FDG PET of infection and inflammation

Neuroimaging evidence of white matter inflammation in newly diagnosed systemic lupus erythematosus

OBJECTIVE

Central nervous system (CNS) involvement occurs frequently in systemic lupus erythematosus (SLE) and frequently results in morbidity. The primary pathophysiology of CNS involvement in SLE is thought to be inflammation secondary to autoantibody-mediated vasculitis. Neuroimaging studies have shown hypometabolism (representing impending cell failure) and atrophy (representing late-stage pathology), but not inflammation. The purpose of this study was to detect the presence and regional distribution of inflammation (hypermetabolism) and tissue failure, apoptosis, or atrophy (hypometabolism).

METHODS

Eighty-five patients with newly diagnosed SLE, who had no focal neurologic symptoms, were studied. Disease activity was quantified using the Safety of Estrogens in Lupus Erythematosus: National Assessment version of the SLE Disease Activity Index (SELENA-SLEDAI), a validated index of SLE-related disease activity. 18Fluorodeoxyglucose (FDG) positron emission tomography (PET) images of glucose uptake were analyzed by visual inspection and as group statistical parametric images, using the SELENA-SLEDAI score as the analysis regressor.

RESULTS

SELENA-SLEDAI-correlated increases in glucose uptake were found throughout the white matter, most markedly in heavily myelinated tracts. SELENA-SLEDAI-correlated decreases were found in the frontal and parietal cortex, in a pattern similar to that seen during visual inspection and presented in previous reports of hypometabolism.

CONCLUSION

The SELENA-SLEDAI-correlated increases in glucose consumption are potential evidence of inflammation, consistent with prior reports of hypermetabolism in inflammatory disorders. To our knowledge, this is the first imaging-based evidence of SLE-induced CNS inflammation in an SLE inception cohort. The dissociation among 18FDG uptake characteristics, spatial distribution, and disease activity correlation is in accordance with the notion that glucose hypermetabolism and hypometabolism reflect fundamentally different aspects of the pathophysiology of SLE with CNS involvement.

Decreased sensitivity of (18)F-fluorodeoxyglucose imaging in infection and inflammation

Nuclear medicine plays an important role in the evaluation of inflammation and infection. Although (99m)Tc-methylene diphosphonate, (67)Ga-citrate, and in vitro labeled autologous leukocyte imaging are useful procedures, there are limitations to each of them. (18)F-fluorodeoxyglucose-positron-emission tomography (PET) and PET/computed tomography offer several advantages over conventional single-photon-emitting tracers and has proved to be a valuable addition to the nuclear medicine infection imaging armamentarium. PET provides high-resolution 3-dimensional images of the whole body that facilitates precise localization of abnormalities. Localization is enhanced with PET/computed tomography. Fluorodeoxyglucose, for the most part, is exquisitely sensitive with a high negative predictive value. In general, the limiting factor of the test is specificity. However, there are some situations in which the limitation to the test is not low specificity but rather low sensitivity.

Nuclear imaging of inflammation: homing-associated molecules as targets

The golden standard in nuclear medicine imaging of inflammation is the use of autologous radiolabeled leukocytes. Although their diagnostic accuracy is precise, the preparation of the leukocytes is both laborious and potentially hazardous for laboratory personnel. Molecules involved in leukocyte migration (homing-associated molecules) could serve as targets for the development of imaging agents for inflammation. An excellent target would be a molecule that is absent or expressed at low levels in healthy tissues, but is present or upregulated at the sites of inflammation. In this paper, we will review the literature concerning the use of homing-associated molecules as imaging targets. We will especially concentrate on vascular adhesion protein-1 due to the promising results regarding its use as a target for the imaging of inflammation.

PET-MR imaging using a tri-modality PET/CT-MR system with a dedicated shuttle in clinical routine

Tri-modality PET/CT-MRI includes the transfer of the patient on a dedicated shuttle from one system into the other. Advantages of this system include a true CT-based attenuation correction, reliable PET-quantification and higher flexibility in patient throughput on both systems. Comparative studies of PET/MRI versus PET/CT are readily accomplished without repeated PET with a different PET scanner at a different time point. Additionally, there is a higher imaging flexibility based on the availability of three imaging modalities, which can be combined for the characterization of the disease. The downside is a somewhat higher radiation dose of up to 3 mSv with a low dose CT based on the CT-component, longer acquisition times and potential misalignment between the imaging components. Overall, the tri-modality PET/CT-MR system offers comparative studies using the three different imaging modalities in the same patient virtually at the same time, and may help to develop reliable attenuation algorithms at the same time.

The Role of Positron Emission Tomography in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD) are a group of pathological conditions characterized by chronic inflammation of the gastrointestinal tract, including Crohn's disease and ulcerative colitis. To date, imaging of IBD is based on several radiological techniques such as barium studies, magnetic resonance imaging, and computed tomography (CT). Endoscopy is the gold standard for the assessment of the large bowel and proximal small intestine in patients with IBD allowing the biopsy of the visualized bowel. Positron emission tomography (PET) and PET/CT with Fluorine-18-fluoro-2-deoxy-D-glucose (FDG) is a functional imaging method used to detect abnormalities in glucose metabolism in a variety of disorders. FDG accumulates mainly in tumours, but increased uptake and retention has been shown also in lesions with a high concentration of inflammatory cells, such as granulocytes and activated macrophages. Recent literature data demonstrate that FDG-PET and PET/CT may be useful noninvasive tools for identifying and localizing active IBD. In patients with an established diagnosis of IBD, FDG-PET and PET/CT may provide information about disease activity, location and extent of the disease within the intestinal tract, allowing early recognition of disease relapse and possible complications. Furthermore, these techniques may play a role in assessing the treatment response to medical therapy in patients with IBD.

The utility of 18F-FDG PET/CT for diagnosis and adjustment of therapy in patients with active chronic sarcoidosis

The purpose of this study was to assess the utility of (18)F-FDG PET/CT for detection of inflammation in granulomatous sites and management of patients with chronic sarcoidosis. The 3 specific aims were to assess differences between (18)F-FDG PET/CT and multidetector CT (MDCT) findings, to compare (18)F-FDG PET/CT results with serum levels of angiotensin-converting enzyme (ACE), and to determine whether (18)F-FDG PET/CT findings are associated with the decision to change therapy.

METHODS

We studied 90 sarcoidosis patients (mean age ± SD, 47 ± 12 y; 32 men and 58 women) with persistent symptoms who were referred for (18)F-FDG PET/CT evaluation to assess the extent of inflammation. They also underwent MDCT and measurement of serum ACE level. After the follow-up (12 ± 5 mo after (18)F-FDG PET/CT), the clinical status and changes in therapy were analyzed.

RESULTS

(18)F-FDG PET/CT detected inflammation in 74 patients (82%) (maximum standardized uptake value, 8.1 ± 3.9). MDCT was positive for sarcoidosis in 6 additional patients (80, 89%). The difference between the 2 methods was not significant (P = 0.238, McNemar test), and their agreement was fair (κ = 0.198). Although ACE levels were significantly higher in patients with positive than negative (18)F-FDG PET/CT results (P = 0.002, Mann-Whitney test), 38 patients (51%) with positive (18)F-FDG PET/CT results had normal ACE levels. The therapy was initiated or changed in 73 out of 90 patients (81%). Both univariate and multivariate logistic regression analyses indicated that positive (18)F-FDG PET/CT results were significantly (P < 0.001) associated with changes in therapy, with no contribution from age, sex, ACE level, CT results, or previous therapy.

CONCLUSION

Our results indicate that (18)F-FDG PET/CT is a useful adjunct to other diagnostic methods for detecting active inflammatory sites in chronic sarcoidosis patients with persistent symptoms, especially those with normal ACE levels. (18)F-FDG PET/CT proved advantageous for determining the spread of active disease throughout the body and influenced the decision to adjust the therapy.

Past and Present Scenario of Imaging Infection and Inflammation: A Nuclear Medicine Perspective

Nuclear medicine techniques provide potential non-invasive tools for imaging infections and inflammations in the body in a precise way. These techniques are further exploited by the use of radiopharmaceuticals in conjunction with imaging tests such as scintigraphy and positron emission tomography. Improved agents for targeting infection exploit the specific accumulation of radiolabeled compounds to understand the pathophysiologic changes involved in the inflammatory process and correlate them with other chronic illnesses. In the recent past, a wide variety of radiopharmaceuticals have been developed, broadly classified as specific radiopharmaceuticals and nonspecific radiopharmaceuticals. New developments in positron emission (leveraging 18F and 18fluorodeoxyglucose) and heterocyclic/peptide chemistry and radiochemistry are resulting in unique agents with high specific activity. Various approaches to visualizing infection and inflammation are presented in this review, in an integral manner, that give a clear view of the existing radiopharmaceuticals in clinical practice and those under development.

Antimicrobial peptides as infection imaging agents: better than radiolabeled antibiotics

Nuclear medicine imaging techniques offer whole body imaging for localization of number and site of infective foci inspite of limitation of spatial resolution. The innate human immune system contains a large member of important elements including antimicrobial peptides to combat any form of infection. However, development of antibiotics against bacteria progressed rapidly and gained popularity over antimicrobial peptides but even powerful antimicrobials failed to reduce morbidity and mortality due to emergence of mutant strains of bacteria resulting in antimicrobial resistance. Differentiation between infection and inflammation using radiolabeled compounds with nuclear medicine techniques has always been a dilemma which is still to be resolved. Starting from nonspecific tracers to specific radiolabeled tracers, the question is still unanswered. Specific radiolabeled tracers included antibiotics and antimicrobial peptides which bind directly to the bacteria for efficient localization with advanced nuclear medicine equipments. However, there are merits and demerits attributed to each. In the current paper, radiolabeled antibiotics and radiolabeled peptides for infection localization have been discussed starting with the background of primitive nonspecific tracers. Radiolabeled antimicrobial peptides have certain merits compared with labeled antibiotics which make them superior agents for localization of infective focus.

¹⁸F-FDG uptake by spleen helps rapidly predict the dose level after total body irradiation in a Tibetan minipig model

OBJECTIVES

To investigate whether (18)F- FDG uptake can be applied in dosimetry to facilitate the rapid and accurate evaluation of individual radiation doses after a nuclear accident.

METHODS

Forty-eight Tibetan minipigs were randomised into a control group (n = 3) and treatment groups (n = 45). (18)F-FDG combined positron-emission tomography and computed tomography (PET/CT) were carried out before total body irradiation (TBI) and at 6, 24 and 72 h after receiving TBI doses ranging from 1 to 11 Gy. Spleen tissues and blood samples were also collected for histological examination, apoptosis and blood analysis.

RESULTS

Mean standardised uptake values (SUVs) of the spleen showed significant differences between the experimental and the control groups. Spleen SUV at 6 h post-irradiation showed significant correlation with radiation dose; Spearman's correlation coefficient was 0.97 (P < 0.01). Histological observations showed that damage to the splenic lymphocyte became more severe with an increase in the radiation dose. Moreover, apoptosis was one of the major routes of splenic lymphocyte death, which was also confirmed by flow cytometry analysis.

CONCLUSIONS

In the Tibetan minipig model, radiation doses have a close relationship with the (18)F-FDG uptake of the spleen. This finding suggests that (18)F-FDG PET/CT may be useful for the rapid detection of individual radiation doses.

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

OBJECTIVE

(99m)Tc labeled hexamethylpropylene amine oxime (HMPAO) white blood cell (WBC) scintigraphy is a frequently used option for acute infection, particularly in pediatric patients. This scintigraphy is applied to detect sites of infection/inflammation in patients with fever of unknown origin, to find and follow up osteomyelitis, and to detect suspicion of acute appendicitis. The aim of this retrospective study was to evaluate the value of (99m)Tc-HMPAO labeled WBC scintigraphy in pediatric patients.

MATERIAL AND METHODS

The study was conducted between January 2006 and December 2008 and included 13 patients (5 boys, 8 girls; mean age 6.9±6.2 years). Those patients who had suspicion of bone infection (n=7), fever of unknown origin (n=3), and suspicion of acute appendicitis (n=3) were evaluated retrospectively. (99m)Tc-HMPAO labeled WBC scintigraphy imaging was performed to all patients. Diagnosis was done according to operation and pathological results or clinical follow-up.

RESULTS

(99m)Tc-HMPAO labeled WBC scintigraphy has been found to be true positive in 6 cases, true negative in 6 cases, and false negative in one patient who had fewer unknown origin. The false negative case has been found to have encephalitis with MRI.

CONCLUSION

Leukocyte scintigraphy has been described as a useful diagnostic tool in the diagnosis of suspicion of bone infection, fever of unknown origin and suspicion of acute appendicitis. (99m)Tc-HMPAO labeled WBC scintigraphy is a rapid and very accurate method for detecting those pathologies. Our results showed that WBC scintigraphy might be reliably used for diagnosis of suspected bone infection and acute appendicitis, fever of unknown origin, and acute appendicitis, in pediatric patient population.

CONFLICT OF INTEREST

None declared.

Lung cancer in HIV Infection

Lung cancer is the most prevalent non-AIDS-defining malignancy in the highly active antiretroviral therapy era. Smoking plays a significant role in the development of HIV-associated lung cancer, but the cancer risk is two to four times greater in HIV-infected persons than in the general population, even after adjusting for smoking intensity and duration. Lung cancer is typically diagnosed a decade or more earlier among HIV-infected persons (mean age, 46 years) compared to those without HIV infection. Adenocarcinoma is the most common histological subtype, and the majority of patients are diagnosed with locally advanced or metastatic carcinoma. Because pulmonary infections are common among HIV-infected individuals, clinicians may not suspect lung cancer in this younger patient population. Surgery with curative intent remains the treatment of choice for early-stage disease. Although there is increasing experience in using radiation and chemotherapy for HIV-infected patients who do not have surgical options, there is a need for prospective studies because this population is frequently excluded from participating in cancer trials. Evidence-based treatments for smoking-cessation with demonstrated efficacy in the general population must be routinely incorporated into the care of HIV-positive smokers.

Mesenchymal bone marrow cell therapy in a mouse model of chagas disease. Where do the cells go?

BACKGROUND

Chagas disease, resulting from infection with the parasite Trypanosoma cruzi (T. cruzi), is a major cause of cardiomyopathy in Latin America. Drug therapy for acute and chronic disease is limited. Stem cell therapy with bone marrow mesenchymal cells (MSCs) has emerged as a novel therapeutic option for cell death-related heart diseases, but efficacy of MSC has not been tested in Chagas disease.

METHODS AND RESULTS

We now report the use of cell-tracking strategies with nanoparticle labeled MSC to investigate migration of transplanted MSC in a murine model of Chagas disease, and correlate MSC biodistribution with glucose metabolism and morphology of heart in chagasic mice by small animal positron emission tomography (microPET). Mice were infected intraperitoneally with trypomastigotes of the Brazil strain of T. cruzi and treated by tail vein injection with MSC one month after infection. MSCs were labeled with near infrared fluorescent nanoparticles and tracked by an in vivo imaging system (IVIS). Our IVIS results two days after transplant revealed that a small, but significant, number of cells migrated to chagasic hearts when compared with control animals, whereas the vast majority of labeled MSC migrated to liver, lungs and spleen. Additionally, the microPET technique demonstrated that therapy with MSC reduced right ventricular dilation, a phenotype of the chagasic mouse model.

CONCLUSIONS

We conclude that the beneficial effects of MSC therapy in chagasic mice arise from an indirect action of the cells in the heart rather than a direct action due to incorporation of large numbers of transplanted MSC into working myocardium.

PET imaging of patients with non-small cell lung cancer employing an EGF receptor targeting drug as tracer

Background:

We have previously developed ¹¹C-erlotinib as a new positron emission tomography (PET) tracer and shown that it accumulates in epidermal growth factor receptor (EGFR)-positive lung cancer xenografts in mice. Here, we present a study in patients with non-small cell lung cancer (NSCLC) investigating the feasibility of ¹¹C-erlotinib PET as a potential method for the identification of lung tumours accumulating erlotinib.

Methods:

Thirteen patients with NSCLC destined for erlotinib treatment were examined by contrast-enhanced computed tomography (CT), ¹¹C-erlotinib PET/low-dose CT and ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) PET/low-dose CT before start of the erlotinib treatment. After 12 weeks treatment, they were examined by ¹⁸F-FDG PET/contrast-enhanced CT for the assessment of clinical response.

Results:

Of the 13 patients included, 4 accumulated ¹¹C-erlotinib in one or more of their lung tumours or lymph-node metastases. Moreover, ¹¹C-erlotinib PET/CT identified lesions that were not visible on ¹⁸F-FDG PET/CT. Of the four patients with accumulation of ¹¹C-erlotinib, one died before follow-up, whereas the other three showed a positive response to erlotinib treatment. Three of the nine patients with no accumulation died before follow-up, four showed progressive disease while two had stable disease after 12 weeks of treatment.

Conclusion:

Our data show a potential for ¹¹C-erlotinib PET/CT for visualizing NSCLC lung tumours, including lymph nodes not identified by ¹⁸F-FDG PET/CT. Large clinical studies are now needed to explore to which extent pre-treatment ¹¹C-erlotinib PET/CT can predict erlotinib treatment response.

Extra-pulmonary manifestations of sarcoidosis

Although, the diagnosis and evaluation of sarcoidosis has traditionally remained confined to the chest, its multi-system nature has been widely recognized. Radiological features of pulmonary sarcoidosis are well known but extra-pulmonary manifestations can produce a plethora of non-specific imaging findings that can affect subcutaneous tissue, and the neurological, cardiac, gastrointestinal, urological, liver, spleen, and skeletal systems. In the literature, there are various case reports and specific system reviews but there are few reviews that encompass all the extra-pulmonary manifestations. In this paper, we comprehensively review the imaging features of extra-pulmonary sarcoidosis with characteristic features as well as atypical presentations. In addition, we discuss the emerging role of nuclear medicine in sarcoidosis.

Bone marrow necrosis secondary to imatinib usage, mimicking spinal metastasis on magnetic resonance imaging and FDG-PET/CT

Imatinib mesylate has become the treatment of choice for gastrointestinal stromal tumors (GISTs) and has made a revolutionary impact on survival rates. Bone marrow necrosis is a very rare adverse event in malignant GIST. Bone metastases are also rarely encountered in the setting of this disease. The authors report on a patient with malignant GIST who developed a bone lesion, mimicking spinal metastasis on both MR imaging and FDG-PET/CT. Corpectomy and anterior fusion was performed, but the pathology report was consistent with bone marrow necrosis. Radiological and clinical similarities made the distinction between metastasis and bone marrow necrosis challenging for the treating physicians. Instead of radical surgical excision, more conservative methods such as percutaneous or endoscopic bone biopsies may be more useful for pathological confirmation, even though investigations such as MR imaging and FDG-PET/CT indicate metastatic disease.

Impact of 18F-FDG PET scan on the prevalence of benign thoracic lesions at surgical resection

OBJECTIVE: The main utility of 18-fluorodeoxyglucose positron emission tomography (FDG-PET) lies in the staging of lung cancer. However, it can also be used to differentiate indeterminate pulmonary lesions, but its impact on the resection of benign lesions at surgery is unknown. The aim of this study was to compare the prevalence of benign lesions at thoracotomy carried out for suspected lung cancer, before and after the introduction of PET scanning in a large thoracic surgical centre. MATERIALS AND METHODS: We reviewed our prospectively recorded surgical database for all consecutive patients undergoing thoracotomy for suspected or proven lung cancer and compared the prevalence of benign lesions in 2 consecutive 2-year groups, before (group I) and after (group II) the introduction of FDG-PET scan respectively. RESULTS: Surgical resection was performed on 1233 patients during the study period. The prevalence of benign lesions at surgery in groups I and II was similar (44/626 and 41/607, both 7%), and also in group II between those who underwent FDG-PET scan and the remainder (21/301 and 20/306 respectively, both 7%). In group II, of the 21 patients with benign lesions, who underwent FDG-PET, 19 had a false positive scan (mean standardised uptake value 5.3 [range 2.6-12.7]). Of these, 13 and 4 patients respectively had non-diagnostic bronchoscopy and percutaneous transthoracic lung biopsy pre thoracotomy. There was no difference in the proportion of different benign lesions resected between group I and those with FDG-PET in group II. CONCLUSION: The introduction of FDG-PET scanning has not altered the proportion of patients undergoing thoracotomy for ultimately benign lesions, mainly due to the avidity for the isotope of some non-malignant lesions. Such false positive results need to be considered when patients with unconfirmed lung cancer are contemplated for surgical resection.

Causes and imaging features of false positives and false negatives on F-PET/CT in oncologic imaging

BACKGROUND: 18F-FDG is a glucose analogue that is taken up by a wide range of malignancies. 18F-FDG PET-CT is now firmly established as an accurate method for the staging and restaging of various cancers. However, 18F-FDG also accumulates in normal tissue and other non-malignant conditions, and some malignancies do not take up F18-FDG or have a low affinity for the tracer, leading to false-positive and false-negative interpretations. METHODS: PET-CT allows for the correlation of two separate imaging modalities, combining both morphological and metabolic information. We should use the CT to help interpret the PET findings. In this article we will highlight specific false-negative and false-positive findings that one should be aware of when interpreting oncology scans. RESULTS: We aim to highlight post-treatment conditions that are encountered routinely on restaging scans that can lead to false-positive interpretations. We will emphasise the importance of using the CT component to help recognise these entities to allow improved diagnostic accuracy. CONCLUSION: In light of the increased use of PET-CT, it is important that nuclear medicine physicians and radiologists be aware of these conditions and correlate the PET and CT components to avoid misdiagnosis, over staging of disease and unnecessary biopsies.

Inflammatory activity assessment by F18 FDG-PET/CT in persistent symptomatic sarcoidosis

BACKGROUND

Establishing inflammatory activity in sarcoidosis patients with persistent disabling symptoms is important. Whole body F(18)-FDG PET/CT (PET) appeared to be a sensitive method to detect inflammatory activity in newly diagnosed symptomatic sarcoidosis. The aim was to assess the presence of inflammatory activity using PET in sarcoidosis patients with unexplained persistent disabling symptoms and the association between PET findings and serological inflammatory markers.

METHODS

Sarcoidosis patients who underwent a PET between June 2005 and June 2010 (n = 89), were retrospectively included. All PET scans were examined and positive findings were classified as thoracic and/or extrathoracic. As serological markers of inflammatory activity angiotensin-converting enzyme (ACE), soluble interleukin-2 receptor (sIL-2R), and neopterin were considered.

RESULTS

In 65/89 (73%) of the studied patients PET was positive, 52 of them (80%) had serological signs of inflammatory activity. In 14/15 patients with a Chest X-ray stage IV PET was positive. In 80% of the PET positive patients extrathoracic inflammatory activity was found. Sensitivity of combined serological inflammatory markers for the presence of inflammatory activity as detected by PET was 80%, specificity 100%, positive predictive value 100%, negative predictive value 65%.

CONCLUSIONS

The majority of sarcoidosis patients with persistent disabling symptoms, even those with radiological stage IV, had PET positive findings with remarkably 80% extrathoracic lesions. In 20% PET was positive without signs of serological inflammatory activity. PET appeared to be of additional value to assess inflammatory activity in patients with persistent symptoms in the absence of signs of serological inflammatory activity and to detect extrathoracic lesions.

PET scanning in sarcoidosis

Sarcoidosis is a multisystem granulomatous disorder that most commonly presents with pulmonary involvement. The diagnosis is suggested on the basis of clinical and radiologic manifestations and is supported by the histological demonstration of noncaseating granulomas in affected tissues. Different imaging modalities, including chest radiography, X-rays, computed tomography, magnetic resonance imaging, and (67) Ga scintigraphy are currently employed to help diagnose and help plan treatment strategy in sarcoidosis patients. Here, we discuss the potential role of positron emission tomography in the diagnosis, assessment of disease activity, and management of patients with sarcoidosis. We also point out some of the limitations of this technique.

(18)F-FDG PET/CT in a rare case of Stewart-Treves syndrome: future implications and diagnostic considerations

BACKGROUND

The aim of this article is to illustrate the possible applications of (18)F-fluorodeoxyglucose positron emission tomography/computer tomography ((18)F-FDG PET/CT) in chronic extremity lymphedema and its complications.

METHODS AND RESULTS

(18)F-FDG PET/CT findings in a rare case of Stewart-Treves Syndrome (STS), angiosarcoma secondary to chronic extremity lymphedema, are presented. Lymphedema of the extremities is a debilitating disease characterized by chronic swelling due to interstitial edema caused by insufficient lymphatic drainage capacity. Progression with skin thickening, subcutaneous fibrosis, and increased adipose tissue volume is common. Chronic inflammation has been suggested as a key pathophysiologic component. STS is a rare complication with a very poor prognosis; however, early diagnosis and radical treatment is associated with increased survival. Thus, accurate pretreatment staging is paramount. (18)F-FDG PET/CT is highly sensitive in detecting increased glucose metabolism as seen in many types of cancer and inflammation. The role of (18)F-FDG PET/CT in the management of lymphedema and its complications has to our knowledge yet to be described. This case documents high (18)F-FDG uptake in STS, but is at the same time an example of the low specificity of this imaging modality.

CONCLUSIONS

We suggest that (18)F-FDG PET/CT has the potential to become an important tool in the staging and treatment planning of Stewart-Treves syndrome. Furthermore, (18)F-FDG-accumulation may be a sensitive tool in detecting low grade inflammation in the skin and subcutis, which has been suggested to cause tissue remodeling in lymphedema progression. However, further studies are needed to elucidate this theory.

[Prolonged fever: specific issues in the young adult population]

Early studies on prolonged fever date back to the 1960s. Fifty years later, prolonged unexplained fever remains a diagnostic challenge to the general internists. Although the aetiologies of prolonged fevers have not changed much in the general population, the distribution between the various causes is not the same anymore. A regular decrease in infectious and neoplastic causes is noticed whatever the age. Prolonged fevers related to inflammatory disorders and fevers that remain of unknown origin still represent approximately 30 to 50% of the cases. In the young adult population, as in the older patients, prolonged fevers can be attributed to four groups: infection, inflammation, neoplasic and other aetiologies (including drug-related fevers). In the young adult population, the management of prolonged fever presents some specific issues that are the purpose of this review coupled with our own experience. The prognosis of undiagnosed prolonged fever is usually favourable, as a life-threatening aetiology is exceptionally diagnosed during the follow-up if the initial management was complete and accurate.

Osteomyelitis of the long bones

Long bone osteomyelitis presents a variety of challenges to the physician. The severity of the disease is staged depending upon the infection's particular features, including its etiology, pathogenesis, extent of bone involvement, duration, and host factors particular to the individual patient (infant, child, adult, or immunocompromised). Long bone osteomyelitis may be either hematogenous or caused by a contiguous spread of infection. A single pathogenic organism is almost always recovered from the bone in hematogenous osteomyelitis; Staphylococcus aureus is the most common organism isolated. A variety of multidrug-resistant organisms of bacteria continue to be a source of concern in arresting infection. The primary weapons to treat these infections are culture-specific antibiotics, aggressive debridement, muscle flaps, and bone grafts. This article offers a basic review of the classification, etiology, epidemiology, pathogenesis, and treatment of long bone osteomyelitis.

Review of Physiologic and Pathophysiologic Sources of Fluorodeoxyglucose Uptake in the Chest Wall on PET

The chest wall can be defined as the osseous and soft tissue structures that form the outer framework of the thorax and move during breathing. Topics discussed in this article include physiologic uptake of fluorodeoxyglucose, benign diseases of the chest wall, and malignant tumors of the chest wall.

Functional imaging of infection: conventional nuclear medicine agents and the expanding role of 18-F-FDG PET

A growing body of literature suggests that 18-fluorine fluorodeoxyglucose positron emission tomography ((18)F-FDG PET), particularly when combined with CT, is a useful tool for the detection of infectious and inflammatory disease processes. This article will briefly review the data to date on the use of FDG PET in diagnosing musculoskeletal infections and fever of unknown origin, comparing it to conventional scintigraphic techniques in both adults and, when available, in children.

Nano-based theranostics for chronic obstructive lung diseases: challenges and therapeutic potential

The major challenges in the delivery and therapeutic efficacy of nano-delivery systems in chronic obstructive airway conditions are airway defense, severe inflammation and mucous hypersecretion. Chronic airway inflammation and mucous hypersecretion are hallmarks of chronic obstructive airway diseases, including asthma, COPD (chronic obstructive pulmonary disease) and CF (cystic fibrosis). Distinct etiologies drive inflammation and mucous hypersecretion in these diseases, which are further induced by infection or components of cigarette smoke. Controlling chronic inflammation is at the root of treatments such as corticosteroids, antibiotics or other available drugs, which pose the challenge of sustained delivery of drugs to target cells or tissues. In spite of the wide application of nano-based drug delivery systems, very few are tested to date. Targeted nanoparticle-mediated sustained drug delivery is required to control inflammatory cell chemotaxis, fibrosis, protease-mediated chronic emphysema and/or chronic lung obstruction in COPD. Moreover, targeted epithelial delivery is indispensable for correcting the underlying defects in CF and targeted inflammatory cell delivery for controlling other chronic inflammatory lung diseases. We propose that the design and development of nano-based targeted theranostic vehicles with therapeutic, imaging and airway-defense penetrating capability, will be invaluable for treating chronic obstructive lung diseases. This paper discusses a novel nano-theranostic strategy that we are currently evaluating to treat the underlying cause of CF and COPD lung disease.

Necrotizing Cervical Lymphadenitis Caused by Mycobacterium simiae in an HIV-Positive Patient: Imaging with (18)F-FDG PET/CT

Mycobacterium simiae (M. simiae) is an opportunistic pathogen rarely associated with human disease, although in recent years M. simiae has been detected with increasing frequency in human immunodeficiency virus (HIV)-infected patients, usually causing disseminated infection with fever, diarrhea and weight loss. We report the case of an HIV-positive man, who was referred for an (18)F-FDG PET/CT to evaluate a solitary pulmonary nodule. The PET/CT showed incidental large necrotic cervical lymph nodes, compatible with necrotizing cervical lymphadenitis. Biopsy and culture of one of the affected lymph nodes were positive for M. simiae. We present the first report of (18)F-FDG PET/CT imaging of an infectious process caused by M. simiae in humans.

Molecular imaging of influenza and other emerging respiratory viral infections

Research on the pathogenesis and therapy of influenza and other emerging respiratory viral infections would be aided by methods that directly visualize pathophysiologic processes in patients and laboratory animals. At present, imaging of diseases, such as swine-origin H1N1 influenza, is largely restricted to chest radiograph and computed tomography (CT), which can detect pulmonary structural changes in severely ill patients but are more limited in characterizing the early stages of illness, differentiating inflammation from infection or tracking immune responses. In contrast, imaging modalities, such as positron emission tomography, single photon emission CT, magnetic resonance imaging, and bioluminescence imaging, which have become useful tools for investigating the pathogenesis of a range of disease processes, could be used to advance in vivo studies of respiratory viral infections in patients and animals. Molecular techniques might also be used to identify novel biomarkers of disease progression and to evaluate new therapies.

Fatal hemorrhage induced by subtilase cytotoxin from Shiga-toxigenic Escherichia coli

Subtilase cytotoxin (SubAB) is an AB(5) type toxin produced by a subset of Shiga-toxigenic Escherichia coli. The A subunit is a subtilase-like serine protease and cleaves an endoplasmic reticulum chaperone BiP. The B subunit binds to a receptor on the cell surface. Although SubAB is lethal for mice, the cause of death is not clear. In this study, we demonstrate in mice that SubAB induced small bowel hemorrhage and a coagulopathy characterized by thrombocytopenia, prolonged prothrombin time and activated partial thromboplastin time. SubAB also induced inflammatory changes in the small intestine as detected by ¹⁸F-fluoro-2-deoxy-d-glucose positron emission tomography imaging and histochemical analysis. Using RT-PCR and ELISA, SubAB was shown to increase interleukin-6 in a time-dependent manner. Thus, our results indicate that death in SubAB-treated mice may be associated with severe inflammatory response and hemorrhage of the small intestine, accompanied by coagulopathy and IL6 production.

Human immunodeficiency virus-associated primary lung cancer in the era of highly active antiretroviral therapy: a multi-institutional collaboration

BACKGROUND

Human immunodeficiency virus (HIV)-infected individuals are at increased risk for primary lung cancer (LC). We wished to compare the clinicopathologic features and treatment outcome of HIV-LC patients with HIV-indeterminate LC patients. We also sought to compare behavioral characteristics and immunologic features of HIV-LC patients with HIV-positive patients without LC.

PATIENTS AND METHODS

A database of 75 HIV-positive patients with primary LC in the HAART era was established from an international collaboration. These cases were drawn from the archives of contributing physicians who subspecialize in HIV malignancies. Patient characteristics were compared with registry data from the Surveillance Epidemiology and End Results program (SEER; n = 169,091 participants) and with HIV-positive individuals without LC from the Adult and Adolescent Spectrum of HIV-related Diseases project (ASD; n = 36,569 participants).

RESULTS

The median age at HIV-related LC diagnosis was 50 years compared with 68 years for SEER participants (P < .001). HIV-LC patients, like their SEER counterparts, most frequently presented with stage IIIB/IV cancers (77% vs. 70%), usually with adenocarcinoma (46% vs. 47%) or squamous carcinoma (35% vs. 25%) histologies. HIV-LC patients and ASD participants had comparable median nadir CD4+ cell counts (138 cells/µL vs. 160 cells/µL). At LC diagnosis, their median CD4+ count was 340 cells/µL and 86% were receiving HAART. Sixty-three HIV-LC patients (84%) received cancer-specific treatments, but chemotherapy-associated toxicity was substantial. The median survival for both HIV-LC patients and SEER participants with stage IIIB/IV was 9 months.

CONCLUSION

Most HIV-positive patients were receiving HAART and had substantial improvement in CD4+ cell count at time of LC diagnosis. They were able to receive LC treatments; their tumor types and overall survival were similar to SEER LC participants. However, HIV-LC patients were diagnosed with LC at a younger age than their HIV-indeterminate counterparts. Future research should explore how screening, diagnostic and treatment strategies directed toward the general population may apply to HIV-positive patients at risk for LC.

Osteonecrosis in an adolescent with non-Hodgkin lymphoma resembling a new metastatic lesion on (18)F-FDG PET/CT

Osteonecrosis may result from complications in a variety of pediatric diseases and, in the early stages of healing, may be characterized by inflammation and hyperemia. While traditionally assessed by bone scintigraphy, osteonecrosis may also present upon [F-18]2-fluoro-2-deoxyglucose PET/CT. Differentiation of osteonecrosis from metastatic lesions is important to ensure accurate disease staging and to avoid unnecessary imaging and biopsy. Osteonecrosis typically presents at the interface of weight-bearing joints after prolonged chemotherapy with corticosteroid administration, although prevalence is greater in adults than in children. We describe a case of unilateral osteonecrosis in the tibia of an adolescent lymphoma patient, which first presented on FDG-PET/CT imaging after 2 months of combination chemotherapy with corticosteroid administration. This report should aid in recognizing rapid-onset osteonecrosis with atypical sites of involvement in pediatric patients.