Leukocyte Scintigraphy Research Articles

Multimodality Imaging in the Diagnosis of Prosthetic Valve Endocarditis: A Brief Review.

Infective endocarditis is a common and treatable condition that carries a high mortality rate. Currently the workup of infective endocarditis relies on the integration of clinical, microbiological and echocardiographic data through the use of the modified Duke criteria (MDC). However, in cases of prosthetic valve endocarditis (PVE) echocardiography can be normal or non-diagnostic in a high proportion of cases leading to decreased sensitivity for the MDC. Evolving multimodality imaging techniques including leukocyte scintigraphy (white blood cell imaging), 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), multidetector computed tomographic angiography (MDCTA), and cardiac magnetic resonance imaging (CMRI) may each augment the standard workup of PVE and increase diagnostic accuracy. While further studies are necessary to clarify the ideal role for each of these imaging techniques, nevertheless, these modalities hold promise in determining the diagnosis, prognosis, and care of PVE. We start by presenting a clinical vignette, then evidence supporting various modality strategies, balanced by limitations, and review of formal guidelines, when available. The article ends with the authors' summary of future directions and case conclusion.

White Blood Cell Scintigraphy for Fracture-Related Infection: Is Semiquantitative Analysis of Equivocal Scans Accurate?

Purpose: White blood cell (WBC) scintigraphy is considered the gold-standard nuclear imaging technique for diagnosing fracture-related infection (FRI). Correct interpretation of WBC scans in FRI is important since a false positive or false negative diagnosis has major consequences for the patient in terms of clinical decision-making. The European Association of Nuclear Medicine (EANM) guideline for correct analysis and interpretation of WBC scans recommends semiquantitative analysis of visually equivocal scans. Therefore, this study aims to assess the diagnostic accuracy of semiquantitative analysis of visually equivocal WBC scans for diagnosing FRI. Methods: A retrospective single-center study was performed in consecutive patients who received WBC scintigraphy in the diagnostic work-up for FRI between February 2012 and January 2017. All the visually equivocal scans were analysed using semiquantitative analysis by comparing leukocyte uptake in the manually selected suspected infection focus with the contralateral bone marrow (L/R ratio). Cut-off points for a ‘positive’ scan result of >0%, >10% and >20% leukocyte increase between the early and late scans were used in separate analyses. The discriminative ability was quantified by calculating the sensitivity, specificity and diagnostic accuracy. Results: In total, 153 WBC scans were eligible for inclusion. After visual assessment of all the scans, 28 visually equivocal scans were included. Dichotomization of the ratios using the cut-off of >0% resulted in a sensitivity of 30%, a specificity of 45% and a diagnostic accuracy of 40%. The >10% cut-off point resulted in a sensitivity of 18%, a specificity of 82% and a diagnostic accuracy of 66%. The >20% cut-off point resulted in a sensitivity of 0%, a specificity of 89% and a diagnostic accuracy of 67%. Conclusion: Semiquantitative analysis of visually equivocal WBC scans is insufficient for correctly diagnosing FRI.

Utility of 99mTc-HMPAO labeled leukocytes scintigraphy in prostatitis

Utility of 99mTc-HMPAO labeled leukocytes scintigraphy in prostatitis

Imaging of Cardiac Device-Related Infection

Cardiac devices are frequently used in different cardiovascular conditions for the purpose of morbidity or mortality prevention. These include cardiac implantable electronic devices (CIED) like permanent pacemakers and implantable cardiac defibrillators, ventricular assistance devices (VADs), left atrial appendage occlusion (LAAO) devices like the Watchman™, atrial and ventricular septal occluders like the Amplatzer™, among others. In the past years, there has been an increase in the development of these devices as a result of a rise in the number of indications for implantation, paired with the aging and more medically complex patient population. This has led to an increase in the incidence of cardiac device-related infections, one of the most feared and serious complications which is associated with significant morbidity, mortality and financial burden. Accurate diagnosis of cardiac device-related infections is essential given the management implications which often involve removal of the infected device, removal of other prosthetic material and long-term antimicrobial therapy. Clinical and laboratory data are useful diagnostic tools but multimodality imaging is often necessary. The recently published 2020 European Heart Rhythm Association International Consensus document, which is endorsed by many expert societies, has recommended the use of multimodality imaging for the diagnosis of CIED infections. (1) This allows better disease characterization by identifying abnormal fluid collections and guiding aspiration for both diagnostic and therapeutic purposes (i.e. soft tissue ultrasound and computed tomography), evaluation for local extent of disease (i.e. transesophageal echocardiogram to evaluate for concomitant infective endocarditis), embolic manifestation of disease (i.e. computed tomography and magnetic resonance imaging) and metabolic tissue characterization (positron emission tomography and tagged white blood cell scan). (2) In addition, computed tomography (CT) allows for pre-procedural planning which has shown to be associated with better procedural outcomes.

COVID-19: How Nuclear Medicine Can Provide A Differential Diagnosis In A Very Dubious Case

Background: We present the case of a 55-year-old woman, admitted to the Infectious Disease Department of Policlinico Umberto I, Rome, in mid-March 2020, with suspicion of COVID-19 infection. Objective: The rRT-PCR was negative, and the following CT scan, performed to exclude false-negative results and help diagnosis, was inconclusive. Methods: It was decided to submit the patient to a 99mTc-HMPAO-labelled leukocyte scan. Results: This exam led to the diagnosis of infective endocarditis. Conclusion: In the present pandemic scenario, 99mTc-HMPAO-labelled leukocyte scan represents a reliable imaging technique for differential diagnosis with COVID-19 in patients with confusing clinical signs, possible false-negative rRT-PCR results, and inconclusive CT scan.

Abstract No. 137 Molecular imaging of infection: [11C]-trimethoprim imaging of biopsy-proven discitis-osteomyelitis

White blood cell scans and [18F]-FDG PET/CT studies provide functional imaging data on leukocyte localization and glucose transport within tissue but are lacking in specificity for infection. Thus, interventional radiologists are frequently consulted for biopsy or aspiration to obtain microbial cultures that provide a definitive diagnosis of infection and guide treatment selection. Carbon-11 trimethoprim ([11C]-TMP) is mechanistically more specific for bacterial infection and can be imaged by PET/CT. A protocol to investigate the human biodistribution of [11C]-TMP was approved by the University of Pennsylvania Institutional Review Board and Radioactive Drug Research Committee (NCT03424525). A patient with clinically suspected discitis-osteomyelitis, who was scheduled for upcoming L4-L5 facet biopsy, was enrolled. [11C]-TMP was injected in this patient and PET/CT images were obtained, both prior to biopsy and after 7 weeks of antibiotic therapy. Left L4-L5 facet aspiration was performed with an 18G 3.5cm spinal needle. Osseous biopsy was obtained with a 11G introducer and 13G bone biopsy system. The [11C]-TMP PET/CT images obtained at the start of therapy demonstrate asymmetric increased tracer uptake in the left L4-L5 facet and above background tracer uptake in the adjacent paraspinal musculature. After 7 weeks of IV cefazolin therapy, this signal is no longer appreciable on both dynamic and 30- to 60-minute summed images. Osseous and soft-tissue regions of geographic tracer uptake correspond with areas of T1 prolongation, T2 prolongation, and contrast enhancement by MRI, compatible with discitis-osteomyelitis with surrounding inflammation. Interventional radiology aspiration yielded a culture of methicillin sensitive Staphylococcus aureus. Bone biopsy confirmed reactive osseous findings compatible with osteomyelitis. Here we present a case of an investigational PET radiotracer [11C]-TMP, which suggests the ability to functionally and specifically image a bacterial infection in a human patient. Further investigations are ongoing, which will evaluate the potential of this technology to inform the interventional management of infection.

Dual-tracer approach vs. dual time-point approach in leukocyte scintigraphy in treatment evaluation of persistent chronic prosthetic joint infection.

BackgroundBoth dual time-point 99mTc-hexamethylpropylene amine oxime (HMPAO)-leukocyte scintigraphy and dual-tracer 99mTc-HMPAO-leukocyte scintigraphy (with the addition of 99mTc-nanocolloid bone marrow scintigraphy) have been used to diagnose prosthetic joint infection (PJI). A treatment evaluation of persistent PJI using these imaging protocols has yet to be presented.ObjectiveThe purpose of this study was to compare the accuracy of dual time-point 99mTc-HMPAO-leukocyte scintigraphy to the dual-tracer alternative of single time-point 99mTc-HMPAO-leukocyte scintigraphy or single-photon emission computed tomography/computed tomography (SPECT/CT) combined with a 99mTc-nanocolloid bone marrow scintigraphy or SPECT/CT, for treatment evaluation of PJI.Material and methodsThirty-one PJI patients under antibiotic treatment were included in this retrospective study. Examinations were organized into three settings. Setting one used dual time-point approach with delayed (2 h) and late (24 h) planar 99mTc-HMPAO-leukocyte scintigraphy, including both visual and semiquantitative analysis. Setting two used delayed (2 h) planar 99mTc-HMPAO-leukocyte scintigraphy combined with 99mTc-nanocolloid bone marrow scintigraphy and for setting three SPECT/CT replaced planar imaging.ResultsAccuracy was 0.68 for visual evaluation and 0.55 for semiquantitative evaluation of setting one; 0.71 for setting two; and 0.68 for setting three. Sensitivity was 0.54 for visual evaluation and 0.31 for semiquantitative evaluation of setting one; 0.38 for setting two; and 0.46 for setting three. Specificity was 0.78 for visual evaluation and 0.72 for semiquantitative evaluation of setting one; 0.94 for setting two; and 0.83 for setting three.ConclusionNo significant difference in accuracy, sensitivity, or specificity between the approaches for treatment evaluation of suspected persistent PJI in the hip or knee was observed.

Unexpected Detection of Abscessualized Lung Carcinoma on Tc-99m-HMPAO-labeled Leukocytes Scintigraphy Misdiagnosed on Chest Computed Tomography.

Technetium-99m (Tc-99m)-hexamethylpropylene amine oxime (HMPAO)-labeled leukocytes scintigraphy is well established for investigating and diagnosing infections in bone and soft tissue, as well as for the detection of occult infection. A 71-year-old female who was recently diagnosed with bronchopulmonary neuroendocrine tumor of the right lung was referred for an intermittent fever of unknown origin associated with chill at night for the last month. Chest computed tomography (CT) scan showed a thrombotic widespread of the superior vena cava and a solid pathological tissue in the superior segment of the inferior lobe of the right lung with consensual atelectasis. Being a carrier of port-a-cath, an infection of this device was suspected. Therefore, Tc-99m-HMPAO-labeled leukocytes single-photon emission computed tomography (SPECT) was performed, and matching pairs of CT scan and Tc-99m-HMPAO-labeled white blood cell SPECT images were fused. Through this means, it was found that the area of the radiotracer increased uptake corresponded with the soft tissue density mass detected by CT scan localized at the inferior lobe of the right lung. The hybrid SPECT/CT fused imaging was crucial for diagnosis of the presence of a lung abscess localized in correspondence with the known lung cancer region.

Diagnostic methodology in labelled leukocyte scan for prosthetic / non-prosthetic osteoarticular infection: Visual or semi-quantitative analysis? One- or two-day protocol?

Objectiveas scarce literature on the topic is available, we aimed to compare diagnostic utility of semi-quantitative versus visual analysis in labelled white blood cell scintigraphy (WBCS) for osteoarticular infection. One-day and two-day protocols were assessed, particularly in orthopaedic devices. Material and methodsprospective study of 79 consecutive patients with suspected osteoarticular infection. In all patients, WBCS were performed at 30min, 4h, 8h and 24h. Images were analysed by grouping in two protocols: one-day-protocol (experts evaluated 30min, 4h and 8h planar images) and two-day-protocol (experts evaluated 30min, 4h and 24h planar images). Planar images were interpreted qualitative and semiquantitatively and also were compared grouping patients with and without orthopaedic devices. To find which cut-off value of the percentage variation could predict of osteoarticular infection, multiple cut-off values were calculated in both protocols from the Youden index. Three blinded readers analysed the images. ResultsComparing final diagnosis visual analysis of the one-day-protocol provided better results with sensitivity of 95.5%, specificity of 93% and diagnostic accuracy of 93.7% (p<001) than the two-day-protocol with values of 86.4%, 94.7% and 92.4%, respectively (p<001). For semi-quantitative analysis, the one-day-protocol also obtained better results with sensitivity of 72.7%, specificity of 78.9% and accuracy of 77.2% (p<001) than two-day-protocol (no significant results; p=0.14), especially in the group of patients with orthopaedic devices (sensitivity of 100%, specificity of 79.5% and accuracy of 82.7%; p<001). Conclusionsmost accurate approach in the diagnosis of osteoarticular infection corresponded to visual analysis in one-day-protocol that showed greater sensitivity and specificity than semi-quantitative analysis. Semi-quantitative analysis only could be useful when visual analysis is doubtful. In patients with joint prostheses, an increase in percentage variation above 9% obtained maximum sensitivity and negative predictive value.

Nuclear Medicine Scans in Total Joint Replacement.

A 3-phase bone scan is a potential first-line nuclear medicine study for pain after total joint arthroplasty (TJA) when there is concern for periprosthetic joint infection or aseptic loosening. In patients who have a positive bone scintigraphy result and suspected infection of the joint, but where aspiration or other studies are inconclusive, labeled leukocyte scintigraphy with bone marrow imaging may be of benefit. Magnetic resonance imaging (MRI), while not a nuclear medicine study, also shows promise and has the advantage of providing information about the soft tissues around a total joint replacement. Radiotracer uptake patterns in scintigraphy are affected by the prosthesis (total knee arthroplasty [TKA] versus total hip arthroplasty [THA]) and the use of cement. Nuclear medicine scans may be ordered 1 year postoperatively but may have positive findings that are due to normal physiologic bone remodeling. Nuclear studies may be falsely positive for up to 2 years after TJA. Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) (SPECT/CT), fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT, and MRI show promise; however, more studies are needed to better define their role in the diagnostic workup of pain after TJA.

Initial results of the use of a novel semiquantitative parameter in three-phase bone scan to predict 99mTc-HMPAO-labeled leukocyte scintigraphy in patients with unilateral total knee replacement.

The aim of the study was to predict the results of 99mTc-hexamethylpropyleneamine oxime (HMPAO)-labeled autologous leukocytes scintigraphy assessing count ratios in the perfusion (Pr) and blood-pool (BPr) phase images in three-phase bone scan (3PBSr) between the prosthetic knee and the 'healthy' knee and a novel semiquantitative parameter (P/BP ratio) in patients with unilateral knee arthroplasty. Patients with unilateral knee arthroplasty and available 3PBS and 99mTc-HMPAO-labeled autologous leukocytes scintigraphic images were searched in two hospitals (A and B). In center A, the perfusion phase was not available. Regions of interest (ROI) were delineated in the perfusion (P) and blood-pool (BP) phase images, incorporating the prosthetic region and applying an isocontour (40% of the maximum pixel activity); corresponding mirror ROIs were placed on the healthy knee. The P/BP ratio was calculated as {[(Pr/BPr) × 100] - 100}. Receiver operator curves (ROCs) were generated for each semiquantitative parameter to identify the optimal cutoff for predicting the results of the autologous leukocytes scintigraphy. In the whole group (79 patients), BPr demonstrated an area under the curve (AUC) of 0.722 (optimal cutoff = 1.43). In center A (52 patients), BPr demonstrated an AUC of 0.737 (cutoff = 1.43), whereas, in center B (27 patients), AUC for BPr was 0.718 (cutoff = 1.6). A better diagnostic performance was obtained selecting Pr (AUC = 0.918; cutoff = 2.34) and P/BP ratio (AUC = 0.947; cutoff = 26.5%) for the discrimination between septic and aseptic loosening. The novel P/BP ratio seems to be a promising semiquantitative parameter to predict septic loosening. These findings warrant confirmation in larger patient samples.

Should scintigraphy be completely excluded from the diagnosis of periprosthetic joint infection?

To analyse the diagnostic performance of bone and leukocyte scintigraphy for periprosthetic joint infection before excluding the test from routine practice, and to analyse the possible benefit of bone marrow scintigraphy in inconclusive cases. From 2012 to 2018, all patients with a total hip or knee arthroplasty who had a bone and leukocyte scintigraphy performed and underwent revision surgery were included. Bone marrow scintigraphy was indicated only in cases in which bone and leukocyte scintigraphy were inconclusive. Diagnosis of periprosthetic joint infection was confirmed by positive intraoperative cultures after revision surgery. A total of 105 patients were included. Eighteen patients had total hip arthroplasties (18.1%) and 86 had total knee arthroplasties (81.9%). Mean age was 74 years. Nineteen cases were diagnosed with a periprosthetic joint infection. Bone and leukocyte scintigraphy had 64% sensitivity and 97% specificity. Bone marrow scintigraphy increased sensitivity and specificity to 88% and 100%, respectively. Bone and leukocyte scintigraphy possesses high sensitivity and specificity for the diagnosis of chronic periprosthetic joint infection. The additional use of bone marrow scintigraphy significantly increases diagnostic performance. For these reasons, bone scintigraphy is reserved for inconclusive cases of chronic periprosthetic joint infection.

Single Photon Emission Tomography in the Diagnostic Assessment of Cardiac and Vascular Infectious Diseases.

Cardiac and vascular infection is an arising cause of mortality and morbidity in the adult population. Diagnosis based on culture and anatomic imaging are frequently inconclusive. Radiolabeled leucocyte scintigraphy plays a useful role in the diagnosis and management of these serious infectious conditions. In this paper, we present an update on the diagnostic performance of single- photon emission tomographic (SPECT) techniques using different radionuclides in the management of patients with cardiac and vascular infections. We performed a thorough search of recent literature on the topic. We present a discussion on the clinical utility of different SPECT tracers in cardiac and vascular infections, including infective endocarditis, cardiac implantable electronic device (CIED) infections, left ventricular assist device infection, and vascular graft infection. Radionuclide technique using SPECT tracers is a useful imaging modality in the diagnosis of cardiac infection. Among the different SPECT tracers for infection imaging, radiolabeled leucocyte scintigraphy is currently the most useful tool in the diagnosis and management of patients with suspected cardiac and vascular infection. Radiolabeled leucocyte scintigraphy has a high specificity, a result of the ability of the leucocytes to accumulate as sites of pyogenic infection but not at sites of sterile inflammation such as seen in the early post-operative period or in response to the presence of a prosthetic cardiac or vascular material. Limited experience with radiotracers for in vivo labelling of leucocytes such as 99mTc-sulesomab and 99mTc-besilesomab show acceptable diagnostic performance without the need for the tedious process of ex-vivo labeling. 67Ga scintigraphy used to be popular for cardiac and vascular infection imaging. Its use has run out of favor following the availability of more effective molecular imaging methods. SPECT techniques with radiolabeled leucocyte scintigraphy has a high diagnostic performance in the evaluation of patients with suspected cardiac or vascular infection. It is able to confirm or reject the presence of infection when results of anatomic imaging or culture remain inconclusive. Its diagnostic performance is not compromised by sterile inflammation occurring in the early post-operative period or in response to implanted prosthetic materials.

Comparative diagnostic accuracy of respective nuclear imaging for suspected fracture-related infection: a systematic review and Bayesian network meta-analysis.

The aim of this study was to compare the accuracy of available nuclear imaging modalities in the diagnosis of suspected fracture-related infection (FRI). We conducted a comprehensive literature search of PubMed, EMBASE and the Cochrane Library to retrieve diagnostic accuracy studies in which FRI was investigated using different nuclear imaging modalities. The pooled sensitivity, specificity, likelihood ratios and diagnostic odds ratios were constructed using the bivariate meta-analysis framework, while the superior index was pooled using Bayesian network meta-analysis. 22 eligible studies (1,565 patients) were included in the quantitative analysis. A broad overlapping confidence interval (CI) of pooled sensitivity was observed among bone scintigraphy (0.94; 95% CI 0.85-0.98), 18F-FDG PET and PET/CT (0.91; 95% CI 0.85-0.94) and leukocyte scintigraphy (0.86; 95% CI 0.53-0.97). Bone scintigraphy (0.34; 95% CI 0.08-0.75) seemed to be less specific than all the other modalities, while leukocyte scintigraphy (0.96, 95% CI 0.92-0.98) was notably more specific than 18F-FDG PET and PET/CT (0.78; 95% CI 0.69-0.85). Based on the superiority index, 18F-FDG PET/CT (3.78; 95% CI 0.14-11.00), 18F-FDG PET (2.98; 95% CI 0.14-9.00) and leukocyte scintigraphy (1.51; 95% CI 0.11-7.00) all achieved high accuracy in detecting FRI. Bone scintigraphy is a highly sensitive nuclear imaging technique but lacks the specificity needed to unequivocally differentiate among various conditions suspected to be FRI. Leukocyte scintigraphy, 18F-FDG PET/CT and PET all present good satisfactory accuracy for the diagnosis of FRI, but their costs should be further reduced to promote their wide application.

Analysis of Cell Fraction of 99mTc-HMPAO Radiolabeled Leukocytes.

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. 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. 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). 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.

MRI and Technetium-99m Hexamethylpropylene Amine Oxime Labeled Leucocyte Scintigraphy in the Diagnosis and Differentiation between Acute Osteomyelitis and Neuroarthropathy in the Diabetic Foot

Abstract Background: Soft tissue and bone infection and neuro osteoarthropathy involving the foot are the most common long-term complications of diabetes mellitus, implying a serious impairment in quality of life for patients in the advanced stages of the disease. Both pathologies often coexist and differentiating between them is crucial because the management may differ substantially. Misdiagnosis may result in high morbidity for the patient such as unnecessary limb amputation. Diagnosis is largely based on clinical signs supplemented by various imaging modalities such as radiography, MR imaging, and hybrid imaging techniques such as F-18 fluorodeoxyglu-cose-positron emission tomography and nuclear imaging studies. Aim of Study: The aim of this study is to evaluate the diagnostic value of MRI and technetium-99m Hexamethyl-propylene Amine Oxime (HMPAO) labeled leukocyte scin-tigraphy in the diagnosis and differentiation between acute osteomyelitis and neuroarthropathy in the diabetic foot. Patients and Methods: The study included 35 patients (20 men and 15 women) aged 62±8.8 years having diabetes mellitus and a total of 43 clinically suspicious infection sites. The basic exploration included standard radiography, three-phase bone scintigraphy and 99mTc-HMPAO Leucocyte Scan (HMPAO-LS) and pre and post contrast enhanced MRI. 16 bone and 10 soft tissue biopsies were obtained from ulceration sites. Clinical follow-up as well as scintigraphy and MRI performed 4 months after initial diagnosis and 1 month after antibiotic withdrawal were performed in suspected osteomy-elitis cases. Results: Among the 43 sites, 23 sites were finally diag-nosed as osteomyelitis. No osteomyelitis was present at 20 sites, of which 9 sites were diagnosed as cellulitis and 11 as neuropathic ulcers based on combined clinical, imaging, pathologic findings and follow-up. The sensitivity and specif-icity of MRI were (95% and 85%) and of Labeled leucocyte scanning were (87% and 90%) respectively.Conclusion: The combined use of 99mTc-HMPAO-LS and MRI yielded higher diagnostic efficacy in diabetic foot related complications.

Diagnostic yield of 18F-FDG PET/CT in suspected diagnosis of vascular graft infection: A prospective cohort study

BackgroundProsthetic vascular graft infection (PVGI) is a severe complication associated with high morbidity and mortality. Clinical diagnosis is complex, requiring image testing such as CT angiography or leukocyte scintigraphy, which has considerable limitations. The aim of this study was to know the diagnostic yield of PET/CT with 18F-Fluorodeoxyglucose (18F-FDG) in patients with suspected PVGI. MethodsWe performed a prospective cohort study including 49 patients with suspected PVGI, median age of 62 ± 14 years. Three uptake patterns were defined following published recommendations: (i) focal, (ii) patched (PVGI criteria), and (iii) diffuse (no PVGI criterion). ResultsSensitivity, specificity, and positive and negative predictive values for 18F-FDG-PET/CT were 88%, 79%, 67%, and 93%, respectively. 18F-FDG-PET/CT identified 14/16 cases of PVGI showing a focal (n = 10) or patched pattern (n = 4), being true negative in 26/33 cases with either a diffuse pattern (n = 16) or without uptake (n = 10). Five of the seven false-positive cases (71%) showed a patched pattern and all coincided with the application of adhesives for PVG placement. Conclusions18F-FDG-PET/CT is a useful technique for the diagnosis of PVGI. A patched pattern on PET/CT in patients in whom adhesives were applied for prosthetic vascular graft placement does not indicate infection.

Molecular Imaging of Pulmonary Inflammation and Infection.

Infectious and inflammatory pulmonary diseases are a leading cause of morbidity and mortality worldwide. Although infrequently used in this setting, molecular imaging may significantly contribute to their diagnosis using techniques like single photon emission tomography (SPET), positron emission tomography (PET) with computed tomography (CT) or magnetic resonance imaging (MRI) with the support of specific or unspecific radiopharmaceutical agents. 18F-Fluorodeoxyglucose (18F-FDG), mostly applied in oncological imaging, can also detect cells actively involved in infectious and inflammatory conditions, even if with a low specificity. SPET with nonspecific (e.g., 67Gallium-citrate (67Ga citrate)) and specific tracers (e.g., white blood cells radiolabeled with 111Indium-oxine (111In) or 99mTechnetium (99mTc)) showed interesting results for many inflammatory lung diseases. However, 67Ga citrate is unfavorable by a radioprotection point of view while radiolabeled white blood cells scan implies complex laboratory settings and labeling procedures. Radiolabeled antibiotics (e.g., ciprofloxacin) have been recently tested, although they seem to be quite unspecific and cause antibiotic resistance. New radiolabeled agents like antimicrobic peptides, binding to bacterial cell membranes, seem very promising. Thus, the aim of this narrative review is to provide a comprehensive overview about techniques, including PET/MRI, and tracers that can guide the clinicians in the appropriate diagnostic pathway of infectious and inflammatory pulmonary diseases.

Can inflammatory markers and clinical indices serve as useful referral criteria for leukocyte scan with inflammatory bowel disease?

In the follow-up of patients with inflammatory bowel disease (IBD), Tc-99m-HMPAO labelled leukocytes scintigraphy (leukocyte scan; LS) has long been established as a valuable diagnostic tool. The aim of this study was to estimate the relationship between scintigraphic results, inflammatory markers (IM) (including white blood cells (WBCs) and C-reactive protein (CRP)), clinical parameters and clinical indices of the disease activity (CI), in order to determine clinical settings in which LS is indicated. A total of 147 patients who underwent LS, (79 males, 68 females, median age 36), were examined from April 2010 until December 2017 at the University Hospital Centre Zagreb, Croatia. Among these, 126 (86%) had Crohn's disease (CD) and 21 (14%) had ulcerative colitis (UC). Either increased IM (either WBCs ≥10x109/L and/or CRP ≥7.4 mg/L) and/or CI, Crohn's disease activity index (CDAI) score ≥220 points, Harvey-Bradshaw index (HBI) score ≥8 points, and severe colitis defined according to Truelove and Witts' criteria (TWC) for UC, respectively, were considered consistent with active disease. Eighty-two patients (56%) had negative scans, while in 65 (44%) the scans were positive. Positive correlations were found between LS and all of the 3 parameters, WBCs, CRP and CI. When combined, the 3 parameters demonstrated even stronger positive correlation with the LS results with the correlation coefficient 0.76 (p<0.0001, 95% CI [0.68-0.82]). Using endoscopy and histological study findings of the obtained specimens as a composite reference standard, the overall sensitivity, specificity, positive predictive value and negative predictive value of IM and CI for LS were determined, being 91%, 85%, 83%, and 92%, respectively. IM and CI were both negative in 76 (52%) out of the total subjects. Of these, 70 had negative LS as well. In the presence of normal IM with CI pointing to no active or mildly active disease, LS is not necessarily indicated.

P1294 Distribution of infective lesions detected with radiolabeled leucocyte scintigraphy in carriers of various types of cardiac implantable electronic devices

Abstract Funding Acknowledgements Grant from the Jagiellonian University Medical College (K/DSC/004383) Background The rate of cardiac device-related infective endocarditis (CDRIE) is increasing disproportionately to the rising rate of device implantations. Hybrid technique of single photon emission tomography and computed tomography with technetium99m-hexamethylpropyleneamine oxime–labeled autologous leukocytes (99mTc-HMPAO-SPECT/CT) is a developing technique in patients with suspected endocarditis. Purpose The aim of this study was to evaluate distribution of both intracardiac and extracardiac inflammatory lesions detected with 99mTc-HMPAO-SPECT/CT in patients with suspected CDRIE depending on the type of carried cardiac implantable electronic device (CIED). Methods During years 2015-2018, we prospectively enrolled 103 consecutive patients with suspected CDRIE (70 males, 61 ± 18 y.o.). Patients undergone evaluation according to current ESC guidelines and subsequently 99mTc-HMPAO-SPECT/CT. Scans were classified as positive in the presence of abnormal tracer uptake involving cardiac or/and intravascular sections of device electrodes. Patients were divided to group 1 with implanted pacemakers (61 patients) and group 2 including 42 carriers of either an implantable cardioverter-defibrillator (ICD) or a cardiac resynchronization therapy device (CRT). Results Overall, in group 2 there was a higher prevalence of diabetes mellitus, coronary artery disease and heart failure (p &amp;lt; 0.05). Moreover, group 2 had worse functional status with higher NYHA class (2.8 ± 0.9 vs. 1.7 ± 1, p = 0.001), NT-proBNP levels (5027 ± 5813 vs. 2320 ± 4279, p = 0.0004) and lower left ventricle ejection fraction (29 ± 12 vs. 54 ± 13, p = 0.0001). Both groups had comparable values of C-reactive protein, procalcitonin and white blood cells (p &amp;gt; 0.05). The mean time since device implantation was 3.4 ± 3.8 years and on average patients had 1.9 implanted electrodes. Patients from group 2 presented more often with 99mTc-HMPAO-SPECT/CT positive for CDRIE (45% vs. 26%, p = 0.045). Frequency of lesions consistent with infection localized within the intravascular section of the electrode and the CIED lodge did not differ between groups (p &amp;gt; 0.05). However, inflammatory foci in the vicinity of the intracardiac portion of the electrode were detected more often in group 2 (43% vs. 21%, p = 0.019). Overall, extracardiac inflammatory foci were found in 34% of patients, with most common localization in the gastrointestinal tract (13%) and musculoskeletal system (8%). Both prevalence and localization of extracardiac foci did not differ between groups (39% vs. 24%, p = 0.16). Conclusions Prevalence and localization of intracardiac inflammatory foci typical for CDRIE detected with 99mTc-HMPAO-SPECT/CT is different in patients with various types of CIEDs. Patients with implanted ICD or CRT have worse functional status and present more frequently with radiotracer uptake typical for CDRIE in 99mTc-HMPAO-SPECT/CT. Distribution of extracardiac inflammatory lesions does not differ between groups.