Imaging infection/inflammation in the new millennium

Abstract

In the closing half of the past century a wide variety of approaches were developed to visualise infection and inflammation by gamma scintigraphy. Use of autologous leucocytes, labelled with indium-111 or technetium-99m, is still considered the "gold standard" nuclear medicine technique for the imaging of infection and inflammation. However, the range of radiopharmaceuticals used to investigate infectious and non-microbial inflammatory disorders is expanding rapidly. Developments in protein/peptide chemistry and in radiochemistry should lead to agents with very high specific activities. Recently, positron emission tomography with fluorine-18 fluorodeoxyglucose has been shown to delineate infectious and inflammatory foci with high sensitivity. The third millennium will witness a gradual shift from basic (non-specific) or cumbersome, even hazardous techniques (radiolabelled leucocytes) to more sophisticated approaches. Here a survey is presented of the different approaches in use or under investigation.

Imaging bacterial infections with radiolabeled 1-(2′-deoxy-2′-fluoro-β-D-arabinofuranosyl)-5-iodouracil

“…Five million cells were injected s.c. into the right flank of each mouse. Tumor volume was calculated as length ϫ width 2 ϫ 0.5, and mice were treated with Clostridium novyi-NT spores when tumors occupied Ϸ250 mm 3 . C. novyi-NT spores were prepared as described (15), and mice were i.v.…”

“…These methods are time-consuming and insensitive, and the results are often obtained too late to guide clinical decision making (1)(2)(3). In particular, it is difficult or impossible to distinguish localized bacterial infections from sites of sterile inflammation.…”

“…Similarly, the increasing use of prosthetic devices has provided new niches for bacterial colonization. These developments, coupled with the emergence of bacterial strains resistant to antibiotics, have elicited an urgent need to develop improved methods for the diagnosis and treatment of bacterial infections (1)(2)(3).…”

“…Several intriguing strategies have been put forward in this regard, such as the use of radiolabeled antibiotics, antibodies, antimicrobial or chemotactic peptides, or bacteriophages (1)(2)(3)(4). 99m Tchexamethyl propyleneamine oxime (HMPAO) and 111 In-oxine have been used to label leukocytes that home to sites of infection, and radiolabeled antigranulocyte antibodies or 18 F-fluorodeoxyglucose have been used for similar purposes (3,5,6). Although all these methods benefit from the inherent high sensitivity of nuclear techniques, most have proved either cumbersome, relatively nonspecific, or logistically difficult due to the challenges in manufacturing materials suitable for clinical use (1-3, 5, 6).…”

Diagnostic value of 99mTc-ubiquicidin scintigraphy for osteomyelitis and comparisons with 99mTc-methylene diphosphonate scintigraphy and magnetic resonance imaging

“…There are significant differences among A/N ratios of the early views in comparison with delayed view at 240 min (P < 0.05). [10,18], whereas nuclear imaging can easily detect an inflammatory process because it is based on functional processes, which are morphologically indistinguishable [19]. In view of this, infection is usually accompanied by inflammation; it is much more valuable to make a distinction between infection and inflammation.…”