Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3616_Библиотеки_им_академика_М_И_Перельмана
.pdf
Chapter 21
https://t.me/med1917
Dual-Energy CT of Aortic Disease
Abdulrahman Almutairi
1
Curtin University, Perth, WA, Australia; 2King Fahad Specialist Hospital, Dammam, Saudi Arabia
1,2
, Zhonghua Sun
1
Chapter Outline
Introduction 223
Principles of DECT 223
DECT Techniques 224
Image Weighting Factor 225
Virtual Noncontrast Images 225
Virtual Monochromatic Imaging 225
Iterative Reconstruction 226
Contrast Medium Dose 226
Applications of DECTA in Aortic Disease 226
Aortic Dissection 226
Aortic Aneurysm 227
Endoleak Detection 227
Radiation Dose 229
Conclusion 229
References 229
INTRODUCTION
Aortic diseases are associated with high morbidity and mortality; thus, an accurate and efficient diagnostic approach is
essential for early diagnosis and improvement in treatment outcomes [1]. In current clinical practice multidetector computed tomography (MDCT) has become the standard reference in the diagnosis and evaluation of patients with aortic diseases with high sensitivity and specificity [2]. Computed tomography angiography (CTA) protocols of the aorta consist of
multiple phases of scanning—noncontrast phase and different timed contrast phases. A good example is the follow-up of
endovascular aneurysm repair (EVAR), which requires frequent follow-up CT examinations, usually once per year [3,4].
Consequently, the CTA protocol of the aorta results in significant radiation exposure to the patients [4]. The introduction
of dual-energy computed tomography (DECT) in the last decade significantly enhances the MDCT applications, and it
represents one of the most exciting technological developments in medical imaging. It adds functional evaluation to the
standard examination based on X-ray attenuation that is obtained in conventional CT examination. With DECT, virtual
noncontrast (VNC) images can be obtained from contrast-enhanced images by subtracting the iodine information [5,6].
Radiation dose can be reduced by 60% by eliminating the true noncontrast images. Virtual monochromatic spectral (VMS)
imaging is another advantage of DECT that improves vascular enhancement and overall image quality, paving the way to
reduce the use of contrast medium. In this chapter, we have discussed the applications of DECT in aortic diseases, with
a focus on common pathologies comprising aortic dissection, aortic aneurysm, and endoleak detection in patients treated
with EVAR.
PRINCIPLES OF DECT
The X-ray attenuation on CT at specific material mainly depends on two aspects: (1) effective atomic number (Z
electron density, which is the kiloelectron volts (keV) energy when interacting with the material. When the interaction
occurs with higher effective atomic number and lower X-ray energy, the CT attenuation (Hounsfield Unit-HU) will be
high. DECT consists of the acquisition of two different data sets of images with different X-ray energies during a single
scan (80–140 kVp) [7]. The difference between high and low energies allows for distinguishing materials in the body [8].
Therefore, DECT imaging depends on various properties in both X-ray attenuation and tissue attenuation, and it is sensitive
to the object’s chemical composition.
New Approaches to Aortic Diseases from Valve to Abdominal Bifurcation. http://dx.doi.org/10.1016/B978-0-12-809979-7.00021-3
Copyright © 2018 Elsevier Inc. All rights reserved.
); (2)
eff
223
224 PART | II Diagnostic Evaluation Methods
https://t.me/med1917
Because DECT is capable of providing material differentiation in addition to the improvement of iodine detection at
low energies, vascular structures and pathologies can be visualized with better image quality than is usually possible with
conventional CT imaging without any increase in radiation dose to the patients. Further advantages of DECT angiography
(DECTA) include (1) bone removal algorithms and plaque visualization [9], (2) metal artifact reduction [10], (3) tissue
recomposition quantification for improved diagnostic accuracy [11], and (4) virtual monochromatic imaging to replace the
true unenhanced scanning.
DECT TECHNIQUES
Understanding DECTA techniques is essential to ensure acquisition of images with consistent quality. This section reviews
current DECTA methods used to evaluate aortic anatomy. The following approach serves as a guidance to use DECTA in
different CT scanners. There are four different techniques that are presently used in DECT imaging, as shown in Table 21.1.
TABLE 21.1 Comparison of Performance Parameters of the Currently Available Dual-Energy Computed Tomography
(DECT) Scanners
192-Slice
Dual
64-Slice
Dual Source
Specifications
Detector
configuration
Slice thickness 0.625/1 mm 0.625/1 mm 0.5/1 mm 0.625/1.25 mm 0.625/1 mm
Field of view 26 cm 33 cm 35 cm 50 cm 50 cm
Time between
images
Technique used
for dual energy
Gantry rotation
time for dualenergy mode
Temporal
resolution for
dual-energy
mode
Strengths For each tube potential, tube current and tube filtration
Weaknesses Requires specialized hardware.
(Definition)
2 × 32 × 0.625 2 × 64 × 0.625 2 × 96 × 0.6 64 × 0.625 2 × 64 × 0.625
83 ms 75 ms NA 0.3–0.5 ms NA
2 tubes 2 tubes 2 tubes Fast kVp switching Multilayered detector
330 ms 300 ms 250 ms 350 ms 270 ms
165 ms 150 ms 125 ms 175 ms 135 ms
can be selected independently.
Relatively low degree of spectral overlap, which
improves contrast-to-noise ratios in material-specific
images.
Beam-hardening corrections are applied prior to
image reconstruction.
Material-specific images to be created in the image
domain.
A 90–95 degrees phase shift between low- and
high-energy data.
The use of both X-ray sources permits cross-scattered
radiation which requires specialized scatter correction.
128-Slice
Dual Source
(Definition Flash)
Source
(Somatom
Force)
64-DECT (Discovery
750HD) Philips IQon CT
Almost simultaneous
acquisition of the 80and 140-kVp data set.
Allows dual-energy
material-decomposition
algorithms in either
projection data or
reconstructed images.
Decreases beam-hardening artefacts in virtual
mono-energetic images.
Requires specific
hardware.
Moderately high overlap
of the energy spectra.
Spectral separation is not
feasible to be improved
by applying filtration.
Ideal alignment of lowand high-energy datasets,
rendering images less likely
to motion artefacts. Perfect
beam-hardening correction.
Affords conventional and
dual-energy datasets with a
single scan without changes
of the clinical workflow.
The accuracy of the different
energy separation is lower
than the other systems using
different X-ray tube voltages.
Spectral separation cannot
be improved by applying
filtration. Relatively high
overlap of the energy spectra.
Dual-Energy CT of Aortic Disease Chapter | 21 225
https://t.me/med1917
Dual-source CT (DSCT) is the most common type of CT scanner used in producing DECT images. It uses two sources
of energy with two X-ray tubes to generate different image sets (80 and 140 kVp) and weights average images from a
single acquisition in the CT image processing workstation [12]. Weighted average images are generated from the combined
HU data attained by two X-ray sources of the DSCT to simulate the image quality of typical 120 kVp acquisition [2]. The
weighting factor is measured by the ratio of the central 35-cm image density in the third generation scanner (33 cm in the
second generation scanner or 26-cm image density in the first generation scanner), which is contributed by the 80-kVp data
sets. Dual-energy postprocessing software adjusts the weighting factor.
The second type of dual-energy scanner is the single source DECT, developed by GE Healthcare. It uses a single X-ray
tube that can rapidly switch between 80 and 140 kVp energy within 0.5 ms using an electronic generator. However, in this
scanner, weighting factor cannot be controlled by the user. The third type for performing DECT is the multilayer detector,
developed by Philips Medical Systems. It uses a single high kVp tube and layered or sandwiched scintillator detectors [13].
The low-energy data from the front detector and the high-energy data from the back detector are collected and analyzed.
The fourth type is the photon-counting detector. The basic principle of this type is based on specific energy thresholds and
related energy of each photon; counts are located into definite energy threshold data set [13]. However, this type of scanner
is not yet available for clinical use.
IMAGE WEIGHTING FACTOR
Some researchers have discussed the effect of weighting factor on radiation dose and image quality. Paul et al. [14] reported
that DECT in the carotid artery imaging using different weighting factors from 0.0 to 1.0 of two data sets affected both
contrast enhancement and image quality. Moreover, the authors also proved that the fused images with a weighting factor
of 0.6 showed the highest contrast-to-noise ratio (CNR) or signal-to-noise ratio instead of 80 or 140 images set separately
[14]. Behrendt et al. [15] also reported that using a weighting factor of 0.5 improved the image quality while imaging aorta
with different weighing factors. Other authors have reported that using weighting factors of 0.3 and 0.4 achieved similar
results in images with characteristics comparable to those achieved by 120 kVp [6,16]. Consequently, the weighting factor
of tube voltage has a direct effect on the image quality. When higher percentages of low energy are used, the reconstructed
images will attain higher contrast but higher image noise, whereas data with higher percentages of higher energy will result
in lower image contrast and lower image noise. With the available tube potentials, 80 and 140 kVp are used in small- to
medium-sized patients, and 100 and 140 kVp are used in large patients for aortic angiography scanning. In such cases, a
weighting factor from 0.4 to 0.5 is recommended to improve the image quality.
VIRTUAL NONCONTRAST IMAGES
In conventional CTA, noncontrast phase of the aorta is routinely used when evaluating aortic dissection, hematoma, or
postoperative aortic stents. VNC image was one of the early applications of DECT and it is considered as a reliable
approach to replace the conventional true noncontrast acquisition in cardiovascular CT protocol, particularly aortic imaging.
In this approach, the iodine from contrast images can be removed by applying a postprocessing algorithm to generate VNC
images, which serves the purpose of reducing radiation dose associated with CT scans.
VIRTUAL MONOCHROMATIC IMAGING
Previously, all X-ray beams produced by MDCT were polychromatic. After the arrival of DECT, X-ray energy is expressed
in kiloelectron volts (keV), which is a simplified way than expressing it in kVp. There are three elements for VMS imaging, all of which can be acquired by DECT. They include (1) X-ray sources producing different energies, (2) a detector
that can differentiate quanta of different energies, and (3) material differentiation [17]. The second generation DS-DECT
makes possible the optimization of spectral separation of photons by introducing Sn prefiltration or “tin filter,” which is a
prefiltration onto the 140 kVp, that is used to filter the high-energy spectrum and increase image contrast [18]. In the third
generation DS-DECT, the addition of Sn prefiltration to the new Vectron X-ray tube further strengthens the X-ray spectrum
by removing low-energy photons that are fully absorbed by the patient’s body.
Spectral imaging can be obtained using conventional polyenergetic images (PEIs) to generate VMS images at different
keV levels [19]. PEI is an image generated by conventional CT with full spectrum of photon energies with kilovolt peak
chosen by the CT technologist, e.g., 80, 100, 120, or 140 kVp [20]. On the other hand, VMS can be obtained from a pair of
material density images and mass attenuation coefficients [21]. As the standard low- and high-tube potential of DECT are
80 and 140 kVp, the mean effective energies are 53 keV and 72 keV, respectively [8] (the effective energies range between
40 and 190 keV).
226 PART | II Diagnostic Evaluation Methods
https://t.me/med1917
ITERATIVE RECONSTRUCTION
All main CT vendors offer iterative reconstruction (IR) algorithms with the aim of reducing image noise at lower radiation
dose [22–25]. However, the concept of IR was introduced before the filtered back projection (FBP) and it was named as
algebraic reconstruction, but due to the limited computational power of CT it has been replaced by the FBP [26]. Primarily,
the IR algorithms were implemented to improve the reconstructed image quality, using two steps of reconstruction, forward and backward. In the backward step, it is a standard FBP, with images generated from the projection data, and in the
forward step the projection data are produced from images. These iterations are repeated for specific time to reach the final
step of optimal image quality compared to the FBP [27]. Consequently, the reconstruction algorithms by themselves do not
directly reduce radiation dose but only improve image quality when low-dose CT is used. Accordingly, CT dose reduction
is achieved indirectly using IR by using nonlinear image processing; especially at a low CT dose, the IR techniques can
avoid an undesirable disagreement between image noise and contrast [28].
Many researchers have found that by using IR in CT procedures, a dose reduction of at least 25% and up to 60%
has been achieved without significantly affecting the image quality [28–31]. According to Leipsic et al. [30] up to 25%
dose reduction has been achieved in chest CT examinations using adaptive statistical iterative reconstruction reconstruction. Winklehner et al. [32] reported dose reduction of more than 25% using sinogram-affirmed iterative reconstruction
compared to FBP in body CTA with high image quality. On the other hand, IR was proved to reduce image noise that
leads to increased CNR [33,34]. Beam hardening artifacts were solved by IR techniques [31,35,36]. Therefore, the key
advantage of IR in DECT is the radiation dose reduction. Indeed, using these methods with aortic examinations might
improve the image quality with a lower radiation dose without the negative effect of a lower radiation dose on the image
quality [37].
CONTRAST MEDIUM DOSE
One of the fundamental advantages of DECTA is the possibility of reducing the contrast volume [38]. The use of iodinebased contrast media increases the DECT ability to improve its enhancement when analyzing the monochromatic images
[39]. The contrast dose is adjusted according to the patient weight. However, the new trend of using optimal contrast
medium in vascular imaging has become increasingly necessary. The optimum arterial enhancement in CTA procedures is
between 250 and 300 HU. Arterial enhancement greater than 350 HU is not preferable due to the impediments of differentiation between contrast medium and vascular calcifications in the arteries. Decreasing the volume of contrast medium is
equally important as that of reducing radiation dose, especially for patients who have the potential risk of contrast-induced
nephropathy or for those who have renal function insufficiency [38]. Balancing between the image quality and the reduction of contrast medium and radiation dose is essential when aortic DECTA is planned. A reduction in contrast volume or
concentration up to 50% in DECT of abdominal aortic aneurysm has been reported [40,41].
In clinical practice, reduction of contrast volume between 50% and 75% based on patient weight in vascular DECTA
was reported, especially, when a low keV image is used with arterial opacification with acceptable diagnostic image quality
[39]. Another approach of contrast reduction is a multiphasic injection protocol, taking into account the fact that the optimal
arterial enhancement resulting from an extended injection is a steady increase in the arterial enhancement [42].
APPLICATIONS OF DECTA IN AORTIC DISEASE
Using DECTA in the diagnosis of aortic disease is one of the main applications showing the technique’s potential value in
cardiovascular imaging. Furthermore, DECTA can be beneficial for bone removal to improve vascular visualization and
reconstruction of virtually unenhanced images, which has been shown to reduce radiation exposure. Virtual monochromatic
imaging generated from DECTA data at different keV levels allows for an improved image quality in different vascular
studies. The following section will discuss the use of DECTA in common aortic diseases.
Aortic Dissection
Aortic dissection is one of the most leading causes of death in both developed and developing countries. It is caused
by interruption of the aortic intima to split it into two lumens, true and false lumen. Stanford system is commonly used
to classify it into type A dissection, which involves the ascending aorta or type B dissection involving any part of the
aorta except the ascending aorta. Among these, 30%–40% of the dissections belong to type B dissection [43]. Recently,
thoracic endovascular aortic repair (TEVAR) is preferred to conventional surgical repair due to significant reduction
of the early mortality rates. However, unlike open surgery, this less-invasive intervention requires a regular imaging
Dual-Energy CT of Aortic Disease Chapter | 21 227
https://t.me/med1917
evaluation to ensure lumen patency and to identify endoleaks. CTA is considered as a reliable, less invasive modality
compared to the conventional angiography to provide preoperative assessment of aortic dissection and post-TEVAR
follow-up.
Type B aortic dissection is usually evaluated by multiphasic CTA protocol that includes noncontrast and arterial phase
acquisitions [44]. The purpose of these phases is to help the detection of extent of dissection in relation to the arterial
branches, and endoleaks or hemorrhage in the aorta. Lifelong imaging follow-up in these patients is mandatory to evaluate
the endovascular repair of the dissection, with the subsequent cumulative radiation dose [21]. DECT reduces radiation dose
by eliminating the noncontrast phase by using VNC images [45]. Chandrana et al. found that VNC can eliminate the true
noncontrast phase for endoleaks detection [46]. Sommer et al. used a single phase and generated VNC and achieved a high
accuracy for endoleaks detection [1]. Another study by Stolzmann et al. using a delayed phase to generate VNC reported a
high accuracy (98%) compared to conventional CTA [4]. On the other hand, Numburi and colleagues investigated the use
of arterial phase only to generate a VNC and concluded that this method provided comparable results to the conventional
method [47]. In addition, arterial phase can be also eliminated because the delayed phase can depict the endoleaks with
high accuracy [3]. As a result, single (delayed phase) or biphasic protocol using DECT (arterial and delayed) to evaluate
aortic dissection might be sufficient for this protocol, resulting in a significant reduction of the radiation dose [2,4,44].
Depending on the endoleaks flow (high-flow or slow-flow), the delayed timing is very important; therefore, the delay of up
to 300 seconds can be selected in this protocol. As a result, the type of endoleaks and the size of aneurysm scan determine
the treatment.
Furthermore, applying spectral imaging in DECTA of the aorta has been shown to improve the image quality beyond the
conventional CTA. Maturen et al. [48] investigated endovascular aneurysm of the aorta and demonstrated high sensitivity in
the detection of endoleaks using 55 keV VMS, compared to standard PEI. Sudarski et al. [6] stated that compared to dualenergy PEI, using a 70 keV VMS achieved a high CNR in the abdominal arteries. Pehno et al. [5] compared the subjective
and objective image quality of virtual VMS and PEI in aortoiliac arteries and demonstrated optimal contrast enhancement
and improved image quality using 70 keV VMS in preference to single-energy CTA. Delesalle et al. [49] assessed the spectral optimization of thoracic arteries and found that virtual monochromatic energy at 60 and 100 keV provided similar or
better image quality compared to standard chest CTA.
Aortic Aneurysm
When the aortic diameter exceeds 50% of its normal diameter, it is considered as an aortic aneurysm. The risk of rupture
increases with the size of the aneurysm. The diagnosis of abdominal aortic aneurysm (AAA) in an early stage is very
important to avoid rupture. The major risk factors for AAA growth include age, smoking, family history, and atherosclerotic
vascular disease [50]. When the AAA is suspected by a physical abdominal examination, the imaging procedure should be
implemented. Aortic aneurysm represents one of the most common cardiovascular diseases and its prevalence increases in
the elderly population. This complex disease involves formation, growth, and rupture of the aortic wall [51]. Plain X-ray,
ultrasound, magnetic resonance imaging (MRI), conventional angiography, and CT are the imaging modalities that can
detect the aneurysms [50]. Plain X-ray occasionally identifies AAA if there is a presence of extensive calcification in the
aneurysm wall, but with very low sensitivity. Ultrasound is a good and safe examination but it might be limited by the
abdominal gases and it is an operator-dependent procedure. MRI procedure suffers from the long-time of scanning and
is limited in imaging poststent grafting patients. On the other hand, CTA is the most widely used modality for detection
of AAA and preoperative planning of EVAR, which is a commonly used minimally invasive procedure compared to open
surgery [4,52].
The most common complication of EVAR is the endoleak, which shows contrast-enhanced area in the aneurysm sac
but outside the stent graft (Fig. 21.1) [1]. During the follow-up of patients with EVAR, conventional CT is the reference
standard procedure for the aortic stent procedures [2,4]. Although triphasic CT protocol provides excellent outcomes for
endoleak detection, it is associated with high radiation dose as well as high iodinated contrast dose, and this is the main
limitation of CTA as a follow-up modality [1,4]. DECT allows for minimizing the acquisition to dual phase or in some
circumstances to a single phase to detect the endoleaks.
Endoleak Detection
Endoleak detection nowadays is more affordable by DECT in a dual-phase acquisition by the elimination of unenhanced
CT images [3]. This technique results in a significant reduction of the radiation dose to patients. Furthermore, with DECTA,
single phase can be used (venous or delayed) to evaluate EVAR. In conventional CT, using low kVp imaging helps to
228 PART | II Diagnostic Evaluation Methods
(A)
(B)
(C)
https://t.me/med1917
FIGURE 21.1 Endoleak in a patient after endovascular aneurysm repair of an abdominal aortic aneurysm in a 65-year-old male. Two-dimensional
axial computed tomography images show type II endoleak present in the aneurysm sac (short arrows). An incidental left renal cyst is also observed (long
arrow).
(D)
FIGURE 21.2 Dual-energy computed tomography (DECT) study in a patient with recent endovascular aneurysm repair (EVAR) for an abdominal aortic
aneurysm (AAA) in a 56-year-old man. Reconstituted conventional two-dimensional axial CT angiogram images (A and B) show hyperdense material
in the right posterolateral aspect of the excluded aneurysm sac (arrow), which is in close proximity to the origin of a left lumbar artery (arrow head).
Postprocessing DECT virtual contrast/iodine overlay images (C and D) clearly depict orange-colored area in the excluded aneurysm sac confirming with
certainty the presence of a type II endoleak. Case courtesy of Dr Charlie Chia-Tsong Hsu, www.radiopaedia.org, rID: 39715.
identify indirect enhancement, such as endoleaks. However, with DECT this phase can be reconstructed from the contrast
phase saving the patients from additional radiation dose. In addition, low keV increases attenuation and even subtle endoleaks could be detected [38]. Another dual-energy postprocessing technique called hard plaque imaging, which enables color
codes for iodine in blue and calcification in red, is found to be a promising technique to distinguish between endoleaks and
aneurysm sac calcifications (Fig. 21.2) [52].
Dual-Energy CT of Aortic Disease Chapter | 21 229
https://t.me/med1917
Combination of VNC and hard plaque imaging from single scan may lead to high diagnostic accuracy for endoleaks and
calcification detection. On the other hand, the recent advances of image-based mono+ algorithm were found to improve the
CNR from high and low keV levels [38]. Thus, improvement of contrast enhancement will be obvious and the use of low
keV will be more beneficial for the clinical purpose [45]. Beers et al. reported a superior image quality with 40 and 50 keV
when mono+ algorithm is used for aortic DECTA [38]. Similarly, Albrecht et al. evaluated this algorithm in abdominal aorta
and found superior image quality compared to the old mono algorithm [53]. As a result, using a combination of low and
high X-ray energies is what distinguishes DECT scanners from conventional MDCT. In addition, DECT can eliminate the
need of nonenhanced phase; moreover, monochromatic reconstruction at low keV contributes to better contrast enhancement, and therefore, improves the detection of aortic endoleaks.
RADIATION DOSE
The main drawback of CT imaging is the use of ionizing radiation, which presents the risks of tissue impairment and
cancer induction. The radiation dose in CT depends on peak tube voltage, tube current, and scan time [54]. The effects
of radiation dose may be represented either in a deterministic or stochastic form. When the radiation dose reaches the
threshold dose level (which differs from one subject to another), deterministic effects are manifested with the damage being significantly correlated to the amount of radiation dose [21]. Deterministic effects most often occur during
interventional radiological procedures, while in contrast, stochastic effects are frequently seen during general X-ray or
CT imaging. With the number of CT phases used for diagnosing aortic disease, the cumulative dose increases, accordingly reducing the acquired phases could be an effective strategy for reducing radiation dose. For patients after EVAR,
replacing the true nonenhanced phase with VNC results in reduction of radiation dose and achieving more reduction by
eliminating the arterial phase without affecting the diagnostic accuracy as shown in recent studies [3,21,52,55]. Another
strategy for dose reduction to those patients is to limit the scan range to 3.0 cm above and below the stent-graft, which
enables evaluation of stent patency [1,45]. In the near future, dose reduction strategies will come from the technological
advancement in image reconstruction. Radiation dose can be saved up to 50% when true unenhanced phase and arterial
phase are eliminated. As mention previously, using IR can enable dose reductions more than 50% when it is utilized
effectively [28–31,56,57]. As a result, applying the IR algorithm with a single phase will reduce the radiation dose even
further.
CONCLUSION
This chapter shows that DECT is a promising imaging modality in the diagnosis of aortic disease with improved image
quality with reduced radiation dose and contrast medium dose. The applications of DECT in the diagnostic assessment of
aortic dissection, aortic aneurysm, and endoleak detection indicate that this technique should be used to supplement conventional CTA as an alternative modality in the follow-up of patients after EVAR.
REFERENCES
[1] Sommer WH, Clevert DA, Bamberg F, Helck A, Albrecht E, Reiser MF, et al. Time-resolved computed tomography imaging of the aorta: a feasibil-
ity study. J Thorac Imaging 2010;25(2):161–7.
[2] Sun Z, Almoudi M, Cao Y. CT angiography in the diagnosis of cardiovascular disease: a transformation in cardiovascular CT practice. Quant
Imaging Med Surg 2014;4:376–96.
[3] Flors L, Leiva-Salinas C, Norton PT, Patrie JT, Hagspiel KD. Endoleak detection after endovascular repair of thoracic aortic aneurysm using dual-
source dual-energy CT: suitable scanning protocols and potential radiation dose reduction. AJR Am J Roentgenol 2013;200(2):451–60.
[4] Stolzmann P, Frauenfelder T, Pfammatter T, Peter N, Scheffel H, Lachat M, et al. Endoleaks after endovascular abdominal aortic aneurysm repair:
detection with dual-energy dual-source CT. Radiology 2008;249(2):682–91.
[5] Pinho DF, Kulkarni NM, Krishnaraj A, Kalva SP, Sahani DV. Initial experience with single-source dual-energy CT abdominal angiography and
comparison with single-energy CT angiography: image quality, enhancement, diagnosis and radiation dose. Eur J Radiol 2013;23(2):351–9.
[6] Sudarski S, Apfaltrer P, Nance Jr JW, Schneider D, Meyer M, Schoenberg SO, et al. Optimization of keV-settings in abdominal and lower extremity
dual-source dual-energy CT angiography determined with virtual monoenergetic imaging. Eur J Radiol 2013;82(10):e574–81.
[7] Coursey CA, Nelson RC, Boll DT, Paulson EK, Ho LM, Neville AM, et al. Dual-energy multidetector CT: how does it work, what can it tell us, and
when can we use it in abdominopelvic imaging? Radiographics 2010;30(4):1037–55.
[8] Kaza RK, Platt JF, Cohan RH, Caoili EM, Al-Hawary MM, Wasnik A. Dual-energy CT with single- and dual-source scanners: current applications
in evaluating the genitourinary tract. Radiographics 2012;32(2):353–69.
[9] Graser A, Johnson TR, Chandarana H, Macari M. Dual energy CT: preliminary observations and potential clinical applications in the abdomen. Eur
J Radiol 2009;19(1):13–23.
230 PART | II Diagnostic Evaluation Methods
https://t.me/med1917
[10] Bamberg F, Dierks A, Nikolaou K, Reiser MF, Becker CR, Johnson TR. Metal artifact reduction by dual energy computed tomography using
monoenergetic extrapolation. Eur J Radiol 2011;21(7):1424–9.
[11] Brockmann C, Jochum S, Sadick M, Huck K, Ziegler P, Fink C, et al. Dual-energy CT angiography in peripheral arterial occlusive disease.
Cardiovasc Intervent Radiol 2009;32(4):630–7.
[12] Macari M, Spieler B, Kim D, Graser A, Megibow AJ, Babb J, et al. Dual-source dual-energy MDCT of pancreatic adenocarcinoma: initial observa-
tions with data generated at 80 kVp and at simulated weighted-average 120 kVp. AJR Am J Roentgenol 2010;194(1):W27–32.
[13] McLaughlin PD, Mallinson P, Lourenco P, Nicolaou S. Dual-energy computed tomography: advantages in the acute setting. Radiol Clin N Am
2015;53(4):619–38.
[14] Paul J, Mbalisike EC, Nour-Eldin NE, Vogl TJ. Dual-source 128-slice MDCT neck: radiation dose and image quality estimation of three different
protocols. Eur J Radiol 2013;82(5):787–96.
[15] Behrendt FF, Schmidt B, Plumhans C, Keil S, Woodruff SG, Ackermann D, et al. Image fusion in dual energy computed tomography: effect on
contrast enhancement, signal-to-noise ratio and image quality in computed tomography angiography. Invest Radiol 2009;44(1):1–6.
[16] Huang SY, Nelson RC, Miller MJ, Kim CY, Lawson JH, Husarik DB, et al. Assessment of vascular contrast and depiction of stenoses in abdomino-
pelvic and lower extremity vasculature: comparison of dual-energy MDCT with digital subtraction angiography. Acad Radiol 2012;19(9):1149–57.
[17] Vlahos I, Chung R, Nair A, Morgan R. Dual-energy CT: vascular applications. AJR Am J Roentgenol 2012;199(5):S87–97.
[18] Petersilka M, Bruder H, Krauss B, Stierstorfer K, Flohr TG. Technical principles of dual source CT. Eur J Radiol 2008;68(3):362–8.
[19] Marin D, Boll DT, Mileto A, Nelson RC. State of the art: dual-energy CT of the abdomen. Radiology 2014;271(2):327–42.
[20] Yu L, Christner JA, Leng S, Wang J, Fletcher JG, McCollough CH. Virtual monochromatic imaging in dual-source dual-energy CT: radiation dose
and image quality. Med Phys 2011;38(12):6371–9.
[21] Buffa V, Solazzo A, D’Auria V, Del Prete A, Vallone A, Luzietti M, et al. Dual-source dual-energy CT: dose reduction after endovascular abdominal
aortic aneurysm repair. Radiol Med 2014;119(12):934–41.
[22] Bittencourt M, Schmidt B, Seltmann M, Muschiol G, Ropers D, Daniel W, et al. Iterative reconstruction in image space (IRIS) in cardiac computed
tomography: initial experience. Int J Cardiovasc Imaging 2011;27(7):1081–7.
[23] Katsura M, Matsuda I, Akahane M, Yasaka K, Hanaoka S, Akai H, et al. Model-based iterative reconstruction technique for ultralow-dose chest CT:
comparison of pulmonary nodule detectability with the adaptive statistical iterative reconstruction technique. Invest Radiol 2013;48(4):206–12.
[24] Korn A, Bender B, Fenchel M, Spira D, Schabel C, Thomas C, et al. Sinogram affirmed iterative reconstruction in head CT: improvement of objec-
tive and subjective image quality with concomitant radiation dose reduction. Eur J Radiol 2013;82(9):1431–5.
[25] Silva AC, Lawder HJ, Hara A, Kujak J, Pavlicek W. Innovations in CT dose reduction strategy: application of the adaptive statistical iterative recon-
struction algorithm. AJR Am J Roentgenol 2010;194(1):191–9.
[26] Fleischmann D, Boas FE. Computed tomography–old ideas and new technology. Eur J Radiol 2011;21(3):510–7.
[27] Willemink MJ, de Jong PA, Leiner T, de Heer LM, Nievelstein RA, Budde RP, et al. Iterative reconstruction techniques for computed tomography
Part 1: technical principles. Eur J Radiol 2013;23(6):1623–31.
[28] Hara AK, Paden RG, Silva AC, Kujak JL, Lawder HJ, Pavlicek W. Iterative reconstruction technique for reducing body radiation dose at CT: feasi-
bility study. AJR Am J Roentgenol 2009;193(3):764–71.
[29] Desai GS, Uppot RN, Yu EW, Kambadakone AR, Sahani DV. Impact of iterative reconstruction on image quality and radiation dose in multidetector
CT of large body size adults. Eur J Radiol 2012;22(8):1631–40.
[30] Leipsic J, Nguyen G, Brown J, Sin D, Mayo JR. A prospective evaluation of dose reduction and image quality in chest CT using adaptive statistical
iterative reconstruction. AJR Am J Roentgenol 2010;195(5):1095–9.
[31] Winklehner A, Karlo C, Puippe G, Schmidt B, Flohr T, Goetti R, et al. Raw data-based iterative reconstruction in body CTA: evaluation of radiation
dose saving potential. Eur J Radiol 2011;21(12):2521–6.
[32] Winklehner A, Goetti R, Baumueller S, Karlo C, Schmidt B, Raupach R, et al. Automated attenuation-based tube potential selection for thoracoab-
dominal computed tomography angiography: improved dose effectiveness. Invest Radiol 2011;46(12):767–73.
[33] Wang R, Schoepf UJ, Wu R, Reddy RP, Zhang C, Yu W, et al. Image quality and radiation dose of low dose coronary CT angiography in obese
patients: sinogram affirmed iterative reconstruction versus filtered back projection. Eur J Radiol 2012;81(11):3141–5.
[34] Yin WH, Lu B, Li N, Han L, Hou ZH, Wu RZ, et al. Iterative reconstruction to preserve image quality and diagnostic accuracy at reduced radiation
dose in coronary CT angiography: an intraindividual comparison. JACC Cardiovasc Imaging 2013;6(12):1239–49.
[35] Nelson RC, Feuerlein S, Boll DT. New iterative reconstruction techniques for cardiovascular computed tomography: how do they work, and what
are the advantages and disadvantages? J Cardiovasc Comput Tomogr 2011;5(5):286–92.
[36] Raman SP, Johnson PT, Deshmukh S, Mahesh M, Grant KL, Fishman EK. CT dose reduction applications: available tools on the latest generation
of CT scanners. J Am Coll Radiol 2013;10(1):37–41.
[37] Renker M, Geyer LL, Krazinski AW, Silverman JR, Ebersberger U, Schoepf UJ. Iterative image reconstruction: a realistic dose-saving method in
cardiac CT imaging? Expert Rev Cardiovasc Ther 2013;11(4):403–9.
[38] Beeres M, Trommer J, Frellesen C, Nour-Eldin NE, Scholtz JE, Herrmann E, et al. Evaluation of different keV-settings in dual-energy CT angiog-
raphy of the aorta using advanced image-based virtual monoenergetic imaging. Int J Cardiovasc Imaging 2016;32(1):137–44.
[39] Liu J, Lv PJ, Wu R, Zhang YG, Hu LL, Hou P, Gao JB. Aortic dual-energy CT angiography with low contrast medium injection rate. J Xray Sci
Technol 2014;22(5):689–96.
[40] Megibow AJ, Sahani D. Best practice: implementation and use of abdominal dual-energy CT in routine patient care. AJR Am J Roentgenol
2012;199(5 Suppl):S71–7.
Dual-Energy CT of Aortic Disease Chapter | 21 231
https://t.me/med1917
[41] Xin L, Yang X, Huang N, Du X, Zhang J, Wang Y, et al. The initial experience of the upper abdominal CT angiography using low-concentration
contrast medium on dual energy spectral CT. Abdom Imaging 2015;40(7):2894–9.
[42] Seehofnerova A, Kok M, Mihl C, Douwes D, Sailer A, Nijssen E, et al. Feasibility of low contrast media volume in CT angiography of the aorta. Eur
J Radiol Open 2015;2:58–65.
[43] Kahn SL, Dake MD. Current endograft therapy of type B aortic dissection. In: Kazui T, Takamoto S, editors. Advances in understanding aortic
diseases. Tokyo (Japan): Springer; 2009. p. 67–78.
[44] Flors L, Leiva-Salinas C, Norton PT, Patrie JT, Hagspiel KD. Imaging follow-up of endovascular repair of type B aortic dissection with dual-source,
dual-energy CT and late delayed-phase scans. J Vasc Interv Radiol 2014;25(3):435–42.
[45] Fuentes-Orrego JM, Pinho D, Kulkarni NM, Agrawal M, Ghoshhajra BB, Sahani DV. New and evolving concepts in CT for abdominal vascular
imaging. Radiographics 2014;34(5):1363–84.
[46] Chandrana H, Godoy MC, Vlahos I, Graser A, Babb J, Leidecker C, et al. Abdominal aorta: evaluation with dual-source dual-energy multidetector
CT after endovascular repair of aneurysms– initial observation. Radiology 2008;249(2):697–700.
[47] Numburi UD, Schoenhagen P, Flamm SD, Greenberg RK, Primak AN, Saba OI, et al. Feasibility of dual-energy CT in the arterial phase: imaging
after endovascular aortic repair. AJR Am J Roentgenol 2010;1195(2):486–93.
[48] Maturen KE, Kaza RK, Liu PS, Quint LE, Khalatbari SH, Platt JF. “Sweet spot” for endoleak detection: optimizing contrast to noise using low keV
reconstructions from fast-switch kVp dual-energy CT. J Comput Assist Tomogr 2012;36(1):83–7.
[49] Delesalle MA, Pontana F, Duhamel A, Faivre JB, Flohr T, Tacelli N, et al. Spectral optimization of chest CT angiography with reduced iodine load:
experience in 80 patients evaluated with dual-source, dual-energy CT. Radiology 2013;267(1):256–66.
[50] Lederle FA. Abdominal aortic aneurysm. Ann Intern Med 2009;150(9). ITC5–1.
[51] Dudeck O, Schnapauff D, Herzog L, Löwenthal D, Bulla K, Bulla B, et al. Can early computed tomography angiography after endovascular aortic
aneurysm repair predict the need for reintervention in patients with type II endoleak? J Vasc Interv Radiol 2015;38(1):45–52.
[52] Muller-Wille R, Borgmann T, Wohlgemuth WA, Zeman F, Pfister K, Jung EM, et al. Dual-energy computed tomography after endovascular aortic
aneurysm repair: the role of hard plaque imaging for endoleak detection. Eur J Radiol 2014;24(10):2449–57.
[53] Albrecht MH, Scholtz JE, Husers K, Beeres M, Bucher AM, Kaup M, et al. Advanced image-based virtual monoenergetic dual-energy CT angiog-
raphy of the abdomen: optimization of kiloelectron volt settings to improve image contrast. Eur J Radiol 2016;26(6):1863–70.
[54] Goldman LW. Principles of CT: radiation dose and image quality. J Nucl Med Technol 2007;35(4):213–25. quiz 26–8.
[55] Machida H, Tanaka I, Fukui R, Ishikawa T, Tate E, Ueno E. Dual-energy spectral CT: various clinical vascular applications. Radiographics
2016;36:1215–32.
[56] Al Shammakhi A, Sun Z. A systematic review of image quality, diagnostic value and radiation dose of coronary CT angiography using iterative
reconstruction compared to filtered back projection in the diagnosis of coronary artery disease. J Med Imaging Health Inf 2015;5:96–102.
[57] Al Shammakhi A, Sun Z. Coronary CT angiography with use of iterative reconstruction algorithm in coronary stenting: a systematic review of image
quality, diagnostic value and radiation dose. J Med Imaging Health Inf 2015;5:103–9.
https://t.me/med1917
Treatment
Соседние файлы в папке Библиотека им академика М.И. Перельмана