Cosmogenic radionuclides in the Antonin meteorite

The Antonin meteorite fell on July 15, 2021 in Wielkopolska Voivodeship. Its fall was recorded by fireball camera network and the meteorite specimen was recovered soon after, during a dedicated search expedition. Main mass of Antonin was provided for scientific research relatively quickly after recovery, thanks to which the studies of cosmogenic radionuclide concentrations were carried out in the g spectrometry laboratory at the National Center for Nuclear Research in Otwock/Świerk. The analyses revealed concentration of 7Be and the traces of the cosmogenic radionuclides of 48V and 51Cr, whose half-lives are in the range of 15–28 days, clearly confirming the relationship of the specimen with the observed fireball. The relatively high concentrations of 58Co, 56Co, 46Sc, 57Co and 54Mn (half-lives of several months) also confirm the recent fall of the specimen. Additionally, collected radionuclide data allow to estimate pre-atmospheric size of the meteoroid. Distribution of 60Co and 26Al indicates a meteoroid chunk with a radius of 20–25 cm. The result of 26Al measurement suggests that the investigated meteorite fragment comes from a rather shallow depth of this meteoroid. In addition, the original mass of the meteoroid from which the Antonin meteorite originated was estimated to be less than 100 kg, most likely 70 kg

Evaluation of qualitative and quantitative data of Y-90 imaging in SPECT/CT and PET/CT phantom studies.

IntroductionWe aimed to assess the feasibility of SPECT and PET Y-90 imaging, and to compare these modalities by visualizing hot and cold foci in phantoms for varying isotope concentrations.Materials and methodsThe data was acquired from the Jaszczak and NEMA phantoms. In the Jaszczak phantom Y-90 concentrations of 0.1 MBq/ml and 0.2 MBq/ml were used, while higher concentrations, up to 1.0 MBq/ml, were simulated by acquisition time extension with respect to the standard clinical protocol of 30 sec/projection for SPECT and 30 min/bed position for PET imaging. For NEMA phantom, the hot foci had concentrations of about 4 MB/ml and the background 0.1 or 0.0 MBq/ml. All of the acquired data was analysed both qualitatively and quantitatively. Qualitative assessment was conducted by six observers asked to identify the number of visible cold or hot foci. Inter-observer agreement was assessed. Quantitative analysis included calculations of contrast and contrast-to-noise ratio (CNR), and comparisons with the qualitative results.ResultsFor SPECT data up to two cold foci were discernible, while for PET four foci were visible. We have shown that CNR (with Rose criterion) is a good measure of foci visibility for both modalities. We also found good concordance of qualitative results for the Jaszczak phantom studies between the observers (corresponding Krippendorf's alpha coefficients of 0.76 to 0.84). In the NEMA phantom without background activity all foci were visible in SPECT/CT images. With isotope in the background, 5 of 6 spheres were discernible (CNR of 3.0 for the smallest foci). For PET studies all hot spheres were visible, regardless of the background activity.ConclusionsPET Y-90 imaging provided better results than Bremsstrahlung based SPECT imaging. This indicates that PET/CT might become the method of choice in Y-90 post radioembolization imaging for visualisation of both necrotic and hot lesions in the liver

LSF estimated from planar images acquired using energy windows of W1 and W2 for a true LSF of (9.8±0.6)% as a function of total ⁹⁰Y activity in the anthropomorphic phantom.

The results are presented for calculations both with and without background correction.</p

CNR calculation methods.

PurposePrior to 90Y radioembolization procedure, a pretherapy simulation using 99mTc-MAA is performed. Alternatively, a small dosage of 90Y microspheres could be used. We aimed to assess the accuracy of lung shunt fraction (LSF) estimation in both high activity 90Y posttreatment and pretreatment scans with isotope activity of ~100 MBq, using different imaging techniques. Additionally, we assessed the feasibility of visualising hot and cold hepatic tumours in PET/CT and Bremsstrahlung SPECT/CT images.Materials and methodsAnthropomorphic phantom including liver (with two spherical tumours) and lung inserts was filled with 90Y chloride to simulate an LSF of 9.8%. The total initial activity in the liver was 1451 MBq, including 19.4 MBq in the hot sphere. Nine measurement sessions including PET/CT, SPECT/CT, and planar images were acquired at activities in the whole phantom ranging from 1618 MBq down to 43 MBq. The visibility of the tumours was appraised based on independent observers’ scores. Quantitatively, contrast-to-noise ratio (CNR) was calculated for both spheres in all images.ResultsLSF estimation. For high activity in the phantom, PET reconstructions slightly underestimated the LSF; absolute difference was Lesion visibility. For SPECT/CT, the cold tumour proved too small to be discernible (CNR 90Y activity in the liver, while hot sphere was visible for activity >200 MBq (CNR>4). For PET/CT, the cold tumour was only visible with the highest 90Y activity (CNR>4), whereas the hot one was seen for activity >100 MBq (CNR>5).ConclusionsPET/CT may accurately estimate the LSF in a 90Y posttreatment procedure. However, at low activities of about 100 MBq it seems to provide unreliable estimations. PET imaging provided better visualisation of both hot and cold tumours.</div

3D MIP PET (top row) and SPECT (bottom row) images of the anthropomorphic phantom for scans performed at high (left) and low (right) activity levels of ⁹⁰Y.

3D MIP PET (top row) and SPECT (bottom row) images of the anthropomorphic phantom for scans performed at high (left) and low (right) activity levels of 90Y.</p

Geometric mean images composed from the anterior and posterior planar images for acquisitions with a total phantom activity of 1582 and 126 MBq.

Geometric mean images composed from the anterior and posterior planar images for acquisitions with a total phantom activity of 1582 and 126 MBq.</p

PET, SPECT and planar data for LSF calculations.

PurposePrior to 90Y radioembolization procedure, a pretherapy simulation using 99mTc-MAA is performed. Alternatively, a small dosage of 90Y microspheres could be used. We aimed to assess the accuracy of lung shunt fraction (LSF) estimation in both high activity 90Y posttreatment and pretreatment scans with isotope activity of ~100 MBq, using different imaging techniques. Additionally, we assessed the feasibility of visualising hot and cold hepatic tumours in PET/CT and Bremsstrahlung SPECT/CT images.Materials and methodsAnthropomorphic phantom including liver (with two spherical tumours) and lung inserts was filled with 90Y chloride to simulate an LSF of 9.8%. The total initial activity in the liver was 1451 MBq, including 19.4 MBq in the hot sphere. Nine measurement sessions including PET/CT, SPECT/CT, and planar images were acquired at activities in the whole phantom ranging from 1618 MBq down to 43 MBq. The visibility of the tumours was appraised based on independent observers’ scores. Quantitatively, contrast-to-noise ratio (CNR) was calculated for both spheres in all images.ResultsLSF estimation. For high activity in the phantom, PET reconstructions slightly underestimated the LSF; absolute difference was Lesion visibility. For SPECT/CT, the cold tumour proved too small to be discernible (CNR 90Y activity in the liver, while hot sphere was visible for activity >200 MBq (CNR>4). For PET/CT, the cold tumour was only visible with the highest 90Y activity (CNR>4), whereas the hot one was seen for activity >100 MBq (CNR>5).ConclusionsPET/CT may accurately estimate the LSF in a 90Y posttreatment procedure. However, at low activities of about 100 MBq it seems to provide unreliable estimations. PET imaging provided better visualisation of both hot and cold tumours.</div

CNR values calculated for the cold and hot lesions in the liver in PET/CT imaging.

The solid lines represent the border values depending on the Rose criterion (middle line at 3 and supporting ones at 2.5 and 3.5).</p

CNR for SPECT and PET.

PurposePrior to 90Y radioembolization procedure, a pretherapy simulation using 99mTc-MAA is performed. Alternatively, a small dosage of 90Y microspheres could be used. We aimed to assess the accuracy of lung shunt fraction (LSF) estimation in both high activity 90Y posttreatment and pretreatment scans with isotope activity of ~100 MBq, using different imaging techniques. Additionally, we assessed the feasibility of visualising hot and cold hepatic tumours in PET/CT and Bremsstrahlung SPECT/CT images.Materials and methodsAnthropomorphic phantom including liver (with two spherical tumours) and lung inserts was filled with 90Y chloride to simulate an LSF of 9.8%. The total initial activity in the liver was 1451 MBq, including 19.4 MBq in the hot sphere. Nine measurement sessions including PET/CT, SPECT/CT, and planar images were acquired at activities in the whole phantom ranging from 1618 MBq down to 43 MBq. The visibility of the tumours was appraised based on independent observers’ scores. Quantitatively, contrast-to-noise ratio (CNR) was calculated for both spheres in all images.ResultsLSF estimation. For high activity in the phantom, PET reconstructions slightly underestimated the LSF; absolute difference was Lesion visibility. For SPECT/CT, the cold tumour proved too small to be discernible (CNR 90Y activity in the liver, while hot sphere was visible for activity >200 MBq (CNR>4). For PET/CT, the cold tumour was only visible with the highest 90Y activity (CNR>4), whereas the hot one was seen for activity >100 MBq (CNR>5).ConclusionsPET/CT may accurately estimate the LSF in a 90Y posttreatment procedure. However, at low activities of about 100 MBq it seems to provide unreliable estimations. PET imaging provided better visualisation of both hot and cold tumours.</div

Coronal (top row) and axial (bottom row) views of the PET (A) and SPECT (B) images of the anthropomorphic phantom for scans performed at high and low activity levels of ⁹⁰Y (middle and right column).

Left column presents corresponding CT slices. Yellow arrows indicate the location of the extrahepatic deposition while the red and blue ones—the locations of the hot and cold hepatic tumours, respectively.</p