Calcium Scoring using Tin Filter spectral shaping · 2020. 7. 10. · For SOMATOM Drive, a 0.4 mm...

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White Paper SOMATOM Drive

Tin Filter spectral shaping –a demonstration of Agatston equivalence

Calcium Scoring using

Thomas Allmendinger, PhD, HC DI CT R&D CTC SA Astrid Hamann, MSc, HC DI CT CRM CMM

Not for distribution in the US.

White Paper | CaSc using Tin Filter spectral shaping

Quantification of coronary artery calcium (CAC) (AlMallah MH, 2015; Parikh S, 2016) is an established task in the risk stratification of coronary artery disease. The standard quantification method, the Agatston score, was introduced by Arthur Agatston and Warren Janowitz et al. (Agatston AS, 1990) and measured initially using electronbeam computed tomography (EBCT) at 130 kV. Despite several drawbacks, which are also discussed in the following, the wide breadth of available clinical data across age, gender, and race (Hoff JA, 2001) as well as large clinical risk stratification studies helped this method become established as the primary measure in clinical practice (Alluri K, 2015; Parikh S, 2016; Budoff MJ, 2007).

When changing the Calcium Score (CaSc) acquisition protocol by spectral shaping, it is essential to achieve a similarly high detectability of CAC as well as comparability of the resulting Agatston score with the results acquired using established 120 kV and 130 kV protocols, respectively. The reason for having two reference voltages is mainly historical in nature because the initial EBCT study used 130 kV only, whereas for most modern CT systems only 120 kV is available (Agatston AS, 1990; McCollough CH, 2007). Therefore, the primary aim of this report is to demonstrate Agatston equivalent Calcium Scoring (CaSc) based on the usage of 100 kV tube voltage combined with tin filtration (Sn100 kV) for spectral shaping.

Furthermore, the secondary aim is to demonstrate of a dose benefit of the Sn100 kV Agatston score compared with the established 120 kV and 130 kV standard tube voltages.

Introduction

Table of contents

Excursion: accuracy of Agatston score . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 03

X-ray tube spectra and spectral shaping with Tin Filter . . . . . . . . . . . . . . . . . . . . . . . 03

Agatston equivalent Calcium Scoring using Sn100 kV spectral shaping . . . . . . . . . 06

Radiation dose reduction by spectral filtration with Sn100 kV for Calcium Scoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

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The success of the Agatston score is based on the vast availability of patient data acquired initially on EBCT at 130 kV in the 1990s up to the present day. With the introduction of multidetector computed tomography (MDCT), this database has been extrapolated for the use of 120 kV and efforts have been made to develop a consensus standard for quantifica tion of CAC (McCollough CH, 2007). However, recent studies clearly show the drawbacks of this approach. Willemink et al. investigated the intervendor variability of the Agatston score of stateoftheart CTs from the four major vendors (Willemink MJ V. R., 2014). The performed measurements resulted in substantially different Agatston scores among the four vendors having the potential to influence classification of individuals at intermediate cardiovascular risk and therefore treatment decisions.

Furthermore, the influence of chest size with regards to the Agatston score measurements performed using the fixed

120 kV acquisition protocols was evaluated in a multivendor phantom study (Willemink MJ A. B., 2015). Here, an extension ring was used to simulate difference in patient size. Results showed a systematic underestimation of Agatston scores among the vendors that may be relevant for both large patients and women with relatively more thoracic fat and breast tissue.

Due to the quantitative nature of this risk stratification an accurate calibration is highly recommended. An estab lished procedure has existed for several years that allows the calculation of coronary calcium mass score (McCollough CH, 2007). Here, the described, standardized procedure can easily be applied to any new scanner system or tube voltage and tube filter combination in order to derive correct conversion factors for calcium mass score calculation. Despite these efforts, the established clinical standard for coronary calcium scoring remains the Agatston score.

Excursion: accuracy of Agatston score

X-ray tube spectra and spectral shaping with Tin Filter

The generated Xray spectra emitted by all commercially available CT systems for human medical imaging are continuous up to an endpoint that corresponds to the initial acceleration peak voltage. The exact shape of the resulting spectra depends on anode material used and on possible additional spectral filtration by thin absorbers deployed directly at the Xray source.

For SOMATOM Drive, a 0.4 mm thick Tin (Sn) Filter is positioned in front of the Xray tube radiation exit window in addition to the existing standard filtration1 for spectral shaping (aluminum (Al) and titanium (Ti) filter). This leads to a narrower Xray tube spectrum with fewer quanta at lower energies and a resulting higher mean energy (Fig. 1, C).

Although, these lowenergy quanta contribute to the increase in iodine contrasttonoise ratio (CNR) in contrastenhanced scans, they are inefficient when it comes to noncontrast scans, like Agatston scoring.

Hence, employing spectral shaping with a Tin Filter offers several advantages and is ideal for: • Highcontrast protocols without contrast media

(e.g., calcium scoring, native lung)• Reduction of beamhardening effects• Reduction of radiation dose

1 This kind of prefiltration applies to nearly all Straton® and all Vectron™ based CT systems and therefore covers a wide range of Siemens Healthineers scanner systems, including the models SOMATOM Definition AS family, SOMATOM Definition Edge, SOMATOM Definition Flash, SOMATOM Drive and SOMATOM Force.

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Figure 1: Spectrum simulations for 120 kV (A), 130 kV (B) and Sn100 kV with 0.4 mm Sn (C) plotted as detector response intensity spectra with an additional 20 cm water attenuation (left column), 30 cm water attenuation (middle column) and 40 cm water attenuation (right column).

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Table 1: Mean keV values derived from the different spectra simulations.

X-ray source spectra and filtration Air [keV] 20 cm [keV] 30 cm [keV] 40 cm [keV]

120 kV 69 78 81 84

130 kV 73 82 86 89

Sn100 kV 75 78 79 80

However, the modification of spectra can have also an effect on the actual object attenuation process, which is energydependent. As is well known from the reconstruction of CT images, this beamhardening effect needs to be corrected, which is usually done in an attenuationdependent form to allow uniform 0 HU for water material regardless of the diameter of the object (Brooks, 1976). The size of the effect is illustrated in Figure 1, which shows the 120 kV detector response with an additional 20 cm, 30 cm and 40 cm water absorber added to the spectral simulation (top row, left to right). The beam hardening effect of the additional water object attenu ation is reflected by the increased values for the mean keV values of 78 keV, 81 keV and 84 keV for 20 cm, 30 cm and 40 cm, respectively. The simulation was also

performed for the 130 kV spectra (middle row) and the Sn100 kV spectra with a 0.4 mm Tin Filter (bottom row). The effective mean keV values are summarized in Table 1 for the different spectra and water thicknesses.

It can be concluded that the effective keV values of the proposed Sn100 kV spectra are in good agreement with the established 120 kV/130 kV spectra values. Consequently, the Hounsfield units (HU) in Sn100 kV CT images for calcium material of different density should also be in agreement with the values found at 120 kV/130 kV. This depends on the size of the actual object due to their different beamhardening behavior, the exact response of the detector material with respect to the incident spectra, and uncertainties in the spectral simulation.

5


Agatston equivalent Calcium Scoring using Sn100 kV spectral shaping

To illustrate the agreement between the three different voltages, HU measurements were performed for the small, medium and large phantom setup and Sn100 kV, 120 kV and 130 kV tube voltages, respectively. An anthropomorphic thorax phantom combined with a calcium calibration insert was used consisting of nine small cylindrical calcifications that vary in size and calcium hydroxyapatite (HA) density. Additionally two large calibration cylinders are included, one composed of waterequivalent material (0 HU water insert) and the other composed of 200 mg/cm3 calcium HA (Figure 2). A complete detailed phantom description can be found in the work of McCollough et al. (McCollough CH, 2007).

All phantom images were acquired in a sequential cardiac quick scan mode according to the clinical default Calcium Scoring protocol of SOMATOM Drive system at maximum tube current in order to minimize statistical uncertainties. The effective mean water equivalent diameter was 20 cm, 28 cm and 35 cm for the small, medium and large phantom. Table 2 summarizes the HU measurements performed by placing of a 1 cm diameter region of interest (ROI) in the large 200 mg/cm3 HA calibration cylinder.

Here, the good overall agreement of the Sn100 kV ROI Hounsfield unit values with the 120 kV and 130 kV values are illustrated. The smaller variation of 12 HU between the large and small phantom setup compared to a 27 HU variation for 120 kV and a 31 HU variation for 130 kV shows nicely the reduced beamhardening effect of the Sn100 kV spectra.

Based on these results, it can be concluded that a scoring method based on thresholds in HU like the Agatston score yields similar scoring results for Sn100 kV images if compared to the established voltages of 120 kV/130 kV in this phantom setup.

In addition, a greater independence of the Agatston score from patient diameter can be expected due to the reduced keV dependency and increased HU stability of the Sn100 kV spectra with respect to the object size. This score dependency on the diameters is known as discussed before and reported in the literature on phantom measurements as well as patient data (Willemink MJ A. B., 2015).

Table 2: Mean ROI Hounsfield unit values derived from the large 200 mg/cm3 HA calibration insert of the reference phantom for the different tube voltages and phantom sizes.

X-ray source spectra and filtration Small [HU] Medium [HU] Large [HU]

120 kV 272 252 246

130 kV 259 240 228

Sn100 kV 242 234 230

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A

B

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Figure 2: Example images of the small phantom for Sn100 kV, 134 eff. mAs/rot (A), 120 kV, 26 eff. mAs/rot (B) and 130 kV, 24 eff. mAs/rot (C).

The field of view (FoV) is 200 mm and the window is (300/1,200) to avoid clipping the 800 mg/cm3 HA inserts in the images. Datasets were reconstructed with a 3 mm slice thickness using the stan dard calcium image reconstruction kernel (B35f). Measurements were also performed for the medium and large phantom, respectively.

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Radiation dose reduction by spectral filtration with Sn100 kV for Calcium Scoring

In order to demonstrate the dose benefit utilizing Sn100 kV instead of the reference 120 kV/130 kV, phantom measurements at different relative dose levels were performed. All scans used CARE Dose4D™ dose modulation utilizing the attenuation information derived from the topogram of each phantom. This allows for the adjustment for a given reference tube current value to the actual applied value while taking into account the size of the phantom. Therefore this helps to mimic clinical practice, where the applied dose also depends on the size of the patient to be imaged.

The default quality reference value of SOMATOM Drive for 120 kV was increased from 80 q. ref. mAs/rot to 320 q. ref. mAs/rot to demonstrate the intrinsic Xray dose dependency of the Agatston score. The initial quality reference values for 130 kV and Sn100 kV were set to 276 q. ref. mAs/rot and 400 q. ref. mAs/rot, respectively.

Based on the acquired sinogram data and established noise insertion techniques (Yu L, 2012; Kramer Manue, 2015; Ellmann S, 2016), images were generated at relative dose levels of 75%, 50%, 25%, 15%, 10% and 5% and repeated five times in order to minimize systematic quick scan artefacts and other systematic effects.

The results of the Agatston scoring for the different phantom sizes, voltages, and Xray dose levels can be found in Table 3 (small phantom), Table 4 (medium phantom), and Table 5 (large phantom). Some Xray dose levels were not realistic for different phantom sizes or spectra and therefore excluded where applicable. Figure 3 illustrates the findings of the small, medium, and large phantom measurement as whisker plots based on the five individual measurements at each point with regards to the different dose levels. The grey area serves as a visual reference (lower limit: 605, upper limit: 672, mean: 630 (dashed line)) based on interscanner variations found by McCollough et al. (McCollough CH, 2007). Although primary conclusions and claims of the applicability of Agatston scoring with Sn100 kV spectra will be made based on the agreement with those numbers, a slight deviation from these limits is not a direct exclusion criterion because the actual variation width for calcium scoring is indeed considerably larger than more recent literature suggests (Willemink MJ A. B., 2015; Willemink MJ V. R., 2014).

Using the grey reference area in Figure 3, one can nicely determine the minimal dose necessary to provide a good agreement for the different spectra and phantom sizes. These values can be found in Table 3, 4 and 5 marked in orange for the different phantom sizes and tube voltages, respectively.

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Figure 3: Agatston score results based on the small (A), medium (B) and large (C) phantom measurements for Sn100 kV (top), 120 kV (middle) and 130 kV (bottom) at different dose levels, respectively.

Total score ( ), 800 mg HA inserts ( ), 400 mg HA inserts ( ) and 200 mg HA inserts ( ) are shown separately. The CTDIvol is given as CTDIvol 32 in units of mGy.

X axis shows individual dose levels from 5%100% (if applicable) in ascending order.

Y axis shows the Agatston score as a whisker plot based on the five individual measure ments at each point. The grey area serves as a visual reference (lower: 605, upper: 672, mean: 630 (dashed line)) based on interscanner variations found by McCollough et al.

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Table 3: Mean Agatston score values obtained for the different inserts and their sum for the different tube voltages and dose levels of the small phantom measurements.

Table 4: Mean Agatston score values obtained for the different inserts and their sum for the different tube voltages and dose levels of the medium phantom measurements.

kV Q. ref mAs/rot

Eff. mAs/rot

CTDIvol [mGy]

200 mg HA AS

400 mg HA AS

800 mg HA AS

Total AS

Sn100

400 134 0.57 64 190 367 620300 (75%) 101 0.43 65 192 367 624200 (50%) 67 0.28 92 220 383 696100 (25%) 34 0.14 224 332 489 1045

120

320 104 3.64 67 200 370 636240 (75%) 78 2.73 67 201 369 637160 (50%) 52 1.82 67 205 371 64380 (25%) 26 0.91 70 213 375 65848 (15%) 16 0.54 84 226 384 69432 (10%) 10 0.36 117 250 410 77716 (5%) 5 0.18 282 374 512 1155

130

276 94 4.15 63 193 355 612207 (75%) 71 3.11 63 197 360 620138 (50%) 47 2.07 64 198 368 63169 (25%) 24 1.04 68 203 367 63941 (15%) 14 0.62 73 208 379 66028 (10%) 9 0.42 85 232 394 71314 (5%) 5 0.21 220 326 496 1044

kV Q. ref mAs/rot

Eff. mAs/rot

CTDIvol [mGy]

200 mg HA AS

400 mg HA AS

800 mg HA AS

Total AS

Sn100

400 275 1.16 58 191 366 615300 (75%) 206 0.87 68 205 383 657200 (50%) 138 0.58 107 235 410 753100 (25%) 69 0.29 304 428 587 1319

120

320 218 7.64 57 193 359 608240 (75%) 164 5.72 60 196 362 618160 (50%) 109 3.81 64 200 364 62780 (25%) 55 1.91 74 208 374 65648 (15%) 33 1.15 90 223 389 70232 (10%) 22 0.76 115 255 417 78816 (5%) 11 0.38 338 460 594 1394

130

276 192 8.36 53 180 350 583207 (75%) 144 6.27 54 182 350 586138 (50%) 96 4.18 54 187 355 59569 (25%) 48 2.10 63 195 367 62541 (15%) 29 1.25 78 204 370 65228 (10%) 19 0.84 111 227 406 74414 (5%) 10 0.42 310 401 575 1285

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Table 5: Mean Agatston score values obtained for the different inserts and their sum for the different tube voltages and dose levels of the large phantom measurements.

As can be seen in the respective 120 kV plots, the 25% relative dose value is in good agreement with the expected values defined by the total Agatston scoring mean value taken from the calibration recommendations stated by McCollough et al. These correspond to the established reference value of 80 q. ref. mAs/rot of the default protocol for CaSc for SOMATOM Drive, making this quality reference dose value a reasonable choice for Agatston scoring based on 120 kV tube voltage spectra. Based on this, one can furthermore derive a conservative dose reduction possibility of up to 50% by utilizing Sn100 kV spectra Agatston scoring compared to the established 120 kV Siemens Healthineers default protocolbased scoring.

Besides its dosesaving potential, the use of Sn100 kV can also improve beamhardening effects as previously shown. However, this could be demonstrated here only partially due to tube power limitations. Whereas there is a clear drop

visible for both the 120 kV (636, 608, 597) and 130 kV (612, 583, 580) scores, which is also in agreement with the published patient size dependency discussed before (Willemink MJ A. B., 2015), this is only partially represented for Sn100 kV (620, 615, 690). Here, the largesize phantom already demonstrates a score increase due to dose and noise dependencies rather than the expected further decrease due to beam hardening as seen for the other voltages. The beneficial effect can be seen only to some extent between the small and mediumsize phantom.

Moreover, the inherent noise and therefore resulting dose dependency of the thresholdbased Agatston score method with a lesion weighting based on a single voxel maximum HU criteria can further be illustrated by the visible upslope for 120 kV and 130 kV in the 25% to 100% dose range for all phantom sizes. This effect is expected, however one can also see the clear deviation towards very high values of the total AS for toolow dose values.

kV Q. ref mAs/rot

Eff. mAs/rot

CTDIvol [mGy]

200 mg HA AS

400 mg HA AS

800 mg HA AS

Total AS

Sn100

360 450 1.89 86 220 383 690270 (75%) 336 1.41 130 253 418 801180 (50%) 224 0.94 252 353 508 111390 (25%) 113 0.47 579 668 818 2067

120

320 450 15.71 58 189 350 597240 (75%) 337 11.78 58 195 351 601160 (50%) 225 7.85 61 196 361 61780 (25%) 113 3.93 70 207 374 65048 (15%) 68 2.35 104 232 394 72832 (10%) 45 1.57 211 318 464 99416 (5%) 23 0.79 482 596 739 1818

130

276 422 18.4 53 177 350 580207 (75%) 316 13.78 52 178 350 581138 (50%) 211 9.18 52 181 353 58569 (25%) 106 4.59 63 204 362 62841 (15%) 63 2.75 86 217 377 68028 (10%) 42 1.84 141 277 424 84114 (5%) 21 0.92 415 529 649 1594

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Figure 4: Agatston score results with 120 kV (left) and Sn100 kV (right) spectra in clinical setup. Courtesy of Medscan Barangaroo, Australia.

Yet it has to be stated that Sn100 kV Agatston scoring is more suitable for small to averagesize patients because the tube limit was reached during the large phantom measurements. Because this corresponds approximately to a typical 80 kg standardsize patient with a 32 cm thorax waterequivalent diameter, it is reasonable to conclude that Sn100 kV CaSc is suitable for patients up to 100 kg. For heavier patients, the recommendation would be to switch to a CaSc based on 120 kV or 130 kV.

Figure 4 illustrates the good agreement in quantitative Agatston scoring numbers for Sn100 kV in a first clinical setup. This example shows a total score of 520.5 with Sn100 kV compared to 579.5 with the established 120 kV spectrum. This slightly lower value is expected because the tinfiltered spectrum is closer to the initially used 130 kV, as has been shown earlier in this paper. Also, with approximately 10% deviation, it lies within the known and accepted intervendor range of 2025% cited in the literature (Willemink MJ V. R., 2014).

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Conclusion

Agatston AS, J. W. (1990, 15 4). Quantification of coronary artery calcium using ultrafast computed tomography. Journal of the American College of Cardiology, pp. 827832.

Alluri K, J. P. (2015). Scoring of Coronary Artery Calcium Scans: History, Assumptions, Current Limitations, and Future Directions. Atherosclerosis.

AlMallah MH, A. A. (2015). Cardiac computed tomography in current cardiology guidelines. Journal of Cardiovascular Computed Tomography.

Alvarez, L. M. (1977). An Inaccuracy in Computed Tomography: The Energy Dependence of CT Values. Radiology, 124, 9197.

Brook OR, A. S. (2014, 38 3). Calcium Score: Semiautomatic Calcula tion Using Different Vendors Versus Fully Automatic Software. Journal of Computer Assisted Tomography, pp. 434438.

Brooks, A. e. (1976). Beam hardening in xray reconstructive tomography. Phys Med Biol, 390398.

Budoff MJ, S. L. (2007). Longterm prognosis associated with coronary calcification: observations from a registry of 25,253 patients,. Journal of the American College of Cardiology, 18601870.

Ellmann S, K. F. (2016). A Novel Pairwise ComparisonBased Method to Determine Radiation Dose Reduction Potentials of Iterative Reconstruction Algorithms, Exemplified Through Circle of Willis Computed Tomography Angiography. Invest Radiology.

Hoff JA, C. E. (2001). Age and gender distributions of coronary artery calcium detected by electron beam tomography in 35,246 adults. Am. J. Cardiol., 13351339.

Kramer Manue, S. E. (2015, April 187). Computed Tomography Angiography of Carotid Arteries and Vertebrobasilar System. Medicine, 1058.

McCollough CH, U. S. (2007, 243 3). Coronary Artery Calcium: A Multiinstitutional, Multimanufacturer Inter national Standard for Quantification at Cardiac CT. Radiology, pp. 527538.

Parikh S, B. M. (2016, 12 1). Calcium Scoring and Cardiac Computed Tomography. Heart Failure Clinics, pp. 97105.

Thompson G, F. S. (1996, 89 8). Electronbeam CT scanning for detection of coronary calcification and prediction of coronary heart disease. QJM, pp. 565570.

Willemink MJ, A. B. (2015, 9 5). Coronary calcium scores are systematically underestimated at a large chest size: A multivendor phantom study. Journal of Cardiovascular Computed Tomography, pp. 415421.

Willemink MJ, V. R. (2014, 273 3). Coronary artery calcification scoring with stateoftheart CT scanners from different vendors has substantial effect on risk classification. Radiology, pp. 695702.

Yu L, S. M. (2012). Development and validation of a prac tical lowerdosesimulation tool for optimizing computed tomography scan protocols. Journal of Computer Assisted Tomography, pp. 477487.

Zatz, L. M. (1976). The Effect of the kVp Level on EMI Values. Radiology, 119, 683688.

References

Based on the measurement findings, it can be stated that a tube voltage of 100 kV combined with 0.4 mm tin filtration (Sn100 kV) is suitable for coronary CaSc based on the established Agatston scoring algorithm. This suitability can be derived from the good overall spectral agreement of Sn100 kV and the established 120 kV and 130 kV tube voltages as well as the good agreement in quantitative Agatston scoring numbers measured in an established reference phantom setup as well as initial clinical evaluations.

Based on phantom measurements, one can also deduce a possible dose reduction of up to 50% using Sn100 kV instead of the Siemens Healthineers 120 kV default scan proto col values. The actual amount of achieved dose reduction can vary indi vidually depending on the size of the patient.

Yet the Sn100 kV reaches the tube power limits on SOMATOM Drive earlier when compared to the standard 120 kV protocol. Judging from the phantom measurements, this limit should be equivalent to a patient size of approximately 100 kg. To overcome this problem, it is recommended to switch to 120 kV or 130 kV Calcium Scoring for heavier patients.

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Calcium Scoring using Tin Filter spectral shaping · 2020. 7. 10. · For SOMATOM Drive, a 0.4 mm...

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