Detection of Low-Contrast Objects: Experimental Comparison of Single– and Multi–Detector Row CT with a Phantom

Verdun, Francis R.; Denys, Alban; Valley, J.-F.; Schnyder, P.; Meuli, Reto

doi:10.1148/radiol.2232010810

Cited by 50 publications

(36 citation statements)

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“…The methodology described in our (21,(26)(27)(28)(29)(30)(31)(32)(33)(34)). An important factor that motivates CD analysis is the inclusion of the human observer as part of the imaging chain, which is a critical consideration in all medical imaging systems (35).…”

Section: Discussionmentioning

confidence: 99%

Detection of Simulated Microcalcifications in a Phantom with Digital Mammography: Effect of Pixel Size

Suryanarayanan¹,

Karellas²,

Vedantham³

et al. 2007

Radiology

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PURPOSE-To evaluate the effect of pixel size on the detection of simulated microcalcifications in digital mammography using a phantom.MATERIALS AND METHODS-A high-resolution prototype imager with variable pixel size of 39 and 78 μm, and a clinical full-field digital mammography (FFDM) system with pixel size of 100 μm were used. X-ray images of a contrast-detail (CD) phantom were obtained to perform alternative forced choice (AFC) observer experiments. Polymethyl-methacrylate (PMMA) was added to obtain phantom thickness of 45 and 58 mm which are typical breast thickness conditions encountered in mammography. Phantom images were acquired with both systems under nearly identical exposure conditions using an anti-scatter grid. Twelve images were acquired for each phantom thickness and pixel size (total of 72 images) and six observers participated in this study. Observer responses were used to compute the fraction of correctly detected disks. A signal detection model was used to fit the recorded data from which CD characteristics were obtained. Repeated-measures analyses using mixed effects linear models were performed for each of the 6 observers. All statistical tests were 2-sided and unadjusted for multiple comparisons. A P value of 0.05 or less was considered to indicate statistical significance. RESULTS-Statistical analysis indicated significantly better CD characteristics with 39 and 78μm pixel sizes compared to the 100 μm pixel for all disk diameters and phantom thickness conditions (p<0.001). Increase in phantom thickness degraded CD characteristics irrespective of pixel size (p<0.001).CONCLUSION-Based on the conditions of this study, reducing pixel size below 100 μm with low imaging system noise enhances the visual perception of small objects that correspond to typical microcalcification size.Corresponding author: Andrew Karellas Ph.D., Professor of Radiology, Hematology, and Oncology, Director of Medical Physics, Department of Radiology, Emory University School of Medicine, Winship Cancer Institute, 1701 Uppergate Drive, Building C, Suite 5018, Atlanta, GA 30322., Email: akarell@emory.edu, Phone: (404) 712 2411, FAX: (404) 712 5813. Advances in Knowledge: The results of this study indicate superior performance of 39 and 78 μm pixel sizes (high-resolution prototype digital imager) compared with 100 μm pixel size (clinical FFDM system). Implications for Patient Care:Based on the conditions investigated in this study, it appears that high-resolution (below 100 μm pixel size) and low-noise digital x-ray mammography systems could potentially improve the detection and visualization of microcalcifications leading to early and more accurate diagnosis.Publisher's Disclaimer: This author manuscript accepted for publication in Radiology has not been copyedited and proofread and is not the official, definitive version that will be published in Radiology online and in print, copyright 2007 The Radiological Society of North America. The RSNA disclaims any responsibility or liability for errors or omissions in this...

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Section: Discussionmentioning

confidence: 99%

Detection of Simulated Microcalcifications in a Phantom with Digital Mammography: Effect of Pixel Size

Suryanarayanan¹,

Karellas²,

Vedantham³

et al. 2007

Radiology

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“…The CTDIw applied was adapted to the recommended dose for abdominal CT by the European Guidelines, which suggest CTDIvol values ranging from 17.5 to 29.5 mGy for liver screening investigation [17][18][19][20][21]. In addition, in a previous experimental study performed with a phantom simulating the X-ray absorption of a standard abdomen, it has been demonstrated that for the detection of 5 mm lesions to achieve a CNR of 1, which ensures a detection rate of 100%, the X-ray dose required correspond to a CTDIw=20 mGy [11]. Thus, we determined the acquisition parameters (tube current setting) in order to obtain a CTDIw=23 mGy for all the protocols tested.…”

Section: Discussionmentioning

confidence: 99%

“…A CNR of 1 was necessary to achieve a 100% detection rate of 5 mm lesions, and a CNR of 0.6 to achieve a 100% detection rate of 9 mm lesions. [11]. The lower efficiency of thinner sections in detecting small hepatic lesions may be attributed to the geometric efficiency of the detectors that deteriorates with thin collimation [11].…”

Section: Discussionmentioning

confidence: 99%

“…[11]. The lower efficiency of thinner sections in detecting small hepatic lesions may be attributed to the geometric efficiency of the detectors that deteriorates with thin collimation [11]. Indeed, the penumbral region of the X-ray beam which was fully used by single detector CT is excluded with MDCT and only the ombra is directed to the active area of the detector.…”

Section: Discussionmentioning

confidence: 99%

“…Thinner collimation should improve lesion detection as partial volume effect is reduced. However, an experimental study comparing a four detector row CT with a single detector CT for the detection of low contrast lesion by using a phantom, has demonstrated that reduction of slice thickness requires a significant increase of radiation dose to achieve an acceptable CNR with MDCT as compared with single slice CT [11]. From the same experimental study, slice thickness of 5 mm offered the best compromise between CNR and dose.…”

Section: Introductionmentioning

confidence: 98%

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Detection of liver metastases under 2 cm: comparison of different acquisition protocols in four row multidetector-CT (MDCT)

et al. 2005

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This study compared different acquisition protocols performance to detect small liver metastases (<2 cm). Thirty consecutive patients with histologically proven hepatic metastases were explored by MDCT at the liver equilibrium phase by four successive acquisitions. We compared the following protocols (1-4): 5/30/1.5 (section thickness/table speed/pitch); 5/15/0.75; 5/11.25/0.75; and 2.5/15/1.5 with the same X-ray dose. The gold standard was based on patient radiological follow-up. Evolutive lesions were considered as true positive (TP). The described lesions, not found on the follow-up exams despite tumoral progression, were considered as false positive (FP). Stable lesions could not be considered as metastasis and were eliminated. One hundred and seventy-six lesions were detected: 61 TP and 91 FP. Twenty-four lesions were eliminated.The mean kappa values for protocols 1, 2, 3 and 4 were, respectively, 0.43, 0.68, 0.73 and 0.51 (0.61-0.80: substantial agreement) and the mean areas under the ROC curve were, respectively, 0.76, 0.87, 0.86 and 0.80. The results of protocols 2 and 3 were significantly superior to those of protocols 1 and 4. MDCT protocols using thin sections or an increased table speed are less efficient in detecting small metastases.

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Optimal slice thickness for object detection with longitudinal partial volume effects in computed tomography

Monnin¹,

Sfameni²,

Gianoli³

et al. 2016

J Applied Clin Med Phys

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Longitudinal partial volume effects (z‐axial PVE), which occur when an object partly occupies a slice, degrade image resolution and contrast in computed tomography (CT). Z‐axial PVE is unavoidable for subslice objects and reduces their contrast according to their fraction contained within the slice. This effect can be countered using a smaller slice thickness, but at the cost of an increased image noise or radiation dose. The aim of this study is to offer a tool for optimizing the reconstruction parameters (slice thickness and slice spacing) in CT protocols in the case of partial volume effects. This optimization is based on the tradeoff between axial resolution and noise. For that purpose, we developed a simplified analytical model investigating the average statistical effect of z‐axial PVE on contrast and contrast‐to‐noise ratio (CNR). A Catphan 500 phantom was scanned with various pitches and CTDI and reconstructed with different slice thicknesses to assess the visibility of subslice targets that simulate low contrast anatomical features present in CT exams. The detectability score of human observers was used to rank the perceptual image quality against the CNR. Contrast and CNR reduction due to z‐axial PVE measured on experimental data were first compared to numerical calculations and then to the analytical model. Compared to numerical calculations, the simplified algebraic model slightly overestimated the contrast but the differences remained below 5%. It could determine the optimal reconstruction parameters that maximize the objects visibility for a given dose in the case of z‐axial PVE. An optimal slice thickness equal to three‐fourth of the object width was correctly proposed by the model for nonoverlapping slices. The tradeoff between detectability and dose is maximized for a slice spacing of half the slice thickness associated with a slice width equal to the characteristic object width.

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Detection of Low-Contrast Objects: Experimental Comparison of Single– and Multi–Detector Row CT with a Phantom

Abstract: Multi-detector CT is less effective than single-detector CT in detection of small low-contrast objects if sections thinner than 5 mm are used. Results for single- and multi-detector CT were similar for sections 5 mm or thicker.

Cited by 50 publications

References 10 publications

Detection of Simulated Microcalcifications in a Phantom with Digital Mammography: Effect of Pixel Size

Detection of Simulated Microcalcifications in a Phantom with Digital Mammography: Effect of Pixel Size

Detection of liver metastases under 2 cm: comparison of different acquisition protocols in four row multidetector-CT (MDCT)

Optimal slice thickness for object detection with longitudinal partial volume effects in computed tomography

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