Film In Phantom Research Articles

Markerless dynamic tumor tracking (MDTT) radiotherapy using diaphragm as a surrogate for liver targets.

To assess the feasibility of using the diaphragm as a surrogate for liver targets during MDTT. Diaphragm as surrogate for markers: a dome-shaped phantom with implanted markers was fabricated and underwent dual-orthogonal fluoroscopy sequences on the Vero4DRT linac. Ten patients participated in an IRB-approved, feasibility study to assess the MDTT workflow. All images were analyzed using an in-house program to back-project the diaphragm/markers position to the isocenter plane. ExacTrac imager log files were analyzed. Diaphragm as tracking structure for MDTT: The phantom "diaphragm" was contoured as a markerless tracking structure (MTS) and exported to Vero4DRT/ExacTrac. A single field plan was delivered to the phantom film plane under static and MDTT conditions. In the patient study, the diaphragm tracking structure was contoured on CT breath-hold-exhale datasets. The MDTT workflow was applied until just prior to MV beam-on. Diaphragm as surrogate for markers: phantom data confirmed the in-house 3D back-projection program was functioning as intended. In patients, the diaphragm/marker relative positions had a mean±RMS difference of 0.70±0.89, 1.08±1.26, and 0.96±1.06mm in ML, SI, and AP directions. Diaphragm as tracking structure for MDTT: Building a respiratory-correlation model using the diaphragm as surrogate for the implanted markers was successful in phantom/patients. During the tracking verification imaging step, the phantom mean±SD difference between the image-detected and predicted "diaphragm" position was 0.52±0.18mm. The 2D film gamma (2%/2mm) comparison (static to MDTT deliveries) was 98.2%. In patients, the mean difference between the image-detected and predicted diaphragm position was 2.02±0.92mm. The planning target margin contribution from MDTT diaphragm tracking is 2.2, 5.0, and 4.7mm in the ML, SI, and AP directions. In phantom/patients, the diaphragm motion correlated well with markers' motion and could be used as a surrogate. MDTT workflows using the diaphragm as the MTS is feasible using the Vero4DRT linac and could replace the need for implanted markers for liver radiotherapy.

Customizable optical tissue phantom platform for characterization of fluorescence imaging device sensitivity.

Optical tissue phantoms serve as inanimate and stable reference materials used to calibrate, characterize, standardize, and test biomedical imaging instruments. Although various types of solid tissue phantoms have been described in the literature, current phantom models are limited in that they do not have a depth feature that can be adjusted in real-time, they cannot be adapted to other applications, and their fabrication can be laborious and costly. Our goal was to develop an optical phantom that could assess the imaging performance of fluorescence imaging devices and be customizable for different applications. We developed a phantom with three distinct components, each of which can be customized. We present a method for fabricating a solid optical tissue that contains (1)an adjustable depth capability using thin film phantoms, (2)a refillable chip loaded with fluorophores of the user's choice in various desired quantities, and (3)phantom materials representative of different tissue types. This article describes the development of phantom models that are customizable, adaptable, and easy to design and fabricate.

Development of Total Lymphoid Irradiation (TLI)-Dedicated Shielding and Image-Guided System and Dose Evaluation Using 3D-Printed Rat Phantom.

PurposeThe purpose of this study is to propose a technique for delivering accurate doses in an image-guided system by developing an experimental setup optimized for total lymphoid irradiation (TLI) in rat lung transplantation.Materials and MethodsIn this study, a position-controlled shielding system was developed, and the dose was quantitatively evaluated using a 3D rat phantom and Gafchromic EBT3 film. In addition, we made our own image-guided system that allows the position of the rat and the shielding system to be confirmed during TLI.ResultsAs a result of using the position-controlled shielding system, it was found that the doses to the head and lungs were reduced by 93.1 and 87.4%, respectively, of the prescribed doses. In addition, it was shown that the position of the shielding system can be easily confirmed by using the image guidance system.ConclusionA shielding apparatus that can control dose delivery according to the size of the rat can optimize the dose for TLI in rat lung transplantation.

Dose distribution in a radiosurgery treatment for an acoustic neuroma

Evaluation of the dose distribution delivered in a radiosurgery treatment of an acoustic neuroma using an adapted Alderson phantom and radiochromic film to assess absolute dose. A system was developed to perform the dose measurements, using the Alderson Rando phantom´s head carrying a modified slice, where a material reproducing the tumor was inserted. The phantom’s head with the modified slice was irradiated in a medical linear accelerator, using a procedure similar to that adopted in real cases, and radiochromic films were used to assess dose values. The suitability of the dose distribution delivered in the treatment was evaluated by comparing the Dose Volume Histograms, obtained from the Treatment Planning System (TPS) and by radiochromic film measurements. An agreement around 3% between experimental data and TPS´s calculations, showing an acceptable concordance with the planning results. The established approach of transforming 2D arrays of dose in a 3D one is satisfactory, validating it. The developed method shows to be an excellent alternative to quality control in radiosurgery using the radiochromic film to assess absolute dose.

Proof-of-concept delivery of intensity modulated arc therapy on the Elekta Unity 1.5 T MR-linac

In this work we present the first delivery of intensity modulated arc therapy on the Elekta Unity 1.5 T MR-linac. The machine’s current intensity modulated radiation therapy based control system was modified suitably to enable dynamic delivery of radiation, for the purpose of exploring MRI-guided radiation therapy adaptation modes in a research setting. The proof-of-concept feasibility was demonstrated by planning and delivering two types of plans, each investigating the performance of different parts of a dynamic treatment. A series of fixed-speed arc plans was used to show the high-speed capabilities of the gantry during radiation, while several fully modulated prostate plans—optimised following the volumetric modulated arc therapy approach—were delivered in order to establish the performance of its multi-leaf collimator and diaphragms. These plans were delivered to Delta4 Phantom+ MR and film phantoms passing the clinical quality assurance criteria used in our clinic. In addition, we also performed some initial MR imaging experiments during dynamic therapy, demonstrating that the impact of radiation and moving gantry/collimator components on the image quality is negligible. These results show that arc therapy is feasible on the Elekta Unity system. The machine’s high performance components enable dynamic delivery during fast gantry rotation and can be controlled in a stable fashion to deliver fully modulated plans.

(Re)producing Marriage

This article considers aspects of Stanley Cavell’s film-philosophy in the light of Paul Thomas Anderson’s 2017 film Phantom Thread, and vice versa. Methodologically, it concentrates on the interpretation of Cavell’s writing and of Anderson’s film. In arguing that Phantom Thread has affinities with Cavell’s famous cinematic genre of remarriage comedy, the article addresses Cavell’s understanding of the production of what Wittgenstein calls “criteria.” Affirming Steven J. Affeldt’s insistence that the production of criteria is occasioned by crisis, the article explores the claim that Phantom Thread can be viewed as the story of the production of criteria in response to a situation of interpersonal confusion and disorientation, criteria according to which a remarriage may, or may not, eventually take place. The results of this enquiry, it is hoped, will help both to clarify aspects of Cavell’s philosophy and to articulate something of the nature of the distinctive cinematic achievement that Anderson’s film represents.

Effective dose and image quality for intraoperative imaging with a cone-beam CT and a mobile multi-slice CT in spinal surgery: A phantom study.

To compare the effective dose (ED) and image quality (IQ) of O-arm cone-beam CT (Medtronic, Minneapolis, MN, USA) and Airo multi-slice CT (Brainlab AG, Munich, Germany) for intraoperative-CT (i-CT) in spinal surgery. The manufacturer-defined protocols available in the O-arm and Airo systems for three-dimensional lumbar spine imaging were compared. Organ dose was measured both with thermo-luminescent dosimeters and GafChromic films in the Alderson RadiationTherapy anthropomorphic phantom. A subjective analysis was performed by neurosurgeons to compare the clinical IQ of the anthropomorphic phantom images acquired with the different i-CT systems and imaging protocols. Image uniformity, noise, contrast-to-noise-ratio (CNR), and spatial resolution were additionally assessed with the Catphan 504 phantom. O-arm i-CT caused 56% larger ED than Airo due to the high definition (HD) imaging protocol. The noise was larger for O-arm images leading to a lower CNR than that measured for Airo. Moreover, scattering and beam hardening effects were observed in the O-arm images. Better spatial resolution was measured for the O-arm system (9 lp/cm) than for Airo (4 lp/cm). For all the investigated protocols, O-arm was found to be better for identifying anatomical features important for accurate pedicle screw positioning. According to phantom measurements, the HD protocol of O-arm offered better clinical IQ than Airo but larger ED. The larger noise of O-arm images did not compromise the clinical IQ while the superior spatial resolution of this system allowed a better visibility of anatomical features important for pedicle screw positioning in the lumbar region.

A dosimetry study of post-mastectomy radiation therapy with AeroForm tissue expander.

PurposeTo evaluate the dosimetric effects of the AeroFormTM (AirXanpders®, Palo Alto, CA) tissue expander in‐situ for breast cancer patients receiving post‐mastectomy radiation therapy.Methods and MaterialsA film phantom (P1) was constructed by placing the metallic canister of the AeroForm on a solid water phantom with EBT3 films at five depths ranging from 2.6 mm to 66.2 mm. A breast phantom (P2), a three‐dimensional printed tissue‐equivalent breast with fully expanded AeroForm in‐situ, was placed on a thorax phantom. A total of 21 optical luminescent dosimeters (OLSDs) were placed on the anterior skin–gas interface and the posterior chest wall–metal interface of the AeroForm. Both phantoms were imaged with a 16‐bit computed tomography scanner with orthopedic metal artifact reduction. P1 was irradiated with an open field utilizing 6 MV and 15 MV photon beams at 0°, 90°, and 270°. P2 was irradiated using a volumetric modulated arc therapy plan with a 6 MV photon beam and a tangential plan with a 15 MV photon beam. All doses were calculated using Eclipse (Varian, Palo Alto, CA) with AAA and AcurosXB (AXB) algorithms.ResultsThe average dose differences between film measurements and AXB in the region adjacent to the canister in P1 were within 3.1% for 15 MV and 0.9% for 6 MV. Local dose differences over 10% were also observed. In the chest wall region of P2, the median dose of OLSDs in percentage of prescription dose were 108.4% (range 95.4%–113.0%) for the 15MV tangential plan and 110.4% (range 99.1%–113.8%) for the 6MV volumetric modulated arc therapy plan. In the skin–gas interface, the median dose of the OLSDs were 102.3% (range 92.7%–107.7%) for the 15 MV plan and 108.2% (range 97.8–113.5%) for the 6 MV plan. Measured doses were, in general, higher than calculated doses with AXB calculations. The AAA dose algorithms produced results with slightly larger discrepancies between measurements compared with AXB.ConclusionsThe AeroForm creates significant dose uncertainties in the chest wall–metal interface. The AcurosXB dose calculation algorithm is recommended for more accurate calculations. If possible, post‐mastectomy radiation therapy should be delivered after the permanent implant is in place.

PSEUDO-3D IMRT VERIFICATION WITH EBT3 RADIOCHROMIC FILM

This work proposes a new method for pseudo-3D verification of intensity-modulated radiation therapy (IMRT) dose distributions. Unlike commercial solutions, it uses measured doses only for gamma evaluation. Its resolution is far better than with electronic detectors within the measured plane and comparable in other directions. It is readily available at clinics because it uses existing resources-a slab phantom and EBT3 films. The method was tested on six IMRT clinical cases. An in-house code for 2D and pseudo-3D gamma analysis was written in MATLAB and compared to OmniPro I'mRT.

Comparison of the radiochromic EBT2 responses for4 MV LINAC in calibration processes

Actually, cancer has gained a larger dimension and become a global public health problem. Radiotherapy (RT) is a neoplasia treatment and RT linear accelerators must undergo a strict dose quality control. Water or solid water phantoms can be used with this intuit. In recent years, radiochromic films with equivalent tissue composition have been widely used as dosimeters in the medical field. In this work the proposal was to analyze two distinct radiochromic film responses in water and solid water phantoms, a LINAC spectrum of 4MV beam. Solid water phantom, water phantom and EBT2 Radiochromic films were set in two distinct process of calibration. Films were exposed to a set of absorbed doses established by distinct monitor units (MU) specified in RT-center. Mathematical relations between the degree of red-intensity from digitized films and the absorbed dose for both methods were established. The coefficients of the polynomial function of the calibration curve were determined from the Origin software. The uncertainty of both processes was analyzed. The efficiency of the two calibration processes was set up. The adjustment of the calibration curve provided the coefficients of the second-order equation that relates the dose absorbed with the optical density of the film. The uncertainty regarding the calibration performed in water and solid water and the dose-error accuracy are in agreement with the literature. Both water and solid water were effective in calibration and can be used in routines of quality-control measurements. The results show that EBT2-radiochromic films are suitable to for dose-calibration in RT.

3 Single shot stereotactic body radiotherapy for localized prostate cancer: Case report

Introduction We report on the quality assurance (QA) and treatment management of the first patient included in the ONE SHOT trial. ONE SHOT, single shot stereotactic body radiotherapy (SBRT) for localized prostate cancer, is a multicenter single arm phase I/II trial which will enrolled 45 patients in total. Its main objective is to determine the safety and efficacy of a single SBRT fraction at a dose of 19 Gy in patients with localized prostate cancer. Indeed, recent data showed good tolerance and biochemical control after single interstitial application of 19/20 Gy to the prostate or after SBRT in five fractions, so that ultra-hypofractionated single-dose SBRT employing imaged-guided radiotherapy and real-time tumour tracking with implanted electromagnetic transponders (Calypso® with DynamicEdge™ gating) may be feasible with a safe toxicity profile and an optimal long-term tumor control. Methods Three Calypso beacons were implanted in the patient prostate 4 days before the planning CT scan. The patient was imaged with empty rectum and full bladder with 1 mm slices thickness. For urethra contouring and visualization during treatment, a non-radiopaque catheter was inserted during CT simulation and before the treatment delivery. The prescription dose was 19 Gy in a single fraction to the whole prostate gland ±proximal seminal vesicles and 17 Gy to the urethra planning-risk volume (PRV). The plan consisted into 2 full VMAT arcs using 10MV FFF beam from the TrueBeam linac with 6 degrees of freedom couch. It was optimized on Eclipse TPS (Varian) with Rapidplan™, a knowledge-based planning software, and the dose was calculated with AAA v13026 algorithm. QA controls included portal dosimetry (PD) (Varian, PDIP v13026), absolute dose measurements with Diamond detector (PTW) inserted in Lucy 3D QA phantom (Standard Imaging) and Gafchromic film measurements (EBT-XD films). Results The treatment plan of the first ONE SHOT patient satisfied the dose-volume constraints for all OARs and the coverage requirement for the PTV and PRV. The total number of monitor units for the two arcs was 7125. The results of the PD QA were within the tolerance, with Gamma index 1%/1 mm = 98.7%. For absolute dose measurement, the difference between expected and measured dose was 1.7% inside PRV and 3% in the PTV region. Film gamma index with 4%/1 mm criteria was 97.4%. Patient positioning before treatment required two cone-beam CT (CBCT) before the first arc, because Calypso detected a 2 mm shift in the longitudinal direction after the couch adjustment made after the 1st CBCT. The first arc was treated without interruption and a third CBCT was acquired between the arcs. However, no shift was observed and the second arc was treated without patient realignment. Conclusions QA results were all within the tolerance for SBRT treatment and the first ONE SHOT patient was treated successfully as planned.

Controlling Voices: Singing in Phantom Films

Controlling Voices: Singing in <i>Phantom</i> Films

15 years of 106Ru eye plaque dosimetry at Memorial Sloan-Kettering Cancer Center and Weill Cornell Medical Center using radiochromic film in a Solid Water phantom

Purpose. 106Ru eye plaques are used for treatment of intraocular malignancies, providing a good alternative to enucleation. We perform our own acceptance testing and commissioning of 106Ru eye plaques using radiochromic film as recommended by ISO standard 21439:2009 ‘Clinical dosimetry-beta radiation sources for brachytherapy’. A Solid Water ‘eye’ phantom with several novel features and related tools were developed for accurate radiochromic film dosimetry of eye plaques. Methods. The phantom enables full 3D dosimetric characterization of eye plaques. Films perpendicular to the central axis of the eye plaques are sandwiched between inserts in the phantom. Small holes in the phantom inserts enable marking the films with respect to the eye plaques, assuring exact geometrical co-registration. Special thin unlaminated radiochromic films were utilized, enabling dosimetric measurements virtually at the surface of the eye plaques. Precise film punches were developed in order to cut films with diameters as small as 8.5 mm and make cutouts in films without damaging the cut edges. Results. Full dosimetric characterization of three CCX type and partial characterization of a CIA type 106Ru eye plaques is presented. Replicate film results were reproducible to within 4%–5%. Even 4% non-uniformities in planar dose rates were easily detected. Comparison with Monte Carlo calculations by Hermida-López 2013 Med. Phys. 40 101705-1–101705-13, found good agreement along the central axis, but some lateral differences. Conclusions. Accurate and precise 106Ru eye plaque dosimetry was achieved utilizing radiochromic film in the phantom introduced here. Co-registration of eye plaques and films permits not only precise treatment planning calculations along the central axis of the plaque, but also accounts for dosimetric non-uniformities using 2D or 3D methodologies. Dose measurements on the inner surface of the plaques provide precise assessment of the scleral dose, its homogeneity, and the active area of the plaques for coverage determination.

Super-resolved thickness maps of thin film phantoms and in vivo visualization of tear film lipid layer using OCT.

In optical coherence tomography (OCT), the axial resolution is directly linked to the coherence length of the employed light source. It is currently unclear if OCT allows measuring thicknesses below its axial resolution value. To investigate spectral-domain OCT imaging in the super-resolution regime, we derived a signal model and compared it with the experiment. Several island thin film samples of known refractive indices and thicknesses in the range 46 - 163 nm were fabricated and imaged. Reference thickness measurements were performed using a commercial atomic force microscope. In vivo measurements of the tear film were performed in 4 healthy subjects. Our results show that quantitative super-resolved thickness measurement can be performed using OCT. In addition, we report repeatable tear film lipid layer visualization. Our results provide a novel interpretation of the OCT axial resolution limit and open a perspective to deeper extraction of the information hidden in the coherence volume.

Concurrent photoacoustic-ultrasound imaging using single-laser pulses.

Conventional ultrasound (US) and photoacoustic (PA) multimodality imaging require the use of a US pulse for US data acquisition and a laser pulse for PA data acquisition. We propose a method for concurrent US and PA data acquisition with a single-laser pulse. A light-absorbing multilayer film that can generate a US pulse based on the thermoelastic effect is used. The selection of appropriate layer thickness, interlayer spacing, and absorption coefficient allows the spectral characteristics of the generated US signal to be adjusted so that it does not overlap with the spectrum of the PA signal generated by the light transmitting through the layer. Thus, the US signal and the PA signal can be generated, received, and separated by using a single-laser pulse combined with spectral filtering. This method is demonstrated using a multilayer film that generates US signals with a center frequency of 24.2 MHz and fractional bandwidth of 26.8%. The synthetic-aperture focusing technique is applied to improve the lateral resolution and the signal-to-noise ratio. A cyst-like phantom and a film phantom were used to demonstrate the feasibility of this method of concurrent PA-US imaging using single-laser pulses.

SU‐E‐T‐339: Dosimetric Verification of Acuros XB Dose Calculation Algorithm On An Air Cavity for 6‐MV Flattening Filter‐Free Beam

Purpose:This study was to verify the accuracy of Acuros XB (AXB) dose calculation algorithm on an air cavity for a single radiation field using 6‐MV flattening filter‐free (FFF) beam.Methods:A rectangular slab phantom containing an air cavity was made for this study. The CT images of the phantom for dose calculation were scanned with and without film at measurement depths (4.5, 5.5, 6.5 and 7.5 cm). The central axis doses (CADs) and the off‐axis doses (OADs) were measured by film and calculated with Analytical Anisotropic Algorithm (AAA) and AXB for field sizes ranging from 2 Χ 2 to 5 Χ 5 cm2 of 6‐MV FFF beams. Both algorithms were divided into AXB_w and AAA _w when included the film in phantom for dose calculation, and AXB_w/o and AAA_w/o in calculation without film. The calculated OADs for both algorithms were compared with the measured OADs and difference values were determined using root means squares error (RMSE) and gamma evaluation.Results:The percentage differences (%Diffs) between the measured and calculated CAD for AXB_w was most agreement than others. Compared to the %Diff with and without film, the %Diffs with film were decreased than without within both algorithms. The %Diffs for both algorithms were reduced with increasing field size and increased relative to the depth increment. RMSEs of CAD for AXB_w were within 10.32% for both inner‐profile and penumbra, while the corresponding values of AAA_w appeared to 96.50%.Conclusion:This study demonstrated that the dose calculation with AXB within air cavity shows more accurate than with AAA compared to the measured dose. Furthermore, we found that the AXB_w was superior to AXB_w/o in this region when compared against the measurements.

Measurement of a multi-layered tear film phantom using optical coherence tomography and statistical decision theory.

To extend our understanding of tear film dynamics for the management of dry eye disease, we propose a method to optically sense the tear film and estimate simultaneously the thicknesses of the lipid and aqueous layers. The proposed method, SDT-OCT, combines ultra-high axial resolution optical coherence tomography (OCT) and a robust estimator based on statistical decision theory (SDT) to achieve thickness measurements at the nanometer scale. Unlike conventional Fourier-domain OCT where peak detection of layers occurs in Fourier space, in SDT-OCT thickness is estimated using statistical decision theory directly on the raw spectra acquired with the OCT system. In this paper, we demonstrate in simulation that a customized OCT system tailored to ~1 µm axial point spread function (FWHM) in the corneal tissue, combined with the maximum-likelihood estimator, can estimate thicknesses of the nanometer-scale lipid and micron-scale aqueous layers of the tear film, simultaneously, with nanometer precision. This capability was validated in experiments using a physical phantom that consists of two layers of optical coatings that mimic the lipid and aqueous layers of the tear film.

Quality assurance of stereotactic alignment and patient positioning mechanical accuracy for robotized Gamma Knife radiosurgery

The automatic patient positioning system and its alignment is critical and specified to be less than 0.35 mm for a radiosurgical treatment with the latest robotized Gamma Knife Perfexion (GKPFX). In this study, we developed a quantitative QA procedure to verify the accuracy and robustness of such a system. In particular, we applied the test to a unit that has performed >1000 procedures at our institution. For the test, a radiochromic film was first placed inside a spherical film phantom and then irradiated with a sequence of linearly placed shots of equal collimator size (e.g. 4 mm) via the Leksell Gamma Knife Perfexion system (PFX). The shots were positioned with either equal or unequal gaps of approximately 8 mm both at center and off-center positions of the patient positioning system. Two independent methods of localizing the irradiation shot center coordinates were employed to measure the gap spacing between adjacent shots. The measured distance was then compared with the initial preset values for the test. On average, the positioning uncertainty for the PFX delivery system was found to be 0.03 ± 0.2 mm (2σ). No significant difference in the positioning uncertainty was noted among measurements in the x-, y- and z-axis orientations. In conclusion, a simple, fast, and quantitative test was developed and demonstrated for routine QA of the submillimeter PFX patient positioning system. This test also enables independent verification of any patient-specific shot positioning for a critical treatment such as a tumor in the brainstem.

Influence of tube voltage on digitized image qualityof patients exposed to occupational dust: phantoms and clinical studies

Background High-voltage analog X-ray examination is a main tool for pneumoconiosis, which is challenged by digital radiography (DR). The tube voltage of DR chest films required for diagnosis and staging of pneumoconiosis is concerned technically. We investigated the influence of the tube voltage on chest X-ray DR image quality of patients exposed to occupational dust. Methods DR images of the CDRAD2.0model, an anatomical chest phantom, and 136 exposed workers were analyzed at different tube voltages by threereaders. Image quality factors (IQF) were calculated and compared using the CDRAD2.0 model. DR images of ten anatomic positions were scored against those of the high-kilovolt chest films in anatomical phantom and clinical cases, and differences in scores were analyzed. Results In the CDRAD2.0 model, all three readers had a minimal IQF at 120 kV (mean: 22.25 kV). The differences in the mean IQF of DR images at different tube voltages was significant (F=13.78, P&lt;0.001). The IQF of DR imaging at 120 kV was similar to high kilovolt analog imaging (t=-0.58, P&gt;0.05). In the anatomic phantom and clinical cases, the DR images at 120 kV were closest in anatomical detail to the high kV analog images, and the means were similar (P&gt;0.05). Conclusions Among different tube voltages, DR image quality is closest to the high kilovolt analog images at 120 kV in patients exposed to occupational dust.

4D optimization of scanned ion beam tracking therapy for moving tumors

Motion mitigation strategies are needed to fully realize the theoretical advantages of scanned ion beam therapy for patients with moving tumors. The purpose of this study was to determine whether a new four-dimensional (4D) optimization approach for scanned-ion-beam tracking could reduce dose to avoidance volumes near a moving target while maintaining target dose coverage, compared to an existing 3D-optimized beam tracking approach. We tested these approaches computationally using a simple 4D geometrical phantom and a complex anatomic phantom, that is, a 4D computed tomogram of the thorax of a lung cancer patient. We also validated our findings using measurements of carbon-ion beams with a motorized film phantom. Relative to 3D-optimized beam tracking, 4D-optimized beam tracking reduced the maximum predicted dose to avoidance volumes by 53% in the simple phantom and by 13% in the thorax phantom. 4D-optimized beam tracking provided similar target dose homogeneity in the simple phantom (standard deviation of target dose was 0.4% versus 0.3%) and dramatically superior homogeneity in the thorax phantom (D5–D95 was 1.9% versus 38.7%). Measurements demonstrated that delivery of 4D-optimized beam tracking was technically feasible and confirmed a 42% decrease in maximum film exposure in the avoidance region compared with 3D-optimized beam tracking. In conclusion, we found that 4D-optimized beam tracking can reduce the maximum dose to avoidance volumes near a moving target while maintaining target dose coverage, compared with 3D-optimized beam tracking.