Purpose

Positron emission tomography (PET) with 89Zr-ibritumomab tiuxetan can be used to monitor biodistribution of 90Y-ibritumomab tiuxetan as shown in mice. The aim of this study was to assess biodistribution and radiation dosimetry of 90Y-ibritumomab tiuxetan in humans on the basis of 89Zr-ibritumomab tiuxetan imaging, to evaluate whether co-injection of a therapeutic amount of 90Y-ibritumomab tiuxetan influences biodistribution of 89Zr-ibritumomab tiuxetan and whether pre-therapy scout scans with 89Zr-ibritumomab tiuxetan can be used to predict biodistribution of 90Y-ibritumomab tiuxetan and the dose-limiting organ during therapy.

Methods

Seven patients with relapsed B-cell non-Hodgkin’s lymphoma scheduled for autologous stem cell transplantation underwent PET scans at 1, 72 and 144 h after injection of ~70 MBq 89Zr-ibritumomab tiuxetan and again 2 weeks later after co-injection of 15 MBq/kg or 30 MBq/kg 90Y-ibritumomab tiuxetan. Volumes of interest were drawn over liver, kidneys, lungs, spleen and tumours. Ibritumomab tiuxetan organ absorbed doses were calculated using OLINDA. Red marrow dosimetry was based on blood samples. Absorbed doses to tumours were calculated using exponential fits to the measured data.

Results

The highest 90Y absorbed dose was observed in liver (3.2 ± 1.8 mGy/MBq) and spleen (2.9 ± 0.7 mGy/MBq) followed by kidneys and lungs. The red marrow dose was 0.52 ± 0.04 mGy/MBq, and the effective dose was 0.87 ± 0.14 mSv/MBq. Tumour absorbed doses ranged from 8.6 to 28.6 mGy/MBq. Correlation between predicted pre-therapy and therapy organ absorbed doses as based on 89Zr-ibritumomab tiuxetan images was high (Pearson correlation coefficient r = 0.97). No significant difference between pre-therapy and therapy tumour absorbed doses was found, but correlation was lower (r = 0.75).

Conclusion

Biodistribution of 89Zr-ibritumomab tiuxetan is not influenced by simultaneous therapy with 90Y-ibritumomab tiuxetan, and 89Zr-ibritumomab tiuxetan scout scans can thus be used to predict biodistribution and dose-limiting organ during therapy. Absorbed doses to spleen were lower than those previously estimated using 111In-ibritumomab tiuxetan. The dose-limiting organ in patients undergoing stem cell transplantation is the liver.

Purpose

To test the extent of variation among nuclear medicine physicians with respect to staging non-small cell lung cancer with positron emission tomography (PET).

Procedures

Two groups of nuclear medicine physicians with different levels of PET experience reviewed 30 PET scans. They were requested to identify and localize suspicious mediastinal lymph nodes (MLN) using standardized algorithms. Results were compared between the two groups, between individuals, and with expert reading.

Results

Overall we found good interobserver agreement (kappa 0.65). Experience with PET translated into a better ability to localize MLN stations (68% vs. 51%, respectively), and experienced readers appeared to be more familiar with translating PET readings into clinically useful statements.

Conclusions

Although our results suggest that clinical experience with PET increases observers’ ability to read and interpret results from PET adequately, there is room for improvement. Experience with PET does not necessarily improve the accuracy of image interpretation.

Purpose

To perform a systematic review and meta-analysis to determine the diagnostic accuracy of attenuation-corrected (AC) vs. nonattenuation-corrected (NAC) 2-deoxy-2-[F-18]fluoro-d-glucose-positron emission tomography (FDG-PET) in oncological patients.

Procedures

Following a comprehensive search of the literature, two reviewers independently assessed the methodological quality of eligible studies. The diagnostic value of AC was studied through its sensitivity/specificity compared to histology, and by comparing the relative lesion detection rate reported with NAC-PET vs. AC, for full-ring and dual-head coincidence PET (FR- and DH-PET, respectively).

Results

Twelve studies were included. For FR-PET, the pooled sensitivity/specificity on a patient basis was 64/97% for AC and 62/99% for NAC, respectively. Pooled lesion detection with NAC vs. AC was 98% [95% confidence interval (95% CI): 96–99%, n = 1,012 lesions] for FR-PET, and 88% (95% CI:81–94%, n = 288 lesions) for DH-PET.

Conclusions

Findings suggest similar sensitivity/specificity and lesion detection for NAC vs. AC FR-PET and significantly higher lesion detection for NAC vs. AC DH-PET.