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

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.

Nuclear Imaging in Pediatric Cardiology: Principles and Applications

Nuclear imaging plays a unique role within diagnostic imaging since it focuses on cellular and molecular processes. Using different radiotracers and detection techniques such as the single photon emission scintigraphy or the positron emission tomography, specific parameters can be assessed: myocardial perfusion and viability, pulmonary perfusion, ventricular function, flow and shunt quantification, and detection of inflammatory processes. In pediatric and congenital cardiology, nuclear imaging can add complementary information compared to other imaging modalities such as echocardiography or magnetic resonance imaging. In this state-of-the-art paper, we appraise the different techniques in pediatric nuclear imaging, evaluate their advantages and disadvantages, and discuss the current clinical applications.

Analysis of Cell Fraction of ⁹⁹mTc-HMPAO Radiolabeled Leukocytes

PURPOSE

99mTc-HMPAO radiolabeled autologous leukocyte scintigraphy is routinely used clinically for infection imaging. Leukocytes are mostly separated via sedimentation. It is unknown whether leukocytes are clearly separated by sedimentation or selectively labeled. Therefore, in this study, the blood cell numbers were investigated after leukocyte radiolabeling to identify the cells strongly radiolabeled by 99mTc-HMPAO.

METHODS

This study was performed with leftover blood samples of the patients who underwent 99mTc-HMPAO scintigraphy at Chonbuk National University Hospital (2018-2019). The blood of 22 patients was drawn for 99mTc-HMPAO scintigraphy. WBCs were separated via conventional sedimentation at our clinic and radiolabeled. The concentration of cell components was determined using an automatic hematology analyzer. The cells in the final sample injectate sample were separated using Histopaque and counted with a dose calibrator.

RESULTS

The average numbers of RBCs, WBCs, and PLTs in the final injection sample were 79 ± 33, 23.26 ± 11.95, and 229.5 ± 206.57 x 103/μL, respectively. The PLT number was almost 10-fold the number of WBCs. The number of RBCs was nearly 3-fold higher than WBCs [RBC/WBC ratio = 4.67 ± 3.58, and PLT/WBC ratio = 10.65 ± 12.46]. Following Histopaque separation, the activity of each layer showed 99mTc-HMPAO labeling of WBC > RBC > PLT in order. The total activity/cell numbers of WBCs, RBCs and PLTs were 0.016 ± 0.010, 0.005 ± 0.005 and 0.003 ± 0.002, respectively (p > 0.05).

CONCLUSION

Although the numbers of RBCs and PLTs were highly increased after sedimentation, their individual cellular activity was lower than that of WBCs. 99mTc-HMPAO was more selective to WBCs than RBCs or PLTs. In conclusion, a higher number of WBCs were radiolabeled compared with RBCs and PLTs.

Methods of Granulocyte Isolation from Human Blood and Labeling with Multimodal Superparamagnetic Iron Oxide Nanoparticles

This in vitro study aimed to find the best method of granulocyte isolation for subsequent labeling with multimodal nanoparticles (magnetic and fluorescent properties) to enable detection by optical and magnetic resonance imaging (MRI) techniques. The granulocytes were obtained from venous blood samples from 12 healthy volunteers. To achieve high purity and yield, four different methods of granulocyte isolation were evaluated. The isolated granulocytes were labeled with multimodal superparamagnetic iron oxide nanoparticles (M-SPIONs) coated with dextran, and the iron load was evaluated qualitatively and quantitatively by MRI, near-infrared fluorescence (NIRF) and inductively coupled plasma mass spectrometry (ICP-MS). The best method of granulocyte isolation was Percoll with Ficoll, which showed 95.92% purity and 94% viability. After labeling with M-SPIONs, the granulocytes showed 98.0% purity with a yield of 3.5 × 10⁶ cells/mL and more than 98.6% viability. The iron-loading value in the labeled granulocytes, as obtained by MRI, was 6.40 ± 0.18 pg/cell. Similar values were found with the ICP-MS and NIRF imaging techniques. Therefore, our study shows that it is possible to isolate granulocytes with high purity and yield and labeling with M-SPIONs provides a high internalized iron load and low toxicity to cells. Therefore, these M-SPION-labeled granulocytes could be a promising candidate for future use in inflammation/infection detection by optical and MRI techniques.

Imaging in acute appendicitis: What, when, and why?

Acute appendicitis (AA) is the commonest cause of pain abdomen requiring surgical intervention. Diagnosis as well as management of acute appendicitis is mired in controversies and contradictions even today. Clinicians often face the dilemma of balancing negative appendectomy rate and perforation rate if the diagnosis is based on clinical scoring alone. Laboratory results are often non-specific. Imaging has an important role not only in diagnosing appendicitis and its complication but also suggesting alternate diagnosis in appropriate cases. However, there is no universally accepted diagnostic imaging algorithm for appendicitis. Imaging of acute appendicitis needs to be streamlined keeping pros and cons of the available investigative modalities. Radiography has practically no role today in the diagnosis and management of acute appendicitis. Ultrasonography (USG) should be the first line imaging modality for all ages, particularly for children and non-obese young adults including women of reproductive age group. If USG findings are unequivocal and correlate with clinical assessment, no further imaging is needed. In case of equivocal USG findings or clinico-radiological dissociation, follow-up/further imaging (computed tomography (CT) scan/magnetic resonance imaging (MRI)) is recommended. In pediatric and pregnant patients with inconclusive initial USG, MRI is the next option. Routine use of CT scan for diagnosis of AA needs to be discouraged. Our proposed version of a practical imaging algorithm, with USG first and always has been incorporated in the article.

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.

Charcot foot and ankle with osteomyelitis

This paper presents a review of the current literature discussing topics of Charcot osteoarthropathy, osteomyelitis, diagnosing osteomyelitis, antibiotic management of osteomyelitis, and treatment strategies for management of Charcot osteoarthropathy with concurrent osteomyelitis.