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Highlights • Test on radiomarked ex-vivo meningioma specimens confirmed feasibility of β -RGS. • Personalized minimal activity to be injected can be evaluated from PET images. • Effective dose is at a level of whole-body PET/CT and personnel exposure negligible. Purpose Radio-guided surgery with β - decays is a novel technique under investigation. One of the main advantages is its capability to detect small (⩽ 0.1 ml) samples after injecting the patient with low activity of radiopharmaceutical. This paper presents an experimental method to quantify this feature based on ex-vivo tests on specimens from meningioma patients. Methods Patients were enrolled on the basis of the standard uptake value (SUV) and the tumour-to-non-tumour activity ratio (TNR) resulted from 68Ga-DOTATOC PET exams. After injecting the patients with 93–167 MBq of 90Y-DOTATOC, 26 samples excised during surgery were analyzed with a β - probe. The radioactivity expected on the neoplastic specimens was estimated according to the SUV found in the PET scan and the correlation with the measured counts was studied. The doses to surgeon and medical personnel were also evaluated. Results Even injecting as low as 1.4 MBq/kg of radiotracer, tumour residuals of 0.1 ml can be detected. A negligible dose to the medical personnel was confirmed. Conclusions Radio-guided surgery with β - decays is a feasible technique with a low radiation dose for both personnel and patient, in particular if the patient is injected with the minimum required activity. A correlation greater than 80% was observed between the measured counts and the expected activity for the lesion samples based on the individual SUV and the TNR. This makes identifiable the minimum injectable radiotracer activity for cases where 90Y is the utilized radionuclide. [ABSTRACT FROM AUTHOR]

Purpose A radio-guided surgery technique with β - -emitting radio-tracers was suggested to overcome the effect of the large penetration of γ radiation. The feasibility studies in the case of brain tumors and abdominal neuro-endocrine tumors were based on simulations starting from PET images with several underlying assumptions. This paper reports, as proof-of-principle of this technique, an ex vivo test on a meningioma patient. This test allowed to validate the whole chain, from the evaluation of the SUV of the tumor, to the assumptions on the bio-distribution and the signal detection. Methods A patient affected by meningioma was administered 300 MBq of 90 Y-DOTATOC. Several samples extracted from the meningioma and the nearby Dura Mater were analyzed with a β - probe designed specifically for this radio-guided surgery technique. The observed signals were compared both with the evaluation from the histology and with the Monte Carlo simulation. Results we obtained a large signal on the bulk tumor (105 cps) and a significant signal on residuals of ∼0.2 ml (28 cps). We also show that simulations predict correctly the observed yields and this allows us to estimate that the healthy tissues would return negligible signals (≈1 cps). This test also demonstrated that the exposure of the medical staff is negligible and that among the biological wastes only urine has a significant activity. Conclusions This proof-of-principle test on a patient assessed that the technique is feasible with negligible background to medical personnel and confirmed that the expectations obtained with Monte Carlo simulations starting from diagnostic PET images are correct. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this study is to validate the use of an innovative detector (edgeless-diode) [1] to measure the dose delivered in stereotactic radiosurgery for brain functional disorders. Methods Three diodes were inserted in a Rando phantom in 'trigeminal', 8 mm cranial and 26 mm caudal positions. In the framework of a dose escalation protocol, a trigeminal target patient's plan was properly optimized. The diode coincident with the PTV-position was prescribed at doses respectively of 75, 100, 140 and 200 Gy in one single fraction. In the 75 Gy delivery case an EBT3 film was placed in correspondence with the caudal diode position and a prescription dose of 12 Gy was imposed in order to validate the diode's recorded value. After the escalation of the dose, quality-assurance (QA) verifications were also performed for three patient planes with different prescription doses and placing the central diode in correspondence with the trigeminal target. Finally, the dose values measured by the three diodes were compared to the planned ones. Results The Rando plan and patient QA results are summarized in the following table. Comparison of the dose values from the edgeless-diode with EBT3 film shows a difference of −4.6%. Conclusions The edgeless-diode detectors were employed to measure the dose distribution of a full trigeminal stereotactic treatment; they record values of the dose in the central part of the PTV within 4% of the planned value for seven different plans. The verification of the value corresponding to a caudal position of the Rando-plan scaled at 75 Gy by EBT3 films shows a difference smaller than 5% in comparison with the edgeless-diode. The edgeless-diode employment in functional treatments QA procedures seems promising. [ABSTRACT FROM AUTHOR]