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arxiv: 2606.25804 · v1 · pith:CIBUEEDLnew · submitted 2026-06-24 · ⚛️ physics.ins-det · physics.med-ph

Positron Emission Tomography with quantum-entangled Compton events: first imaging results at clinically relevant activities

Mihael Makek , Ana Marija Ko\v{z}uljevi\'c , Tomislav Bokuli\'c , Darko Gro\v{s}ev , Zdenka Kuncic , Siddharth Parashari , Luka Paveli\'c This is my paper

Pith reviewed 2026-06-25 19:01 UTC · model grok-4.3

classification ⚛️ physics.ins-det physics.med-ph
keywords positron emission tomographyquantum entanglementCompton scatteringpolarization correlationPET sensitivityNEMA phantomannihilation photons
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The pith

Polarization correlations of annihilation photons can increase PET sensitivity by up to 10% at clinical activities.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper tests whether quantum entanglement between the two photons from positron annihilation, visible through their polarization correlation, can improve PET imaging. They built a demonstrator using single-layer scintillator detectors to select Compton-scattered events that preserve this correlation. In scans of line sources and a NEMA phantom at activities of 45 MBq and 378 MBq, the correlated events showed up to 20% higher signal-to-random background ratio than ordinary single-pixel events, at the cost of modestly coarser spatial resolution. The authors conclude that mixing both event types in reconstruction could deliver a net 10% sensitivity gain while keeping image quality high.

Core claim

A PET demonstrator with single-layer scintillator polarimeters recorded the first images of 68Ge line sources and a 68Ga-filled NEMA NU-4 phantom at clinically relevant activities by selecting Compton events whose polarization correlation matches the expected entanglement of annihilation quanta. These polarization-correlated events delivered up to 20% better average signal-to-random background ratio than single-pixel events, with spatial resolutions between 3.6 mm and 4.9 mm depending on selection cuts. The measured contrast, signal-to-noise, and resolution values support the estimate that combining the two event classes can raise overall sensitivity by as much as 10% without compromising im

What carries the argument

Single-layer scintillator polarimeters that identify polarization-correlated Compton pairs of annihilation photons by their scattering angles.

If this is right

  • Polarization-correlated Compton events can be added to standard single-pixel events in the same reconstruction without separate hardware.
  • The higher signal-to-random ratio permits either lower injected activity or shorter scan times at fixed image quality.
  • Data-selection criteria that trade spatial resolution for background rejection remain compatible with clinical activity levels up to hundreds of MBq.
  • The approach preserves the ability to form high-quality images of standard phantoms at activities used in patient studies.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Existing PET systems could gain sensitivity by adding polarization-sensitive readout to one or more detector layers rather than replacing entire rings.
  • The method might allow reduced patient dose while maintaining diagnostic contrast, provided the resolution trade-off is balanced by reconstruction algorithms.
  • Further refinement of the angular cuts used to select correlated events could narrow the gap between 2.5 mm and 3.6 mm resolution without losing the background-rejection benefit.

Load-bearing premise

The 20% signal-to-random improvement measured on selected polarization events will produce a net 10% sensitivity gain in a full tomographic reconstruction without introducing new biases or artifacts.

What would settle it

A complete tomographic reconstruction of the NEMA phantom using the combined event selection that yields less than a 5% net sensitivity gain or shows visible artifacts or degraded contrast-to-noise ratio.

Figures

Figures reproduced from arXiv: 2606.25804 by Ana Marija Ko\v{z}uljevi\'c, Darko Gro\v{s}ev, Luka Paveli\'c, Mihael Makek, Siddharth Parashari, Tomislav Bokuli\'c, Zdenka Kuncic.

Figure 1
Figure 1. Figure 1: Schematic illustration of (a) one detector module consisting of four [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Acceptance-corrected azimuthal difference distribution, and the po [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Coincidence time spectra for a) single-pixel events and for b) [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Reconstructed axial image of two 68Ge rod sources (31 slices), and the profile for central slices (8-23) using a) single-pixel events, and b) polarization￾correlated Compton events selected by 45◦ < θ1,2 < 90◦ , |ϕ1 − ϕ2| − 90◦ < 45◦ , and 3.1 mm < d1,2 < 10 mm (6.5 mm), with ring diameter 430 mm. 9 [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Reconstructed axial image of two 68Ge rod sources (31 slices), and the profile for central slices (8-23) using a) single-pixel events, and b) polarization￾correlated Compton events selected by 45◦ < θ1,2 < 90◦ , |ϕ1 − ϕ2| − 90◦ < 45◦ , and 3.1 mm < d1,2 < 10 mm (6.5 mm), with ring diameter 620 mm. 10 [PITH_FULL_IMAGE:figures/full_fig_p010_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Reconstructed image of two 68Ge rod sources with merged SPE and PCE, with 45◦ < θ1,2 < 90◦ , |ϕ1 −ϕ2| −90◦ < 45◦ , and 3.1 mm < d1,2 < 10 mm (6.5 mm): a) axial profile (slices 8-23), b) coronal view, with marked regions of interest. 11 [PITH_FULL_IMAGE:figures/full_fig_p011_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Spatial resolution of the SPE-image, PCE-only image and merged [PITH_FULL_IMAGE:figures/full_fig_p012_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: S/B of the merged SPE+PCE image vs spatial resolution of the PCE [PITH_FULL_IMAGE:figures/full_fig_p012_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Reconstructed image of the NEMA-NU4 phantom (slices 3-5) with [PITH_FULL_IMAGE:figures/full_fig_p013_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: Reconstructed image of the NEMA-NU4 phantom (slices 20-26) with [PITH_FULL_IMAGE:figures/full_fig_p014_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: Contrast in the merged SPE+PCE image for varying PCE-only [PITH_FULL_IMAGE:figures/full_fig_p015_11.png] view at source ↗
read the original abstract

In Positron Emission Tomography, a potential, yet unutilized enhancement, may come from exploiting the quantum entanglement of the annihilation quanta, inscribed in the correlation of their polarizations. To investigate this, we built a PET demonstrator capable of measuring polarization correlations of annihilation quanta by their Compton scattering, based on single-layer scintillator polarimeters. We present a detailed study of the imaging of two $^{68}$Ge line sources, 45 MBq each, to extract the spatial resolution and assess image quality. The results show that a spatial resolution of 2.5$\pm$0.1 mm is obtained using single-pixel events, while resolutions obtained with polarization-correlated Compton events range from 3.6$\pm$0.3 mm to 4.9$\pm$0.3 mm, depending on data selection criteria. We also found that the polarization-correlated Compton events exhibit up to 20% higher average signal to random background ratio compared to the single-pixel events. We also present the first imaging of the NEMA NU-4 phantom filled with a $^{68}$Ga solution of 378 MBq initial activity, successfully combining polarization-correlated events with conventional single-pixel event selection. Based on the extracted spatial resolution, signal-to-background, signal-to-noise, contrast, and contrast-to-noise ratio, we estimate that up to 10% sensitivity increase may be attained by exploiting the polarization-correlated events, while preserving a high image quality.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper reports the construction of a PET demonstrator using single-layer scintillator polarimeters to measure polarization correlations of annihilation quanta via Compton scattering. It presents imaging results for two 68Ge line sources (45 MBq each) yielding 2.5±0.1 mm resolution with single-pixel events and 3.6-4.9 mm with polarization-correlated Compton events (depending on selection criteria), a 20% higher average signal-to-random background ratio for the correlated events, and the first NEMA NU-4 phantom imaging with 68Ga (378 MBq initial activity) by combining both event types. From extracted metrics on resolution, S/RB, SNR, contrast and CNR, the authors estimate up to 10% sensitivity increase while preserving image quality.

Significance. If the net sensitivity gain holds after full reconstruction, this would constitute a concrete experimental step toward exploiting quantum entanglement in PET, potentially improving sensitivity at clinically relevant activities without new hardware. The work is strengthened by direct measurements at high activities, successful phantom imaging that combines event classes, and concrete numerical outcomes on resolution and background ratios rather than purely theoretical predictions.

major comments (2)
  1. [Abstract] Abstract: the headline estimate of 'up to 10% sensitivity increase' is presented as derived from the 20% S/RB improvement, resolution values, and phantom metrics, yet no explicit scaling calculation, event-fraction weighting, or side-by-side tomographic reconstruction (with vs. without the selected polarization-correlated events) is shown to confirm a net positive gain once the resolution degradation (3.6-4.9 mm vs 2.5 mm) and selection thresholds are folded in.
  2. [Results (NEMA phantom)] Results section on NEMA phantom: the reconstruction algorithm is not described, nor is any error propagation or uncertainty quantification supplied for the sensitivity estimate or the contrast-to-noise ratios, leaving the quantitative claim that image quality is 'preserved' without a verifiable basis.
minor comments (2)
  1. [Results (line sources)] The dependence of resolution on post-hoc data selection criteria is noted but the exact thresholds and their impact on event yield should be tabulated for reproducibility.
  2. Clarify whether the reported resolutions are FWHM or other metric and how they were extracted from the line-source profiles.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments and for recognizing the significance of our experimental demonstration. We address each major comment below and will revise the manuscript accordingly.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the headline estimate of 'up to 10% sensitivity increase' is presented as derived from the 20% S/RB improvement, resolution values, and phantom metrics, yet no explicit scaling calculation, event-fraction weighting, or side-by-side tomographic reconstruction (with vs. without the selected polarization-correlated events) is shown to confirm a net positive gain once the resolution degradation (3.6-4.9 mm vs 2.5 mm) and selection thresholds are folded in.

    Authors: We agree that the sensitivity estimate would benefit from an explicit derivation. In the revised manuscript we will add a dedicated paragraph (or supplementary note) that details the scaling procedure, including the weighting by the fraction of polarization-correlated events, the measured 20 % S/RB gain, the resolution values, and the trade-off with the 3.6–4.9 mm versus 2.5 mm resolutions, so that the net-gain claim is fully traceable. revision: yes

  2. Referee: [Results (NEMA phantom)] Results section on NEMA phantom: the reconstruction algorithm is not described, nor is any error propagation or uncertainty quantification supplied for the sensitivity estimate or the contrast-to-noise ratios, leaving the quantitative claim that image quality is 'preserved' without a verifiable basis.

    Authors: We accept that the reconstruction method and uncertainty analysis require fuller documentation. The revised manuscript will include a concise description of the reconstruction algorithm used for the NEMA phantom data together with error propagation and uncertainty estimates on the sensitivity gain, CNR, and related metrics, thereby providing a verifiable basis for the statement that image quality is preserved. revision: yes

Circularity Check

0 steps flagged

No circularity: all reported values are direct experimental measurements with no derivation chain reducing to inputs by construction.

full rationale

The paper reports measured spatial resolutions (2.5 mm for single-pixel events, 3.6-4.9 mm for polarization-correlated events), a 20% higher signal-to-random background ratio, and image quality metrics (SNR, contrast, CNR) extracted from line source and NEMA phantom data. The 10% sensitivity estimate is presented as a qualitative extrapolation from these independent experimental quantities rather than any equation, fit, or self-citation that would make the output equivalent to the input by construction. No self-definitional steps, fitted parameters renamed as predictions, or load-bearing self-citations appear in the derivation of the central claims.

Axiom & Free-Parameter Ledger

1 free parameters · 0 axioms · 0 invented entities

The central claim rests on experimental measurements and post-selection of events; no new theoretical axioms or invented particles are introduced. Data selection criteria function as free parameters whose exact values are not reported in the abstract.

free parameters (1)
  • polarization correlation selection thresholds
    Resolution and signal-to-background vary with the strictness of the correlation cut; these thresholds are chosen after data collection and affect the quoted 3.6-4.9 mm range and the 20% background improvement.

pith-pipeline@v0.9.1-grok · 5843 in / 1397 out tokens · 16931 ms · 2026-06-25T19:01:35.714686+00:00 · methodology

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