex 1 was prepared by a ligand exchange reaction using ReOCl(3)(PPh(3))(2) as precursor while [Bu(4)N][(99)TcOCl(4)] and (99)Tc-gluconate were used as precursors in the synthesis of the oxotechnetium-99 complex 2. Both complexes were characterized by elemental analysis and spectroscopic methods. Crystallographic analysis of 1 showed that the rhenium coordination geometry is trigonal bipyramidal. The basal plane of the trigonal bipyramid is defined by the oxo group and two sulphur atoms, one belonging to the [NS] ligand and the other to an aromatic thiol, while the apical positions are occupied by the nitrogen of the [NS] ligand and the sulphur of the second aromatic thiol. The oxotechnetium-99 complex 2 has almost identical unit cell parameters to those of the oxorhenium complex 1 indicating, in combination with the other analytical data, that the complexes are isostructural. The binding affinity of the oxorhenium complex 1 for the 5-HT(1A) receptor subtype was determined in rat brain hippocampal preparations (IC(50)=106 nM). The oxotechnetium-99m complex 3 was prepared by a ligand exchange reaction using (99m)Tc-glucoheptonate as the precursor. Its structure was established by comparative HPLC studies using the oxotechnetium-99 complex 2 as a reference. Complex 3 was administered by intravenous injection in rats. At 2 min post injection, 0.153% of the injected dose per gram of tissue was measured in rat brain.

Effect of low continuous 99Tc intake on its absorption and metabolism in young rats

A continuous daily oral dose of (99)TcO(4)(-) (5 Bq g(-1) day(-1)) was given to young rats for 56 days. In one group the intake was continued for 98 days, while in the other the intake was stopped to facilitate the determination of biological half lives in different organs and tissues. The absorbed fraction of (99)Tc increased from 0.7 to 0.9 during the experimental period (m=0.85 sigma=0.02). The whole body retained fraction (m=0.15 sigma=0.05) indicated a storage in the tissues. The liver and kidneys showed increasing concentrations of (99)Tc until a plateau was reached after 6 and 9 weeks, then a rapid decline after the intake was stopped (half life of 6 and 5 days respectively). In hair and thyroid tissue, the accumulation of (99)Tc increased linearly then declined very slowly after the intake was stopped and did not reach a plateau during the experiment. No significant amounts of (99)Tc were detected in the muscular tissues or in the walls of the digestive tract. After the contamination period, urinary and fecal excretions fell off very quickly (1 week), but significant, though low, quantities of urinary and fecal excretions were still observed 6 weeks after stopping intake.

Intake and excretion of 99Tc in a common sea alga, hijiki (Hizikia fusiforme), as ingested in the daily diet--a measurement in an adult male

Ingestion and excretion of environmental 99Tc was measured in an adult male who ingested 'hijiki' food in his diet that contained a sub-bequerel activity per kg, and which was prepared from a marine alga, Hizikia fusiforme, or hijiki in Japanese, traditionally eaten in the Japanese diet. Harvested hijiki was boiled, dried and cooked. This was eaten at each meal five times over 2 d. All faeces and 24-h urine samples were collected during the 3 d before and subsequent 11 d starting from the day when the intake began. The ingestion intake was measured by analysing the dried hijiki material. 99Tc was determined by using liquid-liquid extraction and low-background beta ray spectrometry. The excreta were also analysed for minerals by atomic absorption spectrometry. The apparent absorption rate in the gastrointestinal tract for 99Tc under these conditions was calculated to be approximately 0.5. The present result from a single subject indicates the need for further studies.

Anti-CEA monoclonal antibody: technetium-99m labeling and the validation process of a scintigraphic animal model with a non-cellular antigenic implant

Animal models are currently used to verify the biodistribution of different radiopharmaceuticals before its clinical application in Nuclear Medicine; however, there may be some limitations. The utilization of labelled anti-tumor monoclonal antibodies (MoAb) in experimental models often requires implant of human antigens (usually a cellular implant), which cannot be achieved in immunocompetent animals. Our purpose was to label an anti-CEA MoAb with technetium-99m (99Tc) and to validate a simplified animal model using a noncellular antigenic implant. MoAb was directly labelled with 99mTc, after reduction with 2-mercaptoethanol. Labeling efficiency was checked by ascending chromatography and immunoreactive fraction was measured in plastic wells sensitized with the antigen. Radiopharmaceutical biodistribution was evaluated by dissection and scintigraphy in 5 mice groups; following the subcutaneous administration of Al(OH)3, CEA adsorbed Al(OH)2 and a control group evaluation. Labeling efficiency was 94+/-3%, which showed to be stable for 24 hr, with immunoreactive fraction above 50%. Invasive biodistribution evaluation showed prolonged blood retention, hepatic and renal uptake. A significant increase in uptake was observed in scintigraphic studies of animals with CEA-adsorbed Al(OH)3 implants compared with the other groups (p<0.05). The non-cellular antigenic implant model simplifies the pre-clinical evaluation of labelled MoAb.