A tin filter’s dose reduction effect revisited: Using the detectability index in low-dose computed tomography for the chest

Hasegawa, Akira; Ichikawa, Katsuhiro; Morioka, Yusuke; Kawashima, Hiroki

doi:10.1016/j.ejmp.2022.05.006

Cited by 6 publications

(5 citation statements)

References 24 publications

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“…Another study evaluated the dose reduction and diagnostic performance of a Sn filter in 44 colorectal cancer patients who underwent Sn filtered 100 kV and standard 120 kV CT on different days, indicating a substantial reduction of 89% in radiation dose, while maintaining good diagnostic performance. 45 On the other hand, in a phantom study,Hasegawa et al 46 reported a lower dose reduction (22%−25%) with the Sn filter. However, a comparison with the present data is difficult as they used a Filtered Back Projection (FBP) reconstruction algorithm, and the dose reduction in all studies mentioned was achieved whilst maintaining the quality of the CT images for diagnostic purposes.…”

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

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Ultra‐low dose CT scanning for PET/CT

Mostafapour,

Greuter,

van Snick

et al. 2023

Medical Physics

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BackgroundThe use of computed tomography (CT) for attenuation correction (AC) in whole‐body PET/CT can result in a significant contribution to radiation exposure. This can become a limiting factor for reducing considerably the overall radiation exposure of the patient when using the new long axial field of view (LAFOV) PET scanners. However, recent CT technology have introduced features such as the tin (Sn) filter, which can substantially reduce the CT radiation dose.PurposeThe purpose of this study was to investigate the ultra‐low dose CT for attenuation correction using the Sn filter together with other dose reduction options such as tube current (mAs) reduction. We explore the impact of dose reduction in the context of AC‐CT and how it affects PET image quality.MethodsThe study evaluated a range of ultra‐low dose CT protocols using five physical phantoms that represented a broad collection of tissue electron densities. A long axial field of view (LAFOV) PET/CT scanner was used to scan all phantoms, applying various CT dose reduction parameters such as reducing tube current (mAs), increasing the pitch value, and applying the Sn filter. The effective dose resulting from the CT scans was determined using the CTDIVol reported by the scanner. Several voxel‐based and volumes of interest (VOI)‐based comparisons were performed to compare the ultra‐low dose CT images, the generated attenuation maps, and corresponding PET images against those images acquired with the standard low dose CT protocol. Finally, two patient datasets were acquired using one of the suggested ultra‐low dose CT settings.ResultsBy incorporating the Sn filter and adjusting mAs to the lowest available value, the radiation dose in CT images of PBU‐60 phantom was significantly reduced; resulting in an effective dose of nearly 2% compared to the routine low dose CT protocols currently in clinical use. The assessment of PET images using VOI and voxel‐based comparisons indicated relative differences (RD%) of under 6% for mean activity concentration (AC) in the torso phantom and patient dataset and under 8% for a source point in the CIRS phantom. The maximum RD% value of AC was 14% for the point source in the CIRS phantom. Increasing the tube current from 6 mAs to 30 mAs in patients with high BMI, or with arms down, can suppress the photon starvation artifact, whilst still preserving a dose reduction of 90%.ConclusionsIntroducing a Sn filter in CT imaging lowers radiation dose by more than 90%. This reduction has minimal effect on PET image quantification at least for patients without Body Mass Index (BMI) higher than 30. Notably, this study results need validation using a larger clinical PET/CT dataset in the future, including patients with higher BMI.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Ultra‐low dose CT scanning for PET/CT

Mostafapour,

Greuter,

van Snick

et al. 2023

Medical Physics

View full text Add to dashboard Cite

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“…Several previous [18][19][20] studies have evaluated the dosage and image quality of low-dose chest CT scans using a tin filter. A study 21 reported that the use of a tin filter resulted in dose reduction ranging from 22% to 25%. The area under the NPS curve decreased by 13% to 17% with the tin filter compared with that without the tin filter.…”

Section: Discussionmentioning

confidence: 99%

Usefulness of Ag Additional Filter on Image Quality and Radiation Dose for Low-Dose Chest Computed Tomography

Kawamoto

Sato

Kogure

2023

J Comput Assist Tomogr

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Objective This study aimed to evaluate the effect of a silver (Ag) additional filter on dose characteristics and image quality in low-dose chest computed tomography (CT). Methods A dose evaluation phantom, physical evaluation phantom, and chest phantom were scanned with and without an Ag additional filter. The doses were adjusted so that the displayed the volume CT dose indexes (CTDIvol) were from 0.3 to 1.6 mGy. For dose characteristics, the spectrum of photon energies and the measured CTDIvol were calculated for each scanning condition. For task-based image quality analysis, task transfer function, noise power spectrum, and system performance were evaluated. Streak artifacts, image noise, and contrast-to-noise ratio were quantified using a chest phantom. Results With the Ag additional filter, mean energy was 22% higher and the CTDIvol was approximately 30% lower than those without the Ag additional filter. The task transfer function and noise power spectrum with the Ag additional filter were lower than those without the Ag additional filter. The system performance with the Ag additional filter was similar to that without the Ag additional filter. The Ag additional filter reduced streak artifact near the lung apex and image noise in the lung fields. The contrast-to-noise ratio was slightly higher with the Ag additional filter than that without the Ag additional filter. Conclusions The output dose and spatial resolution with the Ag additional filter were lower than those without the Ag additional filter. However, this filter helped reduce the radiation dose, image noise, and streak artifacts, particularly when scanning at ultralow doses.

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“…The removable filters are useful to absorb low-energy photons and thus to significantly reduce radiation exposure to the patient not only in the CT scan but also in topograms. [10][11][12][13][14][15][16][17][18][19][20][21][22] The effect of dose reduction is summarized in Table 2. Whether to use a PSP or whether to scan without the filter depends on the imaging task and on patient size.…”

Section: Prefiltersmentioning

confidence: 99%

“…Siemens has a long history in tin prefiltration and offers changeable tin filters in different thicknesses on many systems. The removable filters are useful to absorb low-energy photons and thus to significantly reduce radiation exposure to the patient not only in the CT scan but also in topograms 10–22 . The effect of dose reduction is summarized in Table 2.…”

Section: Prefiltersmentioning

confidence: 99%

Computed Tomography 2.0

Lell

Kachelrieß

2023

Invest Radiol

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Computed tomography (CT) dramatically improved the capabilities of diagnostic and interventional radiology. Starting in the early 1970s, this imaging modality is still evolving, although tremendous improvements in scan speed, volume coverage, spatial and soft tissue resolution, as well as dose reduction have been achieved. Tube current modulation, automated exposure control, anatomy-based tube voltage (kV) selection, advanced x-ray beam filtration, and iterative image reconstruction techniques improved image quality and decreased radiation exposure. Cardiac imaging triggered the demand for high temporal resolution, volume acquisition, and high pitch modes with electrocardiogram synchronization. Plaque imaging in cardiac CT as well as lung and bone imaging demand for high spatial resolution. Today, we see a transition of photon-counting detectors from experimental and research prototype setups into commercially available systems integrated in patient care. Moreover, with respect to CT technology and CT image formation, artificial intelligence is increasingly used in patient positioning, protocol adjustment, and image reconstruction, but also in image preprocessing or postprocessing. The aim of this article is to give an overview of the technical specifications of up-to-date available whole-body and dedicated CT systems, as well as hardware and software innovations for CT systems in the near future.

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A tin filter’s dose reduction effect revisited: Using the detectability index in low-dose computed tomography for the chest

Cited by 6 publications

References 24 publications

Ultra‐low dose CT scanning for PET/CT

Ultra‐low dose CT scanning for PET/CT

Usefulness of Ag Additional Filter on Image Quality and Radiation Dose for Low-Dose Chest Computed Tomography

Computed Tomography 2.0

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