Cardiac Blood Pool Imaging — A Clinical Comparison between Red Blood Cells Labeled with 99mTc in vivo and in vitro and 99mTc-Labeled Human Serum Albumin

On-cartridge preparation and evaluation of 68Ga-, 89Zr- and 64Cu-precursors for cell radiolabelling

INTRODUCTION

Indium-111 when formulated as indium-111 oxine remains the gold standard for long term cell tracking, whereas radiometals for improved PET applications still have to be established. We here describe the on-cartridge formation of gallium-68, zirconium-89 and copper-64 complexes in small volumes suitable for cell labelling, including labelling of red blood cells (RBC) and white blood cells (WBC) and their biological evaluation in vivo.

METHODS

Small volumes (1-2 mL) of tracers (oxine, tropolone) were directly prepared on an anion exchange cartridge (Sep-Pak QMA). Cells were radiolabelled and the labelling efficiency and efflux were evaluated. The in vivo biodistribution of copper-64-labelled WBC using [⁶⁴Cu][Cu(oxinate)₂] and [⁶⁴Cu][Cu(tropolonate)₂] was monitored in an infection and inflammation animal model using BALB/c mice.

RESULTS

On-cartridge concentration of gallium-68, zirconium-89 and copper-64 enabled formation of oxine and tropolone tracers in small volumes with good yields (≥50%) and quality (extraction ≥90%). Prepared tracers radiolabelled the RBC comparable to indium-111 tracers and in vivo biodistribution of copper-64 labelled WBC showed clear accumulation of cells at the site of infection and inflammation.

CONCLUSIONS

This on-cartridge preparation method enables simple formation of various PET tracers for cell radiolabelling. Zirconium-89 and copper-64 tracers radiolabelled cells with sufficient stability. Due to their longer half-life this approach could be promising for routine applications where longer evaluation periods for cell tracking are needed.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

This novel approach for on-cartridge concentration and preparation of oxine and tropolone precursors with different positron emitters, in small volume and suitable pH, offers a versatile tool towards cell labelling for preclinical and clinical PET applications.

Comparison between transesophageal Doppler echocardiography and nuclear cardioangiography for the evaluation of left ventricular filling during coronary artery bypass grafting

This study examines the relative contribution of early (E) and atrial (A) filling of the left ventricle. Ten patients were studied under anesthesia before and after coronary artery bypass grafting (CABG) using measurements of the mitral velocity-time integral (VTI) with transesophageal pulsed Doppler echocardiography and nuclear angiocardiography simultaneously. Thermodilution cardiac output measurements were made simultaneously in order to express the E and A filling in quantitative terms. The mean difference between methods in estimating E filling was -1.0 mL and the figures for the mean +/- 2 SD were 5.7 and -7.8 mL, r = 0.98 using regression analysis. The mean difference during A filling was 0.9 mL and the corresponding figures for the mean +/- 2 SD were 7.9 and -6.1 mL, r = 0.88. There was a reduction in the volume entering the left ventricle during the E filling (42-26 mL) and in the A phase (27-22 mL) from before surgery in comparison to after CABG. There was good agreement between transesophageal Doppler echocardiographic and nuclear angiocardiographic methods concerning the volume contribution during E and A phases of left ventricular filling.