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Despite the introduction of new radiotherapy techniques, such as intensity modulated radiation therapy or stereotactic body radiation therapy, radiation induced lung injury remains a significant treatment related adverse event of thoracic radiation therapy. Functional lung avoidance radiation therapy is an emerging concept in the treatment of lung disease to better preserve lung function and to reduce pulmonary toxicity. While conventional ventilation/perfusion (V/Q) lung scintigraphy is limited by a relatively low spatial and temporal resolution, the recent advent of 68Gallium V/Q lung PET/CT imaging offers a potential to increase the accuracy of lung functional mapping and to better tailor lung radiation therapy plans to the individual's lung function. Lung PET/CT imaging may also improve our understanding of radiation induced lung injury compared to the current anatomical based dose–volume constraints. In this review, recent advances in radiation therapy for the management of primary and secondary lung tumors and in V/Q PET/CT imaging for the assessment of functional lung volumes are reviewed. The new opportunities and challenges arising from the integration of V/Q PET/CT imaging in radiation therapy planning are also discussed.

Introduction The aim of this study was to study the feasibility of an SUV-based 177Lu-DOTATATE SPECT/CT quantification and to assess the correlation of different parameters with the corresponding measured on 68Ga-DOTATOC PET/CT in patients with well-differentiated gastroenteropancreatic neuroendocrine tumors (WD-GEP-NET) treated with peptide receptor radionuclide therapy. Patients and Methods Patients with WD-GEP-NET who benefited from a pretherapeutic 68Ga-DOTATOC PET/CT and a 177Lu-DOTATATE SPECT/CT after the cycle 1 of peptide receptor radionuclide therapy were prospectively included. SPECT/CT acquisitions were performed on a system calibrated with a conversion factor of 9.48 counts/MBq per second and were reconstructed with an iterative algorithm allowing quantification using the SPECTRA Quant software (MIM Software, Cleveland, OH). For each patient, different SUV parameters were recorded on both PET/CT (Ga parameters) and SPECT/CT (Lu parameters) for comparison: physiological uptakes (liver/spleen), tumor uptake (1–10/patient; SUVmax, SUVmean, SUVpeak, MTV), tumor-to-liver and tumor-to-spleen ratios according to liver/spleen SUVmax and SUVmean (TLRmax, TLRmean, TSRmax, and TSRmean, respectively). Results Ten patients (8 female; 2 male) aged from 50 to 83 years presenting with a metastatic progressive WD-GEP-NET (7 small intestine, 2 pancreas, 1 rectum) were included. Median values of lesional Lu-SUV were significantly lower than the corresponding Ga-SUV (P < 0.001), whereas median values of lesional Lu-MTV, Lu-TLR, and Lu-TSR were significantly higher than the corresponding Ga-MTV, Ga-TLR, and Ga-TSR (P < 0.02). Pearson correlation coefficients were strong for both SUV and MTV parameters (0.779–0.845), weak for TLR parameters (0.365–0.394), and moderate-to-strong for TSR parameters (0.676–0.750). Conclusions Our results suggest the feasibility of 177Lu-DOTATATE SPECT/CT quantification in clinical practice and show a strong correlation of several SUV-based parameters with the corresponding in 68Ga-DOTATOC PET/CT.

Lung PET/CT is a promising imaging modality for regional lung function assessment. Our aim was to develop and validate a fast, simple, and fully automated GMP compliant [68Ga]Ga-MAA labeling procedure, using a commercially available [99mTc]Tc-MAA kit, a direct gallium-68 eluate and including a purification of the [68Ga]Ga-MAA.Method: The synthesis parameters (pH, heating temperature) were manually determined. Automated 68Ga-labeling of MAA was then developed on a miniAIO (Trasis®, Ans, Belgium) module. An innovative automated process was developed for the purification. The process was then optimized and adapted to automate both the [68Ga]Ga-MAA synthesis and the isolation of gallium-68 eluate required for the pulmonary ventilation PET/CT.Results: The 15-min process demonstrated high reliability and reproducibility, with high synthesis yield (&gt;95 %). Mean [68Ga]Ga-MAA radiochemical purity was 99 % ± 0.6 %. The 68Ga-labeled MAA particles size and morphology remained unchanged.Conclusion: A fast, user friendly, and fully automated process to produce GMP [68Ga]Ga-MAA for clinical use was developed. This automated process combining the advantages of using a non-modified MAA commercial kit, a gallium-68 eluate without pre-purification and an efficient final purification of the [68Ga]Ga-MAA may facilitate the implementation of lung PET/CT imaging in nuclear medicine departments.