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arxiv: 2511.20514 · v4 · submitted 2025-11-25 · ⚛️ physics.med-ph

Real-time 3D Ultrasonic Needle Tracking with a Photoacoustic Beacon

Christian Baker , Weidong Liang , Richard Colchester , Peng Lei , Francois Joubert , Sebastien Ourselin , Simeon West , Adrien Desjardins
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Athanasios Diamantopoulos Wenfeng Xia
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Pith reviewed 2026-05-17 04:36 UTC · model grok-4.3

classification ⚛️ physics.med-ph
keywords photoacoustic beaconneedle tracking3D ultrasoundminimally invasive proceduresbiopsy guidancetime-of-flight localizationultrasound imaginginterventional ultrasound
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The pith

A photoacoustic beacon in the needle bevel delivers real-time 3D tip tracking during ultrasound procedures with better than 2 mm accuracy.

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

The paper presents a combined 2D ultrasound imaging and 3D needle tracking system for use in minimally invasive procedures such as biopsies. A small photoacoustic source at the needle tip generates sound waves whose arrival times at receivers around the probe are used to compute the tip's location in three dimensions. Experiments in water and tissue phantoms showed tracking errors under 2 mm even at 140 mm depth, and a study with 12 clinicians found that brief training lowered the rate of missed targets from 15.8 percent to 10.3 percent. These results suggest the method can reduce confusion about needle position that currently occurs in 2D images at steep angles or in heterogeneous tissue.

Core claim

The authors developed an interventional ultrasound system that performs standard 2D B-mode imaging while simultaneously tracking the needle tip in 3D. The tip position is obtained from the time-of-flight of ultrasound pulses created by a photoacoustic beacon placed in the needle bevel and detected by a sparse receiver array placed around the curvilinear imaging probe. In water the system maintained accuracy better than 2 mm out to 140 mm depth; in an ex-vivo tissue phantom the average error was approximately 2 mm when compared with CT reference positions. A usability test with 12 clinicians performing biopsy tasks showed that after a few minutes of training the failure rate fell by 35 % from

What carries the argument

Photoacoustic beacon embedded in the needle bevel, whose generated ultrasound signals are timed at a surrounding sparse receiver array to compute 3D tip location.

Load-bearing premise

The photoacoustic signal produced at the needle bevel remains strong and its travel time continues to match the true tip position even when tissue properties, optical absorption, or probe placement vary during use.

What would settle it

A side-by-side comparison in which the 3D tracked tip position differs by more than 2 mm from the actual location measured by CT or MRI in living tissue would disprove the reported accuracy.

Figures

Figures reproduced from arXiv: 2511.20514 by Adrien Desjardins, Athanasios Diamantopoulos, Christian Baker, Francois Joubert, Peng Lei, Richard Colchester, Sebastien Ourselin, Simeon West, Weidong Liang, Wenfeng Xia.

Figure 1
Figure 1. Figure 1: Conceptual graphic and schematic of the 3D ultrasonic needle tracking system, showing [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Diagram of the tracking pipeline, showing how the acquisition of tracking waveforms is [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Visualisations related to registration and cursor rendering: (a) screenshot of the tracking [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: (a) Diagram of the ex vivo tissue phantoms used for the usability studies. Dark purple lesions were present in the phantoms used for both studies, while light purple lesions were only present in the phantom used for the first study. (b) Photograph of the phantom in-use during the usability tests. (c) Screenshot of the tracking software taken during the usability study, annotated (white) to show the locatio… view at source ↗
Figure 5
Figure 5. Figure 5: Results of the measurement of tracking accuracy in water. The top row presents the [PITH_FULL_IMAGE:figures/full_fig_p012_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Comparison of needle tip locations determined by X-ray CT (circles) and the tracking device [PITH_FULL_IMAGE:figures/full_fig_p013_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Cropped frames from the recorded video of the [PITH_FULL_IMAGE:figures/full_fig_p014_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Usability test results. (a) Number of usability participants who succeeded in all procedures [PITH_FULL_IMAGE:figures/full_fig_p015_8.png] view at source ↗
read the original abstract

Many minimally invasive procedures, such as core needle biopsy of focal liver lesions, nerve blocks, and fetal and vascular interventions, are typically performed under ultrasound guidance, which provides real-time, high-resolution visualisation of tissue anatomy. Accurate and efficient localisation of the needle tip relative to patient anatomy is essential for guiding the needle towards the procedure target, avoiding adverse events and reducing the need for repeat procedures. However, the 3D nature of the procedure and poor image contrast of the needle in heterogeneous tissue or at steep insertion angles often lead to confusion over the true location of the tip within the 2D guidance images, and existing methods to enhance needle visibility largely remain limited to 2D. Here, we present a novel interventional ultrasound system capable of 2D B-mode imaging and 3D needle tracking. The tip location is determined from the time-of-flight of ultrasound generated by a photoacoustic beacon embedded in the needle bevel and received by a sparse receiver array distributed around the imaging system's curvilinear ultrasound probe. The measured tracking accuracy was better than 2 mm for depths up to 140 mm in water, and approximately 2 mm on average in an ex vivo tissue phantom, with referenced positions derived from X-ray computed tomography. In a usability study involving 12 clinicians performing biopsy procedures in a ex vivo tissue phantom, the failure rate was reduced by 35%, from 15.8% to 10.3% after only a few minutes of training. These results demonstrate that the proposed system has strong potential to support a wide range of minimally invasive procedures by enabling clinicians to accurately target small anatomical structures, improving the efficiency and effectiveness of diagnostic sampling and therapeutic delivery or ablation, and reducing the risk of adverse events.

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 manuscript presents a novel interventional ultrasound system that enables simultaneous 2D B-mode imaging and real-time 3D needle tracking. A photoacoustic beacon embedded in the needle bevel generates ultrasound signals whose time-of-flight is measured by a sparse receiver array distributed around a curvilinear probe; multilateration then yields the tip coordinates. The authors report tracking accuracy better than 2 mm for depths up to 140 mm in water and approximately 2 mm on average in an ex-vivo tissue phantom, with ground-truth positions obtained from X-ray CT. A usability study with 12 clinicians performing biopsy procedures in an ex-vivo phantom showed a reduction in failure rate from 15.8 % to 10.3 % after brief training.

Significance. The work addresses a clinically relevant problem of needle-tip localization in ultrasound-guided interventions. The reported sub-2 mm accuracy in controlled settings and the observed improvement in clinician performance are promising and could, if robustly validated, reduce repeat procedures and adverse events. The integration of photoacoustic generation with a sparse receiver array is technically inventive; however, the strength of the central claim is currently limited by the absence of detailed error analysis and tests under realistic acoustic heterogeneity.

major comments (2)
  1. [Results / Discussion] The central accuracy claim (better than 2 mm in water to 140 mm; ~2 mm average in ex-vivo phantom) is obtained via time-of-flight multilateration that presupposes a single, known propagation speed and straight-line paths. No quantification of refraction, speed gradients, or path-dependent errors is described, which directly undermines extrapolation to heterogeneous clinical tissue.
  2. [Methods] The manuscript provides no detailed description of the multilateration algorithm, sound-speed calibration procedure, or propagation of measurement uncertainties to the final tip coordinates. Without these elements it is impossible to assess whether the reported CT-referenced errors are statistically supported or merely point estimates.
minor comments (2)
  1. [Abstract] Abstract: 'a ex vivo' should read 'an ex vivo'.
  2. [Results] The usability-study results are presented without p-values, confidence intervals, or details of the statistical test used to support the 35 % failure-rate reduction.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive and positive review of our manuscript. The comments highlight important aspects of error analysis and methodological transparency that we address below. We have revised the manuscript to incorporate additional details and discussion where feasible.

read point-by-point responses

  1. Referee: [Results / Discussion] The central accuracy claim (better than 2 mm in water to 140 mm; ~2 mm average in ex-vivo phantom) is obtained via time-of-flight multilateration that presupposes a single, known propagation speed and straight-line paths. No quantification of refraction, speed gradients, or path-dependent errors is described, which directly undermines extrapolation to heterogeneous clinical tissue.

    Authors: We agree that explicit quantification of refraction and speed-gradient effects would further support extrapolation. In the homogeneous water-tank experiments the constant-speed assumption is valid and the sub-2 mm accuracy is measured directly against known geometry. In the ex-vivo phantom the reported ~2 mm average error is an empirical result obtained by direct comparison with X-ray CT ground truth, thereby capturing the net effect of any residual heterogeneity present in that model. Nevertheless, we acknowledge that clinical tissue may exhibit greater acoustic variation; we have therefore added a dedicated paragraph in the revised Discussion section that (i) cites the empirical CT-validated errors, (ii) discusses the expected magnitude of refraction-induced bias based on literature values for soft-tissue speed variation, and (iii) outlines planned future work on real-time speed calibration. revision: partial

  2. Referee: [Methods] The manuscript provides no detailed description of the multilateration algorithm, sound-speed calibration procedure, or propagation of measurement uncertainties to the final tip coordinates. Without these elements it is impossible to assess whether the reported CT-referenced errors are statistically supported or merely point estimates.

    Authors: We accept this criticism and have substantially expanded the Methods section. The revised text now includes: (a) the explicit multilateration equations and the nonlinear least-squares solver used to obtain 3D tip coordinates from the four time-of-flight measurements; (b) the sound-speed calibration protocol, performed in a temperature-controlled water bath with independent verification against the phantom material; and (c) a first-order uncertainty propagation analysis that combines timing jitter, speed uncertainty, and receiver-position errors to yield position covariance estimates. The reported accuracies are now accompanied by standard deviations computed across repeated trials, confirming that the values are statistically supported rather than single-point estimates. revision: yes

Circularity Check

0 steps flagged

No circularity: accuracy claims are direct experimental comparisons to independent CT references

full rationale

The paper reports measured tracking performance from physical experiments in water and ex vivo phantoms, with tip positions validated against separate X-ray CT scans. No mathematical derivation, fitted parameters, or model equations are presented whose outputs reduce to the inputs by construction. Time-of-flight multilateration is a standard physical method whose accuracy is tested empirically rather than assumed; the uniform sound-speed assumption is an untested limitation but does not create circularity in the reported results. Self-citations are absent from the load-bearing claims.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 1 invented entities

The work is primarily experimental device development; it relies on the established photoacoustic effect and time-of-flight ranging but introduces a custom beacon integration whose performance is validated empirically rather than derived from first principles.

invented entities (1)
  • Photoacoustic beacon embedded in needle bevel no independent evidence
    purpose: Generates localized ultrasound pulse for time-of-flight 3D localization
    New hardware component whose optical and acoustic properties are tailored for this tracking application.

pith-pipeline@v0.9.0 · 5647 in / 1273 out tokens · 24762 ms · 2026-05-17T04:36:54.659745+00:00 · methodology

discussion (0)

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Reference graph

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