Background — Imaging reporter gene expression is useful for noninvasive monitoring of gene therapy. In this study, we imaged cardiac reporter gene expression in living rats using micro positron emission tomography (microPET). Methods and Results — Rats (n=10) underwent intramyocardial injection with 1×10 9 pfu of adenovirus carrying cytomegalovirus promoter-driving herpes simplex virus type 1 mutant thymidine kinase (Ad-CMV-HSV1-sr39tk) as PET reporter gene. Control rats (n=4) received 1×10 9 pfu of adenovirus carrying cytomegalovirus promoter-driving firefly luciferase (Ad-CMV-Fluc). On days 2 to 4, microPET images were obtained after a tail vein injection of nitrogen-13 ammonia ([ 13 N]-NH 3 ) as myocardial perfusion tracer, followed by 9-(4-[ 18 F]-fluoro-3 hydroxymethylbutyl) guanine ([ 18 F]-FHBG) to assess HSV1-sr39tk expression. After imaging, hearts were removed for ex vivo [ 18 F] gamma counting and thymidine kinase enzyme assay. Results show homogenous myocardial distribution of [ 13 N]-NH 3 on all microPET images. Rats injected with Ad-CMV-HSV1-sr39tk have significant [ 18 F]-FHBG uptake in the anterolateral wall compared with background signal in controls. Gamma counting shows 20.0±4.4-fold increase of radioactivity, whereas enzyme assay shows 22.1±6.1-fold increase of thymidine kinase activity in Ad-CMV-HSV1-sr39tk injected rats ( P <0.05). Conclusions — Successful imaging of cardiac HSV1-sr39tk expression was performed in living rats with microPET. The presence of [ 18 F]-FHBG uptake is confirmed by gamma counting and the presence of HSV1-sr39TK protein by thymidine kinase enzyme assay. Cardiac reporter gene imaging by PET may eventually be applied toward human gene therapy studies.

FDG-PET is a useful tool for preoperative evaluation of the neck because it accurately detects metastatic lymph nodes > or =10 mm and has fewer false-positive cases than CT. The high specificity of FDG-PET for lymph node metastases may play an important role in avoiding unnecessary neck dissection.

In women of reproductive age, 18F-FDG imaging should preferably be done within a week before or a few days after the menstrual flow phase to avoid any misinterpretation of pelvic 18F-FDG PET images.

Background-Studies of cardiac gene transfer rely on postmortem analysis using histologic staining or enzyme assays.Noninvasive imaging of the temporal and spatial characteristics of cardiac gene expression in the same subject offers significant advantages. Methods and Results-Rats underwent direct myocardial injection via left thoracotomy with adenovirus-expressing firefly luciferase (Ad-CMV-Fluc; nϭ30). The reporter substrate D-luciferin was injected intraperitoneally. Serial images were acquired by use of a cooled charged couple detector (CCD) camera. Results are expressed as relative light unit per minute (RLU/min). Rats transduced with 1ϫ10 9 plaque-forming units show decremental cardiac luciferase activity over time: 152 070Ϯ21 170 (day 2), 195 806Ϯ62 630 (day 5), 7250Ϯ2941 (day 8), and 2040Ϯ971 RLU/min (day 14). To assess the detection sensitivity, serially diluted titers of Ad-CMV-Fluc were injected: 1ϫ10 9 (195 393Ϯ14 896), 1ϫ10

Reinjection- and MIBI-g-SPECT provide clinically satisfactory various functional data. These functional data in combination with the perfusion information will improve diagnostic and prognostic accuracy without an increase in cost or the radiation dose to the patients.