The Utility of Hepatobiliary Scintigraphy Scans in the Tokyo Guidelines Era for Acute Cholecystitis.

BACKGROUND: Hepatobiliary Scintigraphy (HIDA) aids the diagnosis of acute cholecystitis (AC) but has limitations. We sought to design a model based on the Tokyo Guidelines 2018 (TG18) to predict HIDA results. METHODS: A retrospective review of patients who underwent a HIDA scan during the evaluation of AC was performed. Using logistic regression techniques incorporating the TG18 criterion and additional readily available patient characteristics, a prediction model was created to identify patients likely to test negative for acute cholecystitis by HIDA scan. RESULTS: In 235 patients with suspected AC, a HIDA scan was performed. Variables associated with positive HIDA results were male gender (RR 2.0 (CI 1.33-2.99), age (OR 1.02 (CI 1.01-1.04), right upper quadrant tenderness (RR 1.7 (CI 1.1-2.8)), clinical Murphy's sign (RR 2.2 (CI 1.5-3.4)), ultrasound findings suggestive of AC by any of its components (RR 3.2 (CI 1.6-6.5)), gallbladder wall thickening (RR 2.0 (CI 1.3-3.1)), and gallbladder distention (RR 1.9 (CI 1.3-2.9)). These variables allowed for creation of a model to predict HIDA results. The model predicted HIDA results in 36.9% of patients with an area under the curve of 0.81. CONCLUSIONS: In the era of TG18, HIDA is probably over utilized. We developed an accurate, simple model based on TG18 that identifies a group of patients for whom a HIDA scan is unnecessary to establish the diagnosis of AC.

The Utility of 18FDG PET/CT Versus Bone Scan for Identification of Bone Metastases in a Pediatric Sarcoma Population and a Review of the Literature.

BACKGROUND: Outcome of patients with osteosarcoma (OS) and Ewing sarcoma (EWS) is dependent on presence of metastases. Imaging guidelines for OS and EWS include radiographs, computed tomography (CT), and magnetic resonance imaging for primary tumor evaluation and CT chest and bone scintigraphy (BS) for metastatic detection. 18Fluorodeoxyglucose (18FDG) positron emission tomography (PET)/CT has become more common for disease evaluation, yet there is no consensus for its use in this population. OBJECTIVE: We aimed to compare identification of osseous metastases using BS versus 18FDG PET/CT in our patient population. We hypothesized that 18FDG PET/CT is more likely to detect osseous metastases both at diagnosis and relapse. MATERIALS AND METHODS: We performed retrospective chart reviews of pediatric sarcoma patients treated at our institution from 2008 to 2019. Paired BS and 18FDG PET/CT scans were reviewed. Review of the literature was also performed. RESULTS: Thirty-three patients had paired BS and 18FDG PET/CT during diagnosis or treatment. Fifteen patients had distant osseous metastases. In the OS cohort, 8/16 patients had osseous metastases; 100% of these patients were detected on 18FDG PET/CT and 75% on BS. Thirty-one bony lesions were seen on imaging in OS patients; 100% of these were identified on 18FDG PET/CT but only 29% on BS. In the EWS cohort, 6/15 patients had osseous metastases; 100% of these patients were detected on 18FDG PET/CT and 50% on BS. Eighteen bony lesions were seen on imaging in EWS patients; 94% of these were identified on 18FDG PET/CT, but only 28% on BS. CONCLUSION: For patients in our institution with OS or EWS, osseous metastases were more likely detected using 18FDG PET/CT.

Clinical Utility of 18F-FDG PET/CT in Staging Localized Breast Cancer Before Initiating Preoperative Systemic Therapy.

BACKGROUND: 18F-fluorodeoxyglucose PET/CT is recommended as an optional study in the current NCCN Clinical Practice Guidelines in Oncology for Breast Cancer after CT of the chest, abdomen, and pelvis with contrast and bone scan (CTBS) in stage IIA-IIIC breast cancer. We evaluated our experience with the use of PET/CT in this setting before beginning primary systemic therapy (PST) prior to planned surgery. METHODS: We performed medical record abstractions of all adult female patients with clinical stage IIA-IIIC breast cancer diagnosed at Montefiore Medical Center from January 1, 2014, through January 1, 2019, who underwent PET/CT before PST. We calculated the proportion of patients upstaged after PET/CT and examined the cost and radiation exposure associated with PET/CT compared with CTBS. RESULTS: A total of 195 patients with 196 breast cancers (bilateral disease in 1 patient) met the study inclusion criteria and had PET/CT as the first imaging study before PST. The overall upstaging rate for regional nodal metastasis and/or distant metastasis was 37% (73/196), including 24% for stage IIA (9/38), 39% for stage IIB (31/79), 54% for stage IIIA (22/41), 27% for stage IIIB (8/30), and 37% for stage IIIC (3/8). The overall upstaging rate for distant metastasis was 14% (27/196), including 0% for stage IIA, 13% for stage IIB (10/79), 22% for stage IIIA (9/41), 17% for stage IIIB (5/30), and 37% for stage IIIC (3/8). Medicare reimbursement rates were $1,604.37 for PET/CT and $1,679.94 for CTBS. The radiation dose for PET/CT was 14 mSv versus 21 mSv for CTBS. CONCLUSIONS: Approximately 37% of patients with clinical stage IIA-IIIC breast cancer who underwent PET/CT before PST showed more extensive disease, including 23% with more extensive nodal metastasis and 14% with distant metastasis. Given its high detection rate, comparable cost, lower radiation dose, and greater convenience, PET/CT should be considered as an alternative to CTBS rather than "optional" after CTBS, especially in patients who require an efficient and expeditious workup before initiating PST.

The value of FDG-PET in the staging of gastric adenocarcinoma: A single institution retrospective review.

BACKGROUND: The value of FDG-PET in the staging of gastric adenocarcinoma (GA) has been subject to debate. METHODS: We performed a retrospective review of GA patients between 2006 and 2014 and identified those who had a CT and FDG-PET before initiating treatment. CT and FDG-PET images were analyzed by a blinded body radiologist and nuclear physician, respectively. Disease stage was assessed, looking at primary tumor (PT), locoregional (LLN) and distant lymph node disease (DLN), and metastasis (M). RESULTS: We identified 608 patients who had biopsy-proven GA and 207 (34.0%) had a CT and FDG-PET as part of their staging work-up. Of these, imaging from 166 (27.3%) patients was available for review. CT identified PT, LLN, DLN, and M in 120 (72.3%), 84 (50.6%), 25 (15.1%), and 32 (19.3%) patients, respectively; while FDG-PET identified PT, LLN, DLN, and M in 125 (75.3%), 78 (47.0%), 41 (24.7%), and 27 (16.3%) of patients, respectively. FDG-PET up-staged 31 (18.7%) patients while it down-staged 17 (10.2%) patients. Of patients who were up-staged, 20 (64.5%) developed progressive disease. CONCLUSIONS: Our findings support the use of FDG-PET as a valuable adjunct to CT in the staging of GA, as it changed the stage in 48 (28.9%) patients. J. Surg. Oncol. 2016;113:640-646. © 2016 Wiley Periodicals, Inc.

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.

ACR-ACNM-ASTRO-SNMMI Practice Parameter for Lutetium-177 (Lu-177) DOTATATE Therapy.

OBJECTIVES: This practice parameter (PP) for Lutetium-177 (Lu-177) DOTATATE peptide receptor radionuclide therapy (PRRT) aims to guide authorized users in selection of appropriate adult candidates with gastroeneropancreatic neuroendocrine tumors (GEP-NETs) from foregut, midgut, and hindgut. The essential selection criteria include somatostatin receptor-positive GEP-NETs, which are usually inoperable and progressed despite standard therapy. Lu-177 DOTATATE is a radiopharmaceutical with high avidity for somatostatin receptors that are overexpressed by these tumors. This document ensures safe handling of Lu-177 DOTATATE by the authorized users and safe management of affected patients. METHODS: The document was developed according to the systematic process developed by the American College of Radiology (ACR) and described on the ACR Web site (https://www.acr.org/Clinical-Resources/Practice-Parameters-and-Technical-Standards). The PP development was led by 2 ACR Committees on Practice Parameters (Nuclear Medicine and Molecular Imaging and Radiation Oncology) collaboratively with the American College of Nuclear Medicine, American Society of Radiation Oncology, and Society of Nuclear Medicine and Molecular Imaging. RESULTS: The Lu-177 DOTATATE PP reviewed pharmacology, indications, adverse effects, personnel qualifications, and required clinical evaluation before starting the treatment, as well as the recommended posttherapy monitoring, quality assurance, documentation, and appropriate radiation safety instructions provided in written form and explained to the patients. CONCLUSIONS: Lu-177 DOTATATE is available for therapy of inoperable and/or advanced GEP-NETs when conventional therapy had failed. It can reduce tumor size, improve symptoms, and increase the progression free survival. The PP document provides clinical guidance for authorized users to assure an appropriate, consistent, and safe practice of Lu-177 DOTATATE.

ACR-ACNM-ASTRO-SNMMI Practice Parameter for Lutetium-177 (Lu-177) DOTATATE Therapy.

OBJECTIVES: This practice parameter (PP) for Lutetium-177 (Lu-177) DOTATATE peptide receptor radionuclide therapy (PRRT) aims to guide authorized users in selection of appropriate adult candidates with gastroeneropancreatic neuroendocrine tumors (GEP-NETs) from foregut, midgut, and hindgut. The essential selection criteria include somatostatin receptor-positive GEP-NETs, which are usually inoperable and progressed despite standard therapy. Lu-177 DOTATATE is a radiopharmaceutical with high avidity for somatostatin receptors that are overexpressed by these tumors. This document ensures safe handling of Lu-177 DOTATATE by the authorized users and safe management of affected patients. METHODS: The document was developed according to the systematic process developed by the American College of Radiology (ACR) and described on the ACR Web site (https://www.acr.org/Clinical-Resources/Practice-Parameters-and-Technical-Standards). The PP development was led by 2 ACR Committees on Practice Parameters (Nuclear Medicine and Molecular Imaging and Radiation Oncology) collaboratively with the American College of Nuclear Medicine, American Society of Radiation Oncology, and Society of Nuclear Medicine and Molecular Imaging. RESULTS: The Lu-177 DOTATATE PP reviewed pharmacology, indications, adverse effects, personnel qualifications, and required clinical evaluation before starting the treatment, as well as the recommended posttherapy monitoring, quality assurance, documentation, and appropriate radiation safety instructions provided in written form and explained to the patients. CONCLUSIONS: Lu-177 DOTATATE is available for therapy of inoperable and/or advanced GEP-NETs when conventional therapy had failed. It can reduce tumor size, improve symptoms, and increase the progression free survival. The PP document provides clinical guidance for authorized users to assure an appropriate, consistent, and safe practice of Lu-177 DOTATATE.

Pinhole versus parallel-hole collimators for parathyroid imaging: an intraindividual comparison.

UNLABELLED: This study was undertaken to determine the effects of collimators on the accuracy of preoperative sestamibi parathyroid imaging of the neck. METHODS: Forty-nine patients with primary hyperparathyroidism underwent preoperative (99m)Tc-sestamibi parathyroid imaging. The protocol included early and late pinhole and parallel-hole imaging. One experienced nuclear physician, without knowledge of other test results or final diagnoses, interpreted studies. For both pinhole and parallel-hole images, focally increased sestamibi accumulation outside the normal tracer biodistribution that persisted or increased in intensity from early to late images was interpreted as positive for a parathyroid lesion. Final diagnoses were operatively confirmed in all patients. RESULTS: Fifty-four parathyroid lesions were resected from the 49 patients. Forty-five patients had single-gland disease. Four patients had multigland disease: 3 had 2 lesions and 1 had 3 lesions. Median lesion weight was 840 mg. Pinhole imaging was significantly more sensitive than parallel-hole imaging (89% vs. 56%; P = 0.0003) for all 54 lesions. Specificity did not significantly differ between pinhole and parallel-hole imaging (93% vs. 96%, P = 0.29). Pinhole imaging was significantly more sensitive than parallel-hole imaging for lesions above (100% vs. 68%, P = 0.003) and below (77% vs. 42%, P = 0.03) the median weight and for single-gland disease (96% vs. 67%, P = 0.001). Pinhole imaging also was more sensitive for multigland disease, although the difference was only marginally significant (55% vs. 0%, P = 0.037). CONCLUSION: Because sensitivity is significantly higher, sestamibi parathyroid imaging of the neck should be performed with a pinhole collimator.

Nuclear Medicine Imaging in Fever of Unknown Origin: The New Paradigm.

Fever of Unknown Origin, or FUO, is a challenging condition for patients and clinicians. In up to 50% of cases, no diagnosis is established. Patient workup begins with comprehensive history, physical examination and laboratory tests. Radionuclide imaging has been a second-line procedure. Gallium-67 citrate, which accumulates in infection, inflammation, and tumor, was for many years, the radionuclide test of choice in the workup of FUO. The 24-72 hours between injection and imaging, relatively high radiation dose to patients, and suboptimal image quality are significant disadvantages; imaging results are variable. Although labeled leukocyte imaging accurately localizes infection, infections cause only about 20%-40% of all FUO's. In most cases, this test is not helpful in identifying the source of the fever. Fluorine-18-fluorodeoxyglucose (FDG) uptake is related to cellular glucose metabolism. Increased FDG uptake is present in numerous hypermetabolic conditions, including tumor, infection, and noninfectious inflammation. FDG positron emission tomography (PET) and PET/computed tomography (CT) have rapidly assumed an increasingly important role in the diagnostic workup of patients with FUO. FDG is especially useful for localizing lesions and areas of interest for further evaluation. In contrast to gallium and labeled leukocyte imaging, FDG contributes useful information in children with FUO. Initially utilized as a second-line diagnostic tool in patients with FUO, recent data indicate that FDG contributes more diagnostically useful information than anatomic imaging like ultrasound and CT, which leads to earlier institution of appropriate therapy. These findings suggest that FDG imaging should be performed earlier, rather than later, in the diagnostic evaluation of the patient with FUO.

Diagnosing prosthetic vascular graft infection with the antigranulocyte antibody 99mTc-fanolesomab.

AIM: The objectives of this retrospective investigation were to determine the accuracy of 99mTc-fanolesomab, an antigranulocyte antibody, for diagnosing prosthetic vascular graft infection, ascertain optimum imaging times for this indication, and assess safety of this agent. METHODS: Eighteen patients with 19 prosthetic vascular grafts were included. Indications for graft placement included peripheral vascular disease (8), haemodialysis (7), and aneurysm (4). Patients were imaged 2-5 h and 18-30 h after injection of 555-740 MBq (75-125 microg) 99mTc-fanolesomab. One experienced nuclear physician reviewed images in three separate sessions, early alone, late alone and early plus late images together. When early and late images were read alone, graft activity more intense than native blood pool activity was classified as positive for infection. When early and late images were interpreted together, graft activity which persisted or which increased in intensity over time was classified as positive for infection. Patient records were reviewed for adverse events up to 30 days after injection. RESULTS: Five (26%) prosthetic grafts were infected. Early, late and early plus late imaging were equally sensitive (1.00). Early images were significantly less specific (0.50), than late and early plus late images (0.93) (P<0.05, analysis of proportions). Accuracy of late imaging and early plus late imaging were the same: 0.93. No patient experienced adverse events following radiopharmaceutical injection. CONCLUSIONS: 99mTc-fanolesomab imaging, performed 18-30 h after injection, diagnosed prosthetic vascular graft infection safely and accurately (95%). (Although safety was not an issue in this investigation, following reports of serious, including two fatal, events after administration, 99mTc-fanolesomab was withdrawn from the United States market).

Role of Nuclear Medicine for Diagnosing Infection of Recently Implanted Lower Extremity Arthroplasties.

Infection is an infrequent complication of lower extremity prosthetic joint surgery. Approximately one-third develop within 3 months (early), another third within 1 year (delayed), and the remainder more than 1 year (late) after surgery. Diagnosing prosthetic joint infection, especially in the early postoperative period during the first year, is challenging. Pain is almost always present. The presence of fever is variable, ranging from less than 5% to more than 40% of patients. Leukocytosis is a poor predictor of infection. After primary uncomplicated arthroplasty, the C-reactive protein remains elevated for up to 3 weeks. The erythrocyte sedimentation rate can remain elevated for up to 1 year. Although joint aspiration with culture, the definitive preoperative diagnostic procedure, is specific, its sensitivity is variable. Plain radiographs lack sensitivity and specificity. Radionuclide studies are useful for evaluating painful joint replacements, but data on their utility during the early postoperative period are limited. During the first year after arthroplasty insertion, the bone scan can exclude infection. It is a good "rule-out" test, but it is not reliable for "ruling in" infection. Gallium-67 accumulates in normally healing surgical incisions and in aseptic inflammation. With an accuracy of 60%-80% for diagnosing prosthetic joint infection, there is little role for this radiopharmaceutical for evaluating prosthetic joints, regardless of age. Although data about diagnosing prosthetic joint infection with 18F-FDG in the early postoperative period are lacking, uptake of this radiopharmaceutical in a variety of postoperative settings for variable time periods is well known. Furthermore, its utility for diagnosing prosthetic joint infection in general, after nearly 2 decades of investigation, remains to be established. Indium-111-labeled leukocytes do not accumulate in normally healing surgical wounds, and in combination with marrow imaging, the test is about 90% accurate for diagnosing prosthetic joint infection. Preliminary data indicate a comparable accuracy in the early postoperative period.

Relevance of focal osseous uptake on FDG PET with or without CT changes in oncology patients.

OBJECTIVE: To assess significance of focal FDG uptake in osseous structures, with and without CT correlate, in patients undergoing FDG PET/CT for oncological indications. METHODS: 57 patients with focally increased FDG activity in bones and a definite follow up were included. RESULTS: 85.2% of lesions without changes were found to be malignant. Sensitivity and PPV of a CT correlate in metastatic lesions was expectedly high, 62.9% and 86.7% respectively, however, the NPV was only 14.8%. CONCLUSION: Osseous foci are valuable in predicting metastatic disease even in the absence of low dose CT correlate.

Infection and musculoskeletal conditions: Imaging of musculoskeletal infections.

Imaging procedures are routinely used to evaluate patients suspected of having musculoskeletal infection. Radiographs should be performed whenever musculoskeletal infection is suspected. Even when not diagnostic, radiographs are useful. They provide an anatomic overview of the region of interest, including pre-existing conditions that could influence the selection and interpretation of subsequent procedures. Magnetic resonance imaging (MRI) is sensitive, provides superb anatomic detail, does not use ionizing radiation, and is rapidly completed. This technique is especially valuable for septic arthritis, spinal osteomyelitis, and diabetic foot infections. Among the radionuclide procedures, three-phase bone imaging is readily available, and very accurate in unviolated bone. Labeled leukocyte imaging should be used in cases of 'complicating osteomyelitis' such as prosthetic joint infections. This test is also useful in unsuspected diabetic pedal osteomyelitis and the neuropathic joint. Gallium imaging is a useful adjunct to MIR in spinal infection. 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) will likely play an important role, especially in the evaluation of spinal infection.

Combined labeled leukocyte and technetium 99m sulfur colloid bone marrow imaging for diagnosing musculoskeletal infection.

The use of labeled leukocyte (white blood cell [WBC]) studies in the diagnosis of osteomyelitis can be problematic. A combined study consisting of WBC imaging and complementary bone marrow imaging performed with technetium 99m (99mTc) sulfur colloid is approximately 90% accurate and is especially useful for diagnosing osteomyelitis in situations involving altered marrow distribution. There are limitations and pitfalls associated with a combined study. If there is no labeled WBC activity in the region of interest, marrow imaging is not useful. The sulfur colloid image becomes photopenic within about 1 week after the onset of infection, so that the study should be interpreted cautiously in the acute setting. Labeled WBC accumulation in lymph nodes can also confound image interpretation, although nodal activity can usually be recognized because it is typically round, discrete, multifocal, linear in distribution, and often bilateral. Furthermore, 99mTc-sulfur colloid that is improperly prepared or is more than about 2 hours old degrades image quality, potentially causing erroneous conclusions. Nevertheless, WBC-marrow imaging is a very accurate technique for diagnosing osteomyelitis. Knowledge of the criteria for image interpretation and of the aforementioned limitations and pitfalls, combined with careful attention to imaging technique, will maximize the value of this study.

FDG PET of infection and inflammation.

Nuclear medicine plays an important role in the evaluation of infection and inflammation. Fluorine 18 fluorodeoxyglucose (FDG) is a readily available radiotracer that offers rapid, exquisitely sensitive high-resolution tomography. In patients with acquired immunodeficiency syndrome, FDG positron emission tomography (PET) accurately helps localize foci of infection and is particularly useful for differentiating central nervous system lymphoma from toxoplasmosis. FDG PET can also help localize the source of fever of undetermined origin (FUO), thereby guiding additional testing. In the musculoskeletal system, FDG PET accurately helps diagnose spinal osteomyelitis, and in inflammatory conditions such as sarcoidosis and vasculitis, it appears to be useful for defining the extent of disease and monitoring response to treatment. FDG PET may be of limited usefulness in postoperative patients and in patients with a failed joint prosthesis or a tumor. Nevertheless, this relatively new imaging technique promises to be helpful in the diagnosis of infection and inflammation. FDG PET will likely assume increasing importance in assessing FUO, spinal osteomyelitis, vasculitis, and sarcoidosis and may even become the radionuclide imaging procedure of choice in the evaluation of some or all of these pathologic conditions.

Diagnosing infection in the failed joint replacement: a comparison of coincidence detection 18F-FDG and 111In-labeled leukocyte/99mTc-sulfur colloid marrow imaging.

UNLABELLED: The objectives of this study were to investigate (18)F-FDG imaging, using a coincidence detection system, for diagnosing prosthetic joint infection and to compare it with combined (111)In-labeled leukocyte/(99m)Tc-sulfur colloid marrow imaging in patients with failed lower extremity joint replacements. METHODS: Fifty-nine patients--with painful, failed, lower extremity joint prostheses, 40 hip and 19 knee--who underwent (18)F-FDG, labeled leukocyte, and bone marrow imaging, and had histopathologic and microbiologic confirmation of the final diagnosis, formed the basis of this investigation. (18)F-FDG images were interpreted as positive for infection using 4 different criteria: criterion 1: any periprosthetic activity, regardless of location or intensity; criterion 2: periprosthetic activity on the (18)F-FDG image, without corresponding activity on the marrow image; criterion 3: only bone-prosthesis interface activity, regardless of intensity; criterion 4: semiquantitative analysis--a lesion-to-background ratio was generated, and the cutoff value yielding the highest accuracy for determining the presence of infection was determined. Labeled leukocyte/marrow images were interpreted as positive for infection when periprosthetic activity was present on the labeled leukocyte image without corresponding activity on the marrow image. RESULTS: Twenty-five (42%) prostheses, 14 hip and 11 knee, were infected. The sensitivity, specificity, and accuracy of (18)F-FDG, by criterion, were as follows: criterion 1: 100%, 9%, 47%; criterion 2: 96%, 35%, 61%; criterion 3: 52%, 44%, 47%; criterion 4: 36%, 97%, 71%. The sensitivity, specificity, and accuracy of labeled leukocyte/marrow imaging were 100%, 91%, and 95%, respectively. WBC/marrow imaging, which was more accurate than any of the (18)F-FDG criteria for all prostheses, as well as for hips and knees separately, was significantly more sensitive than criterion 3 (P < 0.001) and criterion 4 (P < 0.001) and was significantly more specific than criterion 1 (P < 0.001), criterion 2 (P < 0.001), and criterion 3 (P < 0.001). CONCLUSION: Regardless of how the images are interpreted, coincidence detection-based (18)F-FDG imaging is less accurate than, and cannot replace, labeled leukocyte/marrow imaging for diagnosing infection of the failed prosthetic joint.

99mTc-fanolesomab Palatin Technologies.

99mTc-fanolesomab is a radiolabeled imaging agent which is being developed by Palatin Technologies for use in the diagnosis of various infections, including appendicitis and osteomyelitis.

Radionuclide imaging of infection.

Although our understanding of microorganisms has advanced significantly and antimicrobial therapy has become increasingly available, infection remains a major cause of patient morbidity and mortality. The role of radionuclide imaging in the evaluation of the patient suspected of harboring an infection varies with the situation. For example, in the postoperative patient, radionuclide imaging is complementary to CT and is used to help differentiate postoperative changes from infection. In the case of the painful joint replacement, in contrast, radionuclide studies are the primary diagnostic imaging modality for differentiating infection from other causes of prosthetic failure. Several tracers are available for imaging infection: (99m)Tc-diphosphonates, (67)Ga-citrate, and (111)In- and (99m)Tc-labeled leukocytes. At the moment, in immunocompetent patients, labeled leukocyte imaging is the radionuclide procedure of choice for detecting most infections. There are, unfortunately, significant limitations to the use of labeled leukocytes. The in vitro labeling process is labor intensive, is not always available, and involves direct handling of blood products. For musculoskeletal infection, the need to frequently perform complementary marrow or bone imaging adds complexity and expense to the procedure and is an inconvenience to patients. Considerable effort has therefore been devoted to the search for alternatives to this procedure, including in vivo methods of labeling leukocytes, (18)F-FDG PET, and radiolabeled antibiotics. This article reviews the current status of nuclear medicine infection imaging and the potential of a murine monoclonal antigranulocyte antibody, fanolesomab, that is currently under investigation. Upon completion of this article, the reader will be familiar with the physical characteristics and uptake mechanisms of tracers currently approved for infection imaging, the indications for the uses of these tracers, and the characteristics and potential indications for a murine monoclonal antigranulocyte antibody under investigation.