Report 87

Boone, John M.; Brink, James A.; Edyvean, Sue; Huda, Walter; Leitz, W.; McCollough, Cynthia H.; McNitt-Gray, Michael F.; Dawson, Peter; Deluca, P. L.M.; Seltzer, S. M.; Brunberg, James A.; Burkett, George W.; Dixon, Robert L.; Geleijns, Jacob; McGahan, John P.; McKenney, Sarah E.; Pelc, Norbert J.; Siewerdsen, Jeffrey H.; Seibert, J. Anthony; Winer-Muram, Helen T.; Wootton‐Gorges, Sandra L.

doi:10.1093/jicru/ndt006

Cited by 19 publications

(16 citation statements)

References 0 publications

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“…One of the often mentioned constraints is that these measurements are complex and time consuming. 41,42 This constraint has been lifted by our Compton spectrometer design for use at CT scanners as for the positioning of the spectrometer, the alignment lasers of the scanner can be used, leading to setting-up times of typically 10-15 min. Combined with spectrum acquisition times of about 5 min per spectrum, a protocol for measuring spectra at two or three energies will not last more than 30-45 min.…”

Section: B Clinical Ct Scannersmentioning

confidence: 99%

Spectra of clinical CT scanners using a portable Compton spectrometer

et al. 2015

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Purpose:Spectral information of the output of x‐ray tubes in (dual source) computer tomography (CT) scanners can be used to improve the conversion of CT numbers to proton stopping power and can be used to advantage in CT scanner quality assurance. The purpose of this study is to design, validate, and apply a compact portable Compton spectrometer that was constructed to accurately measure x‐ray spectra of CT scanners.Methods:In the design of the Compton spectrometer, the shielding materials were carefully chosen and positioned to reduce background by x‐ray fluorescence from the materials used. The spectrum of Compton scattered x‐rays alters from the original source spectrum due to various physical processes. Reconstruction of the original x‐ray spectrum from the Compton scattered spectrum is based on Monte Carlo simulations of the processes involved. This reconstruction is validated by comparing directly and indirectly measured spectra of a mobile x‐ray tube. The Compton spectrometer is assessed in a clinical setting by measuring x‐ray spectra at various tube voltages of three different medical CT scanner x‐ray tubes.Results:The directly and indirectly measured spectra are in good agreement (their ratio being 0.99) thereby validating the reconstruction method. The measured spectra of the medical CT scanners are consistent with theoretical spectra and spectra obtained from the x‐ray tube manufacturer.Conclusions:A Compton spectrometer has been successfully designed, constructed, validated, and applied in the measurement of x‐ray spectra of CT scanners. These measurements show that our compact Compton spectrometer can be rapidly set‐up using the alignment lasers of the CT scanner, thereby enabling its use in commissioning, troubleshooting, and, e.g., annual performance check‐ups of CT scanners.

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Section: B Clinical Ct Scannersmentioning

confidence: 99%

Spectra of clinical CT scanners using a portable Compton spectrometer

et al. 2015

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“…The MTF was calculated using a 50 µm tungsten wire source. This wire source is used to calculate a point spread function (PSF), from which the MTF was computed using a Fourier transform, and normalized to the average intensity of the PSF [55]: containing 5 modules (The Phantom Laboratory, Salem, NY, USA). The phantom was positioned in the isocenter o the scanner as suggested by the user manual [54].…”

Section: Image Quality Of a Dual-layer Ct | Chaptermentioning

confidence: 99%

“…The module was used to measure the accuracy of the system by calculating a mean CT number, and to characterize noise by calculating the standard deviation (SD) of the mean CT number and by measuring the noise power spectrum (NPS). Nine ROIs of 64×64 voxels were selected in the uniform material, o which the SD was calculated and the 2D NPS was computed using the discrete Fourier transform [55]:…”

Section: Image Quality Of a Dual-layer Ct | Chaptermentioning

confidence: 99%

“…and _ are the pixel spacing and the number of pixels in the x-and y-directions. With radial averaging the 2D NPS can be collapsed to a 1D radial frequency [55]. The mean CT number was calculated for each acquisition by calculating the mean CT number of the 9 ROIs.…”

Section: Image Quality Of a Dual-layer Ct | Chaptermentioning

confidence: 99%

“…Module CTP591 was used to measure spatial resolution via the modulation transfer function (MTF) calculated using a 50 µm tungsten wire source. This wire source is used to calculate a point spread from which the MTF was computed using a Fourier transform, and normalized to the average in PSF [55]:…”

Section: Ct Number Linearitymentioning

confidence: 99%

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Dual-energy CT and CT perfusion for improved CT stroke imaging

Ommen¹

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Cardiovascular diseases (CVDs) are the leading causes of death in the world. An estimated 17.9 million people died from a CVD worldwide in 2016. The majority, 85% of deaths, is caused by either a heart attack or a stroke[1]. In the Netherlands, 38199 people died of a CVD in 2018, of which 9176 died of a stroke[2]. Not only does stroke significantly contribute to mortality, it is also a leading cause of disability[3]. Because of the aging population, the number of stroke patients is expected to increase[4]. Strokes can be divided into two groups: 1) ischemic strokes caused by an arterial occlusion, for example by a (temporary) clot, and 2) hemorrhagic strokes caused by a rupture of a vessel[5]. In this thesis we will be focusing on ischemic strokes. Currently, treatment options for ischemic strokes are intravenous administration of tissue plasminogen activator (tPA) for clot dissolution, intra-arterial thrombolysis, and endovascular mechanical clot removal[6]. Therapeutic interventions are most effective when initiated in the early stages after a stroke[7-9]. Guidelines state that intravenous thrombolysis should only be administered to patients within 4.5 hours, and endovascular treatment should only be initiated within 6 hours of ischemic stroke symptom onset[10]. Brain tissue damage may be irreversible, and the loss of brain tissue continues while the arterial occlusion persists. Therefore in stroke care the phrase "time is brain" is often used, meaning that the diagnosis and treatment of a stroke should be as fast as possible. This explains why the preferred imaging modality for acute stroke imaging usually is computed tomography (CT)[11]. CT is fast, relatively cheap and widely available. The acute stroke imaging protocol usually consists of noncontrast CT, CT perfusion and CT angiography scans. CT imaging in stroke Non-contrast CT In stroke imaging, the first acquisition is non-contrast CT (NCCT) of the entire brain. The primary goal of NCCT is to differentiate between ischemic and hemorrhagic strokes. Since blood has a higher attenuation than brain tissue, it appears hyperdense on a CT scan and can therefore be easily detected (Figure 1.1A). In addition to differentiating ischemic from hemorrhagic strokes, NCCT also provides some information on the extent of cerebral ischemia. On NCCT, subtle loss of gray-white matter differentiation and evidence of swelling can be first indications of ischemic stroke[12]. The ischemic area appears hypodense on NCCT (Figure 1.1B). Figure 1.3 | Examples of contrast enhancement curves: A) arterial input function (AIF) and venous output function (VOF), B) gray matter (GM) and white matter (WM). The dashed line shows the partial volume corrected AIF. Figure 1.5 | Illustration of three dual-energy CT techniques. A) Dual-source DECT utilizes two X-ray tubes and two detectors to generate low-and high-energy spectra, B) rapid kV switching utilizes one X-ray tube and detector and switches rapidly between a low and high tube voltage and C) detector-based spectral CT utilizes one X-ray...

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