64Cu-ATSM and 99mTc(CO)3-DCM20 potential in the early detection of rheumatoid arthritis.

OBJECTIVES: Molecular imaging constitutes a promising technique for the early detection of rheumatoid arthritis (RA). Macrophages and hypoxia play significant roles in inflamed synovium. In the present study, we evaluated the efficacy of radiopharmaceuticals that target macrophage mannose receptors (99mTc-labeled mannosylated dextran or 99mTc(CO)3-DCM20) and hypoxia (copper(II) diacetyl-di(N4-methylthiosemicarbazone) or Cu-ATSM) for the early detection of RA in collagen-induced arthritis (CIA) mice models. METHODS: CIA model was developed in DBA/1 mice, and the clinical score for arthritis was visually assessed on a regular basis. Two biodistribution studies were performed in a paired-labeled format using 2-deoxy-2-18F-fluoro-D-glucose (18F-FDG) as a reference: (1) 99mTc(CO)3-DCM20 with 18F-FDG and (2) 67Cu-ATSM with 18F-FDG. RESULTS: The accumulation levels of 99mTc(CO)3-DCM20 and 67Cu-ATSM in forepaws, hindpaws, and knee joints of CIA mice were significantly higher than that of control mice. In contrast, 18F-FDG uptake in hindpaws and knee joints showed no significant difference between CIA and control mice. The radioactivity levels of 99mTc(CO)3-DCM20 and 67Cu-ATSM were significantly correlated with the clinical scores for the paws. CONCLUSION: These results suggest the potential usefulness of 99mTc(CO)3-DCM20 and radiolabeled Cu-ATSM for the imaging and early detection of RA.

Comparison of the radiotoxicity of the 99mTc-labeled compounds 99mTc-pertechnetate, 99mTc-HMPAO and 99mTc-MIBI.

PURPOSE: In addition to gamma radiation, 99mTc emits low-energy Auger electrons with path-lengths of nanometers to micrometers that cannot be utilized for diagnostic procedures; however, they have frequently been discussed for therapeutic applications. We compared radiotoxicity of three 99mTc-labeled radiopharmaceuticals with differences in the subcellular distribution. MATERIALS AND METHODS: The intracellular radionuclide uptake and subcellular distribution of [99mTc]-pertechnetate (99mTc-pertechnetate), [99mTc]Tc-hexamethyl-propylene-aminoxime (99mTc-HMPAO) and [99mTc]Tc-hexakis-2-methoxyisobutylisonitrile (99mTc-MIBI) were quantified in rat thyroid FRTL-5 cells. Radiotoxicity was compared using late phosphorylated histone H2AX (γH2AX) foci as a marker for unrepaired DNA double-strand breaks (DNA-DSB) and clonogenic cell survival. RESULTS: 99mTc-HMPAO showed a substantially higher uptake into the nucleus and the membrane/organelles than 99mTc-pertechnetate or 99mTc-MIBI. The colony-forming assay showed that 99mTc-pertechnetate and 99mTc-HMPAO caused a similar reduction in cell survival. 99mTc-MIBI is less radiotoxic in terms of the estimated nucleus dose and induced the fewest number of γH2AX foci compared with the other 99mTc-tracers, and 99mTc-HMPAO induced a fewer number of γH2AX foci than 99mTc-pertechnetate. CONCLUSIONS: Our findings reveal that clonogenic cellular survival is not solely determined by the DNA-DSB response. This finding may suggest the involvement of extra-nuclear radiosensitive targets in cell inactivation. For example, the mitochondria or the cell membrane could be affected by 99mTc-HMPAO.

Comparative in vitro stability and scintigraphic imaging for trafficking and tumor targeting of a directly and a novel 99mTc(I)(CO)3 labeled liposome.

Liposomes radiolabelling with diagnostic radionuclides is an excellent tool for studying pharmacokinetics with the view of developing liposome-based drug delivery agents. The aim of the present study is to evaluate the in vitro and in vivo behavior of a (99m)Tc-labeled liposome by applying either a direct labeling strategy via a carboxyl group, LP-COOH, or a surface chelating method via pyridyl ethyl cysteine compound (with the intermediate [99mTc(I)(CO)3(H2O)(3)](+)), LP-PEC. 99mTc-LP-COOH was obtained in high radiolabelling yield and radiochemical purity, while 99mTc(I)(CO)3-LP-PEC was initially purified before being in vitro and in vivo evaluated. 99mTc-LP-COOH was less stable in the presence of competitive for 99mTc ligands than 99mTc(I)(CO)3-LP-PEC. According to DLS measurements, the presence of serum as well as the applied radiolabelling conditions did not affect the liposomes' size. The different radiolabelling methods seemed to exert an influence on the biodistribution pattern of the liposomes with the 99mTc(I)(CO)3-LP-PEC showing slow blood clearance, which was also confirmed by in vivo scintigraphic imaging. Nevertheless, passive tumor targeting was attained at a similar extent no matter which radiolabelling technique was followed.

Follow-up of a case of subacute thyroiditis with uncommon thyroid (99m)Tc uptake.

Thyroidal 99mTc uptake in the acute thyrotoxic phase of subacute thyroiditis (SAT) is always inhibited. However, a patient with SAT had signs in the right-side thyroid gland with transient thyrotoxicosis and slightly high 99mTc uptake levels in the right lobe, low 99mTc uptake in the left lobe, and normal overall uptake. Histological examination showed cellular destruction and granulomatous inflammatory changes in the right lobe, with marked interstitial fibrosis in the left lobe. The patient was thyrotrophin-receptor antibody (TRAb) positive. After a short course of prednisolone, SAT-like symptoms and signs improved. TRAb-positivity resolved spontaneously after 22 months, and TSH levels were slightly low for 22 months. Levels then kept normal in the following four years. In conclusion, high 99mTc uptake by the right lobe was due to the combined effects of TRAb and left thyroid gland fibrosis.

Follow-up of a case of subacute thyroiditis with uncommon thyroid 99mTc uptake / Acompanhamento de caso de tiroidite subaguda com absorção incomum de 99mTc pela tiroide

Thyroidal 99mTc uptake in the acute thyrotoxic phase of subacute thyroiditis (SAT) is always inhibited. However, a patient with SAT had signs in the right-side thyroid gland with transient thyrotoxicosis and slightly high 99mTc uptake levels in the right lobe, low 99mTc uptake in the left lobe, and normal overall uptake. Histological examination showed cellular destruction and granulomatous inflammatory changes in the right lobe, with marked interstitial fibrosis in the left lobe. The patient was thyrotrophin-receptor antibody (TRAb) positive. After a short course of prednisolone, SAT-like symptoms and signs improved. TRAb-positivity resolved spontaneously after 22 months, and TSH levels were slightly low for 22 months. Levels then kept normal in the following four years. In conclusion, high 99mTc uptake by the right lobe was due to the combined effects of TRAb and left thyroid gland fibrosis.

A absorção tiroidiana de 99mTc no estado tirotóxico agudo da tireoidite subaguda (SAT) é sempre inibida. Entretanto, um paciente com SAT apresentou sinais na tiroide direita, com tirotoxicose transitória e níveis levemente elevados de 99mTc no lobo direito, baixa absorção de 99mTc no lobo esquerdo e absorção geral normal. O exame histológico mostrou destruição celular e alterações inflamatórias granulomatosas no lobo direito, com fibrose intersticial marcada no lobo esquerdo. O paciente foi positivo para anticorpos antirreceptores da tireotropina (TRAb). Após um curto tratamento com prednisolona, os sintomas e sinais da SAT melhoraram. A positividade para TRAb foi resolvida espontaneamente em 22 meses. Os níveis de TSH permaneceram levemente baixos por 22 meses e, depois, se mantiveram normais nos quatro anos seguintes. Concluiu-se que a alta absorção de 99mTc pelo lobo direito foi devida à combinação entre TRAb e fibrose da tiroide esquerda.

Novel cancer-targeting SPECT/NIRF dual-modality imaging probe (99m)Tc-PC-1007: synthesis and biological evaluation.

Synthesis, characterization, in vitro and in vivo biological evaluation of a heptamethine cyanine based dual-mode single-photon emission computed tomography (SPECT)/near infrared fluorescence (NIRF) imaging probe (99m)Tc-PC-1007 is described. (99m)Tc-PC-1007 exhibited preferential accumulation in human breast cancer MCF-7 cells. Cancer-specific SPECT/CT and NIRF imaging of (99m)Tc-PC-1007 was performed in a breast cancer xenograft model. The probe uptake ratio of tumor to control (spinal cord) was calculated to be 4.02±0.56 at 6 h post injection (pi) and 8.50±1.41 at 20 h pi (P<0.0001). Pharmacokinetic parameters such as blood clearance and organ distribution were assessed.

Patient-specific dosimetry for intracavitary 32P-chromic phosphate colloid therapy of cystic brain tumours.

PURPOSE: (32)P-chromic phosphate colloid treatments of astrocytoma and craniopharyngioma cystic brain tumours in paediatric patients are conventionally based on a sphere model under the assumption of uniform uptake. The aims of this study were to determine the distribution of the absorbed dose delivered by (32)P on a patient-specific basis and to evaluate the accuracy with which this can be predicted from a pretherapy administration of (99m)Tc-Sn colloid. METHODS: Three patients were treated with (32)P-chromic phosphate colloid following (99m)Tc-Sn colloid administrations. Convolution dosimetry was performed using pretherapy and posttherapy sequential SPECT imaging, and verified with EGSnrc Monte Carlo radiation transport simulations. Mean absorbed doses to the cyst wall and dose-volume histograms were also calculated and compared with those obtained by the sphere model approach. RESULTS: Highly nonuniform uptake distributions of both the (99m)Tc and (32)P colloids were observed and characterized by dose-volume histograms to the cyst wall. Mean absorbed doses delivered to the cyst wall, obtained with the convolution method, were on average 21 % (SD 18 %) and 50 % (SD 30 %) lower than those predicted by the (99m)Tc distribution and the uniform assumption of the sphere model, respectively. CONCLUSION: Absorbed doses delivered to the cyst wall by (32)P are more accurately predicted from image-based patient-specific convolution dosimetry than from simple sphere models. These results indicate the necessity to perform personalized treatment planning and verification for intracavitary irradiation of cystic brain tumours treated with radiocolloids. Patient-specific dosimetry can be used to guide the frequency and levels of repeated administrations and would facilitate data collection and comparison to support the multicentre trials necessary to progress this therapy.

99mTc-(Me)FGCDEVD, a potential tracer for apoptosis detection.

(Me)FGC(Bz)DEVD was radiolabeled with technetium-99m in high yield. This tracer was preferentially accumulated in apoptotic cells in the in vitro studies. Tumor uptake occurred in vivo after cisplatin injection due to the apoptosis induction, which not observed in the untreated tumors. Therefore, (99m)Tc-(Me)FGCDEVD is a potential tracer for apoptosis detection.

PEGylation and biodistribution of an anti-MUC1 aptamer in MCF-7 tumor-bearing mice.

Aptamers are characterized by a rapid renal clearance leading to a short in vivo circulating half-life. In order to use aptamers as anticancer therapeutic agents, their exposure time to the tumor has to be enhanced via increasing residency in the bloodstream. A way to achieve this goal is by conjugating the aptamer to poly(ethylene glycol) (PEG). Herein, we present the conjugation of a bifunctionalized anti-MUC1 aptamer (NH(2)-AptA-SR) with the (99m)Tc coordinating moiety MAG2 and either a conventional branched PEG or the comb-shaped PolyPEG via a two-step synthesis. The isolated products were radiolabeled with (99m)Tc and their biodistribution and tumor-targeting properties in MCF-7 tumor bearing mice were analyzed and compared.

Radiotracers for different angiogenesis receptors in a melanoma model.

Early and reliable diagnosis of melanoma, a skin tumor with a poor prognosis, is extremely important. Phage display peptide libraries are a convenient screening resource for identifying bioactive peptides that interact with cancer targets. The aim of this study was to evaluate two technetium-99m tracers for angiogenesis detection in a melanoma model, using cyclic pegylated pentapeptide with RGD and NGR motifs conjugated with the bifunctional chelator mercaptoacetyltriglycine (MAG(3)). The conjugated peptides (10 µl of a µg/µl solution) were labeled with technetium-99m using a sodium tartrate buffer. Radiochemical evaluation was carried out by instant thin-layer chromatography and confirmed by high-performance liquid chromatography. The partition coefficient was determined and internalization assays were performed in two melanoma cell lines (B16F10 and SKMEL28). Biodistribution evaluation of the tracers was carried out in healthy animals at different time points and also in tumor-bearing mice, 120 min post injection. Blocking studies were also conducted by coinjection of cold peptides. The conjugates displayed a rather similar pharmacokinetic profile. They were radiolabeled with high radiochemical purity (>97%) and both were hydrophilic with preferential renal excretion. Yet, tumor uptake was higher for human than for murine melanoma cells, especially for [(99m)Tc]-MAG(3)-PEG(8)-c(RGDyk) (7.85±2.34%injected dose/g 120 min post injection). The performance of [(99m)Tc]-MAG(3)-PEG(8)-c(RGDyk) was better than the NGR tracer with regard to human melanoma uptake. In this sense, it should be considered for future radiotracer studies of tumor diagnosis.

Pathophysiological premises to radiotracers for bone metastases.

Aim of our paper is to review the most important radio-compounds that can be successfully used to detect and/or characterize bone metastases. From a didactic point of view, we made a distinction between two main categories , the first allowing to individuate bone's reaction (osteotropic agents), the second trying to detect metastatic tumor cells (oncotropic agents). A wide description of the most diffuse Tc-99m diphosphonates , including analysis of uptake mechanisms and pharmacokinetics, is followed by a brief report on pathophysiological premises to the clinical use of F-18 fluoride and of specific (radioiodine, radiolabeled somatostatin or cathecolamine analogues) or non specific, as Tc-99m sestamibi, F-18 fluorodeoxhyglucose, F-18 choline, F-18 thymidine) oncotropic agents. At the end, the possibility to use diagnostic radiotracers to act both in recruiting patients with bone metastases undergoing radionuclide therapy and for their dosimetric evaluation is also discussed.

Synthesis, radiolabeling and In Vivo tissue distribution of an anti-oestrogen glucuronide compound, (99m)Tc-TOR-G.

Toremifene (TOR) has been used as an anti-oestrogen drug for the treatment and prevention of human breast cancer. The aim of this study was the addition of the hydrophilic groups diethylenetriamine pentaacetic acid (DTPA) and glucuronic acid to the starting substance TOR and to label it with technetium-99m ((99m)Tc) radionuclide and to investigate radiopharmaceutical potential of the new compound. The synthesis reactions are completed in four steps, including enzymatic reaction, with the following substeps; preparation of microsomal fraction from Hutu 80 cell line and subsequent purification of UDP-glucuronyl transferase (UDPGT), estimation of protein quantity in microsomal samples and glucuronidation reaction. The results indicate that (99m)Tc-TOR-G may be proposed as a new anti-oestrogen glucuronide imaging agent for ovarian tumours.

Factors affecting sentinel lymph node detection failure in breast cancer patients using intradermal injection of the tracer.

OBJECTIVE: The standard method for axillary lymph node staging in early breast cancer is sentinel lymph node biopsy. In some patients the sentinel lymph node can not be localized during surgery and these patients have to undergo standard axillary lymph node dissection. In this study we have evaluated the predictors of sentinel lymph node localization failure using (99m)Tc-antimony sulfide colloid and intradermal injection combined with blue dye technique. MATERIAL AND METHODS: 202 consecutive patients with early stage breast cancer (clinically stage I or II) were retrospectively evaluated. Patients whose sentinel lymph node was localized during surgery were compared to those with localization failure considering several variables. RESULTS: Sentinel lymph node was successfully located on the pre-operative lymphoscintigraphy images in 180 patients (89%). Both univariate and multivariate analyses showed that only sentinel lymph node non-visualization by pre-operative lymphoscintigraphy, experience of the surgeon, and axillary lymph node involvement are associated with sentinel node localization failure during surgery. CONCLUSIONS: This study shows the importance of pre-operative lymphoscintigraphy in order to identify the group of patients with possible localization failure during surgery and warning the surgeon beforehand. We also recommend that all surgeons pass the learning curve of sentinel lymph node biopsy before routinely performing this procedure.

The ratio of maximum percent tumour accumulations of the pretargeting agent and the radiolabelled effector is independent of tumour size.

Our previous studies have indicated that the optimal dosage ratio of pretargeting antibody to effector is proportional to their maximum percent tumour accumulations (MPTAs). This study quantitatively describes how both MPTAs and their ratio change with tumour size, to simplify pretargeting optimisation when tumour size varies. The CC49 antibody dosages below saturation of the tumour antigen level were first examined for the LS174T tumour mouse model. Then the MPTAs of the antibody in mice bearing tumours of different sizes were determined, always at antibody dosages below antigen saturation. Historical data from this laboratory were used to collect the MPTAs of the (99m)Tc-cMORF effector for different tumour sizes, always at effector dosages below that required to saturate the MORF in tumour. The MPTAs versus tumour sizes for both the antibody and the effector were fitted non-linearly. The best fit of the antibody MPTA (Y(antibody)) with tumour size (x) in grams was Y(antibody)=19.00 x(-0.65) while that for the effector was Y(effector)=4.51x(-0.66). Thus, even though the MPTAs of both vary with tumour size, the ratio (Y(antibody)/Y(effector)) is a constant at 4.21. In conclusion, the MPTA ratio of the antibody to the effector was found to be constant with tumour size, an observation that will simplify pretargeting optimisation because remeasurement of the optimum dosage ratio for different tumour sizes can be avoided. Theoretical considerations also suggest that this relationship may be universal for alternative antibody/effector pairs and for different target models, but this must be experimentally confirmed.

Preparation and evaluation of 99mTc(CO)3-labeled pentadecanoic acid derivative and its suspension in lipiodol.

Abstract Transarterial embolization by the intra-arterial administration of 131I-lipiodol is a modality used in the treatment of liver cancer. Long-chain fatty acids, being highly lipophilic, are also known to localize in the liver, thus constituting favorable vectors for this modality of treatment. Toward this, we envisaged the derivatization of 15-bromopentadecanoic acid, rendering it suitable for incorporation of a tridentate chelating moiety, for radiolabeling with the [99mTc(CO)3(H2O)3]+ precursor. The complex prepared, being lipophilic, was expected to behave as a lipiodol surrogate. The radiolabeled complex could be obtained in >95% radiochemical yield, as characterized by high-performance liquid chromatography. The intravenous injection of the radiolabeled complex in mice resulted in 23.5% +/- 4.3% uptake of injected dose (ID) organ in the liver at 3 hours postinjection. However, the uptake of the lipiodol suspension of the complex at 3 hours postinjection in the liver was found to be 43.8 +/- 13.4% ID/organ, when injected via the portal vein.

False-negative sentinel node biopsy because of obstruction of lymphatics by metastatic melanoma: the value of ultrasound in conjunction with preoperative lymphoscintigraphy.

The aim of this study was to describe how metastatic melanoma obstructing lymphatic flow to sentinel nodes can result in a false-negative sentinel node biopsy and to show that the use of ultrasound in conjunction with preoperative lymphoscintigraphy can avoid this potential diagnostic pitfall. A series of three patients in whom metastatic melanoma obstructed lymphatic flow to sentinel nodes is reported. In these patients, lymphoscintigraphy failed to identify nodes containing metastatic disease. This resulted in a false-negative sentinel node biopsy result in two patients. A sentinel node biopsy was not carried out in the third patient, but the same dilemma was encountered. These cases provide further insights into the dynamics of lymphatic flow and suggest possible reasons for occasional inaccuracy of sentinel node biopsy. They also highlight the advantages of using ultrasound to assess lymph nodes in any node fields to which lymphatic drainage occurs from a primary tumour site.

Replacing 99mTc with 111In improves MORF/cMORF pretargeting by reducing intestinal accumulation.

PURPOSE: To reduce accumulation in the abdomen by MORF/cMORF pretargeting, 111In was compared to 99mTc as the radiolabel. PROCEDURES: After receiving either 99mTc (MAG3)-cMORF or 111In (DTPA)-cMORF, normal mice were imaged and killed for pharmacokinetics. Thereafter, tumored mice were pretargeted withMORF-antibody, 48 h later were given an injection of 99mTc- or 111In-cMORF, and finally were imaged repeatedly. RESULTS: The cMORF biodistribution in both normal and pretargeted tumored mice was influenced by its radiolabel. While excretion of both 99mTc-cMORF and 111In-cMORF was rapid and mainly through the kidneys, about 2% of 99mTc accumulated in the intestines compared toessentially no intestinal accumulation for 111In at any time. Tumor accumulation was unchanged. CONCLUSION: In applications of MORF/cMORF pretargeting intended to image organs deep within the abdomen such as the pancreas, radiolabeling with 111In may be superior to 99mTc.

Clinical usefulness of thallium-201 scintigraphy and magnetic resonance imaging in the diagnosis of chondromyxoid fibroma.

Chondromyxoid fibroma (CMF) is a benign bone tumor. However, it is sometimes difficult to distinguish this tumor from chondrosarcoma. We report a rare case arising from the proximal fibula, presenting multimodality imaging features. An 18-year-old man presented with a 2-year history of gradually increasing pain and swelling in his left knee. Radiograph showed an area of osteolysis with lobulation. Magnetic resonance (MR) imaging demonstrated that almost the whole lesion was enhanced with Gd-DTPA. Scintigraphy examination with (99m)Tc-biphosphonate showed strong accumulation in the periphery. On Ga-67-citrate scintigraphy, there was a little uptake. Thallium-201 scintigraphy showed strong accumulation of the whole lesion in early and late scans. The tumor was diagnosed as CMF by open biopsy. It is important that CMF is correctly distinguished from other tumors because this may be histologically overdiagnosed as chondrosarcoma. Contrast-enhanced MR imaging and thallium-201 scintigraphy may be useful to distinguish CMF from benign bone tumors or chondrosarcoma.

Modificación de la biodistribución de los glóbulos rojos marcados con 99mtc en la anemia ferropénica / Alteration in the biodistribution of 99mTc-RBC in an animal model of ferropenic anemia

Objetivo: Evaluar la biodistribución de 99mTc-GR en un modelo animal de anemia ferropénica. Materiales y métodos: Se utilizaron ratas alimentadas con dietas con diferente contenido de Fe: grupo A (anemia severa, 6.5 ppm), grupo B (anemia moderada, 18 ppm) y grupo C (control, 100 ppm). Se realizó la marcación in vivo de los 99mTc-GR y se evaluó la EBM y su biodistribución a los 30 minutos y a las 24 horas en sangre, hígado, bazo, tracto gastrointestinal, riñones, corazón y pulmones. Los resultados se expresaron como concentración de actividad porcentual (CA por ciento). Resultados: En todos los grupos la EBM fue superior al 98 por ciento. Se observó un aumento de CA por ciento en bazo a las 24 horas en el grupo A, acompañado de una disminución de la CA por ciento del pool sanguíneo posiblemente por aumento del secuestro esplénico de los GR. En los tres grupos hubo un aumento de la CA por ciento en riñón a las 24 horas. Conclusión: La biodistribución de 99mTc-GR se ve modificada en la anemia ferropénica.

Aim: To evaluate the biodistribution of 99mTc-RBC in an animal model of ferropenic anemia. Materials and methods: We used rats which were fed with different iron contents diets: group A (severeanemia, 6.5 ppm), group B (moderate anemia, 18 ppm) and group C (control, 100 ppm). We performed the in vivo labeling of RBC and evaluated the labeling efficiency and the biodistribution at 30 minutes and 24 hours in blood, liver, spleen, gastrointestinal tract, kidneys, heart and lungs. The results were expressed as activity concentration percentage (CA percent). Results: In all groups the labeling efficiency was higher than 98 percent. We observed an increase of CA percent in spleen at 24 hours in the group A, followed by a decrease of CA percent in blood. This could be a consequence of an increase of splenic uptake of RBC. An increase in CA percent in kidney was obtained at 24 hours for all the groups. Conclusion: An alteration in the RBC biodistribution is observed in an animal model of ferropenic anemia.