Fluorine 18 fluorodeoxyglucose positron emission tomography in the diagnosis and follow-up of three patients with vasculitis

The "Ant-farm"-like Appearance of Restricted Lower Limb Vasculitis on Fluorodeoxyglucose-positron Emission Tomography

Restricted lower limb vasculitis is a type of localized muscle vasculitis limited to the lower limbs. The usefulness of fluorodeoxyglucose-positron emission tomography (FDG-PET) for the diagnosis of this entity has not yet been reported. We herein report three patients with a fever and persistent lower limb pain. FDG-PET revealed linear and patchy FDG uptakes in their lower limbs. Combined with magnetic resonance imaging and histological findings, they were diagnosed with lower limb vasculitis. Linear and patchy FDG uptakes are considered to reflect the presence of muscle vasculitis. The characteristic "ant-farm"-like FDG-PET images can be a diagnostic clue for the currently overlooked vasculitis.

Imaging features of 18F-FDG PET/CT in different types of systemic vasculitis

OBJECTIVE

To analyze ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) image features in different types of systemic vasculitis and explore its classification and diagnostic significance for systemic vasculitis.

METHODS

Clinical and ¹⁸F-FDG PET/CT imaging data of 71 consecutive patients (34 males, 37 females, mean age 53.4 ± 20.5 years) who were examined at Peking University People's Hospital and diagnosed with active systemic vasculitis were analyzed retrospectively, and ¹⁸F-FDG PET/CT imaging features of different types of systemic vasculitis were analyzed in patients with positive ¹⁸F-FDG PET/CT findings.

RESULTS

The proportions of large-, medium-, small-, and variable-vessel vasculitis were 36.6%, 15.5%, 29.6%, and 18.3%, respectively, and 93.0% of patients had positive findings on PET/CT, of which 63.6% had vascular involvement and 53.0% had extravascular involvement. Different types of vasculitis had different lesion sites, distribution patterns, and morphological changes. Large-vessel vasculitis mainly affected the aorta and its branches to the head and neck. Takayasu arteritis showed segmental involvement of the vascular and morphological changes of the vessel wall. Giant cell arteritis manifested as diffuse vascular involvement, which usually involved the temporal artery and the abdominal aorta and its branches. Medium-vessel vasculitis polyarteritis nodosa manifested as diffuse vascular involvement of both lower extremities. Small-vessel vasculitis anti-neutrophil cytoplasmic antibody-associated vasculitis manifested as granulomatous inflammation of extravascular regions. Variable-vessel vasculitis Behcet's disease involved both blood vessels and extravascular regions.

CONCLUSION

Different types of systemic vasculitis show characteristic manifestations in ¹⁸F-FDG PET/CT images, which may be useful for the diagnosis and classification of systemic vasculitis.

KEY POINTS

• Determining an early diagnosis of systemic vasculitis may be challenging. • Different types of systemic vasculitis show characteristic manifestations in ¹⁸F-FDG PET/CT images. • ¹⁸F-FDG PET/CT may be useful for the diagnosis and classification of systemic vasculitis.

Assessment of Therapy Response by FDG PET in Infection and Inflammation

Positron emission tomography (PET) is a well-known imaging modality in assessing the treatment response to chemotherapy or radiotherapy in various malignancies. A systematic review of the literature reveals a few publications reporting evaluation of the treatment response in benign conditions using PET/computed tomography. PET holds a promising future role in the follow-up of inflammatory or infectious diseases. In this article, [(18)F]Fluorodeoxyglucose PET as a tool in the evaluation, treatment, and follow-up of infectious and inflammatory diseases is discussed.

Polyarteritis nodosa: A contemporary overview

Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis predominantly targeting medium-sized arteries. PAN is a rare form of vasculitis, and the precise frequency of this disease is difficult to determine. The major environmental factor associated with PAN is HBV infection. The pathogenesis of "idiopathic PAN" remains enigmatic, although the clinical responses to immunosuppressive therapy support the concept that immunological mechanisms play an active pathogenic role. The spectrum of disease ranges from involving a single organ to polyvisceral failure. Any organ might be affected; however, for reasons that are not understood, PAN does not affect the lungs. In addition to the systemic idiopathic form, called "idiopathic generalized PAN," there are 2 clinical variants of this disease: "cutaneous PAN" and "hepatitis B virus (HBV)-associated PAN". Diagnosis requires the integration of clinical, angiographic, and biopsy findings. The overall prognosis of this disease has been improved in recent decades, primarily reflecting early diagnosis and more effective treatments. Idiopathic generalized PAN should be treated with a combination of glucocorticoids and cyclophosphamide. The treatment of HBV-associated PAN involves a different approach, centered on the use of an antiviral agent to control the infection. The therapy for cutaneous PAN requires a less aggressive approach based on the administration of non-steroidal anti-inflammatory drugs over short periods of time.

[Systemic vasculitic neuropathy diagnosed by means of (18)F-FDG PET CT]

We report a 43-year-old man experienced numbness in the distal portion of both legs, which progressed over following two months. Neurological examination showed hypesthesia and muscle weakness in the distal portion of both legs. No abnormal findings were seen on blood test and whole-body contrast enhanced computed tomography (CT). Histopathological findings of the sural nerve and the peroneus brevis muscle showed decreased myelinated nerve fibers with scattered myelin ovoids, vascular occlusion in the epineurium, and inflammatory cell around the arteriole in the muscle bundle. These findings suggested falling in the category as non-systemic vasculitic neuropathy (NSVN). (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) revealed the increase of FDG uptake in the rectum. Inflammatory cell infiltration was found around the arteriole with fibrinoid necrosis in the histopathological specimen of the rectal mucosal biopsy. This result represented the diagnosis as systemic vasculitis. The diagnosis of NSVN may depend on the sensitivity of diagnostic procedure, and (18)F-FDG PET CT might be a useful tool to detect small or medium-sized vasculitis.

Radionuclide imaging of inflammation and infection in the acute care setting

Although infection may be suggested by signs and symptoms such as fever, pain, general malaise, and abnormal laboratory results, imaging tests often are used to confirm its presence. Morphologic imaging tests identify structural alterations of tissues or organs that result from a combination of microbial invasion and the inflammatory response of the host. Functional imaging studies use minute quantities of radioactive material, which are taken up directly by cells, tissues, and organs, or are attached to substances that subsequently migrate to the region of interest. Bone scintigraphy is extremely sensitive and can be positive within 2 days after the onset of symptoms. With an accuracy of more than 90%, 3-phase bone scintigraphy is the radionuclide procedure of choice for diagnosing osteomyelitis in unviolated bone. In patients with acute renal failure, gallium imaging facilitates the differentiation of acute interstitial nephritis from acute tubular necrosis. Gallium imaging also is useful in the evaluation of pulmonary infections and inflammation. Many opportunistic infections affect the lungs, and a normal gallium scan of the chest excludes infection with a high degree of certainty, especially when the chest x-ray is negative. In the human immunodeficiency virus positive patient, lymph node uptake usually is associated with mycobacterial disease or lymphoma. Focal pulmonary parenchymal uptake suggests bacterial pneumonia. Diffuse pulmonary uptake suggests an opportunistic pneumonia. Gallium imaging provides useful information about other acute respiratory conditions, including radiation pneumonitis and hypersensitivity pneumonitis. In vitro labeled leukocyte imaging with indium-111 and technetium-99m labeled leukocytes is useful in various acute care situations. The test facilitates the differentiation of normal postoperative changes from infection and is useful for diagnosing prosthetic vascular graft infection. In inflammatory bowel disease, labeled leukocyte imaging is useful for initial screening, monitoring treatment response, detecting recurrent disease, and evaluating patients with discordant physical presentation and laboratory test results. Labeled leukocyte imaging, combined with bone marrow scintigraphy accurately diagnoses complicating osteomyelitis. Fluorine-18-fluorodeoxyglucose, imaging is rapidly completed and provides high-resolution images. This test is especially valuable in patients with fever of unknown origin, patients in septic shock, and mechanically ventilated patients suspected of harboring infection. Fluorine-18-fluorodeoxyglucose imaging also shows promise in inflammatory bowel disease.

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.

A Rationale for the Use of F18-FDG PET/CT in Fever and Inflammation of Unknown Origin

This review focuses on the diagnostic value of hybrid F18-FDG Positron Emission Tomography/Computerized tomography (PET/CT) in fever of unknown origin (FUO) and inflammation of unknown origin (IUO). Due to the wide range of possible causes both FUO and IUO remain a clinical challenge for both patients and physicians. In addition, the aetiology of IUO shows the same variation in diseases as the FUO spectrum and probably requires the same diagnostic approach as FUO. There are numerous historically used diagnostic approaches incorporating invasive and non-invasive, and imaging techniques, all with relative high specificity but limited sensitivity. This hampers the generalization of these diagnostic approaches. However, recently published reports show that F18-FDG PET/CT in FUO and IUO has a high sensitivity and a relative non-specificity for malignancy, infection and inflammation. This makes F18-FDG PET/CT an ideal diagnostic tool to start the diagnostic process and to guide subsequent focused diagnostic approaches with higher specificity. In addition, F18-FDG PET/CT has a relative high negative predictive value. Therefore F18 FDG PET/CT should be incorporated in the routine diagnostic work-up of patients with FUO and IUO, preferably at an early stage in the diagnostic process.

The impact of 18F-FDG PET on the management of patients with suspected large vessel vasculitis

PURPOSE

We aimed to assess the impact of (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) on the management of patients with suspected large vessel vasculitis.

METHODS

An international expert panel determined diagnoses and clinical management in patients with suspected large vessel vasculitis, with and without the results of (18)F-FDG PET, respectively. The accuracy of the clinical diagnosis and the resulting clinical management with and without the (18)F-FDG PET results were compared using logistic regression models.

RESULTS

The analysis included 30 patients referred to a tertiary care centre with large vessel vasculitis and 31 controls. (18)F-FDG PET had an overall sensitivity of 73.3% [95% confidence interval (CI) 54.1-87.7%], a specificity of 83.9% (95% CI 66.3-94.5%), a positive predictive value of 81.5% (95% CI 61.9-93.7%) and a negative predictive value of 76.5% (95% CI 58.8-89.3%). The diagnostic accuracy of (18)F-FDG PET was higher in patients not receiving immunosuppressive drugs (93.3 vs 64.5%, p = 0.006). Taken in context with other available diagnostic modalities, the addition of (18)F-FDG PET increased the clinical diagnostic accuracy from 54.1 to 70.5% (p = 0.04). The addition of (18)F-FDG PET increased the number of indicated biopsies from 22 of 61 patients (36.1%) to 25 of 61 patients (41.0%) and changed the treatment recommendation in 8 of 30 patients (26.7%) not receiving immunosuppressive medication and in 7 of 31 patients (22.6%) receiving immunosuppressive medication.

CONCLUSION

(18)F-FDG PET is a sensitive and specific imaging tool for large vessel vasculitis, especially when performed in patients not receiving immunosuppressive drugs. It increases the overall diagnostic accuracy and has an impact on the clinical management in a significant proportion of patients.

[Giant cell arteritis-related upper/lower limb vasculitis]

Upper/lower limb vasculitis has been considered an uncommon manifestation of giant cell arteritis, occurring in 3 to 16% of patients. Upper/lower limb vasculitis is still associated with significant morbidity, leading to limb/toe amputation in 5.6 to 15.8% of patients. Yearly clinical vascular examination should be performed systematically to screen upper/lower limb vasculitis at an early stage in patients with giant cell arteritis. Duplex ultrasound has proved to be a reliable non-invasive imaging method for detecting arterial stenoses of the upper/lower limbs in patients with giant cell arteritis. Patients with giant cell arteritis-related upper/lower limb vasculitis should undergo routine investigations to detect underlying aortic complications, concomitant aortic localizations being encountered in more than 50% of cases. Prednisone is the first-line therapy at an initial dose of 0.7-1 mg/kg daily. Prevention of platelet aggregation with low-dose aspirin is potentially effective in preventing ischemic complications of GCA. The indication of surgical therapy should be based on the severity of giant cell arteritis-related upper/lower limb clinical symptoms to avoid unnecessary morbidity in the course of interventional therapy.

Long-term follow-up of upper and lower extremity vasculitis related to giant cell arteritis: a series of 36 patients

We conducted this retrospective study to determine the prevalence of giant cell arteritis (GCA) in patients exhibiting nonatherosclerotic upper and/or lower extremity arterial involvement and to evaluate the clinical features and long-term outcome of those patients.From January 1997 to March 2008, 36 consecutive patients in the Department of Internal Medicine at the University of Rouen medical center received a diagnosis of symptomatic upper/lower extremity vasculitis related to GCA. In the 36 patients, upper/lower extremity vasculitis preceded the initial GCA diagnosis in 7 patients (19.4%), it was identified in association with GCA in 13 patients (36.1%), and it developed after the onset of GCA in the remaining 16 patients (44.4%). GCA clinical manifestations were severe resulting in ischemic complications of the extremities in 10 patients (27.8%). GCA-related large-vessel involvement was located in the upper extremity alone in 21 patients (58.3%), the lower extremity alone in 7 patients (19.4%), and both the upper and lower extremities in 8 patients (22.2%).Arterial involvement in GCA patients with upper extremity vasculitis was distributed in the subclavian (55.6%), axillary (47.2%), and brachial (22.2%) arteries. In patients with lower extremity vasculitis, involvement included the internal iliac artery (11.1%), common femoral artery (13.9%), superficial femoral artery (33.3%), deep femoral artery (5.6%), and popliteal and anterior tibial arteries (5.6%). Aortic localizations were common in GCA patients with upper/lower extremity vasculitis (68.9% of cases).All patients were given steroid therapy at a median daily dose of 1 mg/kg initially. Reconstructive study was performed in 10 patients (27.8%): venous bypass graft (n = 6), angioplasty (n = 1), thromboendarteriectomy (n = 2), or thrombectomy (n = 1); 2 other patients with extremity ischemia underwent amputation. The median observation time was 32 months; the outcome of upper/lower extremity vasculitis was disappearance of clinical symptoms (44.4%), improvement of clinical manifestations (44.4%), and deterioration of clinical manifestations (11.1%). At last follow-up, the median daily dose of prednisone was 6 mg. Steroid therapy could be discontinued in 12 patients (33.3%).We found that upper/lower extremity vasculitis is not uncommon in patients with GCA, and may be present in the early acute phase of GCA. Nevertheless, because upper/lower extremity vasculitis occurs during the course of GCA, yearly clinical vascular examinations may be adequate to screen for upper/lower extremity vasculitis at an early stage in GCA patients. Early diagnosis of GCA-related upper/lower extremity vasculitis is crucial, and can result in decreased severe ischemic complications. Because aortic localizations were common, GCA patients with upper/lower extremity vasculitis should undergo routine investigations for underlying life-threatening aortic complications (aortic ectasia/aneurysm). We also suggest that patients exhibiting aortic complications should undergo routine clinical vascular examination to detect upper/lower extremity vasculitis.

[Vasculitis assessment with [18F]FDG positron emission tomography]

[18F]fluorodeoxyglucose positron emission tomography (PET) is a noninvasive metabolic imaging modality that is well-suited to the assessment of activity and extent of large vessel vasculitis. PET imaging has demonstrated its usefulness in diagnosing giant cell arteritis (notably in its silent form), Takayasu's arteritis, and unclassified aortitis. PET imaging could be more effective than magnetic resonance imaging in detecting the earliest stages of vascular wall inflammation. The visual grading of vascular [18F]FDG uptake makes it possible to discriminate arteritis from active atherosclerosis, providing therefore high specificity. High sensitivity can also be achieved provided scanning is performed during active inflammatory phase, preferably before starting corticosteroid treatment. Prospective studies are needed to determine the exact value of PET imaging in assessing other vasculitis subsets, infectious aortitis, and large vessel vasculitis outcome and response to immunosuppressive treatment.

F-18-fluorodeoxyglucose positron emission tomography combined with CT in critically ill patients with suspected infection

Purpose

To assess the value of F-18-fluorodeoxyglucose positron emission tomography (FDG-PET) combined with CT in critically ill patients suspected of having an infection.

Methods

FDG-PET CT scans requested for evaluation of a suspected infection or inflammatory process in critically ill, mechanically ventilated patients were analyzed (blinded for the final clinical diagnosis) and compared with clinical follow-up.

Results

Thirty-five FDG-PET/CT scans performed in 33 ICU patients (28 adults and 5 children), median age 58 years (range 1 month–72 years), were analyzed. Twenty-one FDG-PET/CT scans were true positive. Three FDG-PET/CT scans were considered false positive, in one case leading to additional diagnostic procedures (specificity 79%). Additionally, 11 true negatives were found (sensitivity 100%), leading to an overall accuracy of 91%.

Conclusions

FDG-PET/CT scanning is of additional value in the evaluation of suspected infection in critically ill patients in whom conventional diagnostics did not lead to a diagnosis. Apart from the high accuracy, in this study it appeared that, in addition to conventional diagnostic techniques that were routinely performed, a normal FDG-PET/CT ruled out important infections requiring prolonged antibiotic therapy or drainage. Since sensitivity is lower in highly metabolic active tissues (e.g., endocarditis, meningitis), the FDG-PET/CT scan is not suited to detect infections in these tissues.

Long-term follow-up of aortic involvement in giant cell arteritis: a series of 48 patients

To date, only a few series have analyzed the long-term outcome of giant cell arteritis (GCA) patients with aortic involvement, which prompted us to conduct the current retrospective study. Our aims were to 1) determine the prevalence of GCA in patients exhibiting nonatherosclerotic aortic involvement (that is, aortitis, aortic ectasia, and/or aneurysm); and 2) evaluate clinical features and long-term outcome of GCA patients exhibiting aortitis, aortic ectasia, and/or aortic aneurysm.From January 1997 to March 2008, 66 consecutive patients in the Department of Internal Medicine at the University of Rouen medical center received a diagnosis of nonatheromatous aortic complications (aortitis, aortic ectasia, and/or aneurysm). In these 66 patients, aortic involvement was related to GCA (n = 48), Takayasu arteritis (n = 6), relapsing polychondritis (n = 1), and infection (n = 11).Of the 48 patients with GCA, aortic involvement preceded the initial GCA diagnosis in 1 patient. Aortic involvement was identified in association with GCA in 40 patients (83.3%), and developed after the onset of GCA in the 7 remaining patients (14.6%). Aortic involvement was more often asymptomatic (77.1%). The aortic helical computed tomography (CT)-scan procedure principally showed isolated aortitis (circumferential thickening of the aortic wall >3 mm) in 41 patients (85.4%). In the remaining 7 patients with GCA (14.6%), aortic helical CT scan demonstrated aortic thoracic ectasia and aortitis (n = 3), aortic thoracic aneurysm and both thoracic and abdominal aortitis (n = 3), and both aortic abdominal aneurysm and aortitis (n = 1). All patients were given steroid therapy at a median daily dose of 1 mg/kg initially.At 6-month follow-up, 34 of 48 patients systematically underwent both thoracic and abdominal CT scan. Aortic helical CT scan demonstrated complete disappearance of aortitis in 8.8% of patients, improvement of aortitis in 47.1%, unchanged pattern of aortitis and/or aortic thoracic ectasia/aneurysm in 41.2%, and deterioration of aortic thoracic aneurysm in 1 patient (2.9%). At 18-month follow-up, 11 patients systematically underwent both thoracic and abdominal CT scan. Aortic helical CT scan showed complete disappearance of aortitis (n = 1), improvement of aortitis (n = 1), unchanged pattern of aortic thoracic ectasia/aneurysm (n = 2), and deterioration of aortic thoracic aneurysm (n = 1). At patients' last follow-up, the median daily dose of prednisone was 7 mg. Steroid therapy could be discontinued in 17 patients (35.4%).The current retrospective study suggests that aortic impairment may be more prevalent than previously reported. Our findings suggest that specific inflammatory thickening of the aortic wall is common at the time of GCA diagnosis, and that aortitis may be the first manifestation of GCA-associated aortic complications. Whether isolated aortitis leads to vascular wall injury responsible for late-onset aneurysmal disease remains to be determined. At this time, we recommend long-term monitoring for aortic aneurysms, especially in high-risk subjects, although the optimal frequency and imaging modality have not yet been determined. A yearly screening strategy for thoracic/abdominal aortic aneurysms has been proposed for patients with GCA, including physical examination, 2-view chest radiograph, and abdominal ultrasound.

Application of PET/SPECT imaging in vascular disease

BACKGROUND

Nuclear medicine imaging differs from other imaging modalities by showing physiological processes instead of anatomical details.

OBJECTIVE

To describe the current applications of positron emission tomography (PET) and single photon emission computed tomography (SPECT) as a diagnostic tool for vascular disease as relevant to vascular surgeons.

METHODS

A literature search identified articles focussing on vascular disease and PET or SPECT using the Pubmed database. Manual cross referencing was also performed.

RESULTS

PET and SPECT may be used to assess plaque vulnerability, biology of aneurysm progression, prosthetic graft infection, and vasculitis. The ability to combine computerized tomography scanning or magnetic resonance imaging with PET or SPECT adds detailed anatomical information and enhances the potential of nuclear medicine imaging in the investigation of vascular disease.

DISCUSSION

Considerable further information will be needed to define whether and where PET or SPECT will fit in a clinical strategy. The necessary validation studies represent an exciting challenge for the future but also may require the development of interdisciplinary imaging groups to integrate expertise and optimize nuclear diagnostic potential.

Diagnostic imaging tests and microbial infections

Despite significant advances in the understanding of its pathogenesis, infection remains a major cause of patient morbidity and mortality. While the presence of infection may be suggested by signs and symptoms, imaging tests are often used to localize or confirm its presence. There are two principal imaging test types: morphological and functional. Morphological tests include radiographs, computed tomography (CT), magnetic resonance imaging, and sonongraphy. These procedures detect anatomic, or structural, alterations produced by microbial invasion and host response. Functional imaging tests reflect the physiological changes that are part of this process. Prototypical functional tests are radionuclide procedures such as bone, gallium, labelled leukocyte and fluorodeoxyglucose (FDG)-positron emission tomography (PET) imaging. In-line functional/morphological tomographic imaging systems, PET/CT and single photon emission tomography (SPECT)/CT, have revolutionized diagnostic imaging. These devices consist of a functional imaging device (PET or SPECT) joined together with a CT scanner. The patient undergoes both tests sequentially without leaving the examination table. Images from each study can be viewed separately and as fused images, providing precisely localized anatomic and functional information. It must be noted, however, that none of the current morphological or functional tests, either alone or in combination, are specific for infection and the goal of finding such an imaging test remains elusive.

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.

Aortite inflammatoire et maladie de Horton. À propos du suivi évolutif scanographique prospectif d'une série de 11 patients

PURPOSE

To determine clinical and radiological features, using computed tomography (CT-scan) in patients with aortic involvement related to giant cell arteritis (GCA), and to assess both clinical and CT-scan outcome after therapy institution.

METHODS

Aortic involvement due to GCA was investigated in all patients, using CT-scan at diagnosis, and at 3, 6 and 12 months follow-up after therapy institution.

RESULTS

The 11 consecutive patients consisted of 4 men and 7 women with mean age of 64.5 years. Patients exhibited: constitutional symptoms (N=9; 82%), dorsalgia (N=3; 27%), clinical signs of GCA (N=3; 27%) and of upper limb large vessel impairment (N=6; 55%). CT-scan showed aortitis involving both thoracic and abdominal aorta (N=6; 55%), abdominal (N=2; 18%) or thoracic aorta (N=2; 18%) and thoracic aortic aneurysm (N=1; 9%). At one-year follow-up, CT-scan revealed: complete resolution (N=7; 64%) and improvement (N=3; 27%) of aortic damage; the patient, who had thoracic aortic aneurysm, underwent surgical treatment, as aortic lesion remained unchanged on CT-scan.

CONCLUSION

Our study underlines that CT-scan is a helpful test in diagnosis and follow-up of aortic involvement in patients with GCA.

Polyarteritis nodosa revisited

Polyarteritis nodosa (PAN), the prototype of systemic vasculitis, is a rare condition characterized by necrotizing inflammation of medium-sized or small arteries without glomerulonephritis or vasculitis in arterioles, capillaries, or venules. Signs and symptoms of this disease are primarily attributable to diffuse vascular inflammation and ischemia of affected organs. Virtually any organ with the exception of the lungs may be affected, with peripheral neuropathy and symptoms from osteoarticular, renal artery, and gastrointestinal tract involvement being the most frequent clinical manifestations. A clear distinction between limited versus systemic disease and idiopathic versus hepatitis B related PAN should be done because there are differences in the implicated pathogenetic mechanisms, their treatment, and prognosis. Currently, corticosteroids plus cyclophosphamide is the standard of care for idiopathic PAN, in particular for patients with adverse prognostic factors (more severe disease), in whom this combination prolonged survival. In contrast for hepatitis B related PAN treatment consists of schemes that include plasmapheresis and antiviral agents.

Use of ultrasonography and positron emission tomography in the diagnosis and assessment of large-vessel vasculitis

PURPOSE OF REVIEW

Ultrasonography and positron emission tomography have been increasingly studied and, in part, introduced in clinical practice to diagnose large-vessel vasculitides, such as temporal arteritis, Takayasu arteritis, large-vessel giant cell arteritis, and isolated aortitis.

RECENT FINDINGS

Ultrasonography reveals characteristic homogenous, concentric wall thickening in vasculitis, often combined with stenoses and, less frequently, with acute occlusions. Thirteen studies describe sensitivities of 40 to 100% (median, 86%) for temporal artery vessel wall edema compared with histology, and of 35 to 86% (median, 70%) compared with clinical diagnosis. If wall edema, stenoses, and occlusions are included, sensitivities increase to 91 to 100% (median, 95%) compared with histology, and to 83 to 100% (median, 88%) compared with clinical diagnosis. Specificities for wall edema are 68 to 100% (median, 93%) compared with histology, and 78 to 100% (median, 97%) compared with clinical diagnosis. One should be aware of large-vessel giant cell arteritis in all patients with temporal arteritis and polymyalgia rheumatica. Ultrasonography reveals characteristic wall thickening, particularly of the distal subclavian, axillary, and proximal brachial arteries. Findings in Takayasu arteritis are similar, but the vessel wall swelling is usually brighter. Positron emission tomography reveals vasculitis in arteries with a diameter of more than 4 mm. Ultrasonography and positron emission tomography agreed completely in the anatomic distribution of changes in patients with large-vessel giant cell arteritis. It reveals asymptomatic large-vessel vasculitis in giant cell arteritis and Takayasu arteritis. Positron emission tomography is not suitable for the assessment of temporal arteries.

SUMMARY

Ultrasonography and positron emission tomography are new, promising techniques to assess large-vessel vasculitides.

The value of [18F]FDG-PET in the diagnosis of large-vessel vasculitis and the assessment of activity and extent of disease

PURPOSE

This study was performed to investigate the value of( 18)F-fluorodeoxyglucose positron emission tomography ([(18)F]FDG-PET) in the diagnosis of large-vessel vasculitis and the assessment of activity and extent of disease.

METHODS

Twenty-six consecutive patients (21 females, 5 males; median age - years, range 17-86 years) with giant cell arteritis or Takayasu's arteritis were examined with [(18)F]FDG-PET. Follow-up scans were performed in four patients. Twenty-six age- and gender-matched controls (21 females, 5 males; median age 71 years, range 17-86 years) were included. The severity of large-vessel [(18)F]FDG uptake was visually graded using a four-point scale. C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) were measured and correlated with [(18)F]FDG-PET results by logistic regression.

RESULTS

[(18)F]FDG-PET revealed pathological findings in 18 of 26 patients. Three scans were categorised as grade I, 12 as grade II and 3 as grade III arteritis. Visual grade was significantly correlated with both CRP and ESR levels (p=0.002 and 0.007 respectively; grade I: CRP 4.0 mg/l, ESR 6 mm/h; grade II: CRP 37 mg/l, ESR 46 mm/h; grade III: CRP 172 mg/l, ESR 90 mm/h). Overall sensitivity was 60% (95% CI 40.6-77.3%), specificity 99.8% (95% CI 89.1-100%), positive predictive value 99.7% (95% CI 77-100%), negative predictive value 67.9% (95% CI 49.8-80.9%) and accuracy 78.6% (95% CI 65.6-88.4%). In patients presenting with a CRP <12 mg/l or an ESR <12 mm/h, logistic regression revealed a sensitivity of less than 50%. In patients with high CRP/ESR levels, sensitivity was 95.5%/80.7%.

CONCLUSION

[(18)F]FDG-PET is highly effective in assessing the activity and the extent of large-vessel vasculitis. Visual grading was validated as representing the severity of inflammation. Its use is simple and provides high specificity, while high sensitivity is achieved by scanning in the state of active inflammation.