Imaging Pearls ❯ Vascular ❯ Dual Energy
|
-- OR -- |
|
- “The implementation of dual-energy CT (DECT) with novel applications such as material decomposition (MD) and virtual monochromatic (VM) imaging presents opportunities to assess vascular disease from a new perspective, expanding the role of CT angiography in vascular imaging from a traditional anatomic-morphologic tool to a functional and quantitative tool.”
New and evolving concepts in CT for abdominal vascular imaging. Fuentes-Orrego JM et al. Radiographics. 2014 Sep-Oct;34(5):1363-84 - “DECT images are acquired with (a) a single x-ray tube with rapid kilovoltage switching (single-source or ssDECT) (Discovery 750HD; GE Healthcare, Milwaukee,Wis) or (b) a configuration of two x- ray tubes (double-source or dsDECT) (Somatom Definition and Definition Flash; Siemens Medical Solutions, Forchheim, Germany). In the ssDECT system, fast switching alternates between 80 and 140 kVp in under 0.5 msec throughout the gantry rotation.This approach preserves the native tem- poral registration of the scan for both sets of im- ages. In ssDECT, both tube voltages (80 and 140 kVp) have to be coupled with a fixed tube current– time product .”
New and evolving concepts in CT for abdominal vascular imaging. Fuentes-Orrego JM et al. Radiographics. 2014 Sep-Oct;34(5):1363-84 - “Iodine images provide higher image contrast due to suppression of tissue lacking iodine or having minimal iodine and therefore comple- ment standard and VM images. Distinguishing intramural hematoma from dissection can be facilitated with more ease based on the iodine distribution. Similarly, diagnosis of small endoleaks can be enabled.”
New and evolving concepts in CT for abdominal vascular imaging. Fuentes-Orrego JM et al. Radiographics. 2014 Sep-Oct;34(5):1363-84 - “MIP displays regions with high attenuation values, so that enhanced vessels are depicted along with calcified plaques and bone; this may limit the ability to measure the degree of vessel stenosis accurately using these datasets alone. Therefore, bone and plaque subtraction techniques need to be applied to overcome these obstacles. However, MIP offers an easy way to create vascular maps for different clinical indications for treatment planning.”
New and evolving concepts in CT for abdominal vascular imaging. Fuentes-Orrego JM et al. Radiographics. 2014 Sep-Oct;34(5):1363-84 - “Volume rendering offers a good 3D impression of the vessel, with better 3D visualization
of the vasculature as well as important adjacent structures, thus enabling the reader to assess for anatomic variations in vessel branching and angulation as well. Volume rendering has ad- vantages over MIP, as it provides better depth perception and superior 3D visualization of overlapping structures and depicts soft-tissue landmarks—especially for treatment planning— that are not demonstrated on MIP images.”
New and evolving concepts in CT for abdominal vascular imaging. Fuentes-Orrego JM et al. Radiographics. 2014 Sep-Oct;34(5):1363-84 - “Besides use of a low-kilovoltage approach, a straightforward strategy for reducing radiation dose is restricting the scan length to the anatomic region of interest. This approach of restricting the scan length has alone provided us with dose sav- ings of 15%. For instance, in patients who have undergone EVAR, limiting the scan range to 3.0 cm above and below the stent can facilitate evaluation of stent patency and integrity.”
New and evolving concepts in CT for abdominal vascular imaging. Fuentes-Orrego JM et al. Radiographics. 2014 Sep-Oct;34(5):1363-84 - “The relationship between the iodine concen- tration in the contrast medium and intravascular attenuation is linear when the scans are per- formed at a constant kilovoltage and using similar injection rates. However, the intravascular at- tenuation almost doubles at lower kilovoltage (80 kV) for similar iodine concentrations.The substantial gain in the intravascular enhancement with low kilovoltage can enable iodine dose re- duction for CT angiography.”
New and evolving concepts in CT for abdominal vascular imaging. Fuentes-Orrego JM et al. Radiographics. 2014 Sep-Oct;34(5):1363-84
- “A thoracic vascular imaging protocol was achievable using lower kilovoltage (80 vs. 100 kVp), lower contrast volume (75 vs. 100 mL), and a slower delivery (3 mL/s vs. 4 mL/s), and still resulted in better vascular attenuation,comparable CNR, and reduced radiation exposure.Inherent to this advantage are cost savings in relation to the utilization of contrast media, but also the potential reduction of contrast dose shown and, hence, contrast induced nephropathy in patients with existing renal impairment.”
Dual-energy Computed Tomography Imaging of the Aorta
Vlahos I, Godoy MCB, Naidich DP
J Thorac Imaging 2010;25:289–300 - “Virtual noncontrast images are slightly noisier in their appearance with regard to noncontrast images, as they are susceptible to noise in the constituent 80- and 140-kVp
images from which they are derived. However, the images are diagnostic, as their intended purpose is to identify preexisting high-attenuation structures or areas.”
Dual-energy Computed Tomography Imaging of the Aorta
Vlahos I, Godoy MCB, Naidich DP
J Thorac Imaging 2010;25:289–300 - “Image reconstruction at a lower monochromatic energy level (50keV) allows for a 50% reduction in iodine load at CT pulmonary angiography (CTPA) while maintaining signal intensity and diagnostic image quality.”
Reduced Iodine Load at CT Pulmonary Angiography with
Dual-Energy Monochromatic Imaging: Comparison with StandardCT Pulmonary Angiography—A Prospective Randomized Trial
Yuan R et al.
Radiology 2012;262:290-297 - “In summary, we conclude projection based dual-energy monochromatic imaging enables significant reduction in iodine load CTPA while maintaining
compatible SNR, CNR, and effective radiation dose.”
Reduced Iodine Load at CT Pulmonary Angiography with
Dual-Energy Monochromatic Imaging: Comparison with StandardCT Pulmonary Angiography—A Prospective Randomized Trial
Yuan R et al.
Radiology 2012;262:290-297 - “ Although our data demonstrate that the dual-energy CTPA protocol maintains high SNR and CNR, we are cautious about its appropriate application, as we do note a slight reduction in image quality and increased image noise. Future integration of iterative reconstruction and other noise reduction tools in dual energy CT may
allow for further improvements in image quality.”
Reduced Iodine Load at CT Pulmonary Angiography with
Dual-Energy Monochromatic Imaging: Comparison with StandardCT Pulmonary Angiography—A Prospective Randomized Trial
Yuan R et al.
Radiology 2012;262:290-297 - “In summary, we conclude projection based dual-energy monochromatic imaging enables significant reduction in iodine load CTPA while maintaining
compatible SNR, CNR, and effective radiation dose. Although our data demonstrate that the dual-energy CTPA protocol maintains high SNR and CNR, we are cautious about its appropriate application, as we do note a slight reduction in image quality and increased image noise. Future integration of iterative reconstruction and other noise reduction tools in dual energy CT may
allow for further improvements in image quality.”
Reduced Iodine Load at CT Pulmonary Angiography with
Dual-Energy Monochromatic Imaging: Comparison with StandardCT Pulmonary Angiography—A Prospective Randomized Trial
Yuan R et al.
Radiology 2012;262:290-297 - “One major advantage of dual-energy CT is the capability of material differentiation. In general, this property can be applied to bone removal in CT angiography for easier and faster postprocessing. In neuroradiology, material decomposition allows detection of hemorrhage on contrast-enhanced CT scans and facilitates the search for the underlying pathologic mechanism of hematomas. The combination of low radiation dose and advantageous spectral information (blood vs contrast) from these datasets justifies broad clinical implementation of dual-energy CT in neuroradiology.”
Dual-Energy CT of the Brain and Intracranial Vessels
Postma AA et al.
AJR 2012; 199:S26-33 - “One major advantage of dual-energy CT is the capability of material differentiation. In general, this property can be applied to bone removal in CT angiography for easier and faster postprocessing.”
Dual-Energy CT of the Brain and Intracranial Vessels
Postma AA et al.
AJR 2012; 199:S26-33 - “Bone removal in DECT angiography
allows easier and faster acquisition and postprocessing compared with conventional (subtraction) CTA. Removal of bone at the skull base remains a matter of concern, but the development of better reconstruction algorithms and dedicated dual-energy kernels may offer a solution.”
Dual-Energy CT of the Brain and Intracranial Vessels
Postma AA et al.
AJR 2012; 199:S26-33 - Dual-energy bone subtraction has been
shown to be faster and technically superior to threshold-based bone subtraction techniques
even when the latter are manually corrected. However, even with dual-energy bone subtraction, bone subtraction is not infrequently
incomplete.
Dual Energy CT: Vascular Applications
Vlahos I et al
AJR 2012: 199:S87-S97 - “ Compared with DSA-diagnosed stenoses
(> 75%), interpretation of dual-energy bone subtraction lower limb CT arteriography MIP
reconstructions alone show high sensitivity,
specificity, and accuracy (94–97%). Comparatively, threshold-based bone subtraction CT arteriography–derived MIPs exhibit lower corresponding values (71–77%). Dual-energy bone subtraction superiority is maintained in heavily calcified vessels (91–96%), whereas this decreases dramatically for threshold based bone subtraction (57–74%).
Dual Energy CT: Vascular Applications
Vlahos I et al
AJR 2012: 199:S87-S97 - “Dual-energy bone subtraction for cervical
CT arteriography compares very favorably
to threshold-based bone subtraction.
Early studies confirmed that dual-energy
bone subtraction was faster and more accurate versus threshold-based bone subtraction without user modification (88% vs 7% technically adequate). Threshold-based bone subtraction inferiority was predominantly due to residual bone, vessel truncations, and poorer vessel delineation, the result of extensive anatomic contact of vessels with bone.”
Dual Energy CT: Vascular Applications
Vlahos I et al
AJR 2012: 199:S87-S97
- Why can we separate bone from contrast enhanced vessels on dual energy CT scans-
Bone Removal on Contrast Enhanced CT
- X-ray attenuation is caused by the Compton effect, coherent scatter, and the photoelectric effect
- The photoelectric effect depends on the atomic number of the material and increases with higher atomic element numbers
- Most elements in the human body have low atomic number (hydrogen, oxygen, carbon, nitrogen) and have weak photoelectric effect while some (calcium, magnesium) have a stronger photoelectric effect
- Contrast material (iodine, barium) have very strong photoelectric effect. The photoelectric effect peaks at element 55 (cesium) with iodine (53) and barium (56) in close proximity - “DEBR provides significant advantages, even over manually corrected SBBR. As it works completely automatically, it can effectively help to cope with the data load of CT angiography exams. Furthermore, it enables the removal of intraluminal plaques, which provides a benefit for the estimation of the residual lumen.”
The value of dual-energy bone removal in maximum intensity projections of lower extremity computed tomography angiography
Sommer WH et al
Invest Radiol 2009 May;44(5) 285-92 - “Dual-energy computed tomography (CT) makes it possible to remove bones and intraluminal plaques from angiography datasets on the basis of spectral differentiation separating iodine from calcium. The objective of this study was to evaluate the feasibility and efficiency of this technique by comparing maximum intensity projections (MIP) created with different bone removal techniques: (a) dual-energy bone removal (DEBR); (b) purely software-based bone removal without manual corrections (SBBR - MC); and (c) manually corrected software-based bone removal (SBBR + MC).”
The value of dual-energy bone removal in maximum intensity projections of lower extremity computed tomography angiography
Sommer WH et al
Invest Radiol 2009 May;44(5) 285-92 - “DE CTA has substantial advantages over conventional CTA. Automatic bone subtraction is more time efficient and reliable. Automatic plaque subtraction for the first time provides a true CTA-luminogram which is easy to interpret and reduces the need for further post-processing. DE CTA provides best results in arteries of the thigh; below the knee, plaque subtraction is less accurate.”
Dual energy CT of peripheral arteries: effect of automatic bone and plaque removal on image quality and grading of stenosis
Meyer BC et al
Eur J Radiol 2008 Dec; 68(3):414-22 - “ Dual-energy bone subtraction has been shown to be faster and technically superior to threshold-based bone subtraction techniques even when the latter are manually corrected. However, even dual-energy bone subtraction is not infrequently incomplete.”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97 - “ Although heavily calcified plaque in contact with bone can also be misclassified as bone and removed with dual energy subtraction , DECT’s reliance on iodine-calcium material differentiation reduces the incidence and severity of these artifacts .”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97 - “ The clinical interpretation advantage of 3D-rendered volumetric data are limited by the need for software assisted Hounsfield unit-threshold-based bone subtraction. This is not only time consuming, but the quality of bone subtraction is subject to patient and user dependent variation.”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97 - “Dual energy vascular imaging is a versatile tool for the evaluation of the aorta, craniocervical, and lower limb vasculature. Appropriate use of techniques can save radiation dose, decrease interpretation time, or improve diagnostic accuracy.”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97 - Carotid CT Angiography: Challenges
- Acquisition timing
- Venous contamination
- Difficulty in segmenting vascular structures from the skull base
- Artifacts generated by bone removal algorithms - “ The use of CT arteriography for the evaluation of carotid atherosclerosis is justified as an accurate and cost effective alternative to DSA and MR angiography.”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97 - Bone removal techniques for Carotid CTA
- Threshold based bone subtraction
- Unenhanced mask bone subtraction
- Dual energy CT - “ Dual energy bone subtraction for cervical CT arteriography compares very favorably to threshold-based bone subtraction. Early studies confirmed that dual energy bone subtraction was faster and more accurate versus threshold based bone subtraction without user modification (88% vs 7% technically adequate).”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97 - “ In comparison with DSA, dual energy bone subtraction including plaque removal shows good intertechnique correlation (r>0.9), although possible mild overestimation of stenosis with dual energy bone subtraction is possible, particularly in distinguishing severely stenotic and completely occluded vessels.”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97
- “ DECT is an innovative imaging technique that can have a considerable effect on the care of oncologic patients. The possibility of obtaining different material specific datasets in the same acquisition can improve lesion detection and characterization. This approach can also aid in evaluation of response to therapy, and detection of oncology related disorders.”
Dual-Energy CT: Oncologic Applications
De Cecco CN et al.
AJR 2012; 199:S98-S105 - “ Dual-energy bone subtraction has been shown to be faster and technically superior to threshold-based bone subtraction techniques even when the latter are manually corrected. However, even dual-energy bone subtraction is not infrequently incomplete.”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97 - “ Although heavily calcified plaque in contact with bone can also be misclassified as bone and removed with dual energy subtraction , DECT’s reliance on iodine-calcium material differentiation reduces the incidence and severity of these artifacts .”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97 - “ The clinical interpretation advantage of 3D-rendered volumetric data are limited by the need for software assisted Hounsfield unit-threshold-based bone subtraction. This is not only time consuming, but the quality of bone subtraction is subject to patient and user dependent variation.”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97 - “Dual energy vascular imaging is a versatile tool for the evaluation of the aorta, craniocervical, and lower limb vasculature. Appropriate use of techniques can save radiation dose, decrease interpretation time, or improve diagnostic accuracy.”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012; 199:S87-S97
- “ Dual energy CT permits a variety of image reconstructions for the depiction and characterization of vascular disease. Techniques include visualization of low and high peak kilovoltage spectra image datasets and also material specific reconstructions combining both low and high kilovoltage data.”
Dual-Energy CT: Vascular Applications
Vlahos I et al.
AJR 2012;199:S87-S97 - “Intimal flap, thrombosed false lumen and aneurysmal dilatation are the most common CT findings of spontaneous splanchnic artery dissection. In splanchnic artery dissection, conservative management without anticoagulation had good outcome except in patients with bowel ischemia, aneurysmal dilatation three times larger than a normal segment or progression of dissection. ”
Spontaneous Dissection of the Splanchnic Arteries: CT Findings, Treatment and Occlusion
Jung SC et al.
AJR 2013;200:219-225 - “Although surgery should be considered first in the presence of CT findings of bowel infarction, conservative management without anticoagulation therapy has good outcomes in the care of ptients with no bowel ischemia, rupture risk or symptoms.”
Spontaneous Dissection of the Splanchnic Arteries: CT Findings, Treatment and Occlusion
Jung SC et al.
AJR 2013;200:219-225
- “Best results for both postprocessing methods were achieved in the vascular segments of the upper leg. In severely calcified segments, sensitivity, specificity, and accuracy stayed above 90% by the dual-energy bone removal technique, whereas the conventional bone removal technique showed a substantial decrease of sensitivity, specificity, and accuracy.”
Dual-energy CT angiography in peripheral arterial occlusive disease
Brockmann C et al.
Cardiovasc Intervent radiol 2009 Jul;32(4):630-7 - “Compared with digital subtraction angiography, sensitivity, specificity, and accuracy, respectively, of CTA was 97.2%, 94.1%, and 94.7% by the dual-energy bone removal technique. The conventional bone removal tool delivered a sensitivity of 77.1%, a specificity of 70.7%, and an accuracy of 72.0%.”
Dual-energy CT angiography in peripheral arterial occlusive disease
Brockmann C et al.
Cardiovasc Intervent radiol 2009 Jul;32(4):630-7 - “ DE-CTA is a feasible and accurate diagnostic method in the assessment of symptomatic peripheral arterial occlusive disease. Results obtained by DE-CTA are superior to the conventional bone removal technique and less dependent on vessel wall calcifications.”
Dual-energy CT angiography in peripheral arterial occlusive disease
Brockmann C et al.
Cardiovasc Intervent radiol 2009 Jul;32(4):630-7