Clinical experience with 99mTc-hexamethylpropylene-amineoxime for labelling leucocytes and imaging inflammation

The Emerging Role of FDG PET/CT in Diagnosing Endocarditis and Cardiac Device Infection

Infective endocarditis and cardiac implantable electronic device infection (CIEDI) have witnessed an increasing incidence in clinical practice and associated with increasing health care expenditure. Expanding indications of CIED in various cardiovascular conditions have also contributed to the surge of these infections. Early diagnosis of these infections is associated with a favorable prognosis. Given the lack of a single definitive diagnostic method and the limitations of echocardiography, which is considered a central diagnostic imaging modality, additional imaging modalities are required. Recent studies have highlighted the diagnostic utility of FDG PET and CT. In this review article, we discuss the existing limitations of echocardiography, acquisition protocols of PET/CT, and indications of these advanced imaging modalities in infective endocarditis and CIEDI diagnosis.

Evaluation of different 89Zr-labeled synthons for direct labeling and tracking of white blood cells and stem cells in healthy athymic mice

Cell based therapies are evolving as an effective new approach to treat various diseases. To understand the safety, efficacy, and mechanism of action of cell-based therapies, it is imperative to follow their biodistribution noninvasively. Positron-emission-tomography (PET)-based non-invasive imaging of cell trafficking offers such a potential. Herein, we evaluated and compared three different ready-to-use direct cell radiolabeling synthons, [⁸⁹Zr]Zr-DFO-Bn-NCS, [⁸⁹Zr]Zr-Hy₃ADA⁵-NCS, and [⁸⁹Zr]Zr-Hy₃ADA⁵-SA for PET imaging-based trafficking of white blood cells (WBCs) and stem cells (SCs) up to 7 days in athymic nude mice. We compared the degree of ⁸⁹Zr complexation and percentage of cell radiolabeling efficiencies with each. All three synthons, [⁸⁹Zr]Zr-DFO-Bn-NCS, [⁸⁹Zr]Zr-Hy₃ADA⁵-NCS, and [⁸⁹Zr]Zr-Hy₃ADA⁵-SA, were successfully prepared, and used for radiolabeling of WBCs and SCs. The highest cell radiolabeling yield was found for [⁸⁹Zr]Zr-DFO-Bn-NCS, followed by [⁸⁹Zr]Zr-Hy₃ADA⁵-NCS, and [⁸⁹Zr]Zr-Hy₃ADA⁵-SA. In terms of biodistribution, WBCs radiolabeled with [⁸⁹Zr]Zr-DFO-Bn-NCS or [⁸⁹Zr]Zr-Hy₃ADA⁵-NCS, were primarily accumulated in liver and spleen, whereas SCs radiolabeled with [⁸⁹Zr]Zr-DFO-Bn-NCS or [⁸⁹Zr]Zr-Hy₃ADA⁵-NCS were found in lung, liver and spleen. A high bone uptake was observed for both WBCs and SCs radiolabeled with [⁸⁹Zr]Zr-Hy₃ADA⁵-SA, suggesting in-vivo instability of [⁸⁹Zr]Zr-Hy₃ADA⁵-SA synthon. This study offers an appropriate selection of ready-to-use radiolabeling synthons for noninvasive trafficking of WBCs, SCs and other cell-based therapies.

Direct Cell Radiolabeling for in Vivo Cell Tracking with PET and SPECT Imaging

The arrival of cell-based therapies is a revolution in medicine. However, its safe clinical application in a rational manner depends on reliable, clinically applicable methods for determining the fate and trafficking of therapeutic cells in vivo using medical imaging techniques─known as in vivo cell tracking. Radionuclide imaging using single photon emission computed tomography (SPECT) or positron emission tomography (PET) has several advantages over other imaging modalities for cell tracking because of its high sensitivity (requiring low amounts of probe per cell for imaging) and whole-body quantitative imaging capability using clinically available scanners. For cell tracking with radionuclides, ex vivo direct cell radiolabeling, that is, radiolabeling cells before their administration, is the simplest and most robust method, allowing labeling of any cell type without the need for genetic modification. This Review covers the development and application of direct cell radiolabeling probes utilizing a variety of chemical approaches: organic and inorganic/coordination (radio)chemistry, nanomaterials, and biochemistry. We describe the key early developments and the most recent advances in the field, identifying advantages and disadvantages of the different approaches and informing future development and choice of methods for clinical and preclinical application.

Lack of Clinical Utility of Labeled White Blood Cell Scintigraphy in Patients with Fever of Unknown Origin

Background

Labeled white blood cell scintigraphy (WBCS) has been used for over 40 years to localize an infection source in patients with fever of unknown origin (FUO). It continues to be in widespread use for such patients in modern times, despite the tremendous advances in modern radiological imaging and laboratory medicine.

Methods

We critically evaluated the clinical contribution of WBCS performed in 132 patients with FUO at 7 hospitals from mid-2015 to the end of 2019. For each patient, all radiographic and laboratory results and all electronic clinical notes were carefully evaluated as many days before and after the scan as necessary to arrive at a final diagnosis.

Results

Although 50 WBCS (38%) showed positive findings, the majority of these were false positive (FP). Of the 19 true-positive (TP) scans, most were already known or about to become known by tests already ordered at the time of the scan. Only 2 TP scans (1.5%) contributed to the final diagnosis, and these did so only indirectly. FP scans led to 7 unnecessary procedures.

Conclusions

In FUO patients for whom an infection source is not discovered following an appropriate radiographic and laboratory workup, WBCS is not a useful procedure.

White blood cell labeling with Technetium-99m (99mTc) using red blood cell extracellular vesicles-mimetics

BACKGROUND

Extracellular vesicles, have gained increasing attention for their application in drug delivery. Here, we developed a novel method for radiolabeling WBCs with ^99mTc using RBC-derived extracellular vesicles -mimetics (EVMs), and monitored in vivo inflammation tracking of ^99mTc-WBC using gamma camera in acute inflammation mouse model.

METHODS

Engineered EVMs from RBCs were produced by a one-step extrusion method. RBC-EVMs were analyzed by NTA and TEM. Cells were labeled with ^99mTc by using ^99mTc-RBC-EVMs. Inflammation mice model was prepared and confirmed by ¹⁸F-FDG PET/CT. ^99mTc-WBCs were injected in mice, and their biodistribution was analyzed by gamma camera.

FINDING

The radiochemical purity of ^99mTc-RBC-EVMs was 100%. The ^99mTc-labeling did't affect the size and morphology. The ^99mTc in the cytoplasm of RBC-EVMs was successfully confirmed by high angle annular dark field STEM (scanning transmission electron microscope). Cells were successfully labeled with ^99mTc using ^99mTc-RBC-EVMs, and the counts per minute was increased in dose- and time-dependent manners. The ¹⁸F-FDG PET/CT images confirmed establishment of acute inflammation (left mouse foot). ^99mTc-WBCs showed higher uptake in the inflamed foot than non-inflamed foot.

INTERPRETATION

This novel method for radiolabeling WBCs using RBC-EVMs. ^99mTc labeling may be a feasible method to monitor the in vivo biodistribution of cells.

On-cartridge preparation and evaluation of 68Ga-, 89Zr- and 64Cu-precursors for cell radiolabelling

INTRODUCTION

Indium-111 when formulated as indium-111 oxine remains the gold standard for long term cell tracking, whereas radiometals for improved PET applications still have to be established. We here describe the on-cartridge formation of gallium-68, zirconium-89 and copper-64 complexes in small volumes suitable for cell labelling, including labelling of red blood cells (RBC) and white blood cells (WBC) and their biological evaluation in vivo.

METHODS

Small volumes (1-2 mL) of tracers (oxine, tropolone) were directly prepared on an anion exchange cartridge (Sep-Pak QMA). Cells were radiolabelled and the labelling efficiency and efflux were evaluated. The in vivo biodistribution of copper-64-labelled WBC using [⁶⁴Cu][Cu(oxinate)₂] and [⁶⁴Cu][Cu(tropolonate)₂] was monitored in an infection and inflammation animal model using BALB/c mice.

RESULTS

On-cartridge concentration of gallium-68, zirconium-89 and copper-64 enabled formation of oxine and tropolone tracers in small volumes with good yields (≥50%) and quality (extraction ≥90%). Prepared tracers radiolabelled the RBC comparable to indium-111 tracers and in vivo biodistribution of copper-64 labelled WBC showed clear accumulation of cells at the site of infection and inflammation.

CONCLUSIONS

This on-cartridge preparation method enables simple formation of various PET tracers for cell radiolabelling. Zirconium-89 and copper-64 tracers radiolabelled cells with sufficient stability. Due to their longer half-life this approach could be promising for routine applications where longer evaluation periods for cell tracking are needed.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

This novel approach for on-cartridge concentration and preparation of oxine and tropolone precursors with different positron emitters, in small volume and suitable pH, offers a versatile tool towards cell labelling for preclinical and clinical PET applications.

Synthesis of 99m Tc-roxithromycin: A novel diagnostic agent to discriminate between septic and aseptic inflammation

Roxithromycin is a second-generation macrolide antibiotic derived from erythromycin. In the current study, roxithromycin (ROX) was successfully labeled with technetium-99m for early diagnosis of bacterial infection and discrimination between septic and aseptic inflammation. The highest radiochemical purity of ≥95% was achieved by investigating different labeling parameters such as pH, ligand/reducing agent concentration, temperature, and amount of stabilizing agent. For this purpose, 0.3-0.5 mg ligand, 2-6 μg SnCl₂ ·2H₂ O as a reducing agent at basic pH (8-10 pH) and 2 mg mannitol used as a stabilizing agent, in the end, 370 MBq ^99m Tc added into the reaction vials and incubated for a wide range of temperature (-4 to 65°C). The percent radiochemical purity of ^99m Tc-roxithromycin was assessed with the help of the radio-thin-layer chromatography technique. The characterization studies were carried out using electrophoresis and Radio-HPLC techniques as well as saline stability and serum stability studies were also performed. Furthermore, biodistribution study was also performed in an inflamed animal model to discriminate between septic (heat-killed Staphylococcus aureus) and aseptic (turpentine oil) inflammatory lesions. The results were elaborated that ^99m Tc-roxithromycin (^99m Tc-ROX) was clearly bounded at the septic inflammation site (T/NT ratio of 7.08 ± 1.14) at 30 min postadministration, and maximum accumulation was seen in heart, lungs, liver, stomach, kidneys, and intestine. The results were suggested that ^99m Tc-ROX might be used to discriminate between septic and aseptic inflammatory lesions at an early stage.

Study of Binding Kinetics and Specificity of 99mTc-SSS-Complex and 99mTc-HMPAO to Blood Cells

Nuclear medicine offers several techniques and procedures to image infection, but radiolabelled autologous white blood cells (WBCs) are still the gold standard. These cells are usually labelled with ¹¹¹In or ^99mTc bound to a hydrophobic chelating agent that allows these isotopes to pass through the plasma membrane and enter in the cytoplasm. The most common compound in Europe is HMPAO that efficiently chelates ^99mTc. However, up to 20–40% of the complex is released from the cells in the first few hours. The aim of this study was to radiolabel a new compound, (S₃CPh)₂ (S₂CPh)-complex (SSS-complex) with ^99mTc and compare its binding kinetics and specificity for WBC with HMPAO. The SSS-complex was labelled with ^99mTc and analysed by iTLC and RP-HPLC. In vitro quality controls included a stability assay in serum and saline. Results showed a labelling efficiency of 95 ± 1.2% and 98 ± 1.4% for ^99mTc-SSS-complex and ^99mTc-HMPAO, respectively (p=ns). ^99mTc-SSS-complex was stable in serum and in saline up to 24 h (94 ± 0.1%). Cell labelling experiments showed a higher incorporation of ^99mTc-SSS-complex than ^99mTc-HMPAO by granulocytes (62.6 ± 17.8% vs 40.5 ± 15%, p=0.05), lymphocytes (59.9 ± 22.2% vs 29.4 ± 13.5%; p=0.03), and platelets (44.4 ± 24% vs 20.5 ± 10.7%; p=ns), but the release of radiopharmaceutical from granulocytes at 1 h was lower for HMPAO than for SSS-complex (10.3 ± 1.9% vs 21.3 ± 1.8%; p=0.001). In conclusion, ^99mTc-SSS-complex, although showing high labelling efficiency, radiochemical purity, and stability, is not a valid alternative to ^99mTc-HMPAO, for example, in vivo white blood cells labelling because of high lymphocyte and platelet uptake and rapid washout from granulocytes.

Novel approach for quality assessment and improving diagnostic accuracy in cell-based infection imaging using 99mTc-HMPAO labeled leukocytes

Background and aim: Labeled leukocytes with ^99mTc-HMPAO are routinely used for infection imaging. Although cell labeling with ^99mTc-HMPAO represents an imaging probe to detect infection sites, the diagnostic efficiency of the probe is largely influenced by cell manipulation, multidisciplinary interventions (i.e., biologist, technicians) and available technology (i.e., SPECT, SPECT/CT). The aim of the study was to assess in vitro and in vivo accuracy of a comprehensive approach for quality assessment (QA) of all steps of the procedure. Methods: Radiochemical purity (RCP), pH, labeling efficiency (LE) were measured in 320 procedures. White Cell Viability Factor (WVF) was determined in consecutive blood samples. Images (490 studies) were scored using a 5-point scale. Training program was evaluated using a Learning Questionnaire and a score system. Results: Pre/post-labelling WVF was 0.99% (max value 1%) in all blood samples. LE (mean value 72%) and RCP (>80% until 55 minutes) yielded considerably high values. The vast majority of images were scored as diagnostic by three independent observer (90% with score ≥4). Conclusions: This method appears highly reproducible and easy to use in clinical routine for leukocyte labeling, especially when standardized training and total QA system are implemented. (www.actabiomedica.it)

Currently Available Radiopharmaceuticals for Imaging Infection and the Holy Grail

Infection is ubiquitous. However, its management is challenging for both the patients and the health-care providers. Scintigraphic imaging of infection dates back nearly half a century. The advances in our understanding of the pathophysiology of disease at cellular and molecular levels have paved the way to the development of a large number of radiopharmaceuticals for scintigraphic imaging of infection. These include radiolabeling of blood elements such as serum proteins, white blood cells (WBCs), and cytokines, to name a few. Infectious foci have also been imaged using a radiolabeled sugar molecule by taking advantage of increased metabolic activity in the infectious lesions. Literature over the years has well documented that none of the radiopharmaceuticals and associated procedures that facilitate imaging infection are flawless and acceptable without a compromise. As a result, only a few compounds such as 99mTc-hexamethylpropyleneamineoxime, 18F-FDG, the oldest but still considered as a gold standard 111In-oxine, and, yes, even 67Ga-citrate in some countries, have remained in routine clinical practice. Nonetheless, the interest of scientists and physicians to improve the approaches to imaging and to the management of infection is noteworthy. These approaches have paved the way for the development of numerous, innovative radiopharmaceuticals to label autologous WBCs ex vivo or even those that could be injected directly to image infection or inflammation without direct involvement of WBCs. In this review, we briefly describe these agents with their pros and cons and place them together for future reference.

Preincubation with Sn-complexes causes intensive intracellular retention of 99mTc in thyroid cells in vitro

Technetium radiopharmaceuticals are well established in nuclear medicine. Besides its well-known gamma radiation, 99mTc emits an average of five Auger and internal conversion electrons per decay. The biological toxicity of these low-energy, high-LET (linear energy transfer) emissions is a controversial subject. One aim of this study was to estimate in a cell model how much 99mTc can be present in exposed cells and which radiobiological effects could be estimated in 99mTc-overloaded cells. Methods: Sodium iodine symporter (NIS)- positive thyroid cells were used. 99mTc-uptake studies were performed after preincubation with a non-radioactive (cold) stannous pyro - phosphate kit solution or as a standard 99mTc pyrophosphate kit preparation or with pure pertechnetate solution. Survival curves were analyzed from colony-forming assays. Results: Preincubation with stannous complexes causes irreversible intracellular radioactivity retention of 99mTc and is followed by further pertechnetate influx to an unexpectedly high 99mTc level. The uptake of 99mTc pertechnetate in NIS-positive cells can be modified using stannous pyrophosphate from 3–5% to >80%. The maximum possible cellular uptake of 99mTc was 90 Bq/cell. Compared with nearly pure extracellular irradiation from routine 99mTc complexes, cell survival was reduced by 3–4 orders of magnitude after preincubation with stannous pyrophosphate. Conclusions: Intra cellular 99mTc retention is related to reduced survival, which is most likely mediated by the emission of low-energy electrons. Our findings show that the described experiments constitute a simple and useful in vitro model for radiobiological investigations in a cell model.

Technetium-99m radiochemistry for pharmaceutical applications

Technetium-99m (^99m Tc) is a widely used radionuclide, and the development of ^99m Tc imaging agents continues to be in demand. This overview discusses basic principles of ^99m Tc radiopharmaceutical preparation and design and focuses on the ^99m Tc radiochemistry relevant to its pharmaceutical applications. The ^99m Tc complexes are described based on the most typical examples in each category, keeping up with the state-of-the-art in the field. In addition, the main current strategies to develop targeted ^99m Tc radiopharmaceuticals are summarized.

Left ventricular assist pump pocket infection: conservative treatment strategy for destination therapy candidates

BACKGROUND

Heart failure is a major cause of mortality and morbidity, particularly among patients with advanced disease and no access to cardiac transplantation. LVAD implantation is not only a bridge-to-transplantation option for patients awaiting a heart donor, but is often used as bridge-to-destination therapy in patients unsuited for transplantation for various reasons. LVAD infection is considered the second-most common cause of death in patients who survive the initial 6 months on LVAD support. Few reports describe the indications for chronic suppressing antibiotic therapy, device exchange, methods for exchanging infected devices, post-exchange antimicrobial management status, and the outcomes of such patients.

CASE PRESENTATION

This is the case of a 74-year-old male patient with numerous comorbidities who received urgent surgical management for severe heart failure with a HeartMate II. Six months later he developed an LVAD pump infection with methicillin-resistant Staphylococcus epidermidis, which was diagnosed with leucocyte scintigraphy. The patient received an omental graft over the LVAD and a chronic suppressive antibiotic regime. A marked leukocyte scintigraphy showed the infection's regression 6 months after the initiation of antibiotic treatment.

DISCUSSION

We concisely reviewed the driveline infections and the main aspects of the LVAD pump infection. We reviewed options for conservative and nonconservative management and showed that conservative management of the LVAD pump infection is possible.

CONCLUSIONS

There are no defined recommendations for the management of LVAD pump infection. This case is among the few in the literature showing that conservative treatment of an LVAD pump infection is possible.

In vivo biodistribution and imaging studies with a 99mTc-radiolabeled derivative of the C-terminus of prothymosin alpha in mice bearing experimentally-induced inflammation

Prothymosin alpha (ProTα) is a highly conserved mammalian polypeptide (109 amino acids in man) exerting in vitro and in vivo immunoenhancing activities. Recently, our team has developed a ^99mTc-radiolabeled derivative of the C-terminal bioactive decapeptide of ProTα ([^99mTc]C1) and employed it in in vitro studies, the results of which support the existence of binding sites on human neutrophils that recognize [^99mTc]C1, intact ProTα as well as the C-terminal decapeptide of ProTα and presumably involve Toll-like receptor 4. In the present work, [^99mTc]C1 was administered to Swiss albino mice with experimentally-induced inflammation for in vivo biodistribution and imaging studies, in parallel with a suitable negative control, which differs from [^99mTc]C1 only in bearing a scrambled version of the ProTα decapeptide. The biodistribution data obtained with [^99mTc]C1 demonstrated fast clearance of radioactivity from blood, heart, lungs, normal muscle, and predominantly urinary excretion. Most importantly, slow clearance of radioactivity from the inflammation focus was observed, resulting in a high ratio of inflamed/normal muscle tissue (9.15 at 30min post injection, which remained practically stable up to 2h). The inflammation-targeting capacity of [^99mTc]C1 was confirmed by imaging studies and might be attributed to neutrophils, which are recruited at the inflamed areas and bear binding sites for [^99mTc]C1. In this respect, apart from being a valuable tool for further studies on ProTα in in vitro and in vivo systems, [^99mTc]C1 merits further evaluation as a radiopharmaceutical for specific imaging of inflammation foci.

Clinical Comparison of 99Tcm-Hmpao Labelled Leucocytes and 99Tcm-Nanocolloid in the Detection of Inflammation

Forty-five patients with various inflammatory diseases were imaged with 99Tcm-HMPAO labelled leucocytes and 99Tcm-nanocolloid within 7 days. The overall sensitivity of 99Tcm-leucocytes was 97% and that of 99Tcm-nanocolloid 59% and both agents had a 100% specificity. The 99Tcm-leucocyte method showed reliable results in various inflammatory and infectious conditions, and seems suitable as a primary imaging method. On the contrary, 99Tcm-nanocolloid cannot be recommended for use in inflammatory bowel diseases, soft tissue abscesses or prosthetic vascular graft infections. However, 99Tcm-nanocolloid gave reliable information in inflammatory and infectious bone and joint diseases in which it had a 90% sensitivity and 100% specificity. In those lesions the 99Tcm-nanocolloid method may be useful, because it is simple, fast and cheap. Yet, further evaluation is needed.

Validation of the leukocyte labeling procedure with a new kit for the preparation of technetium-99m exametazime injection

The labeling of leukocytes with technetium-99m (Tc)-HMPAO is a frequent procedure in our laboratory, which was first validated before initiation of clinical studies with the commercial kit of Tc-D,L-hexamethylpropylene amine oxime (Tc-D,L-HMPAO), available from 1988. Recently, a new kit of exametazime has been introduced, with a similar composition and clinical indications, but with some technical improvements. Validation of the labeling procedure with this new kit is proposed, including a comparison between both commercial kits. Requirements for validation were achieved successfully and a comparative study showed no statistically significant differences; nevertheless, labeling of leukocytes may be expected routinely with the new kit on account of its longer shelf-life and lower cost.

Noninvasive imaging of radiolabeled exosome-mimetic nanovesicle using (99m)Tc-HMPAO

Exosomes known as nano-sized extracellular vesicles attracted recent interests due to their potential usefulness in drug delivery. Amid remarkable advances in biomedical applications of exosomes, it is crucial to understand in vivo distribution and behavior of exosomes. Here, we developed a simple method for radiolabeling of macrophage-derived exosome-mimetic nanovesicles (ENVs) with (99m)Tc-HMPAO under physiologic conditions and monitored in vivo distribution of (99m)Tc-HMPAO-ENVs using SPECT/CT in living mice. ENVs were produced from the mouse RAW264.7 macrophage cell line and labeled with (99m)Tc-HMPAO for 1 hr incubation, followed by removal of free (99m)Tc-HMPAO. SPECT/CT images were serially acquired after intravenous injection to BALB/c mouse. When ENVs were labeled with (99m)Tc-HMPAO, the radiochemical purity of (99m)Tc-HMPAO-ENVs was higher than 90% and the expression of exosome specific protein (CD63) did not change in (99m)Tc-HMPAO-ENVs. (99m)Tc-HMPAO-ENVs showed high serum stability (90%) which was similar to that in phosphate buffered saline until 5 hr. SPECT/CT images of the mice injected with (99m)Tc-HMPAO-ENVs exhibited higher uptake in liver and no uptake in brain, whereas mice injected with (99m)Tc-HMPAO showed high brain uptake until 5 hr. Our noninvasive imaging of radiolabeled-ENVs promises better understanding of the in vivo behavior of exosomes for upcoming biomedical application.

Quantification of the chromosomal radiation damage induced by labelling of leukocytes with [18F]FDG

INTRODUCTION

The aim of our work is to quantify the radiation damage in lymphocytes after labelling with [18F]FDG. Comparison with gold standard [99mTc]HMPAO labelling is established. An approach to cellular dosimetry is proposed.

METHODS

Mixed leukocytes were separated from fresh venous blood and labelled with [18F]FDG and [99mTc]HMPAO following published guidelines. Cytokinesis-block micronucleus (CBMN) assay was performed for both sets of experiments. Tests for quality control of labelling described in guidelines were followed. Cellular dosimetry was calculated according to MIRD.

RESULTS

MN scored after labelling with 37 MBq of [18F]FDG were 956 ± 172 and 347 ± 26 for [99mTc]HMPAO (p < 0.05). Absorbed dose in cell nucleus was of 0.23 Gy for [18F]FDG and 0.08 Gy for [99mTc]HMPAO labelling. The CBMN assay after labelling with ~290 MBq of [18F]FDG showed radiation induced inhibition of proliferation capacity of the lymphocytes, confirmed by proliferation study.

CONCLUSIONS

[18F]FDG labelling of mixed leukocytes causes severe radiation damage to the cell, higher than with [99mTc]HMPAO in accordance with the absorbed dose. Labelling of mixed leukocytes for clinical purpose induces high cytotoxicity reflected in the loss of proliferation capacity in lymphocytes this statement allows us to consider a low oncogenic risk however the association between MN formation in the PBL and subsequent risk of cancer is not well established.

ADVANCES IN KNOWLEDGE

This is the first work about radiation damage with [18F]FDG labelled cells. We focused on [18F]FDG labelling of leukocytes due to the growing number of research and review articles about this technique.

IMPLICATIONS FOR PATIENT CARE

The possibility of an increased risk of lymphoid malignancies associated with the administration of radiolabelled lymphocytes is a very controversial subject. Studies on radiation damage on new labelling procedures as the one exposed in this work must be considered.

(89)Zr-Oxine Complex PET Cell Imaging in Monitoring Cell-based Therapies

PURPOSE

To develop a clinically translatable method of cell labeling with zirconium 89 ((89)Zr) and oxine to track cells with positron emission tomography (PET) in mouse models of cell-based therapy.

MATERIALS AND METHODS

This study was approved by the institutional animal care committee. (89)Zr-oxine complex was synthesized in an aqueous solution. Cell labeling conditions were optimized by using EL4 mouse lymphoma cells, and labeling efficiency was examined by using dendritic cells (DCs) (n = 4), naïve (n = 3) and activated (n = 3) cytotoxic T cells (CTLs), and natural killer (NK) (n = 4), bone marrow (n = 4), and EL4 (n = 4) cells. The effect of (89)Zr labeling on cell survival, proliferation, and function were evaluated by using DCs (n = 3) and CTLs (n = 3). Labeled DCs (444-555 kBq/[5 × 10(6)] cells, n = 5) and CTLs (185 kBq/[5 × 10(6)] cells, n = 3) transferred to mice were tracked with microPET/CT. In a melanoma immunotherapy model, tumor targeting and cytotoxic function of labeled CTLs were evaluated with imaging (248.5 kBq/[7.7 × 10(6)] cells, n = 4) and by measuring the tumor size (n = 6). Two-way analysis of variance was used to compare labeling conditions, the Wilcoxon test was used to assess cell survival and proliferation, and Holm-Sidak multiple tests were used to assess tumor growth and perform biodistribution analyses.

RESULTS

(89)Zr-oxine complex was synthesized at a mean yield of 97.3% ± 2.8 (standard deviation). It readily labeled cells at room temperature or 4°C in phosphate-buffered saline (labeling efficiency range, 13.0%-43.9%) and was stably retained (83.5% ± 1.8 retention on day 5 in DCs). Labeling did not affect the viability of DCs and CTLs when compared with nonlabeled control mice (P > .05), nor did it affect functionality. (89)Zr-oxine complex enabled extended cell tracking for 7 days. Labeled tumor-specific CTLs accumulated in the tumor (4.6% on day 7) and induced tumor regression (P < .05 on day 7).

CONCLUSION

We have developed a (89)Zr-oxine complex cell tracking technique for use with PET that is applicable to a broad range of cell types and could be a valuable tool with which to evaluate various cell-based therapies.

Longitudinal monitoring adipose-derived stem cell survival by PET imaging hexadecyl-4-¹²⁴I-iodobenzoate in rat myocardial infarction model

This study aims to monitor how the change of cell survival of transplanted adipose-derived stem cells (ADSCs) responds to myocardial infarction (MI) via the hexadecyl-4-(124)I-iodobenzoate ((124)I-HIB) mediated direct labeling method in vivo. Stem cells have shown the potential to improve cardiac function after MI. However, monitoring of the fate of transplanted stem cells at target sites is still unclear. Rat ADSCs were labeled with (124)I-HIB, and radiolabeled ADSCs were transplanted into the myocardium of normal and MI model. In the group of (124)I-HIB-labeled ADSC transplantation, in vivo imaging was performed using small-animal positron emission tomography (PET)/computed tomography (CT) for 9 days. Twenty-one days post-transplantation, histopathological analysis and apoptosis assay were performed. ADSC viability and differentiation were not affected by (124)I-HIB labeling. In vivo tracking of the (124)I-HIB-labeled ADSCs was possible for 9 and 3 days in normal and MI model, respectively. Apoptosis of transplanted cells increased in the MI model compared than that in normal model. We developed a direct labeling agent, (124)I-HIB, and first tried to longitudinally monitor transplanted stem cell to MI. This approach may provide new insights on the roles of stem cell monitoring in living bodies for stem cell therapy from pre-clinical studies to clinical trials.

Current imaging techniques in rheumatology: MRI, scintigraphy and PET

The first-line imaging technique for diagnosis inflammation in musculo-skeletal organs in rheumatoid arthritis (RA) is planar X-ray examination, which was for many years the first and the only single tool for RA diagnostics and response evaluation. Today, in the era of more aggressive RA treatment, ultrasound examination (US) and magnetic resonance imaging (MRI) are also frequently used. US is used to detect early signs of inflammation within the soft tissue. MRI allows to assess the soft tissue and bone marrow involvement in case of inflammation and/or infection. MRI is capable of detecting more inflammatory lesions and erosions than US, X-ray, or CT. Standard scintigraphy plays a crucial role, and data from positron emission tomography (PET) are also promising. These functional imaging techniques are used in detection of inflammation and/or infection in case of ambiguous results being obtained by other techniques or at other clinics. In patients with RA, scintigraphy plays a key role in the differential diagnosis of hip, knee, etc. endoprosthesis disorders, including mechanical or septic loosening.

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

Rationale

Acute respiratory distress syndrome (ARDS) affects over 200 000 people annually in the USA. Despite causing severe, and often refractory, hypoxaemia, the high mortality and long-term morbidity of ARDS results mainly from extra-pulmonary organ failure; however the mechanism for this organ crosstalk has not been determined.

Methods

Using autologous radiolabelled neutrophils we investigated the pulmonary transit of primed and unprimed neutrophils in humans. Flow cytometry of whole blood samples was used to assess transpulmonary neutrophil priming gradients in patients with ARDS, sepsis and perioperative controls.

Main results

Unprimed neutrophils passed through the lungs with a transit time of 14.2 s, only 2.3 s slower than erythrocytes, and with <5% first-pass retention. Over 97% of neutrophils primed ex vivo with granulocyte macrophage colony-stimulating factor were retained on first pass, with 48% still remaining in the lungs at 40 min. Neutrophils exposed to platelet-activating factor were initially retained but subsequently released such that only 14% remained in the lungs at 40 min. Significant transpulmonary gradients of neutrophil CD62L cell surface expression were observed in ARDS compared with perioperative controls and patients with sepsis.

Conclusions

We demonstrated minimal delay and retention of unprimed neutrophils transiting the healthy human pulmonary vasculature, but marked retention of primed neutrophils; these latter cells then ‘deprime’ and are re-released into the systemic circulation. Further, we show that this physiological depriming mechanism may fail in patients with ARDS, resulting in increased numbers of primed neutrophils within the systemic circulation. This identifies a potential mechanism for the remote organ damage observed in patients with ARDS.

SPECT- and PET-based approaches for noninvasive diagnosis of acute renal allograft rejection

Molecular imaging techniques such as single photon emission computed tomography (SPECT) or positron emission tomography are promising tools for noninvasive diagnosis of acute allograft rejection (AR). Given the importance of renal transplantation and the limitation of available donors, detailed analysis of factors that affect transplant survival is important. Episodes of acute allograft rejection are a negative prognostic factor for long-term graft survival. Invasive core needle biopsies are still the “goldstandard” in rejection diagnostics. Nevertheless, they are cumbersome to the patient and carry the risk of significant graft injury. Notably, they cannot be performed on patients taking anticoagulant drugs. Therefore, a noninvasive tool assessing the whole organ for specific and fast detection of acute allograft rejection is desirable. We herein review SPECT- and PET-based approaches for noninvasive molecular imaging-based diagnostics of acute transplant rejection.

(99m)Tc-MORF oligomers specific for bacterial ribosomal RNA as potential specific infection imaging agents

PURPOSE

Radiolabeled oligomers complementary to the 16S rRNA in bacteria were investigated as bacterial infection imaging agents.

METHODS AND RESULTS

Identical sequences with backbones phosphorodiamidate morpholino (MORF), peptide nucleic acid (PNA), and phosphorothioate DNA (PS-DNA) were (99m)Tc-labeled and evaluated for binding to bacterial RNA. MORF binding to RNA from Escherichia coli strains SM101 and K12 was 4- and 150-fold higher compared to PNA and PS-DNA, respectively. Subsequently MORF oligomer in fluorescence in situ hybridization showed a stronger signal with study MORF compared to control in fixed preparations of two E. coli strains and Klebsiella pneumoniae. Flow cytometry analysis showed study MORF accumulation to be 8- and 80-fold higher compared to the control in live K. pneumoniae and Staphylococcus aureus, respectively. Further, fluorescence microscopy showed increased accumulation of study MORF over control in live E. coli and K. pneumonia. Binding of (99m)Tc-study MORF to RNA from E. coli SM101 and K12 was 30.4 and 117.8pmol, respectively, per 10(10) cells. Mice with K. pneumoniae live or heat-killed (sterile inflammation) in one thigh at 90min for both (99m)Tc-study MORF and control showed higher accumulation in target thighs than in blood and all other organs expect for kidneys and small intestine. Accumulation of (99m)Tc-study MORF was significantly higher (p=0.009) than that of the control in the thigh with sterile inflammation.

CONCLUSION

A (99m)Tc-MORF oligomer complimentary to the bacterial 16S rRNA demonstrated binding to bacterial RNA in vitro with specific accumulation into live bacteria. Radiolabeled MORF oligomers antisense to the bacterial rRNA may be useful to image bacterial infection.

PET with 18F-FDG-labeled T lymphocytes for diagnosis of acute rat renal allograft rejection

We proposed small-animal PET with (18)F-FDG-labeled T lymphocytes as a new method for image-based diagnosis of acute allogeneic renal transplant rejection (AR) established in a rat model.

METHODS

One and 2 h after tail vein injection of 30 × 10(6) ex vivo (18)F-FDG-labeled human T cells into male 10-wk-old uninephrectomized, allogeneically transplanted rats (aTX; Lewis-brown Norway [LBN] to Lewis), whole-body radioactivity distribution was assessed in vivo by small-animal PET (postoperative day 4), and percentage injected dose (%ID) as a parameter of T-cell infiltration was assessed and compared between graft and native kidney. In vivo results were confirmed by autoradiography and staining of human CD3 after postmortem dissection. Syngeneically transplanted rats (sTX) (LBN to LBN), rats with ischemia-reperfusion injury (IRI) (45-min warm ischemia), and rats subjected to acute cyclosporine A (CSA) toxicity (50 mg/kg for 2 d intraperitoneally) served as controls.

RESULTS

The accumulation of labeled cells was significantly elevated in allografts with AR (1.07 ± 0.28 %ID), compared with native control kidneys (0.49 ± 0.18 %ID) (P < 0.0001). No differences were found among native controls, sTX, CSA toxicity, and kidneys with IRI. In vivo uptake of (18)F-FDG cells measured in the PET scanner correlated with results obtained by autoradiography, histologic evaluation, and polymerase chain reaction.

CONCLUSION

We proposed graft PET imaging using (18)F-FDG-labeled T cells as a new option to detect rat renal AR with a low dose of (18)F-FDG in a noninvasive, fast, and specific manner in rats.

Antimicrobial peptides as infection imaging agents: better than radiolabeled antibiotics

Nuclear medicine imaging techniques offer whole body imaging for localization of number and site of infective foci inspite of limitation of spatial resolution. The innate human immune system contains a large member of important elements including antimicrobial peptides to combat any form of infection. However, development of antibiotics against bacteria progressed rapidly and gained popularity over antimicrobial peptides but even powerful antimicrobials failed to reduce morbidity and mortality due to emergence of mutant strains of bacteria resulting in antimicrobial resistance. Differentiation between infection and inflammation using radiolabeled compounds with nuclear medicine techniques has always been a dilemma which is still to be resolved. Starting from nonspecific tracers to specific radiolabeled tracers, the question is still unanswered. Specific radiolabeled tracers included antibiotics and antimicrobial peptides which bind directly to the bacteria for efficient localization with advanced nuclear medicine equipments. However, there are merits and demerits attributed to each. In the current paper, radiolabeled antibiotics and radiolabeled peptides for infection localization have been discussed starting with the background of primitive nonspecific tracers. Radiolabeled antimicrobial peptides have certain merits compared with labeled antibiotics which make them superior agents for localization of infective focus.

Tc-99m Labeled HMPAO white Blood Cell Scintigraphy in Pediatric Patients

OBJECTIVE

(99m)Tc labeled hexamethylpropylene amine oxime (HMPAO) white blood cell (WBC) scintigraphy is a frequently used option for acute infection, particularly in pediatric patients. This scintigraphy is applied to detect sites of infection/inflammation in patients with fever of unknown origin, to find and follow up osteomyelitis, and to detect suspicion of acute appendicitis. The aim of this retrospective study was to evaluate the value of (99m)Tc-HMPAO labeled WBC scintigraphy in pediatric patients.

MATERIAL AND METHODS

The study was conducted between January 2006 and December 2008 and included 13 patients (5 boys, 8 girls; mean age 6.9±6.2 years). Those patients who had suspicion of bone infection (n=7), fever of unknown origin (n=3), and suspicion of acute appendicitis (n=3) were evaluated retrospectively. (99m)Tc-HMPAO labeled WBC scintigraphy imaging was performed to all patients. Diagnosis was done according to operation and pathological results or clinical follow-up.

RESULTS

(99m)Tc-HMPAO labeled WBC scintigraphy has been found to be true positive in 6 cases, true negative in 6 cases, and false negative in one patient who had fewer unknown origin. The false negative case has been found to have encephalitis with MRI.

CONCLUSION

Leukocyte scintigraphy has been described as a useful diagnostic tool in the diagnosis of suspicion of bone infection, fever of unknown origin and suspicion of acute appendicitis. (99m)Tc-HMPAO labeled WBC scintigraphy is a rapid and very accurate method for detecting those pathologies. Our results showed that WBC scintigraphy might be reliably used for diagnosis of suspected bone infection and acute appendicitis, fever of unknown origin, and acute appendicitis, in pediatric patient population.

CONFLICT OF INTEREST

None declared.

Prosthetic joint infections: radionuclide state-of-the-art imaging

Prosthetic joint replacement surgery is performed with increasing frequency. Overall the incidence of prosthetic joint infection (PJI) and subsequently prosthesis revision failure is estimated to be between 1 and 3%. Differentiating infection from aseptic mechanical loosening, which is the most common cause of prosthetic failure, is especially important because of different types of therapeutic management. Despite a thorough patient history, physical examination, multiple diagnostic tests and complex algorithms, differentiating PJI from aseptic loosening remains challenging. Among imaging modalities, radiographs are neither sensitive nor specific and cross-sectional imaging techniques, such as computed tomography and magnetic resonance imaging, are limited by hardware-induced artefacts. Radionuclide imaging reflects functional rather than anatomical changes and is not hampered by the presence of a metallic joint prosthesis. As a result scintigraphy is currently the modality of choice in the investigation of suspected PJI. Unfortunately, there is no true consensus about the gold standard technique since there are several drawbacks and limitations inherent to each modality. Bone scintigraphy (BS) is sensitive for identifying the failed joint replacement, but cannot differentiate between infection and aseptic loosening. Combined bone/gallium scintigraphy (BS/GS) offers modest improvement over BS alone for diagnosing PJI. However, due to a number of drawbacks, BS/GS has generally been superseded by other techniques but it still may have a role in neutropenic patients. Radiolabelled leucocyte scintigraphy remains the gold standard technique for diagnosing neutrophil-mediated processes. It seems to be that combined in vitro labelled leucocyte/bone marrow scintigraphy (LS/BMS), with an accuracy of about 90%, is currently the imaging modality of choice for diagnosing PJI. There are, however, significant limitations using in vitro labelled leucocytes and considerable effort has been devoted to developing alternative radiotracers, such as radiolabelled HIGs, liposomes, antigranulocyte antibodies and fragments, as well as more investigational tracers such as radiolabelled antibiotics, antimicrobial peptides, bacteriophages and thymidine kinase. On the other hand, positron emission tomography (PET) is still growing in the field of PJI imaging with radiotracers such as (18)F-fluorodeoxyglucose (FDG), (18)F-FDG white blood cells and (18)F-fluoride. But unfortunately this superb tomographic technique will only receive full acceptance when specific PET uptake patterns can be successfully developed. The emergence of hybrid modality imaging using integrated single photon emission computed tomography (SPECT) and PET with computed tomography (SPECT/CT and PET/CT) may also have a contributing role for more accurate assessment of joint replacement complications, especially combined with new radiotracers such as (68)Ga and (64)Cu. Finally, in searching for infection-specific tracers, currently there is no such diagnostic agent available.

99mTc-HMPAO labelled white blood cell scintigraphy in the diagnosis and monitoring of response of the therapy in patients with active bronchiectasis

AIM

The aim of this study was to assess the role of labelled leukocyte scintigraphy in the diagnosis and monitorization of response to therapy of patients with active bronchiectasis.

MATERIAL AND METHODS

Twenty patients underwent (99m)Technetium hexamethylpropyleneamine oxime ((99m)Tc-HMPAO) labelled white blood cell (WBC) scintigraphy. A second scintigraphy was performed in 13 patients at 10 day of the treatment. Regional (99m)Tc-HMPAO WBC uptake and radiologic imaging findings (high resolution computed tomography or Chest X-Ray) in the lungs were classified into 3 categories in 6 lung areas. scintigraphic, radiological and clinical disease scores were calculated for all patients.

RESULTS

An abnormal accumulation was visually observed in 19 of 20 patients on the pre-treatment scans, the scintigraphy showing 95% sensitivity. A significant difference was found between early and late ratios (P=0.001) in the pre-treatment scans. The infected areas revealed a significant decrease in uptake ratios on the post-treatment scans compared to the pre-treatment scans (P=0.001). However, no significant correlation was determined between clinical and radiological scores, clinical and scintigraphic scores and also between scintigraphic and radiological scores (P ≥ 0.05).

CONCLUSIONS

(99m)Tc-HMPAO WBC scintigraphy may be a useful tool to evaluate response to therapy in patients with active bronchiectasis.

A (99m)Tc-labeled dual-domain cytokine ligand for imaging of inflammation

INTRODUCTION

Interleukin (IL)-1 and IL-18 are potent proinflammatory cytokines in inflammation-related diseases. Their actions are regulated by IL-1 receptor antagonist (IL-1ra) and IL-18 binding protein (IL-18bp). This study was designed to (99m)Tc-radiolabel an IL-1ra and IL-18bp dual-domain cytokine ligand, IL-18bp-Fc-IL-1ra, for specific inflammation targeting.

METHODS

The (99m)Tc-IL-18bp-Fc-IL-1ra was obtained by direct labeling via 2-iminothiolane reduction. Competitive binding of (99m)Tc-labeled and unlabeled IL-18bp-Fc-IL-1ra to rat polymorphonuclear leukocytes was assessed in vitro. A mouse ear edema model was used to evaluate specific targeting properties of (99m)Tc-IL-18bp-Fc-IL1ra in vivo. The correlation between (99m)Tc-IL-18bp-Fc-IL-1ra uptake and (111)In-labeled polymorphonuclear neutrophil infiltration was studied using ischemic-reperfused rat hearts.

RESULTS

Direct (99m)Tc-labeling yielded a stable dual-domain cytokine radioligand with radiochemical purity greater than 95% after gel filtration. Competitive binding studies showed specific targeting of (99m)Tc-IL-18bp-Fc-IL-1ra to inflammatory cells. The (99m)Tc-IL-18bp-Fc-IL-1ra uptake was 1.80±0.17 % injected dose per gram (%ID/g) in the inflamed ear without blocking, whereas uptake in the presence of IL-18bp-Fc-IL-1ra was 1.09±0.08 %ID/g (P<.05). The amounts of IL-1β and IL-18 were significantly increased in the inflamed ears compared to the vehicle controls. A significant correlation of (99m)Tc-IL-18bp-Fc-IL-1ra with (111)In-labeled neutrophil distribution was observed in the ischemic-reperfused hearts (P<.001).

CONCLUSION

Targeting proinflammatory cytokines with (99m)Tc-IL-18bp-Fc-IL-1ra may provide a suitable approach for specific detection of inflammatory sites.

The labeled-leukocyte scan in the study of abdominal abscesses

AIM

The purpose of the present paper was to review the literature over the last 30 years to assess the value of radionuclide imaging, particularly labeled leukocyte scan, as compared to other imaging modalities in the management of abdominal abscesses.

METHODS

A systematic review of the published studies in humans cited in PubMed written in English, French, German, Italian, and Spanish was made.

RESULTS

Ultrasound (US) has lower sensitivity than leukocyte scan (LS), particularly in patients without localizing signs, while CT has higher sensitivity than US, but less than LS. On the other hand, CT had higher specificity than both LS and US.

DISCUSSION

LS is the more sensitive method to localize abdominal abscesses and may guide dedicated US and CT investigations to improve their diagnostic potential. Further diagnostic evolution is expected from the routine use of hybrid SPECT/CT systems.

Non-invasive diagnosis and grading of postsurgical endoscopic recurrence in Crohn's disease: usefulness of abdominal ultrasonography and (99m)Tc-hexamethylpropylene amineoxime-labelled leucocyte scintigraphy

Non-invasive techniques aim to be an alternative to endoscopy in the assessment of postsurgical recurrence of Crohn's disease (CD). The object of this study was to evaluate the accuracy of abdominal ultrasonography (AUS) and (99m)Tc-hexamethylpropylene amineoxime ((99m)Tc-HMPAO)-labelled leucocyte scintigraphy (LLS) compared with endoscopy in the diagnosis and grading of postsurgical recurrence of CD. Between January 2006 and May 2007, all patients with CD and resection with ileocolic anastomosis were included prospectively. Within three days they underwent an ileocolonoscopy, AUS with evaluation of bowel wall thickness and the presence of Doppler flow, and LLS. Forty patients who met the study conditions were included; 5 patients did not agree to have the ileocolonoscopy and it was not possible to assess the anastomosis in 2 patients. Endoscopic recurrence was detected in 26 patients (78.8%), in 15 of whom it was moderate-severe. For the diagnosis of recurrence, both AUS and LLS showed acceptable sensitivity and positive predictive value, with an accuracy of 72.7% and 78.1%, respectively. The results of the AUS and LLS for diagnosing moderate-severe recurrence were better, with an accuracy of 78.8% and 81.3%, respectively. The best assessment of the severity of the recurrence was obtained with the combination of both techniques (sensitivity, specificity, positive and negative predictive values, accuracy and kappa index were, respectively: 93.3%, 72.2%, 73.7%, 92.9%, 81.8% and 0.64). The variables evaluated, both sonographic and scintigraphic, had areas under the curve that were similar and significantly different from 0.5.

CONCLUSION

Abdominal ultrasonography and (99m)Tc-HMPAO-labelled leucocyte scintigraphy are two useful non-invasive techniques for the assessment of postsurgical recurrence of Crohn's disease.

Leukocyte SPECT/CT for detecting infection of left-ventricular-assist devices: preliminary results

We report our experience with using integrated molecular and anatomic hybrid imaging to assess infection in patients who have a left-ventricular-assist device (LVAD).

METHODS

Thirteen (99m)Tc-exametazime-leukocyte planar and SPECT/CT scans were obtained for 8 consecutive patients who had an implanted LVAD. SPECT/CT was used to assess suspected device-related infections (n = 8) and to evaluate the efficiency of current antibiotic therapy (n = 5).

RESULTS

Device-related infection was seen on 8 of the 13 scans. SPECT/CT was positive for infection in all 8 patients, whereas planar scans were positive in 6 of 8. SPECT/CT provided relevant information on the extent of infection and its exact location in all patients. Additional distant infectious foci were demonstrated in 3 of 13 patients.

CONCLUSION

SPECT/CT led to an accurate diagnosis of LVAD-related infection, revealing both anatomic location and extent. This noninvasive approach could lead to improved therapeutic strategies.

Guidelines for the labelling of leucocytes with (99m)Tc-HMPAO. Inflammation/Infection Taskgroup of the European Association of Nuclear Medicine

We describe here a protocol for labelling autologous white blood cells with (99m)Tc-HMPAO based on previously published consensus papers and guidelines. This protocol includes quality control and safety procedures and is in accordance with current European Union regulations and International Atomic Energy Agency recommendations.

Leukocyte-technetium-99m uptake in Crohn’s disease: Does it show subclinical disease?

AIM: To evaluate inflammatory activity in patients with Crohn’s disease (CD) using technetium-99m-hexamethylpropyleneamine oxime (99mTc-HMPAO) granulocyte scintigraphy.

METHODS: Twenty patients (7 male and 13 female) with CD and five healthy volunteers were selected for 99mTc-HMPAO granulocyte scintigraphy. The Crohn’s Disease Activity Index (CDAI), blood tests and C-reactive protein (CRP) of each patient were performed 7 d before the scintigraphic images. The leukocytes were labeled according to the International Society of Radiolabeled Blood Elements (ISORBE) consensus protocol and the scintigraphic images, including single photon emission computed tomography, were obtained 30 min and 2 h after injection of the radiolabeled leukocytes.

RESULTS: The labeling yield of the leukocytes with the lipophilic complex 99mTc-HMPAO was 55.0% ± 10%. Six of the 20 patients (30%) presented congruent results for the three parameters investigated (CDAI, Scintigraphic Index and CRP). On the other hand, 14 patients (70%) did not show congruent results. There was no significant correlation between the indices analyzed according to the Spearman test (P > 0.05, n = 20).

CONCLUSION: The results suggest that 99mTc-HMPAO-labeled leukocyte scintigraphy could be important for determining inflammatory activity in CD even in the absence of clinical symptoms.

Advances in radionuclide molecular imaging in myocardial biology

Molecular imaging is a new and evolving field that employs a targeted approach to noninvasively assess biologic processes in vivo. By assessing key elements in specific cellular processes prior to irreversible end-organ damage, molecular tools will allow for earlier detection and intervention, improving management and outcomes associated with cardiovascular diseases. The goal of those working to expand this field is not just to provide diagnostic and prognostic information, but rather to guide an individual's pharmacological, cell-based, or genetic therapeutic regimen. This article will review molecular imaging tools in the context of our current understanding of biological processes of the myocardium, including angiogenesis, ventricular remodeling, inflammation, and apoptosis. The focus will be on radiotracer-based molecular imaging modalities with an emphasis on clinical application. Though this field is still in its infancy and may not be fully ready for widespread use, molecular imaging of myocardial biology has begun to show promise of clinical utility in acute and chronic ischemia, acute myocardial infarction, congestive heart failure, as well as in more global inflammatory and immune-mediated responses in the heart-like myocarditis and allogeneic cardiac transplant rejection. With continued research and development, molecular imaging promises to be an important tool for the optimization of cardiovascular care.

Role of scintigraphy in inflammatory bowel disease

The diagnosis of inflammatory bowel disease (IBD) depends on direct endoscopic visualization of the colonic and ileal mucosa and the histological study of the obtained samples. Radiological and scintigraphic methods are mainly used as an adjunct to endoscopy. In this review, we focus on the diagnostic potential of nuclear medicine procedures. The value of all radiotracers is described with special reference to those with greater experience and more satisfactory results. Tc-99m hexamethylpropylene amine oxime white blood cells remain a widely acceptable scintigraphic method for the diagnosis of IBD, as well as for the evaluation of disease extension and severity. Recently, pentavalent Tc-99m dimercaptosuccinic acid has been recommended as an accurate variant and a complementary technique to endoscopy for the follow-up and assessment of disease activity. Positron emission tomography alone or with computed tomography using fluorine-18 fluorodeoxyglucose appears to be a promising method of measuring inflammation in IBD patients.

New molecular imaging targets to characterize myocardial biology

Molecular imaging represents a targeted approach to noninvasively assess biologic (both physiologic and pathologic) processes in vivo. Ideally the goal of molecular imaging is not just to provide diagnostic and prognostic information based on identification of the molecular events associated with a pathologic process but rather to guide individually tailored pharmacologic, cell-based, or genetic therapeutic regimens. This article reviews the recent advances in myocardial molecular imaging in the context of the cardiovascular processes of angiogenesis, apoptosis, inflammation, and ventricular remodeling. The focus is on radiotracer-based single photon emission computed tomography and positron emission tomography molecular imaging approaches.

Discrepancies between the fate of myoblast xenograft in mouse leg muscle and NMR label persistency after loading with Gd-DTPA or SPIOs

1H-NMR (nuclear magnetic resonance) imaging is regularly proposed to non-invasively monitor cell therapy protocols. Prior to transplantation, cells must be loaded with an NMR contrast agent (CA). Most studies performed so far make use of superparamagnetic iron oxide particles (SPIOs), mainly for favorable detection sensitivity. However, in the case of labeled cell death, SPIO recapture by inflammatory cells might introduce severe bias. We investigated whether NMR signal changes induced by preloading with SPIOs or the low molecular weight gadolinium (Gd)-DTPA accurately monitored the outcome of transplanted cells in a murine model of acute immunologic rejection. CA-loaded human myoblasts were grafted in the tibialis anterior of C57BL/6 mice. NMR imaging was repeated regularly until 3 months post-transplantation. Label outcome was evaluated by the size of the labeled area and its relative contrast to surrounding tissue. In parallel, immunohistochemistry assessed the presence of human cells. Data analysis revealed that CA-induced signal changes did not strictly reflect the graft status. Gd-DTPA label disappeared rapidly yet with a 2-week delay compared with immunohistochemical evaluation. More problematically, SPIO label was still visible after 3 months, grossly overestimating cell survival (<1 week). SPIOs should be used with extreme caution to evaluate the presence of grafted cells in vivo and could hardly be recommended for the long-term monitoring of cell transplantation protocols.

[Algodystrophy versus postoperative infection: use of labelled white cell scans in differential diagnosis in the hand; a case report]

The differential diagnosis between complex regional pain syndrome (CRPS) and postoperative infection is sometimes difficult. We discuss such a case following surgical release of a trigger finger. Because of lack of an accurate diagnosis, the patient was subjected to more and more costly investigations and was operated one more (and unnecessary) time. As white blood cell scintigraphy ((99m)technetium hexamethylpropyleneamineoxime leukocyte [(99m)Tc HMPAO leu]) proved negative, it allowed us to identify with high specificity, a non infectious cause for the problem, and to stop over-investigation and inflation of the costs of treatment. However, the use of white blood cell scintigraphy should remain exceptional, because of its complexity and expense.

Tc-99m HMPAO labeled white blood cell imaging in a child with eosinophilic lung disease

In radiolabeled leukocyte imaging, Tc-99m HMPAO has a significantly higher selectivity for eosinophils than neutrophils, but this may be clinically meaningful in disorders with eosinophilic infiltration. We present the case of a 2-year-old boy with infection who also developed drug-induced eosinophilic lung disease, as established later by bronchoalveolar lavage and discontinuation of the responsible antistaphylococcal agent. In the investigation of sepsis, diffusely increased pulmonary accumulation of Tc-99m HMPAO labeled leukocytes was observed. These findings were consistent with eosinophilic lung infiltration and underline the importance of clinical and laboratory data in the comprehensive interpretation of Tc-99m HMPAO labeled leukocytes scans.