Leukocyte Scintigraphy Research Articles

Nuclear Imaging in Orthopaedic Practice: A Critical Analysis Review.

» Nuclear imaging techniques, including bone scintigraphy, labeled leukocyte scintigraphy, positron emission tomography (PET), and single-photon emission computed tomography (SPECT) combined with computed tomography (CT), have wide applications in orthopaedics for evaluating trauma, painful total joint arthroplasty, musculoskeletal infection, and orthopaedic oncology.» Three-phase bone scintigraphy is a first-line, highly sensitive nuclear medicine study for evaluating orthopaedic pathology when initial studies are inconclusive. However, its specificity is limited, and findings may be falsely positive for up to 2 years after total joint arthroplasty because of physiologic bone remodeling.» Labeled leukocyte scintigraphy or gallium scintigraphy can improve diagnostic accuracy in patients with a positive bone scan and suspected musculoskeletal or periprosthetic joint infection.» 18-Fluorodeoxyglucose PET/CT demonstrates high sensitivity and specificity for diagnosing bone neoplasms, infections, and metabolic disorders. Emerging PET/magnetic resonance imaging technology offers reduced radiation exposure and greater soft-tissue detail but presents technical and cost challenges.» SPECT/CT provides valuable functional and anatomic detail for characterizing the extent and location of bone pathology, serving as an important adjunct to other imaging modalities.» Ultimately, the choice of nuclear imaging modality should consider the specific clinical context, diagnostic accuracy, impact on management, and cost-effectiveness on a case-by-case basis.

Development and evaluation of a radiolabelling agent for white blood cell scans

Radiolabelled autologous leukocytes have been used for the clinical diagnosis of inflammation and infection. To develop a stable and efficient radiopharmaceutical for labelling leukocytes, we prepared a novel radioiodinated cell-penetrating peptide, 125I-TAT, using a bi-functional linker. 125I-TAT was stable for two days under three different temperature conditions of −20 °C, 4 °C, and 40 °C, with its radiochemical purity remaining over 99%. Iodinated TAT was non-toxic to leukocytes with an IC50 value of over 100 μM. The labelling efficiency of 125I-TAT using 1ｘ107 cells ranged from 27% to 53% when the three leukocyte cell lines were pre-treated with DMSO. This is comparable to the labelling efficiency recommended by the guideline for conventional labelling agents using 2ｘ108 cells. Radioiodinated cell-penetrating peptide may be an improved radiopharmaceutical for white blood cell scans by further optimization.

Complicated Inguinal Hernia Incidentally Detected on a Radiolabelled Autologous White Blood Cell Scan.

A 73-year-old male with left hip prosthesis infection performed a 99mTc HMPAO-labelled autologous WBC (WBC) scan to evaluate the response to antibiotic therapy. Since the early planar scan, an area of increased activity was visible extending from the left groin region to the ipsilateral flank. At late planar images, the area progressively focused in the left groin, site of a painful inguinal hernia. The contextual tomographic acquisition showed increased activity partly referable to non-specific intestinal contents and partly localized at the parietal wall of the herniated intestinal loop. Our case suggests that the incidental detection of increased accumulation of WBC in correspondence of the intestinal wall of an inguinal hernia may indicate inflammatory involvement and subsequent further complications.

An overview of the current diagnostic approach to Periprosthetic Joint Infections.

The diagnosis of periprosthetic joint infections (PJI) presents a formidable challenge to orthopaedic surgeons due to its complex and diverse manifestations. Accurate diagnosis is of utmost importance, as even mild pain following joint replacement surgery may indicate PJI in the absence of a definitive gold standard diagnostic test. Numerous diagnostic modalities have been suggested in the literature, and international societies have continually updated diagnostic criteria for this debilitating complication. This review article aims to comprehensively examine the latest evidence-based approaches for diagnosing PJI. Through a thorough analysis of current literature, we explore promising diagnostic strategies that have demonstrated effectiveness in identifying PJI. These strategies encompass the utilization of laboratory markers, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), alongside imaging techniques such as magnetic resonance imaging (MRI) and leukocyte scintigraphy. Additionally, we highlight the importance of synovial fluid analysis, including the potential role of alpha-defensin as a biomarker, and examine evolving international diagnostic criteria to standardize and improve diagnostic accuracy.

18F-FDG PET/CT and radiolabeled leukocyte SPECT/CT imaging for the evaluation of cardiovascular infection in the multimodality context: ASNC Imaging Indications (ASNC I2) Series Expert Consensus Recommendations from ASNC, AATS, ACC, AHA, ASE, EANM, HRS, IDSA, SCCT, SNMMI, and STS.

This document on cardiovascular infection, including infective endocarditis, is the first in the American Society of Nuclear Cardiology Imaging Indications (ASNC I2) series to assess the role of radionuclide imaging in the multimodality context for the evaluation of complex systemic diseases with multi-societal involvement including pertinent disciplines. A rigorous modified Delphi approach was used to determine consensus clinical indications, diagnostic criteria, and an algorithmic approach to diagnosis of cardiovascular infection including infective endocarditis. Cardiovascular infection incidence is increasing and is associated with high morbidity and mortality. Current strategies based on clinical criteria and an initial echocardiographic imaging approach are effective but often insufficient in complicated cardiovascular infection. Radionuclide imaging with 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and single photon emission computed tomography/CT leukocyte scintigraphy can enhance the evaluation of suspected cardiovascular infection by increasing diagnostic accuracy, identifying extracardiac involvement, and assessing cardiac implanted device pockets, leads, and all portions of ventricular assist devices. This advanced imaging can aid in key medical and surgical considerations. Consensus diagnostic features include focal/multi-focal or diffuse heterogenous intense 18F-FDG uptake on valvular and prosthetic material, perivalvular areas, device pockets and leads, and ventricular assist device hardware persisting on non-attenuation corrected images. There are numerous clinical indications with a larger role in prosthetic valves, and cardiac devices particularly with possible infective endocarditis or in the setting of prior equivocal or non-diagnostic imaging. Illustrative cases incorporating these consensus recommendations provide additional clarification. Future research is necessary to refine application of these advanced imaging tools for surgical planning, to identify treatment response, and more.

Head-to-Head Comparison Between 18F-FDG PET and Leukocyte Scintigraphy to Monitor Treatment Responses in Necrotizing Otitis Externa.

Necrotizing otitis externa (NOE) is a rare disease associated with high morbidity and mortality, and there is currently no available accurate biomarker to assess treatment responses. The aim of the current study was to evaluate and directly compare the diagnostic performances of 18-Fluoro-deoxyglucose positron emission tomography (18F-FDG PET) and labeled leukocyte scintigraphy (LS) to monitor treatment responses in NOE. Consecutive patients with NOE who underwent 18F-FDG PET at the end of antibiotic therapy and planar as well as single photon emission computed tomography-labeled leukocyte scintigraphy after completing the initial antibiotic treatment were retrospectively included. Semiquantitative analyses were performed to determine the ratios of affected/nonaffected sides for PET and 4 hour and 24 hour LS acquisitions as well as the kinetic PET ratios (at diagnosis and post-treatment) and LS (4 and 24 hours). The final treatment responses were assessed by 2 experienced ENT physicians based on clinical, otoscopic, and biological data and subsequent 3-month follow-up. Seventeen patients (74.0 ± 10.6 years old, 5 women) were included. The best diagnostic performances were obtained with the PET maximum standardized uptake value (SUVmax)-lesion-to-background ratio and the tomographic LS lesion-to-background ratio at the 4-hour acquisition timepoint (thresholds of 4.1 and 1.19, yielding accuracies of 100% and 88%, respectively). In the multivariate analysis, the PET SUVmax-lesion-to-background ratio was the only predictive factor of recovery when associated with all clinical parameters (P < .001). 18F-FDG PET is the first-line imaging modality for evaluating NOE treatment responses, with excellent diagnostic performances. LS with only 4-hour acquisitions appeared to suffice to evaluate NOE treatment responses. Both biomarkers constitute early prognostic biomarkers for predicting antibiotic treatment response in patients with NOE. The institutional ethics committee (Comité d'Ethique du CHRU de Nancy) approved the evaluation of retrospective patient data, and the trial was registered at ClinicalTrials.gov (n°2023PI003-404).

Secondary aorto-duodenal fistula: a diagnostic challenge in a patient with fever and anemia.

A 69-year-old male, three years post-endovascular exclusion for an abdominal aortic aneurysm, presented with asthenia and fever. An abdominal CT scan showed no gastrointestinal tract communications, abscess, or contrast extravasation. Tc-99m-HMPAO-labeled leukocytes scintigraphy with SPECT/CT revealed increased uptake on the posterior surface of the aortic graft, along with air bubbles in its right iliac limb. Upper gastrointestinal endoscopy was performed, revealing a duodenal ulcer in the transition between the second and third portions. The ulcer exhibited yellow graft tissue at its center. The patient underwent in situ reconstruction, involving the replacement of the infected prosthetic graft, and the duodenal defect was addressed through segmental resection and duodenojejunal anastomosis. Secondary aorto-duodenal fistula (SADF), a rare complication of vascular surgery, may arise from factors such as local infection or graft-bowel contact. SADF, often located in the duodenum, poses a high mortality risk, necessitating early diagnosis. Clinical presentation varies from significant upper gastrointestinal bleeding to obscured bleeding.

Imaging of Vascular Graft/Endograft Infection with Radiolabeled White Blood Cell Scan and [18F]FDG PET/CT

Diagnosis of vascular graft/endograft infection (VGEI) is a challenge for clinicians due to the heterogeneity of clinical presentation and the complexity of its management. Microbiological culture is the gold standard, but it often fails to isolate the causative microorganism. A non-invasive imaging approach is therefore needed to assess VGEI. CTA is currently the first-choice imaging modality. Nuclear medicine techniques are recommended in case of negative or doubtful CTA results with persisting clinical suspicion. This review aims to summarize data from original studies published in the last decades regarding the role of both white blood cell (WBC) scans and fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT), their respective diagnostic performances, and their integration into the diagnostic approach for patients with a suspicion of VGEI.

Tc-99m HMPAO ile işaretli lökosit sintigrafisi verileri ile sistemik inflamatuar markerların (NLR, PLR, SII) karşılaştırılması

Aims: Technetium-99m-hexamethylpropylene amine oxime (99mTc-HMPAO) labeled leukocyte scintigraphy is frequently used for infection imaging. The systemic immune-inflammation index is a new marker. In this study, we aim to investigate the relationship between 99mTc-HMPAO-labeled leukocyte scintigraphy findings and systemic inflammatory markers such as Neutrophil/lymphocyte ratios (NLR) and Platelet lymphocyte ratio (PLR) and systemic immune-inflammation index (SII).&#x0D; Methods: Patients who underwent 99mTc-HMPAO-labeled leukocyte scintigraphy between 2014 and 2020 due to suspected infection such as diabetic foot infection or prosthesis infection vs. in any part of the body were included in our study. In addition, a negative control group consisting of 19 normal subjects who had no leukocyte scintigraphy and had hemogram examination was added to the study. Cases with findings consistent with infection in labeled leukocyte scintigraphy and infectious symptoms in this area of involvement in the clinical examination were considered as the positive group. The data were evaluated with the SPSS 23.0 program.&#x0D; Results: Our study included 36 patients (28 males,8 females, mean age: 59.7). The mean SII was 1526±787 x109 cells/L in patients with positive findings in leukocyte scintigraphy that might be compatible with infection, while it was 1025 ± 370 x109 cells/L in patients who did not (p=0.017). The mean PLR was 183.95±68.30 in patients with positive findings in leukocyte scintigraphy that might be compatible with infection, while it was 145.81±58.30 in patients who did not (p=0.102). The mean NLR was 4.82±1.91 in patients with positive findings on leukocyte scintigraphy that might be compatible with infection, while it was 4.15±1.40 in patients who did not (p=0.181). While the negative control group and the patients who were considered positive in leukocyte scintigraphy were compared; a statistically significant difference was found between SII, NLR and PLR values. When the relationship between SII was evaluated, the mean SII was 1526±787 x109 cells/L in patients with involvement that may be compatible with infection in leukocyte scintigraphy, while it was 762±224 x109 cells/L in the negative control group (p

Unusual Case of Pseudomembranous Colitis Presenting as Fever of Unknown Origin Diagnosed by Tc-99m-HMPAO-labeled Leukocytes SPECT/CT.

The fever of unknown origin (FUO) represents a complex diagnostic challenge due to the wide range of etiologies that could cause it, including neoplastic, infectious, rheumatic/inflammatory, and miscellaneous disorders. Several nuclear medicine techniques have proven to be valuable tools for guiding etiologic diagnosis in the setting of FUO. One of these is technetium-99m (Tc-99m)-hexamethylpropylene amine oxime (HMPAO)-labeled leukocyte scintigraphy, which is a diagnosis method that allows in most cases the localization and evaluation of the extension of an occult infection. This paper presents an uncommon case of pseudomembranous colitis without diarrhea as etiology of FUO diagnosed by Tc-99m-HMPAO-labeled leukocytes.

Chronic Suppressive Antibiotic Treatment for Staphylococcal Bone and Joint Implant-Related Infections.

Prosthetic joint infection (PJI) and fracture-related infection (FRI) are difficult-to-treat conditions in patients with severe comorbidity or significant surgical risk. In cases not eligible for standard strategy, debridement procedures with the retention of prosthesis or internal fixation device, combined with long-term antibiotic treatment and subsequent indefinite chronic oral antimicrobial suppression (COAS), can be the only reasonable choice. The aim of this study was to investigate the role of COAS and its follow-up in the management of these cases. We retrospectively analyzed a cohort of 16 patients with a follow-up of at least 6 months (mean age 75 yo, 9F, 7M, 11 PJI, 5 FRI). All microbiological isolates were tetracycline-susceptible staphylococci and for this reason a minocycline-based COAS was adopted after debridement and 3 months of antibiogram-guided antibiotic treatment. Patient monitoring was carried out on a clinical basis, with bimonthly execution of the inflammation indices and serial radiolabeled leukocyte scintigraphy (LS). The overall median time of COAS follow-up was 15 months (min 6-max 30). Moreover, 62.5% of patients were still taking COAS with no relapse after cure at the last evaluation available. Clinical failure with a relapse of the infection was observed in 37.5% of patients; interestingly, 50% of them had previously stopped COAS due to side effects of the antibiotic used. In the COAS follow-up, a combination of clinical, laboratory and LS evaluation seems to monitor the infection properly. COAS can be considered as an interesting approach in patients not suitable for standard treatments of PJI or FRI but it requires careful monitoring.

The Use of 99mTc-Mononuclear Leukocyte Scintigraphy for Necrotizing External Otitis Diagnosis.

Necrotizing external otitis (NEO) is a severe infectious disease in the external acoustic meatus (EAM) and mastoid that may extend to the cranial base. Due to the lack of a gold standard examination technique, the diagnosis is often difficult and delayed. This study aimed to evaluate the sensitivity and specificity of 99mTc-mononuclear leukocyte scintigraphy associated with 99mTc-phytate in suspected NEO compared to 99mTc-MDP and 67Ga-citrate. A prospective study (32 patients) was conducted between 2011 and 2016. At the end, twenty-four patients remained for the study conduction; nineteen had confirmed NEO diagnosis, one had sarcoma, one had EAM cholesteatoma, one had diffuse simple external otitis, and two had an inconclusive diagnosis. 99mTc-mononuclear leukocyte scintigraphy plus 99mTc-phytate was as sensitive as 99mTc-MDP bone scintigraphy (19/19X9/19), and more sensitive than 67Ga scintigraphy (19/19 x 17/19). Regarding specificity, it was superior to bone scintigraphy, 100% × 40% (5/5 × 2/5), and 67Ga scintigraphy, 100% × 20% (5/5 × 1/5). After the infection resolution, all NEO patients had their leukocyte scintigraphy negativized. To the best of our knowledge, this is the first study that evaluates this technique in patients with suspected NEO. 99mTc-mononuclear leukocyte was revealed to be the best option for NEO because of its specificity.

Leukocyte Labeling with Tc-99m-HMPAO: The Role of Leucocyte Numbers and Medication on the Labeling Efficacy and Image Quality.

The aim of this study is to evaluation of Tc-99m-hexamethylpropyleneamineoxime (HMPAO)-labeled leukocytes in terms of radiochemical, biochemical, and microbiological quality controls and to examine the effect of leukocyte numbers of the blood obtained from patients and the medications currently used by the patients on the radiochemical yields of Tc-99m-HMPAO-labeled leukocytes, and imaging quality was evaluated. Thirty paients were included in our study who applied to Istanbul University-Cerrahpasa, Cerrahpasa Faculty of Medicine, Department of Nuclear Medicine for Tc-99m-HMPAO-labeled leukocyte scintigraphy. Devices and chemicals used in the preparation of Tc-99m-HMPAO-labeled laukocytes were compared with other nuclear medicine clinics. Tc-99m-HMPAO-labeled leukocytes were evaluated in terms of radiochemical, biochemical, and microbiological quality controls. The effect of leukocyte numbers of the blood obtained from patients and the medications currently used by the patients on the radiochemical yields of Tc-99m-HMPAO-labeled leukocytes and imaging quality was evaluated. The pH range of Tc-99m-HMPAO was 6-8 and the radiochemical purity was 90±2.04% (n=30), the radiochemical yield of Tc-99m-HMPAO-labeled leukocytes was 51±2.18% (n=30), the radiolabeling yield of Tc-99m-HMPAO-labeled leukocyte increased as the amount of white blood cell in the blood increased and whether the patients used any antibiotic, blood thinners, insulin and blood pressure medications did not affect the radiolabeling yield of Tc-99m-HMPAO-labeled leukocytes. The number of erythrocytes were removed at a rate of >99% in LPR by starch solution (6% HES; in the hemocytometric examination of Tc-99m-HMPAO-labeled leukocytes performed zeroth and 4th h, living/dead cell ratio was found 97.5% and the product was sterile. Tc-99m-HMPAO was labeled with leukocytes successfully, and Tc-99m-HMPAO-labeled leukocytes was safely injected to the patients as sterile without loss of vitality and aggregation.

Application of Phage Therapy in a Case of a Chronic Hip-Prosthetic Joint Infection due to Pseudomonas aeruginosa: An Italian Real-Life Experience and In Vitro Analysis.

Prosthetic joint infection (PJI) caused by Pseudomonas aeruginosa represents a severe complication in orthopedic surgery. We report the case of a patient with chronic PJI from P. aeruginosa successfully treated with personalized phage therapy (PT) in combination with meropenem. A 62-year-old woman was affected by a chronic right hip prosthesis infection caused by P. aeruginosa since 2016 . The patient was treated with phage Pa53 (I day 10 mL q8h, then 5 mL q8h via joint drainage for 2 weeks) in association with meropenem (2gr q12h iv) after a surgical procedure. A 2-year clinical follow up was performed. An in vitro bactericidal assay of the phage alone and in combination with meropenem against a 24-hour-old biofilm of bacterial isolate was also carried out. No severe adverse events were observed during PT. Two years after suspension, there were no clinical signs of infection relapse, and a marked leukocyte scan showed no pathological uptake areas. In vitro studies showed that the minimum biofilm eradicating concentration of meropenem was 8 µg/mL. No biofilm eradication was observed at 24 hours incubation with phages alone (108 plaque-forming units [PFU]/mL). However, the addition of meropenem at suberadicating concentration (1 µg/mL) to phages at lower titer (103 PFU/mL) resulted in a synergistic eradication after 24 hours of incubation. Personalized PT, in combination with meropenem, was found to be safe and effective in eradicating P. aeruginosa infection. These data encourage the development of personalized clinical studies aimed at evaluating the efficacy of PT as an adjunct to antibiotic therapy for chronic persistent infections.

Management of periprosthetic knee joint infections: focus on the role of Nuclear Medicine (v2)

When faced with a painful knee replacement, ruling out infection is mandatory to set the correct therapeutic approach. However, it is not always easy, especially in subclinical/chronic infections. A multidisciplinary approach is necessary to assess in the most correct way each case of suspected periprosthetic knee joint infection. This review explores the role of nuclear medicine investigations in the management of periprosthetic knee infections and their proper use within a multidisciplinary pathway. A PubMed search was conducted selecting studies from the past 10 years. Triphasic bone scintigraphy has high sensitivity (93%) but poor specificity (56%) for periprosthetic joint infections of the knee, with a high negative predictive value (NPV), ranging from 96% to 100%. Consequently, a negative bone scan is useful in ruling out infection. In contrast, radiolabeled leukocyte scintigraphy is characterized by a sensitivity of 85.7-93%, specificity of 93.6-100%, diagnostic accuracy of 92.6-98%, NPV of 93-97.8%, and positive predictive value (PPV) of 66.7-100%. By adding a tomographic acquisition with hybrid single-photon emission computed tomography combined with computed tomography technique (SPECT/CT), the diagnostic accuracy increases. Because 18F-fluorodeoxyglucose (FDG) accumulates at both sites of inflammation and infection, FDG positron emission tomography (PET/CT) shows low specificity. A common decision-making process in the diagnosis of periprosthetic joint infection is not yet validated and multidisciplinary integration is mandatory. In this context, nuclear medicine can contribute decisively.

Necrotising Otitis Externa: An Overview Of Imaging Modalities.

Necrotising Otitis Externa (NOE) has often posed some challenges in view of diagnosis and management by clinicians. One such challenge is the appropriate and timely use of imaging techniques, since its use is critical not only in diagnosis but also determining the extent and resolution of the disease. Hence, doctors in both primary and secondary health care need to be familiar with presenting symptoms, while specialists need to be appraised of advances in imagining techniques in management of NOE. Whilst there is a general consensus amongst clinicians on some aspects of management of NOE, there is very limited consensus on the use of imaging modalities. There is no single modality of imaging that can provide a complete picture of diagnosis, disease progression and resolution. There are some advantages and limitation of each methodology, which indicate that a multi-modal imaging technique at particular stages of the disease may provide better management outcomes. However, further research in this area is required, as there is not yet an established 'gold standard' for imaging in NOE.

This Month's Highlights.

Our aim was to evaluate the role of SPECT/CT for the diagnosis of diabetic foot infection by labeled leukocytes. <b>Methods:</b> Seventeen patients with 19 clinically suspected sites of infection were included. After leukocyte labeling and administration, planar scans were acquired at 30 min, 4 h, and 24 h for 18 consecutive patients. SPECT/CT was obtained at 6 h. The final diagnosis was established by clinical follow-up (24 mo) in all cases and by bone biopsy for 14 sites. <b>Results:</b> Leukocyte scanning was positive in 16 of 19 lesions and negative in 3. SPECT/CT changed the interpretation of the planar and SPECT images for 10 of 19 suspected sites (52.6%): it excluded osteomyelitis in 6 cases, revealed bone infection in 1 case, and revealed both bone and soft-tissue infection in 3 cases. The hybrid device did not significantly contribute to the evaluation of patients with negative scan results. <b>Conclusion:</b> SPECT/CT can be useful for a more accurate diagnosis of diabetic foot infection by labeled leukocyte imaging.

To what extent does prior antimicrobial therapy affect the diagnostic performance of radiolabeled leukocyte scintigraphy in infective endocarditis?

AimsThis prospective, single-center study sought to assess to what extent there is interference between the hybrid technique of single-photon emission tomography-computed tomography with technetium99m-hexamethylpropyleneamine oxime–labeled leukocytes (99mTc-HMPAO-SPECT/CT) and antimicrobial therapy in patients with infective endocarditis (IE). Methods and resultsDuring the years 2015–2019, we enrolled 205 consecutive adults with suspected IE, all underwent 99mTc-HMPAO-SPECT/CT. The study population was divided into those who had received antimicrobial therapy up to 30 days prior to 99mTc-HMPAO-SPECT/CT (group 1, n = 96) and those who had not (group 2, n = 109). Patients were prospectively observed for 12 ± 10 months. Group 1 presented higher positive predictive values (91.89% vs. 60.00%, = 0.001), and decreased negative predictive values (77.97% vs. 90.54%, P = 0.04). Patients treated with antimicrobial therapy displayed false-negative 99mTc-HMPAO-SPECT/CT results more often [odds ratio (OR), 4.63; 95% confidence interval (CI), 1.41–15.23, P = .01], particularly when intravenous (OR 5.37; 95% CI 1.73–16.62, P = .004), definite (OR 9.43; 95% CI 2.65–33.51, P = .001), and combination antibiotic regimens (OR 8.1; 95% CI 2.57–25.64, P = .001) had been administered. ConclusionPrior antibiotic therapy affects 99mTc-HMPAO-SPECT/CT diagnostic properties. Patients treated with antimicrobial therapy display false-negative 99mTc-HMPAO-SPECT/CT results more often, especially if intravenous, definite, or combination regimens are administered. Graphical abstract▪

Lymphopenia in patients affected by SARS-CoV-2 infection is caused by margination of lymphocytes in large bowel: an [18F]FDG PET/CT study

BackgroundTo investigate the cause of lymphopenia in patients with newly diagnosed COVID-19, we measured [18F]FDG uptake in several tissues, including the ileum, right colon, and caecum at diagnosis and after recovery and correlated these measurements with haematological parameters.MethodsWe studied, by [18F]FDG PET/CT, 18 newly diagnosed patients with COVID-19. Regions of interest were drawn over major organs and in the terminal ileum, caecum, and right colon, where the bowel wall was evaluable. Five patients were re-examined after recovery, and three of them also performed a white blood cell scan with 99mTc-HMPAO-WBC on both occasions. Complete blood count was performed on both occasions, and peripheral blood lymphocyte subsets were measured at diagnosis. Data were analysed by a statistician.ResultsPatients had moderate severity COVID-19 syndrome. Basal [18F]FDG PET/CT showed focal lung uptake corresponding to hyperdense areas at CT. We also found high spleen, ileal, caecal, and colonic activity as compared to 18 control subjects. At recovery, hypermetabolic tissues tended to normalize, but activity in the caecum remained higher than in controls. Regression analyses showed an inverse correlation between CD4 + lymphocytes and [18F]FDG uptake in the caecum and colon and a direct correlation between CD8 + lymphocytes and [18F]FDG uptake in lungs and bone marrow. WBC scans showed the presence of leukocytes in the caecum and colon that disappeared at recovery.ConclusionsThese findings indicate that lymphopenia in COVID-19 patients is associated with large bowel inflammation supporting the hypothesis that CD4 + lymphocytes migrate to peripheral lymphoid tissues in the bowel.

Classification and management options for prosthetic joint infection.

Periprosthetic joint infection (PJI) is one of the major complications following arthroplasty implantation. Management of PJIs is a challenge for surgeons and various classification systems have been introduced, which consider variables such as onset of symptoms, pathogenesis and clinical manifestation. In an attempt to overcome the shortcomings which may limit their usefulness in borderline cases, a new classification system focusing on the topography of the infectious process has been proposed. This theory relies on the identification of the exact location of the bacterial colonization thus allowing to decide between a conservative or a more radical intervention irrespectively of the timing. The use of nuclear medicine device like radiolabelled white blood cells (WBC) scan could lead the path in identifying pathogenetic processes and their exact location thus guiding orthopaedic surgeons to the most appropriate diagnosis and treatment options. Currently management relies on debridement, antibiotics and implant retention (DAIR), which is traditionally performed at early stages, 1- or 2-stage revision arthroplasty which is commonly limited to chronic cases. Reports have demonstrated similar rates of infection recurrence following one and two-stage revisions, and the use of one-stage revision surgery is gaining popularity. More recently, satisfying results following partial implant retention during revision total arthroplasty for septic failures have been reported. In addition, in severe cases, definitive articulating antibiotic spacer, excision arthroplasty, arthrodesis or amputation can be performed.