[Positron emission tomography in internal medicine]

PET-CT in Critically Ill Patients: Diagnosing the Unsuspected

OBJECTIVE

Quick identification of septic source is fundamental in patients with severe sepsis of unknown origin. The purpose of this case report was to assess the benefit and feasibility of an early PET-CT in critically ill patients with undiagnosed sepsis.

DATA SOURCES

Clinical observations of two patients.

STUDY SELECTION

Case reports.

DATA EXTRACTION

Data extracted from medical records, after patient's consent. Illustrations were collected from the imaging software.

DATA SYNTHESIS

We admitted two critically ill patients for suspected sepsis and altered mental state. As all bacteriological samples were initially sterile, diagnostic workups in both patients led us to suspect underlying malignant hemopathy. In fact, the lumbar puncture of the first patient revealed a large B-cell lymphoma, and an acquired thrombotic thrombocytopenic purpura was suspected in the second patient. However, PET-CTs performed in both patients displayed infra-clinical underlying infectious foci. Within 48 hours, both patients developed a clearly identified sepsis linked to the described focus, and favorable outcome thanks to the precious information delivered by the PET-CT.

CONCLUSIONS

PET-CT precisely detected the deep foci of infection about 48 hours prior to the diagnosis of sepsis. The cases reports suggested the use of this image technique in ICU for patients with sepsis of unknown origin.

64Cu Core-labeled nanoparticles with high specific activity via metal-free click chemistry

A novel strategy based on metal-free "click" chemistry was developed for the copper-64 radiolabeling of the core in shell-cross-linked nanoparticles (SCK-NPs). Compared with Cu(I)-catalyzed click chemistry, this metal-free strategy provides the following advantages for Cu-64 labeling of the core of SCK-NPs: (1) elimination of copper exchange between nonradioactive Cu in the catalyst and DOTA-chelated Cu-64; (2) elimination of the internal click reactions between the azide and acetylene groups in the same NPs; and (3) increased efficiency of the click reaction because water-soluble Cu(I) does not need to reach the hydrophobic core of the NPs. When 50 mCi Cu-64 was used for the radiolabeling, the specific activity of the radiolabeled product was 975 Ci/μmol at the end of synthesis, which represents the attachment of ca. 500 Cu-64 atoms per SCK-NP, giving in essence a 500-fold amplification of specific activity of the NP over that of the Cu-64 chelate. To the best of our knowledge, this is the highest specific activity obtained for Cu-64-labeled nanoparticles.

[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.