Chronic berylliosis. Demonstration by gallium-67 imaging and magnetic resonance imaging

Molecular Imaging of Pulmonary Inflammation and Infection

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

Biomonitoring of chromium(VI) deposited in pulmonary tissues: Pilot studies of a magnetic resonance imaging technique in a post-mortem rodent model

The biomonitoring of individuals exposed to chromium(VI) by inhalation is often based on determinations of chromium in body fluids such as blood, plasma or urine, or on assessments of DNA damage in non-lung surrogate tissues such as peripheral blood lymphocytes. These techniques are of some use as biomarkers of internal exposure or biological effect, mainly in the case of soluble chromium(VI) compounds, but they provide at best only indirect information about chromium(VI) concentrations in the main target organ of interest - the lung. An urgent need exists for a non-invasive technique to permit the visualization and quantification of chromium(VI) in the lung of exposed humans. This study details the development of a lung imaging technique based on the detection of paramagnetic chromium using magnetic resonance imaging (MRI). The intracellular reductive conversion of chromium(VI) is a crucial bioactivation step in its carcinogenicity, and the MRI method described here relies on the conversion of non-paramagnetic (MRI 'silent') chromium(VI) to detectable paramagnetic species such as chromium(III). Initial studies with chromium(III) revealed that a range of 2.5-5 microg chromium(III) instilled in rat lung is considered to be the lower limit of detection of this method. It was possible to demonstrate the presence of 30 microg chromium(VI) in our post-mortem rat model. The ultimate objective of this work is to determine whether this technique has applicability to the biomonitoring of chromium(VI) inhalation exposures that result in internalized lung doses in human subjects.

Bérylliose pulmonaire chronique (2e partie)

INTRODUCTION

Chronic beryllium disease (CBD) is an occupational lung disease caused by the inhalation of beryllium dust, fumes or metallic salts.

CURRENT DATA

Beryllium affects the lungs via particles deposited in the pulmonary alveoli. These are ingested by alveolar macrophages which act as antigen presenting cells to CD4+ T lymphocytes. T lymphocytes proliferate in response to beryllium antigens and combined with macrophages produce numerous epithelioid granulomas with the release of inflammatory cytokines (IFNgamma, IL-2, TNFalpha and IL6) and growth factors. Beryllium induces macrophage apoptosis which reduces its clearance from the lung which in turn contributes to the host's continual re-exposure and thus a chronic granulomatous disorder. Pulmonary granulomatous inflammation is the primary manifestation of CBD, but the disease occasionally involves other organs such as the liver, spleen, lymph nodes and bone marrow. The clinical, radiological, and histopathological features of CBD can be difficult to distinguish from sarcoidosis. The Beryllium lymphocyte proliferation test (BeLPT) demonstrates a beryllium specific immune response, confirms the diagnosis of CBD, and excludes sarcoidosis.

CONCLUSIONS AND PERSPECTIVES

CBD provides a human model of pulmonary granulomatous disease produced by an occupational exposure, occurring more frequently in those with a genetic pre-disposition. It can be differentiated from sarcoidosis by specific immunological testing.

Gallium and other agents in diseases of the lung

The use of gallium for pulmonary diseases is hampered by its relative lack of specificity, typical 1- to 3-day delay between injection and imaging time, and suboptimal imaging characteristics. Other nuclear and nonnuclear imaging modalities, such as (18)F-fluorodeoxyglucose positron emission tomography (PET) and high-resolution chest computed tomography, have replaced gallium in many clinical algorithms. Yet gallium and other radiotracers, such as thallium, sestamibi, and labeled white blood cells, are useful in many specific clinical situations involving lymphoma and other neoplasias, inflammatory processes such as sarcoid and interstitial pneumonia, tuberculosis and other infections, and the acquired immune deficiency syndrome. Gallium and some of the other single-photon agents still have value in establishing a diagnosis, assessing the location and extent of disease, differentiating active disease from chronic scarring, guiding potential biopsy, and determining recurrence and response to therapy in patients with certain lung diseases, particularly when access to PET imaging is not available.