67Gallium scanning in talc-induced pulmonary granulomatosis

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.

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.

Pulmonary complications of intravenous drug misuse. 1. Epidemiology and non-infective complications

Images

Talcosis presenting as pulmonary infiltrates in an HIV-positive heroin addict

A case of an HIV-positive young drug addict presenting with fever, respiratory distress, and pulmonary infiltrates is reported. Pulmonary talcosis was diagnosed by transbronchial biopsy. The differential diagnosis of pulmonary infiltrates in HIV-positive patients is reviewed and the predisposition of drug addicts to develop both HIV infection, as well as pulmonary talcosis, is discussed. Pulmonary talcosis must be considered in the differential diagnosis of pulmonary infiltrates of HIV-positive drug addicts.

Severe precocious emphysema in intravenous methylphenidate (Ritalin) abusers

Intravenous (IV) drug abuse is known to cause pulmonary tale granulomatosis. Reports have documented a syndrome of pulmonary vascular sclerosis in long-term IV methylphenidate users. Although this would be expected to produce restrictive lung disease, we hereby report six patients who have severe obstructive lung disease. All had used IV methylphenidate for at least four years. One of these patients died of progressive respiratory insufficiency and the others are clinically disabled. Their symptoms and airflow obstruction are more severe than those of most patients with chronic obstructive pulmonary disease. In these individuals, we cannot say that precocious obstructive lung disease is not due to a combination of smoking and other factors, nor can we be certain that methylphenidate is the offending agent. However, this cluster of cases among methylphenidate abusers suggests that long-term IV exposure to this drug might lead to early severe obstructive lung disease.

Thoracic imaging with gallium-67

In the past, gallium-67 imaging has undergone several ups and downs related to its clinical importance. After a period of initial enthusiasm, its role and indications are now established. At present, there are two fields of clinical interest for ⁶⁷Ga-imaging: (1) mediastinal staging in bronchogenic carcinoma and the staging of malignant lymphoma; (2) assessment of activity in interstitial lung diseases, especially sarcoidosis and inflammatory lung disorders. The advantage of ⁶⁷Ga-imaging is that it is highly sensitive for the detection of neoplastic and inflammatory processes, independent of anatomical barriers. Particularly with the challenge of AIDS, ⁶⁷Ga-imaging will gain increasing importance in the future. The low specificity of gallium for detecting underlying disorders precludes its use as a primary diagnostic tool. Therefore, and because of the cost and radiation load, the indications for application will have to be selected very carefully.