Introduction
Autologous WBC and anti-G-mAbs
Osteomyelitis and spondylodiscitis
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Peripheral bone osteomyelitis (OM)
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Suspected OM
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Evaluation of extent of OM
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Evaluation of treatment response
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Spondylodiscitis
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Para-vertebral soft tissue infection in spondylodiscitis
Joint prosthesis and other orthopedic hardware
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Suspected septic loosening
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Evaluation of extent of infection
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Evaluation of treatment response
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Suspected infective post-traumatic pseudo-arthrosis
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Exclusion of infection in patients with antibiotic spacer before prosthesis re-implant
Inflammatory bowel diseases
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Evaluation of activity of disease
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Evaluation of extent of disease
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Differential diagnosis between inflammatory and fibrotic strictures
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Early assessment of disease relapse after surgery
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Evaluation of treatment response
Fever of unknown origin
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Evaluation of unknown site of infection in patients with high pre-test probability of infection
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Evaluation of extent of disease
Soft-tissue infections
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Infective endocarditis (IE)
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Suspected IE with doubtful ultrasound
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Evaluation of septic embolism in certain IE
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Evaluation of treatment response
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Differential diagnosis with marantic vegetations
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Vascular graft infections
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Diagnosis of infection
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Evaluation of extent of disease
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Evaluation of disease activity
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Evaluation of treatment response
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Diagnosis of bacterial pneumonia
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Differential diagnosis of infective and neoplastic lesions
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Evaluation of treatment response
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Cerebral hypodensity CT lesions with hypervascularized peripheral ring
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Differential diagnosis of cerebral lesions in HIV patients
Other applications of radiolabelled WBC and mAbs
Image acquisition protocols
Acquisition protocols for 99mTc-labeled WBC and anti-G-mAb scintigraphy
A | ||||||
Hoursa | Acquisition time (seconds) for 99mTc decay corrected images | exp(-λt) | λt | |||
0
(Early images)
| 100 | 150 | 200 | 300 | ||
1
| 112 | 168 | 224 | 337 | 0.8909 | 0.1155 |
2
| 126 | 189 | 252 | 378 | 0.7937 | 0.231 |
3
| 141 | 212 | 283 | 424 | 0.7072 | 0.3465 |
4
| 159 | 238 | 317 | 476 | 0.6300 | 0.462 |
6
| 200 | 300 | 400 | 600 | 0.5001 | 0.693 |
8
| 252 | 378 | 504 | 756 | 0.3969 | 0.924 |
14
| 504 | 756 | 1008 | 1511 | 0.1985 | 1.617 |
20
| 1007 | 1511 | 2015 | 3022 | 0.0993 | 2.31 |
22
| 1269 | 1904 | 2538 | 3808 | 0.0788 | 2.541 |
B | ||||||
Hoursa | Acquisition time (seconds) for 111In decay corrected images | exp(-λt) | λt | |||
0
(Early images)
| 100 | 200 | 300 | 400 | ||
1
| 101 | 202 | 303 | 404 | 0.9897 | 0.0103 |
2
| 102 | 204 | 306 | 408 | 0.9795 | 0.0206 |
3
| 103 | 206 | 309 | 413 | 0.9694 | 0.0310 |
4
| 104 | 208 | 313 | 417 | 0.9595 | 0.04137 |
6
| 106 | 213 | 319 | 426 | 0.9398 | 0.06205 |
8
| 109 | 217 | 326 | 435 | 0.9206 | 0.08274 |
14
| 118 | 236 | 354 | 472 | 0.8475 | 0.16549 |
20
| 123 | 246 | 369 | 492 | 0.8131 | 0.20686 |
22
| 125 | 250 | 374 | 499 | 0.7965 | 0.22755 |
Acquisition protocols for 111In-labeled WBC scintigraphy
Acquisition protocol for bone marrow scintigraphy (for bone and prosthetic joint infection)
Interpretation criteria for WBC and anti-G-mAbs
Location | 99mTc-WBC early (30′-1 h) | 99mTc-WBC delayed (3-4 h) | 99mTc-WBC late (20-24 h) | 111In-WBC (3 h/24 h) | 99mTc-mAbs (3 h/24 h) |
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Blood/heart | +++ | + | – | ± | ± |
Lung | + | – | – | −/− | −/− |
Liver | ++ | ++ | ++ | ++/++ | +++/+++ |
Spleen | +++ | +++ | +++ | +++/+++ | +/++ |
Kidneys | + | + | + | −/− | +/+ |
Bladder | – | + | + | −/− | +/+ |
Bowel | – | + | ++ | −/−a | −/− |
Bone marrow | + | ++ | ++ | ++/++ | +++/+++ |
Examination | Acquisition protocol | Image interpretation | Pitfalls |
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Osteomuscular (osteomyelitis, and prosthetic joint infection) | Labeled WBC and 99mTc-mAb-anti-granulocytes: 30 min p.i. planar images for QC and ROI - 3-4 h p.i. total-body and planar images ROI 20-24 h p.i.: planar and SPECT(/CT) ROI - 99mTc-sulfur colloid 20–360 min p.i. planar images ROI | Qualitative analysis: Infective lesions show an uptake that arise over time while aseptic flogistic lesions show a decreasing uptake over time. In doubtful cases it is necessary to compare the images with 99mTc-sulfur colloids: infective lesion shows a mismatch pattern of radiopharmaceutical uptake. Semi-quantitative analysis: Calculate the target/background ratio drawing ROI on the regions that show an increased uptake over time (T) and on contralateral bone marrow (B) FP results can be obtained if the scintigraphy is performed within 3–4 months after surgery | Assess timing after surgical procedure. Assess the presence of artifacts related to the attenuation over-correction in patients with metallic devices |
Discitis, spondylitis and spondylodiscitis | 99mTc-HDP/MDP: i.v. injection during dynamic acquisition 4 h p.i. total-body, planar and SPECT(/CT) images ROI 67Ga-citrate 4 h p.i. total body, planar and SPECT(/CT) images ROI 24 h p.i. planar images ROI 48 h p.i. planar and SPECT(/CT) images ROI, if necessary [18F]FDG PET/CT 1 h p.i. PET/CT | Clinical history (timing from surgical procedure, and type of metallic implant, etc). Anatomic location of tracer uptake. 99mTc-HDP/MDP + 67Ga-citrate: Infective lesions show usually greater uptake of 67Ga in comparison to 99mTc-HDP/MDP while an aseptic process (arthritis, fracture etc) shows greater uptake of 99mTc-HDP/MDP than that of 67Ga. [18F]FDG PET/CT: Infective lesions show greater uptake of [18F]FDG than healthy vertebral body | Assess timing after surgical procedure. Assess the presence of artifacts related to the attenuation over-correction in patients with metallic devices |
Sternal infections | Labeled WBC and 99mTc-mAb-anti-granulocytes: 30 min p.i. Planar images for QC and ROI 3–4 h p.i. total-body, planar and SPECT(/CT) images ROI. 20–24 h p.i. planar and SPECT(/CT) images ROI | Qualitative analysis: an increased uptake with time of sternum and/or mediastinum is indicative of infection. Semi-quantitative analysis: Pattern I: Presence of deep infection. Widespread and intense uptake of the sternum, greater than liver uptake, after 3–4 and 20–24 h. Pattern II: Presence of superficial infection. Moderate increase or irregular uptake of sternum that does not change or decrease between 3 and 4 and 20–24 h. Pattern III: Absence of infection. Medium intensity uptake with uniform distribution of the sternum, abnormal uptake (“cold” areas) on the midline or cold areas with focal distribution in the midline | Medicate the wound before scintigraphic acquisition to avoid FP results. FP results: missed clearing of wound before scintigraphic acquisition |
Diabetic foot | Labeled WBC and 99mTc-mAb-anti-granulocytes: 30 min p.i. planar images for QC and ROI 3–4 h p.i. total-body and planar images ROI 20–24 h p.i. planar and SPECT(/CT) images ROI 99mTc-sulfur colloids 20–360 min p.i. planar images | Semi-quantitative analysis: Infective lesions show an uptake that rises over time while aseptic flogistic lesions show a decreasing uptake over time. In doubtful cases it is necessary to compare the images with 99mTc-sulfur colloids infective lesion to check for a mismatch pattern of radiopharmaceuticals uptake | Clean the wound before scintigraphy acquisition to avoid FP. Assess the presence of lesions of size lower than spatial resolution of method |
Examination | Acquisition protocol | Image interpretation | Pitfalls |
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Central nervous system infections | Labeled WBC: 30 min p.i. planar images for QC and ROI 3–4 h p.i. total-body and planar images ROI 20–24 h p.i. planar and SPECT(/CT) images ROI | Semi-quantitative analysis: Infective lesions show usually an uptake equal to +++/++++ while aseptic lesions show no uptake or equal to +/++ | |
Infective endocarditis | Labeled WBC: 30 min p.i. planar images for QC and ROI 3–4 h p.i. total-body, planar and SPECT(/CT) images ROI 20–24 h p.i. planar and SPECT(/CT) images ROI | Qualitative analysis: analysis of cardiac region (valve plans) and other regions (CNS, spleen and axial skeleton, lung) Anatomic location of WBC uptake. Correlation with flogosis markers and echocardiography. | Assess the presence of artifacts related to the attenuation overcorrection for the presence of surgical implants (mechanical valve prostheses and CIED). FN results: fungal endocarditis FP results: atherosclerotic plaques, sarcoidosis, tumor, vasculitis etc |
Post surgical infections (dermal filler infections and abscesses) | Labeled WBC: 30 min p.i. Planar images for QC and ROI 3–4 h p.i. total-body, planar and SPECT(/CT) images ROI 20–24 h p.i. planar and SPECT(/CT) images ROI | Clinical history (date and sort of surgical procedure). Anatomic location of WBC uptake. Correlation with flogosis markers | Assess the presence of artifacts related to the attenuation overcorrection in patients with metallic devices |
Pulmonary infections | Labeled WBC: 30 min p.i. Planar images for QC and ROI 3–4 h p.i. total-body planar and SPECT(/CT) images ROI 20–24 h p.i. planar and SPECT(/CT) images ROI | Focal pulmonary uptake that arise over time is usually associated with bacterial pneumonia. Diffuse pulmonary activity on images obtained 4 h p.i. can be due to opportunistic infections, radiation pneumonitis, pulmonary drug toxicity and adult respiratory distress syndrome | FP results: cystic fibrosis, faulty labelling or reinjection |
Examination | Acquisition protocol | Image interpretation | Pitfalls |
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Fever of unknown origin | Labeled WBC and 99mTc-mAb-anti-granulocytes: 30 min p.i. planar images for QC and ROI 3–4 h p.i. total-body and planar images ROI 20–24 h p.i. planar and SPECT(/CT) images ROI | Evaluation of all regions of increased uptake having regard to the possible differential diagnosis (inflammation, cancer) | Assess the presence of artifacts related to the attenuation overcorrection in patients with metallic devices or prostheses |
Inflammatory bowel diseases | Labeled WBC and 99mTc-mAb-anti-granulocytes: 30 min-1 h p.i. planar images for QC and ROI 2–2.5 h p.i. planar and SPECT(/CT) images ROI planar image of the chest (in patients with suspected oesophageal localization of disease). 24 h p.i. planar images ROI for 99mTc mAb or for abscesses and fistulae | Abscesses and fistulae can appear only at late images. Better to use SPECT/CT in case of doubt. FP results can be obtained in tumor. Aspecific uptake in colitis, bleeding and diabetic patients | Starting from 3 h p.i. due to aspecific accumulation of secondary hydrophilic complexes of Tc in caecum and ascending colon after 2 h p.i. |
Vascular prosthesis | Labeled WBC and 99mTc-mAb-anti-granulocytes: i.v. injection during dynamic acquisition (one image every 5–10 s for 3–5 min) 30 min p.i. planar images for QC and ROI 3–4 h p.i. total-body, planar and SPECT(/CT) images ROI 20–24 h p.i. recommended if the chest is the ROI | Clinical history (date and sort of vascular prosthesis implant, etc). Anatomic location of WBC uptake (in vascular prosthesis wall, at the site of surgical clips and/or in soft tissues) | Assess the presence of artifacts related to the attenuation overcorrection in patients with metallic clips. FN results: chronic flogistic process with low recruitment of WBC |
Additional strategies that may improve accuracy
Physiologic biodistribution, pitfalls and artifacts
Report of scintigraphic findings
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Identification: this includes the patient identification, the institution where the scintigraphy was performed, the date of scintigraphy, the type of scintigraphy, the name of radiopharmaceutical and the activity administered to patient (MBq), and any other specification required by national regulations, e.g. the name of the radiographer performing the study.
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Clinical question: this includes the clinical question and brief clinical history of the patient. Current treatment with antibiotics or other interfering drugs should be reported.
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Procedure description: this includes the description of instrumentation used, the administration method of the radiopharmaceutical and the acquisition protocol. The use of SOPs should be mentioned as well as the European Guidelines for labelling, image acquisition and interpretation.
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Report text: this includes the description of qualitative and/or semi-quantitative analysis. The qualitative analysis should describe the presence/absence of radiopharmaceutical uptake, the site and size of uptake, and the intensity of uptake, preferably supported by semi-quantitative data. The possible presence of factors that may have limited the sensitivity and specificity of the study, such as the presence of motion artifacts, should be described.
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Conclusions: This is the clear and conclusive answer to the clinical question. It can also suggest other diagnostic procedures to be performed to confirm or exclude the diagnosis made. The anatomical structures involved, as well as the presence, extent and the intensity of the infectious process have to be specified. At the end of the conclusions the name and surname of the Nuclear Medicine Physician reporting the study and of the technician performing the scan have to be clearly stated.