Preliminary report on virtual monochromatic spectral imaging with fast kVp switching dual energy head CT: comparable image quality to that of 120-kVp CT without increasing the radiation dose

Purpose

This study aimed to evaluate whether the image quality of virtual monochromatic spectral imaging with fast kVp switching dual-energy CT (DECT) can be comparable to that of 120-kVp single-energy CT (SECT) without increasing the radiation dose.

Materials and methods

We retrospectively identified 15 postoperative patients who had undergone both DECT and 120-kVp SECT within a short period of time for follow-up after brain surgery. Simulated 65 keV monochromatic images were reconstructed from DECT data. Subjective image noise, gray–white matter contrast, and overall image quality were rated using a four-point scale. Quantitative measurement of noise, contrast-to-noise ratio (CNR), and posterior fossa beam-hardening artifact were also performed. The figure of merit (FOM), calculated as CNR²/CTDI_vol, was used to quantify image quality improvement per exposure risk.

Results

The mean CTDI_vol was 70.2 ± 0.3 mGy for DECT, which was 11 % lower than SECT (78.9 ± 2.1 mGy). All images were graded above clinically acceptable. Quantitative and qualitative measures for simulated 65-keV images were comparable with SECT images, except for increase in subjective noise. FOM was significantly greater for simulated 65-keV images (P = .03).

Conclusion

Our results indicate that virtual monochromatic imaging possibly provides comparable image quality to that afforded by 120-kVp SECT without increasing the dose in routine head CT.     

Metal artifact reduction in cervix brachytherapy with titanium applicators using dual‐energy CT through virtual monoenergetic images and an iterative algorithm: A phantom study

PURPOSETo evaluate an iterative metal-artifact reduction (iMAR) algorithm, dual-energy CT (DECT) through virtual monoenergetic images (VMI), and a combination of iMAR and DECT for reducing metal artifact severity (AS) induced by Fletcher titanium applicators used in cervix brachytherapy, the efficacy of which are hitherto unreported.METHODS AND MATERIALS120 kV_p single-energy CT (SECT) (Siemens) of BEBIG tandem applicators, varying in shape (straight or curved) and diameter (3.5 mm or 5 mm) in a custom-made water-filled phantom, and their DECT images obtained from extrapolation of 80 kVp and 140 kVp, were reconstructed using four methods: DECT through VMI±iMAR, and SECT±iMAR. The DECT images were reconstructed monoenergetically at 70, 150, and 190 keV. AS was evaluated using measured values and statistical analysis.RESULTSiMAR, DECT, and combined DECT and iMAR reduced AS (p < 0.05). DECT had a lower AS than SECT, even without iMAR (p < 0.025). SECT+iMAR was more effective than DECT-iMAR with VMI at 70 and 190 keV (p < 0.05), whereas showing no statistically significant difference at 150 keV. With DECT and iMAR combined, AS was reduced more effectively compared to the SECT+iMAR or DECT alone. It also reduced the mean interobserver uncertainty by 0.2 mm.CONCLUSIONSThese findings indicate that iMAR reduces the AS caused by Fletcher titanium applicators for both SECT and DECT, a combination of iMAR and DECT is superior to either strategy alone, and at low energies, DECT+iMAR also produces similar artifact reduction. These practical strategies promise more accurate source-position and structure definitions in CT-based gynecological brachytherapy treatment planning.     

The potential of iodinated contrast reduction in dual-energy CT thoracic angiography; an evaluation of image quality

IntroductionThe purpose of this study was to compare a dual energy CT (DECT) protocol with 50% reduction of iodinated contrast to a single energy CT (SECT) protocol using standard contrast dose in imaging of the thoracic aorta.MethodsDECT with a 50% reduction in iodinated contrast was compared with SECT. For DECT, monoenergetic images at 50, 55, 60, 65, 68, 70, and 74 keV were reconstructed with adaptive statistical iterative reconstruction (ASiR-V) of 50% and 80%. Objective image quality parameters included intravascular attenuation (HU), image noise (SD), contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR). Two independent radiologists subjectively assessed the image quality for the 55 and 68 keV DECT reconstructions and SECT on a five-point Likert scale.ResultsAcross 14 patients, the intravascular attenuation at 50–55 keV was comparable to SECT (p > 0.05). The CNRs were significantly lower for DECT with ASIR-V 50% compared to SECT for all keV-values (p < 0.05 for all). For ASIR-V 80%, CNR was comparable to SECT at energies below 60 keV (p > 0.05). The subjective image quality was comparable between DECT and SECT independent of keV level.ConclusionThis study indicates that a 50% reduction in iodinated contrast may result in adequate image quality using DECT with monoenergetic reconstructions at lower energy levels for the imaging of the thoracic aorta. The best image quality was obtained for ASiR-V 80% image reconstructions at 55 keV.Implications of practiceDual energy CT with a reduction in iodinated contrast may result in adequate image quality in imaging of the thoracic aorta. However, increased radiation dose may limit the use to patients in which a reduction in fluid and iodinated contrast volume may outweigh this risk.     

双源CT单能谱成像减少脊柱金属固定器伪影的研究

目的：探讨双源CT单能谱成像技术减少脊柱金属内固定器伪影的可能性。方法：31例后路脊柱金属内固定植入术后复查患者行双源CT双能量扫描,获得100、140和120kV图像。其中颈椎9例,胸椎7例,腰椎l5例。扫描数据采用双能量软件内的单能谱技术（Monoenergetic）处理,每例患者数据分别重建成64、69、88、105keV共4组图像以及主观目测图像质量最好的keV图像。由2位有经验的放射诊断医师分别对上述4组图像和主观目测最佳keV（OPT-keV）图像,以及平均加权120kV等图像共6组图像按照4分法进行图像质量评分。采用Kruskal—wallis检验分别对上述各组不同keV图像的质量进行统计学分析;采用Kappa检验评价2位医师评分的一致性。结果：单能谱最佳图像评分在3分及以上者27例,平均加权120kV图像3分及以上者仅3例,两者之间差异有统计学意义（F=118．139,P〈0．01）。金属固定器CT值在不同脊柱节段问存在统计学差异（P〈0．01）;与120kV图像相比,较高单能谱值组（105keV组）图像质量改善明显（V=0．62,P〈0．001）;脊柱金属内固定成像最佳单能谱值为123～144keV。结论：双能量CT单能谱技术能够有效减少脊柱内固定器金属伪影,明显改善脊柱金属内固定术后的CT图像质量,此外还可根据脊柱金属内固定所在不同脊柱节段,采用个性化的单能谱值进行后处理,使图像质量进一步提高。     

Reducing the effects of metal artefact using high keV monoenergetic reconstruction of dual energy CT (DECT) in hip replacements

Purpose

The aim of this study was to determine whether high keV monoenergetic reconstruction of dual energy computed tomography (DECT) could be used to overcome the effects of beam hardening artefact that arise from preferential deflection of low energy photons.

Materials and Methods

Two phantoms were used: a Charnley total hip replacement set in gelatine and a Catphan 500. DECT datasets were acquired at 100, 200 and 400 mA (Siemens Definition Flash, 100 and 140 kVp) and reconstructed using a standard combined algorithm (1:1) and then as monoenergetic reconstructions at 10 keV intervals from 40 to 190 keV. Semi-automated segmentation with threshold inpainting was used to obtain the attenuation values and standard deviation (SD) of the streak artefact. High contrast line pair resolution and background noise were assessed using the Catphan 500.

Results

Streak artefact is progressively reduced with increasing keV monoenergetic reconstructions. Reconstruction of a 400 mA acquisition at 150 keV results in reduction in the volume of streak artefact from 65 cm³ to 17 cm³ (74 %). There was a decrease in the contrast to noise ratio (CNR) at higher tube voltages, with the peak CNR seen at 70–80 keV. High contrast spatial resolution was maintained at high keV values.

Conclusion

Monoenergetic reconstruction of dual energy CT at increasing theoretical kilovoltages reduces the streak artefact produced by beam hardening from orthopaedic prostheses, accompanied by a modest increase in heterogeneity of background image attenuation, and decrease in contrast to noise ratio, but no deterioration in high contrast line pair resolution.     

Comparison of virtual monochromatic series,iodine overlay maps,and single energy CT equivalent images in head and neck cancer conspicuity

ObjectiveTo compare lesion conspicuity amongst DECT monochromatic series (40, 45, 50 keV), and single-energy CT (SECT) equivalent images in head and neck squamous cell carcinomas (HNSCC).MethodsTwo readers compared DECT images to 70 keV SECT equivalent series in 39 patients with HNSCC on lesion margin, enhancement, and overall conspicuity.ResultsThe 45 keV and 50 keV images were significantly better (p-values ≤ 0.001) than the SECT equivalent in lesion enhancement, margins, and overall conspicuity for both readers. Readers mostly preferred the 50 keV monochromatic series.ConclusionDECT can provide better lesion visualization than SECT in HNSCC.     

Dual energy computed tomography: simulated monoenergetic and material-selective imaging

A dual beam-quality technique was used to reduce the beam hardening artifact in CT and to obtain separate images of osseous and soft-tissue structures in phantom and clinical CT studies. Recordings were made with pulsed low and high kVp spectra with the Somatom DR2. Conventional polyenergetic and simulated monoenergetic images were reconstructed from the measurements. In the monoenergetic images the beam hardening artifacts were 60-90% lower than in the high kVp polyenergetic images whereas the noise was of the same order of magnitude in the two types. Noise in the monoenergetic images was lowest around 70-80 keV both in body and skull examinations although the contrast in the monoenergetic image was rather independent of energy.     

CT arthrography: in vitro evaluation of single and dual energy for optimization of technique

The purpose of this study was to optimize CT arthrography technique and determine if dual energy CT (DECT) can provide any benefit over single energy CT (SECT). Iodinated contrast attenuation at different concentrations was measured using DECT and SECT at different beam energies (140, 120, and 80 kVp). Dose and noise were measured on phantoms at different tube currents. Three bovine femoral condyles with artificially created cartilage defects were scanned with dose-equivalent protocols. Contrast-to-noise ratio (CNR) between cartilage and iodine was measured, and the appearance of cartilage defects was graded by two readers. DECT scans were post-processed for iodine quantification. The beam energy 80 kVp had the highest iodine signal, 50% greater than DECT, 75% greater than 120 kVp, and 100% greater than 140 kVp. Noise was nearly identical for all techniques when dose was matched. The 80 kVp level had the highest CNR, 25% higher than 120 kVp and DECT, and 33% greater than 140 kVp. The 80 kVp technique was also preferred by both readers. DECT iodine quantification was significantly limited by the post-processing application, noise, and beam hardening. In this in-vitro study, the SECT 80 kVp CT arthrography technique was superior to currently performed 120 and 140 kVP SECT techniques and DECT.     

Evaluation of monoenergetic late iodine enhancement dual-energy computed tomography for imaging of chronic myocardial infarction

Objectives

To evaluate image quality and diagnostic accuracy of selective monoenergetic reconstructions of late iodine enhancement (LIE) dual-energy computed tomography (DECT) for imaging of chronic myocardial infarction (CMI).

Methods

Twenty patients with a history of coronary bypass surgery underwent cardiac LIE-DECT and late gadolinium enhancement (LGE) magnetic resonance imaging (MRI). LIE-DECT images were reconstructed as selective monoenergetic spectral images with photon energies of 40, 60, 80, and 100 keV and the standard linear blending setting (M_0.6). Images were assessed for late enhancement, transmural extent, signal characteristics and subjective image quality.

Results

Seventy-nine myocardial segments (23 %) showed LGE. LIE-DECT detected 76 lesions. Images obtained at 80 keV and M_0.6 showed a high signal-to-noise ratio (15.9; 15.1), contrast-to-noise ratio (4.2; 4.0) and sensitivity (94.9 %; 92.4 %) while specificity was identical (99.6 %). Differences between these series were not statistically significant. Transmural extent of LIE was overestimated in both series (80 keV: 40 %; M_0.6: 35 %) in comparison to MRI. However, observers preferred 80 keV in 13/20 cases (65 %, κ?=?0.634) over M_0.6 (4/20 cases) regarding subjective image quality.

Conclusions

Post-processing of LIE-DECT data with selective monoenergetic reconstructions at 80 keV significantly improves subjective image quality while objective image quality shows no significant difference compared to standard linear blending.

Key Points

? Late enhancement dual-energy CT allows for detection of chronic myocardial infarction. ? Monoenergetic reconstructions at 80 keV significantly improve subjective image quality. ? 80 keV and standard linear blending reconstructions show no significant differences. ? Extent of CMI detected with LIE-DECT is overestimated compared with MRI.     

Application and advantages of monoenergetic reconstruction images for the reduction of metallic artifacts using dual-energy CT in knee and hip prostheses

Objective

The study aimed to assess image quality when using dual-energy CT (DECT) to reduce metal artifacts in subjects with knee and hip prostheses.

Methods

Twenty-two knee and 10 hip prostheses were examined in 31 patients using a DECT protocol (tube voltages 100 and 140 kVp). Monoenergetic reconstructions were extrapolated at 64, 69, 88, 105, 110, 120, 140, 170, and 190 kilo-electron volts (keV) and the optimal energy was manually selected. The B60–140 and Fast DE reconstructions were made by CT. The image quality and diagnostic value were subjectively and objectively determined. Double-blind qualitative assessment was performed by two radiologists using a Likert scale. For quantitative analysis, a circular region of interest (ROI) was placed by a third radiologist within the most evident streak artifacts on every image. Another ROI was placed in surrounding tissues without artifacts as a reference.

Results

The inter-reader agreement for the qualitative assessment was nearly 100%. The best overall image quality (37.8% rated “excellent”) was the Fast DE Siemens reconstruction, followed by B60–140 and Opt KeV (20.5 and 10.2% rated excellent). On the other hand, DECT images at 64, 69 and 88 keV had the worse scores. The number of artifacts was significantly different between monoenergetic images. Nevertheless, because of the high number of pairwise comparisons, no differences were found in the post hoc analysis except for a trend toward statistical significance when comparing the 170 and 64 keV doses.

Conclusions

DECT with specific post-processing may reduce metal artifacts and significantly enhance the image quality and diagnostic value when evaluating metallic implants.

     

Value of dual-energy CT angiography in patients with treated intracranial aneurysms

Purpose

To evaluate the ability of dual-energy CT angiography (DECTA) in metal artifact reduction in patients with treated intracranial aneurysms by comparing DECTA-based virtual monoenergetic extrapolations (VMEs) and mixed images (MI).

Methods

Thirty-five patients underwent prospectively a dual-source DECTA (Somatom Force, Siemens Medical Solutions, Forchheim, Germany) after aneurysm repair. A total number of 40 aneurysms (23 treated by coil embolization and 17 treated by surgical clipping) were analyzed. Mixed images (equivalent to a conventional single-energy CT angiography) were compared to VMEs at 75, 95, and 115 keV. Artifact severity was assessed quantitatively by measuring the mean attenuation value and standard deviation within regions of interest placed in the most hypodense coil or clip artifact area. Artifact severity score and contrast vessel score were also assessed qualitatively by two independent blinded readers.

Results

In those aneurysms treated by surgical clipping, quantitative and qualitative analyses showed significant reduction of artifacts on VMEs compared to MI with the best compromise being obtained at 95 keV in order to keep an optimal vessel contrast in the adjacent vessel. In those aneurysms treated by coil embolization, there was no significant reduction of artifacts both on quantitative and qualitative analyses.

Conclusion

Dual-source DECTA was helpful in order to reduce clip artifacts on VMEs with the optimal adjacent vessel visualization obtained at 95 keV, whereas this technique was not helpful in aneurysms treated by coiling.

     

Head and neck single- and dual-energy CT: differences in radiation dose and image quality of 2nd and 3rd generation dual-source CT

Objectives:To compare radiation dose and image quality of single-energy (SECT) and dual-energy (DECT) head and neck CT examinations performed with second- and third-generation dual-source CT (DSCT) in matched patient cohorts.Methods:200 patients (mean age 55.1 ± 16.9 years) who underwent venous phase head and neck CT with a vendor-preset protocol were retrospectively divided into four equal groups (n = 50) matched by gender and BMI: second (Group A, SECT, 100-kV; Group B, DECT, 80/Sn140-kV), and third-generation DSCT (Group C, SECT, 100-kV; Group D, DECT, 90/Sn150-kV). Assessment of radiation dose was performed for an average scan length of 27 cm. Contrast-to-noise ratio measurements and dose-independent figure-of-merit calculations of the submandibular gland, thyroid, internal jugular vein, and common carotid artery were analyzed quantitatively. Qualitative image parameters were evaluated regarding overall image quality, artifacts and reader confidence using 5-point Likert scales.Results:Effective radiation dose (ED) was not significantly different between SECT and DECT acquisition for each scanner generation (p = 0.10). Significantly lower effective radiation dose (p < 0.01) values were observed for third-generation DSCT groups C (1.1 ± 0.2 mSv) and D (1.0 ± 0.3 mSv) compared to second-generation DSCT groups A (1.8 ± 0.1 mSv) and B (1.6 ± 0.2 mSv). Figure-of-merit/contrast-to-noise ratio analysis revealed superior results for third-generation DECT Group D compared to all other groups. Qualitative image parameters showed non-significant differences between all groups (p > 0.06).Conclusion:Contrast-enhanced head and neck DECT can be performed with second- and third-generation DSCT systems without radiation penalty or impaired image quality compared with SECT, while third-generation DSCT is the most dose efficient acquisition method.Advances in knowledge:Differences in radiation dose between SECT and DECT of the dose-vulnerable head and neck region using DSCT systems have not been evaluated so far. Therefore, this study directly compares radiation dose and image quality of standard SECT and DECT protocols of second- and third-generation DSCT platforms.     

Dual-energy CT in vertebral compression fractures: performance of visual and quantitative analysis for bone marrow edema demonstration with comparison to MRI

Objective

To prospectively evaluate the performance of virtual non-calcium (VNC) dual-energy CT (DECT) images for the demonstration of trauma-related abnormal marrow attenuation in collapsed and non-collapsed vertebral compression fractures (VCF) with MRI as a reference standard.

Materials and methods

Twenty patients presenting with non-tumoral VCF were consecutively and prospectively included in this IRB-approved study, and underwent MRI and DECT of the spine. MR examination served as a reference standard. Two independent readers visually evaluated all vertebrae for abnormal marrow attenuation (“CT edema”) on VNC DECT images; specificity, sensitivity, predictive values, intra and inter-observer agreements were calculated. A last reader performed a quantitative evaluation of CT numbers; cut-off values were calculated using ROC analysis.

Results

In the visual analysis, VNC DECT images had an overall sensitivity of 84 %, specificity of 97 %, and accuracy of 95 %, intra- and inter-observer agreements ranged from k?=?0.74 to k?=?0.90. CT numbers were significantly different between vertebrae with edema on MR and those without (p?<?0.0001). Cut-off values provided sensitivity of 85 % (77 %) and specificity of 82 % (74 %) for “CT edema” on thoracic (lumbar) vertebrae.

Conclusions

VNC DECT images allowed an accurate demonstration of trauma-related abnormal attenuation in VCF, revealing the acute nature of the fracture, on both visual and quantitative evaluation.     

光谱CT头部虚拟平扫图像:不同单能量图像质量的对比

目的:探讨双层探测器光谱CT不同单能量图像在头部影像诊断中的临床应用效能。方法:回顾性分析2019年6-12月因头晕、晕厥和头痛等临床症状而在本院行光谱CT(IQon Spectral CT)头部CT平扫检查的38例患者的影像资料。从光谱CT扫描中可获取常规混合能量图像和40~120 keV的光谱成像数据,以5 keV为间隔增量将光谱数据重建为17组单能级图像。分别测量每组图像上幕上灰质和白质的CT值和噪声值(SD),并计算信号噪声比(SNR)和对比信噪比(CNR)。同时对常规图像与120 keV单能级图像的伪影区域的脑组织结构(灰、白质)的对比及后颅窝伪影情况进行主、客观评分和比较。采用Bonferroni法进行统计学分析。结果:各组单能图像之间脑灰质CT值(P<0.001)、噪声(P=0.012)和CNR(P<0.001)的差异均有统计学意义,而脑白质CT值的差异无统计学意义(P=0.107)。其中65 keV图像的脑灰质CT值,脑灰、白质的噪声和SNR均高于其它单能级和常规混合能量图像(P<0.05),CNR亦高于其它单能级图像和常规图像(P<0.05)。与常规图像比较,120keV单能级图像上颅底层面伪影区域的脑灰、白质CT值(P=0.046)、噪声(P<0.01)、SNR(P<0.001)和CNR(P<0.001)的差异均具有统计学意义,且图像质量评分(P<0.001)和伪影评分(P<0.001)的差异亦有统计学意义。结论:和常规图像相比,从双层探测器光谱CT重建的单能图像在65 keV灰、白质对比度好,图像噪声降低、软组织分别率提高。120 keV单能级图像在由颅骨引起的X线束硬化伪影方面,能有效还原周围组织结构,提升图像质量。     

Optimized energy of spectral coronary CT angiography for coronary plaque detection and quantification

BackgroundTo optimize spectral coronary computed tomography angiography (CTA) for quantification of coronary artery plaque components.Materials and methodsFifty-one subjects were prospectively enrolled (88.2% male) (NCT02740699). Dual energy coronary CTA was performed at 90/Sn150 kVp using a 3rd generation dual-source CT scanner (SOMATOM Force, Siemens Healthcare). Dual energy images were reconstructed with a) linear mixed blending of 90 and Sn150 kVp data, b) virtual monoenergetic algorithm from 40 to 150 keV (at 10- keV intervals), and c) noise-optimized virtual monoenergetic algorithm from 40 to 150 keV. Image noise, iodine signal-to-noise-ratio (SNR), and contrast-to-noise ratio (CNR) for calcified and non-calcified plaque were measured. Qualitative readings of image quality were performed. Semi-automated software (QAngioCT, Medis) was used to quantify coronary plaque. Linear mixed-models that account for within-subject correlation of plaques were used to compare the results.Results100–150 keV noise-optimized virtual monoenergetic images had lower image noise than linear mixed images (all P < 0.05). The highest iodine SNR was achieved in 40 keV noise-optimized virtual monoenergetic images (33.3 ± 0.6 vs 23.3 ± 0.7 for linear mixed images, P < 0.001). 40–70 keV noise-optimized virtual monoenergetic images and 70 keV virtual monoenergetic images had superior coronary plaque CNR versus linear mixed images (all P < 0.01) with a maximum improvement of 20.1% and 22.7% for calcified plaque and non-calcified plaque (38.8 ± 2.2 vs 32.3 ± 2.3 and 17.3 ± 1.3 vs 14.1 ± 1.4, respectively). Using 90/Sn150 kVp linear mixed images as a reference, the plaque quantity was similar for 70 keV noise-optimized virtual monoenergetic images whereas low keV images (e.g. 40 keV) yielded significantly higher coronary plaque volumes (all P < 0.001).ConclusionSpectral coronary CTA with low energy (40–70 keV) post-processing can improve the CNR of coronary plaque components. However, low energies (such as 40 keV) resulted in different absolute volumes of coronary plaque compared to “conventional” mixed 90/Sn150 kVp images.     

Noise-optimized monoenergetic post-processing improves visualization of incidental pulmonary embolism in cancer patients undergoing single-pass dual-energy computed tomography

Purpose

To evaluate noise-optimized monoenergetic postprocessing of dual-energy CT (DE-CT) on image quality in patients with incidental pulmonary embolism in single-pass portal-venous phase CT (CT_pv).

Materials and methods

20 Consecutive patients with incidental pulmonary embolism in contrast-enhanced oncological follow-up DE-CT_pv examination were included in this study. Images were acquired with a 3rd generation DE-CT system in DE mode (100/Sn150 kV) and activated tube current modulation 90 s after contrast agent administration. Subsequently, virtual monoenergetic images (MEI+) were reconstructed at five different keV levels (40, 55, 70, 85, 100) and compared to the standard linearly blended (M_0.8) CT_pv images. Image quality was assessed qualitatively (vascular contrast and detectability of embolism, image noise, iodine influx artifact; two independent readers; 5-point Likert scale; 5 = excellent) and quantitatively by calculating signal-to-noise (SNR) and contrast-to-noise ratios (CNR).

Results

Highest vessel contrast and highest detectability of embolism were observed in MEI+ at 40 keV (4.7 ± 0.4) and 55 keV (4.2 ± 0.6) with significant differences as compared to CT_pv (3.6 ± 0.5) and high keV reconstructions (70, 85, 100; p ≤ 0.01). Image noise significantly increased at 40 keV MEI+ compared to all other MEI+ reconstructions and CT_pv (p < 0.001). SNR and CNR calculations were highest at 40 keV MEI+ followed by 55 keV and CT_pv with significant differences to high keV MEI+ (85–100).

Conclusions

Computed MEI+ at low keV levels allow for improved vessel contrast and visualisation of incidental pulmonary embolism in patients with portal-venous phase CT scans by substantially increasing CNR and SNR.

     

Evaluation of deep myometrial invasion in endometrial cancer patients: is dual-energy CT an option?

Objectives

Assessment of deep (>50%) myometrial invasion by dual-energy CT (DECT) and Trans-Vaginal US (TVUS) in patients with endometrial cancer.

Methods

We retrospectively enrolled patients with endometrial cancer who underwent DECT and TVUS for pre-surgical staging. Three sets of images were evaluated: 70 keV (routine CT images), 50 keV, and iodine-water reconstructions. The gold standard was pathology after surgery. The agreement between the different imaging modalities and the gold standard was estimated. Sensitivity, specificity and accuracy for each imaging modality were evaluated with 95% confidence intervals (CI).

Results

Thirty-nine patients were included. Median time from CT and TVUS to surgery was 23 and 18 days, respectively. The best agreement between evaluation of myometrial infiltration and the gold standard was 0.88 (0.72, 1.00) for the 50 keV images; the worst agreement was 0.43 (0.00, 0.88) for the 70 keV images. CT iodine reconstructions and US agreement were comparable. Specificity, sensitivity and accuracy were 0.91, 1.00, 0.94; 0.57, 0.86, 0.71; 0.82, 1.00, 0.87; 0.91, 0.77, 0.86 for 50 keV, 70 keV, iodine reconstructions and ultrasound, respectively.

Conclusions

DECT is a promising tool for assessment of myometrial invasion in endometrial cancer patients, with a special focus on 50 keV images.

     

Feasibility of extracellular volume quantification using dual-energy CT

ObjectiveTo assess the feasibility of dual energy CT (DECT) to derive myocardial extracellular volume (ECV) and detect myocardial ECV differences without a non-contrast acquisition, compared to single energy CT (SECT).MethodsSubjects (n = 35) with focal fibrosis (n = 17), diffuse fibrosis (n = 10), and controls (n = 9) underwent non-contrast and delayed acquisitions to calculate SECT-ECV. DECT-ECV was calculated using the delayed acquisition and the derived virtual non-contrast images. In the control and diffuse fibrotic groups, the entire myocardium of the left ventricle was used to calculate ECV. Two ROIs were placed in the focal fibrotic group, one in normal and one in fibrotic myocardium.ResultsMedian ECV was 33.4% (IQR, 30.1–37.4) using SECT and 34.9% (IQR, 31.2–39.2) using DECT (p = 0.401). For both techniques, focal and diffuse fibrosis had significantly higher ECV values (all p < 0.021) than normal myocardium. There was no systematic bias between DECT and SECT (p = 0.348). SECT had a higher radiation dose (1.1 mSv difference) than DECT (p < 0.001).ConclusionECV can be measured using a DECT approach with only a delayed acquisition. The DECT approach provides similar results at a lower radiation dose compared to SECT.     

Metal artifact reduction by dual-layer computed tomography using virtual monoenergetic images

ObjectiveThe aim of the study was to investigate the performance and diagnostic value of metal artifact reduction in virtual monoenergetic images generated from dual-layer computed tomography (DLCT).Methods35 patients that received a DLCT at the University Hospital Cologne and had an orthopedic implant in the examined region were included in this study. For each DLCT virtual monoenergetic images of different energy levels (64 keV, 70 keV, 105 keV, 140 keV, 200 keV and an optimized photon energy) were reconstructed and analyzed by three blinded observers. Images were analyzed with regard to subjective criteria (extent of artifacts, diagnostic image quality) and objective criteria (width and density of artifacts).Results21 patients had implants in the spine, 8 in the pelvis and 6 patients in the extremities. Diagnostic image quality improved significantly at high photon energies from a Likert-score of 4.3 (±0.83) to 2.3 (±1.02) and artifacts decreased significantly from a score of 4.3 (±0.66) to 2.6 (±2.57). The average optimized photon energy was 149.2 ± 39.4 keV. The density as well as the width of the most pronounced artifacts decreased from−374.6 ± 251.89 HU to −12.5 ± 205.84 HU and from 14.5 ± 8.74 mm to 6.4 ± 10.76 mm, respectively.ConclusionUsing virtual monoenergetic images valuable improvements of diagnostic image quality can be achieved by reduction of artifacts associated with metal implants. As preset for virtual monoenergetic images, 140 keV appear to provide optimal artifact reduction. In 20% of the patients, individually optimized keV can lead to a further improvement of image quality compared to 140 keV.     

Subjective and Objective Assessment of Monoenergetic and Polyenergetic Images Acquired by Dual-Energy CT in Breast Cancer

ObjectiveTo objectively and subjectively assess and compare the characteristics of monoenergetic images [MEI (+)] and polyenergetic images (PEI) acquired by dual-energy CT (DECT) of patients with breast cancer.Materials and MethodsThis retrospective study evaluated the images and data of 42 patients with breast cancer who had undergone dual-phase contrast-enhanced DECT from June to September 2019. One standard PEI, five MEI (+) in 10-kiloelectron volt (keV) intervals (range, 40–80 keV), iodine density (ID) maps, iodine overlay images, and Z effective (Z_eff) maps were reconstructed. The contrast-to-noise ratio (CNR) and the signal-to-noise ratio (SNR) were calculated. Multiple quantitative parameters of the malignant breast lesions were compared between the arterial and the venous phase images. Two readers independently assessed lesion conspicuity and performed a morphology analysis.ResultsLow keV MEI (+) at 40–50 keV showed increased CNR and SNR_{breast lesion} compared with PEI, especially in the venous phase ([CNR: 40 keV, 20.10; 50 keV, 14.45; vs. PEI, 7.27; p < 0.001], [SNR_{breast lesion}: 40 keV, 21.01; 50 keV, 16.28; vs. PEI, 10.77; p < 0.001]). Multiple quantitative DECT parameters of malignant breast lesions were higher in the venous phase images than in the arterial phase images (p < 0.001). MEI (+) at 40 keV, ID, and Z_eff reconstructions yielded the highest Likert scores for lesion conspicuity. The conspicuity of the mass margin and the visual enhancement were significantly better in 40-keV MEI (+) than in the PEI (p = 0.022, p = 0.033, respectively).ConclusionCompared with PEI, MEI (+) reconstructions at low keV in the venous phase acquired by DECT improved the objective and subjective assessment of lesion conspicuity in patients with malignant breast lesions. MEI (+) reconstruction acquired by DECT may be helpful for the preoperative evaluation of breast cancer.