Approaches to reducing photon dose calculation errors near metal implants

Huang, Jessie Y.; Followill, David S; Howell, Rebecca M.; Liu, Xinming; Mirković, Dragan; Stingo, Francesco C.; Kry, Stephen F.

doi:10.1118/1.4960632

Cited by 41 publications

(50 citation statements)

References 45 publications

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“…3,4 In photon therapy, calculation errors were found to exceed 10% in an oral cavity clinical target volume when fillings are present, compared with 3% when no metal was present, emphasizing the potential severity of metal artifacts on dose calculations. 5 The consequences for dose calculation accuracy are also particularly relevant in proton therapy because of the strong dependency between a correct relative linear stopping power prediction and accurate representation of HU values. [6][7][8][9] Proton treatment plans could display erroneous beam ranges and dose distributions when artifacts are present.…”

Section: Introductionmentioning

confidence: 99%

Development of a stereoscopic CT metal artifact management algorithm using gantry angle tilts for head and neck patients

Branco

Kry

Taylor

et al. 2020

J Applied Clin Med Phys

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Dental amalgams are a common source of artifacts in head and neck (HN) images. Commercial artifact reduction techniques have been offered, but are substantially ineffectual at reducing artifacts from dental amalgams, can produce additional artifacts, provide inaccurate HU information, or require extensive computation time, and thus offer limited clinically utility. The goal of this work was to define and validate a novel algorithm and provide a phantom-based testing as proof of principle. An initial clinical comparison to a vendor's current solution was also performed. The algorithm uses two-angled CT scans in order to generate a single image set with minimal artifacts posterior to the metal implants. The algorithm was evaluated using a phantom simulating a HN patient with dental fillings. Baseline (no artifacts) geometrical measurements of the phantom were taken in the anterior-posterior, leftright, and superior-inferior directions and compared to the metal-corrected images using our algorithm to evaluate possible distortion from application of the algorithm. Mean HU numbers were also compared between the baseline scan and corrected image sets. A similar analysis was performed on the vendor's algorithm for comparison. The algorithm developed in this work successfully preserved the image geometry and HU and corrected the CT metal artifacts in the region posterior to the metal. The average total distortion for all gantry angles in the AP, LR, and SI directions was 0.17, 0.12, and 0.14 mm, respectively. The HU measurements showed significant consistency throughout the different reconstructed images when compared to the baseline image sets. The vendor's algorithm also showed no geometrical distortion but performed inferiorly in the HU number analysis compared to our technique. Our novel metal artifact management algorithm, using CT gantry angle tilts, provides a promising technique for clinical management of metal artifacts from dental amalgam.

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Section: Introductionmentioning

confidence: 99%

Development of a stereoscopic CT metal artifact management algorithm using gantry angle tilts for head and neck patients

Branco

Kry

Taylor

et al. 2020

J Applied Clin Med Phys

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“…Many researchers reported dose increases with various magnitudes in their studies, at the upper sides of the high Z eff implant materials . Magnitude of radiation backscattering that causes an increase in dose depends on the beam properties and also on the density and composition of the implant material.…”

Section: Resultsmentioning

confidence: 99%

Effects of metal implants and a metal artifact reduction tool on calculation accuracy of AAA and Acuros XB algorithms in small fields

Akdeniz

Yeğingil

2019

Medical Physics

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Purpose: In this study, the dosimetric accuracy of analytical anisotropic algorithm (AAA) and Acuros XB (AXB) dose calculation algorithms (Varian Medical Systems, Palo Alto, CA) was investigated for small radiation fields incident on phantoms of various metals that include stainless steel grade 316L (SS316L) and titanium alloy grade 5 (Ti5) implants. In addition, the effects of using metal artifact reduction for orthopedic implants (O-MAR, Philips Healthcare, Cleveland, OH) were evaluated. Methods: The evaluations of AAA and AXB were performed by comparing the crossline profiles calculated by AAA and AXB with GafChromic TM EBT3 film measurements at the phantom-implant interfaces and in close vicinity of implant materials for small field sizes (1 9 1 cm 2 , 2 9 2 cm 2 , 3 9 3 cm 2 , and 4 9 4 cm 2 ) of a 6 MV flattening filter free photon beam. O-MAR corrected and uncorrected (UC) computed tomography (CT) images were used for dose calculations. The values of average and standard deviations (SD) of Hounsfield unit (HU) for selected regions of each case were evaluated. The differences in average dose percentages in defined regions were calculated to quantify the relative dosimetric changes between doses calculated on UC and O-MAR corrected CT images. Results: Compared to UC images, the values of SD were reduced, and the average HU became closer to its reference value in the O-MAR images. There was some discrepancy in average dose percentage differences between calculations using UC and O-MAR images at 1 cm above the SS316L implant (average dose percentage differences were AXB/UC = 5.9% and AXB/O-MAR = À1.2%; AAA/UC = 2.2%, and AAA/O-MAR = À0.8%). Neither AAA nor AXB algorithms predict increase in dose at upper phantom-implant interface (4.9%, 9.9%. 13.5%, and 13.8% for the fields from 1 9 1 cm 2 to 4 9 4 cm 2 , respectively). At the side of the SS316L implant (where dark streak artifacts exist), dose difference averages were estimated as À 1.1% and 22.3% when AXB/O-MAR and AXB/UC calculations are compared with EBT3 measurements, respectively. Dose predictions at 1 cm below the SS316L implant were underestimated by AXB/O-MAR (average À0.5%) and AXB/ UC (average 2.0%). Conclusions:The O-MAR tool was shown to have a favorable dosimetric effect or no effect on the calculations in the upper proximity of the implant materials. The dose differences between EBT3 film measurements and calculations at upper phantom-implant interfaces were smaller when they were calculated using O-MAR images. However, the dose differences increased when O-MAR corrected images were used for AAA calculations at lower phantom-implant interfaces. Use of O-MAR enabled closer agreement for the AXB algorithm, especially in the dark streak artifact regions. The O-MAR algorithm should be used when the dose is calculated with the AXB algorithm in cases of patients with the metal implants. The estimations using AAA and AXB algorithms, in phantom setups, with Ti5 implant material were found to be closer to the EBT3 film measurements, when compared with th...

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“…High Z material can cause under-dosage of 20% -25% in the region surrounding the metal and over-dosage of 10% -15% downstream of the object [17]. Huang et al [21] discovered the success of MAR may depend on the type of metal and the size of the implant. In addition, the largest dosimetric impact is due to the metal size accuracy instead of successful artifact reduction.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of New Commercially Available Metal Artifact Reduction (MAR) Algorithm on Both Image Quality and Relative Dosimetry for Patients with Hip Prosthesis or Dental Fillings

Huang¹,

Kohli²

2017

IJMPCERO

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Streaking artifacts on computed tomography (CT) images are caused by high density materials such as hip prosthesis, surgical clips and dental fillings. The artifacts can lead to compromised clinical outcome due to the inability to differentiate tumor volume and the uncertainties in dose calculation. The goals of our study are to evaluate how GE's smart metal artifact reduction (MAR) algorithm impacts image quality on phantoms and dosimetry on head and neck patients with dental fillings and pelvic patients with hip prosthesis. Treatment plans calculated on the MAR and non-MAR datasets with the same beam arrangements and fluence are compared. Dose differences between the MAR and non-MAR datasets are not significant. However, substantial reductions of metal artifacts are observed when MAR algorithm is applied. Planning on the MAR dataset is recommended since it improves image quality and CT number accuracy. It also negates the need to contour the artifacts and override the density which can be time consuming.

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Approaches to reducing photon dose calculation errors near metal implants

Cited by 41 publications

References 45 publications

Development of a stereoscopic CT metal artifact management algorithm using gantry angle tilts for head and neck patients

Development of a stereoscopic CT metal artifact management algorithm using gantry angle tilts for head and neck patients

Effects of metal implants and a metal artifact reduction tool on calculation accuracy of AAA and Acuros XB algorithms in small fields

Evaluation of New Commercially Available Metal Artifact Reduction (MAR) Algorithm on Both Image Quality and Relative Dosimetry for Patients with Hip Prosthesis or Dental Fillings

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