Optimal Virtual Monochromatic Images for Evaluation of Normal Tissues and Head and Neck Cancer Using Dual-Energy CT

Lam, Stephanie; Gupta, Rajiv; Levental, Mark; Yu, Eugene; Curtin, Hugh D.; Forghani, Reza

doi:10.3174/ajnr.a4314

Cited by 91 publications

(56 citation statements)

References 22 publications

(25 reference statements)

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“…The reason was explained by the fact that a hypervascular tumor takes up iodine more than the OARs such as brainstem and spinal cord . Lam et al demonstrated that the tumor attenuation of the primary tumor for the HNC was highest in the VMI 40 keV (207.9 ± 46.8 HU) . A similar CT number was observed in the VMI 40 keV for the CTVb in this study (Table ).…”

Section: Discussionsupporting

confidence: 75%

“…Wichmann et al reported that the VMIs at 60 keV significantly improve the contrast noise ratio (CNR), subjective overall image quality, and tumor delineation of head and neck squamous cell carcinoma . According to another report by Lam et al , the difference in CT number between tumor and muscle is the highest on the VMI at 40 keV for HNC . The high quality of image has the potential for improving the accuracy of target/OARs delineation for radiotherapy treatment planning …”

Section: Introductionmentioning

confidence: 99%

“…Especially, the CT number of iodine contained in the contrast‐enhanced agent is markedly increased in the VMI at a low energy level due to the K‐shell photon absorption . Although the VMI at a low energy level provides a high image quality, the difference in CT number between CE‐ and nCE‐VMI was prominent as the energy level of the VMI decreased . These physical characteristics of VMI can affect the treatment planning in the dose calculation process, and unexpected radiation side effect can occur.…”

Section: Introductionmentioning

confidence: 99%

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Volumetric modulated arc therapy treatment planning based on virtual monochromatic images for head and neck cancer: effect of the contrast‐enhanced agent on dose distribution

Komiyama

Ohira

Kanayama

et al. 2019

J Applied Clin Med Phys

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Virtual monochromatic images (VMIs) at a lower energy level can improve image quality but the computed tomography (CT) number of iodine contained in the contrast-enhanced agent is dramatically increased. We assessed the effect of the use of contrastenhanced agent on the dose distributions in volumetric modulated arc therapy (VMAT) planning for head and neck cancer (HNC). Based on the VMIs at 40 keV (VMI 40keV ), 60 keV(VMI 60keV ), and 77 keV (VMI 77keV ) of a tissue characterization phantom, lookup tables (LUTs) were created. VMAT plans were generated for 15 HNC patients based on contrast-enhanced-(CE-) VMIs at 40-, 60-, and 77 keV using the corresponding LUTs, and the doses were recalculated based on the noncontrast-enhanced-(nCE-) VMIs. For all structures, the difference in CT numbers owing to the contrast-enhanced agent was prominent as the energy level of the VMI decreased, and the mean differences in CT number between CE-and nCE-VMI was the largest for the clinical target volume (CTV) (125.3, 55.9, and 33.1 HU for VMI 40keV , VMI 60keV , and VMI 77keV, respectively). The mean difference of the dosimetric parameters (D 99% , D 50% , D 1% , D mean , and D 0.1cc ) for CTV and OARs was <1% in the treatment plans based on all VMIs. The maximum difference was observed for CTV in VMI 40keV (2.4%), VMI 60keV (1.9%), and VMI 77keV (1.5%) plans. The effect of the contrast-enhanced agent was larger in the VMAT plans based on the VMI at a lower energy level for HNC patients.This effect is not desirable in a treatment planning procedure. K E Y W O R D S contrast agent, dual energy CT, head and neck cancer, virtual monochromatic image

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Section: Discussionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Volumetric modulated arc therapy treatment planning based on virtual monochromatic images for head and neck cancer: effect of the contrast‐enhanced agent on dose distribution

Komiyama

Ohira

Kanayama

et al. 2019

J Applied Clin Med Phys

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“…reported 65–75 keV maximizing brain parenchymal image quality in GE Discovery CT750HD DECT scanner with fast‐kVp‐switching mode. For this GE scanner, Lam et al . demonstrated that 65 keV is optimal to achieve best signal‐to‐noise ratio for tissues in head and neck region.…”

Section: Discussionmentioning

confidence: 99%

Optimal virtual monoenergetic image in “TwinBeam” dual‐energy CT for organs‐at‐risk delineation based on contrast‐noise‐ratio in head‐and‐neck radiotherapy

Wang

Ghavidel

Beitler

et al. 2019

J Applied Clin Med Phys

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PurposeDual‐energy computed tomography (DECT) using TwinBeam CT (TBCT) is a new option for radiation oncology simulators. TBCT scanning provides virtual monoenergetic images which are attractive in treatment planning since lower energies offer better contrast for soft tissues, and higher energies reduce noise. A protocol is needed to achieve optimal performance of this feature. In this study, we investigated the TBCT scan schema with the head‐and‐neck radiotherapy workflow at our clinic and selected the optimal energy with best contrast‐noise‐ratio (CNR) in organs‐at‐risks (OARs) delineation for head‐and‐neck treatment planning.Methods and materialsWe synthesized monochromatic images from 40 keV to 190 keV at 5 keV increments from data acquired by TBCT. We collected the Hounsfield unit (HU) numbers of OARs (brainstem, mandible, spinal cord, and parotid glands), the HU numbers of marginal regions outside OARs, and the noise levels for each monochromatic image. We then calculated the CNR for the different OARs at each energy level to generate a serial of spectral curves for each OAR. Based on these spectral curves of CNR, the mono‐energy corresponding to the max CNR was identified for each OAR of each patient.ResultsComputed tomography scans of ten patients by TBCT were used to test the optimal monoenergetic image for the CNR of OAR. Based on the maximized CNR, the optimal energy values were 78.5 ± 5.3 keV for the brainstem, 78.0 ± 4.2 keV for the mandible, 78.5 ± 5.7 keV for the parotid glands, and 78.5 ± 5.3 keV for the spinal cord. Overall, the optimal energy for the maximum CNR of these OARs in head‐and‐neck cancer patients was 80 keV.ConclusionWe have proposed a clinically feasible protocol that selects the optimal energy level of the virtual monoenergetic image in TBCT for OAR delineation based on the CNR in head‐and‐neck OAR. This protocol can be applied in TBCT simulation.

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“…Recently, emerging dual-energy CT techniques have been investigated for head and neck cancer imaging with the potential for improved tumor visualization and characterization. [14][15][16][17][18][19][20][21] In particular, techniques using iodine overlay (IO) images were found useful for distinguishing iodine-enhanced tumors from nonossified cartilage 11,14,19,22 and for having higher specificity than conventional CT, without a deterioration of sensitivity, in particular for the evaluation of thyroid cartilage invasion. 14 Furthermore, interobserver agreement is usually poor for conventional CT and was found to be higher for dual-energy CT. 14,23 These new dualenergy CT techniques have prompted re-evaluations of the diagnostic performance of CT compared with MR imaging in diagnostic fields where MR imaging has been routinely used.…”

mentioning

confidence: 99%

Comparison of MR Imaging and Dual-Energy CT for the Evaluation of Cartilage Invasion by Laryngeal and Hypopharyngeal Squamous Cell Carcinoma

Kuno

Sakamaki

Fujii³

et al. 2018

AJNR Am J Neuroradiol

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Optimal Virtual Monochromatic Images for Evaluation of Normal Tissues and Head and Neck Cancer Using Dual-Energy CT

Cited by 91 publications

References 22 publications

Volumetric modulated arc therapy treatment planning based on virtual monochromatic images for head and neck cancer: effect of the contrast‐enhanced agent on dose distribution

Volumetric modulated arc therapy treatment planning based on virtual monochromatic images for head and neck cancer: effect of the contrast‐enhanced agent on dose distribution

Optimal virtual monoenergetic image in “TwinBeam” dual‐energy CT for organs‐at‐risk delineation based on contrast‐noise‐ratio in head‐and‐neck radiotherapy

Comparison of MR Imaging and Dual-Energy CT for the Evaluation of Cartilage Invasion by Laryngeal and Hypopharyngeal Squamous Cell Carcinoma

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