“…Firstly, subtraction of a uniform background [4, 14] or a linear background fitted to the sinogram data outside the object [4, 15] (shown for 76 Br in Fig. 5) has been suggested.…”
Section: Prompt or Cascade Gamma Coincidencesmentioning
confidence: 99%
“…5 and 8. Therefore, Kull et al [15] used a second-order series expansion to describe the shape of the background for 2-D scans with 86 Y, where they determined the second-order term using a measurement with a body phantom and the linear portion of the background by fitting to the sinogram tails of the individual patient, and also included a recalibration of the scanner based on the trues to singles ratio. Fig.…”
Section: Prompt or Cascade Gamma Coincidencesmentioning
The quantitative accuracy and image quality of positron emission tomography (PET) measurements with 124I and 86Y is affected by the prompt emission of gamma radiation and positrons in their decays, as well as the higher energy of the emitted positrons compared to those emitted by 18F. PET scanners cannot distinguish between true coincidences, involving two 511-keV annihilation photons, and coincidences involving one annihilation photon and a prompt gamma, if the energy of this prompt gamma is within the energy window of the scanner. The current review deals with a number of aspects of the challenge this poses for quantitative PET imaging. First, the effect of prompt gamma coincidences on quantitative accuracy of PET images is discussed and a number of suggested corrections are described. Then, the effect of prompt gamma coincidences and the increased singles count rates due to gamma radiation on the count rate performance of PET is addressed, as well as possible improvements based on modification of the scanner’s energy windows. Finally, the effect of positron energy on spatial resolution and recovery is assessed. The methods presented in this overview aim to overcome the challenges associated with the decay characteristics of 124I and 86Y. Careful application of the presented correction methods can allow for quantitatively accurate images with improved image contrast.
“…Firstly, subtraction of a uniform background [4, 14] or a linear background fitted to the sinogram data outside the object [4, 15] (shown for 76 Br in Fig. 5) has been suggested.…”
Section: Prompt or Cascade Gamma Coincidencesmentioning
confidence: 99%
“…5 and 8. Therefore, Kull et al [15] used a second-order series expansion to describe the shape of the background for 2-D scans with 86 Y, where they determined the second-order term using a measurement with a body phantom and the linear portion of the background by fitting to the sinogram tails of the individual patient, and also included a recalibration of the scanner based on the trues to singles ratio. Fig.…”
Section: Prompt or Cascade Gamma Coincidencesmentioning
The quantitative accuracy and image quality of positron emission tomography (PET) measurements with 124I and 86Y is affected by the prompt emission of gamma radiation and positrons in their decays, as well as the higher energy of the emitted positrons compared to those emitted by 18F. PET scanners cannot distinguish between true coincidences, involving two 511-keV annihilation photons, and coincidences involving one annihilation photon and a prompt gamma, if the energy of this prompt gamma is within the energy window of the scanner. The current review deals with a number of aspects of the challenge this poses for quantitative PET imaging. First, the effect of prompt gamma coincidences on quantitative accuracy of PET images is discussed and a number of suggested corrections are described. Then, the effect of prompt gamma coincidences and the increased singles count rates due to gamma radiation on the count rate performance of PET is addressed, as well as possible improvements based on modification of the scanner’s energy windows. Finally, the effect of positron energy on spatial resolution and recovery is assessed. The methods presented in this overview aim to overcome the challenges associated with the decay characteristics of 124I and 86Y. Careful application of the presented correction methods can allow for quantitatively accurate images with improved image contrast.
“…The publications by other groups [48,49,50] are not based on the use of the Scanditronix/GE PC4096-WB, but of different scanners with smaller septa (as described above for the Siemens HR+, for example). In our own study with the Siemens HR+ operated in 2D- and 3D-acquisition modes, images of the three-rod-phantom filled with 86 Y showed false radioactivity uptake in all cold rods (Figure 7).…”
Section: 86y For Pet Imagingmentioning
confidence: 99%
“…These findings did not differ between 2D- and 3D-mode. Using a larger phantom, the IEC whole body phantom [52], Kull et al, [50] found that a parabolic approximation to the background caused by the gamma coincidences resulted in a better correction than a mere linear interpolation. More sophisticated methods to remove the gamma coincidences in the sinograms were suggested by Walrand et al, [53], who applied a patient-dependent method based on sinogram tail fitting using an 86 Y point spread function library, and by Beattie et al, [54], who applied convolution kernels to the entire two-dimensional sinogram (and not just to projection lines).…”
In the context of radiopharmacy and molecular imaging, the concept of theranostics entails a therapy-accompanying diagnosis with the aim of a patient-specific treatment. Using the adequate diagnostic radiopharmaceutical, the disease and the state of the disease are verified for an individual patient. The other way around, it verifies that the radiopharmaceutical in hand represents a target-specific and selective molecule: the “best one” for that individual patient. Transforming diagnostic imaging into quantitative dosimetric information, the optimum radioactivity (expressed in maximum radiation dose to the target tissue and tolerable dose to healthy organs) of the adequate radiotherapeutical is applied to that individual patient. This theranostic approach in nuclear medicine is traced back to the first use of the radionuclide pair 86Y/90Y, which allowed a combination of PET and internal radiotherapy. Whereas the β-emitting therapeutic radionuclide 90Y (t½ = 2.7 d) had been available for a long time via the 90Sr/90Y generator system, the β+ emitter 86Y (t½ = 14.7 h) had to be developed for medical application. A brief outline of the various aspects of radiochemical and nuclear development work (nuclear data, cyclotron irradiation, chemical processing, quality control, etc.) is given. In parallel, the paper discusses the methodology introduced to quantify molecular imaging of 86Y-labelled compounds in terms of multiple and long-term PET recordings. It highlights the ultimate goal of radiotheranostics, namely to extract the radiation dose of the analogue 90Y-labelled compound in terms of mGy or mSv per MBq 90Y injected. Finally, the current and possible future development of theranostic approaches based on different PET and therapy nuclides is discussed.
“…This "nonstandard" PET radionuclide has found its application in the assessment of personalized biodistribution of 90 Y labeled radiopharmaceuticals prior to their administration [1][2][3][4][5][6][7][8]. The absence of γ -rays makes high resolution imaging of 90 Y impossible, therefore biodistribution and dosimetry evaluation is done with a different radionuclide.…”
Yttrium-86 / Yttrium-90 / PET nuclide / Intermediate energy reaction / Chemical separation Summary. Proton irradiation of natural and enriched SrCl 2 targets was used to produce PET radioisotope 86 Y. The proton energy was degraded from the incident 117.8 MeV to induce the 88 Sr( p, 3n) reaction. For the irradiation three pellets made of nat SrCl 2 (6.61 and 74.49 g) and 88 SrCl 2 (5.02 g) were pressed and individually encapsulated in stainless steel target bodies. The two smaller targets were irradiated for 0.5-1 h at the energy ∼ 46 → 37 MeV to take advantage of the peak in the excitation function of the 88 Sr( p, 3n) reaction. The larger target was irradiated at 66.4 → 44.6 MeV. The irradiated pellets were chemically processed to selectively separate 86 Y radioisotope using Eichrom DGA (N,N,N ,N -tetra-noctyldiglycolamide) resin. The production yields of 86 Y were determined to be 10-13 mCi/µA h. Coproduction of 87m Y in the final product was 34% for nat SrCl 2 and 54% for 88 SrCl 2 target. The chemical separation yield of yttrium reached 88-92%. The developed chemical procedure allows for the same day processing and shipment of the isotope to users.
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