Dose and image quality at CT pulmonary angiography—comparison of first and second generation dual-energy CT and 64-slice CT

Nonrigid temporal registration of multiphase CT pulmonary angiography using low-kV and low contrast: a feasibility study with dual-source CT

AIM

This study aimed to compare the nonrigid temporal registration of multiphase computed tomography pulmonary angiography (CTPA) with single-phase CTPA in terms of radiation dose, contrast agent usage, objective and subjective image quality.

MATERIALS AND METHODS

Consecutive patients suspected of acute pulmonary embolism were prospectively included in this study, and randomly received multiphase or single-phase CTPA. Regarding the contrast media, 15 mL was applied in the multiphase CTPA in comparison with 40 mL applied in the single-phase CTPA. Temporal registration was performed for multiphase CTPA during post-processing. Two experienced radiologists independently evaluated the image quality (IQ) based on objective measurements, subjective impression and diagnostic confidence. Patient demographics, scan parameters and image quality were compared between the two groups.

RESULTS

A total of 72 patients were analysed (37 multiphase CTPA and 35 single-phase CTPA). Positive pulmonary embolism was confirmed in five and seven patients, respectively. The two patient groups had similar demographics besides older age in those who underwent single-phase CTPA. Radiation dose and the contrast-to-noise ratio (CNR) were also similar between groups except for the CNR in the right main pulmonary artery. Both readers rated the multiphase CTPA with a statistically superior subjective IQ over the single-phase CTPA. The diagnostics confidence of the two CTPA protocols was similarly rated by one reader and slightly different according to the second reader.

CONCLUSION

The nonrigid temporal registration of multiphase CT pulmonary angiography could offer similar or even better image quality than the single-phase protocol and significantly reduce the amount of contrast usage.

Evaluation Of a New Reconstruction Technique for Dual-Energy (DECT) Lung Perfusion: Preliminary Experience In 58 Patients

PURPOSE

To compare dual-energy (DE) lung perfused blood volume generated by subtraction of virtual monoenergetic images (Lung Mono) with images obtained by three-compartment decomposition (Lung PBV).

MATERIAL AND METHODS

The study included 58 patients (28 patients with and 30 patients without PE) with reconstruction of Lung PBV images (i.e., the reference standard) and Lung Mono images. The inter-technique comparison was undertaken at a patient and segment level.

RESULTS

The distribution of scores of subjective image noise (patient level) significantly differed between the two reconstructions (p<0.0001), with mild noise in 58.6% (34/58) of Lung Mono images vs 25.9% (15/58) of Lung PBV images. Detection of perfusion defects (segment level) was concordant in 1104 segments (no defect: n=968; defects present: n=138) and discordant in 2 segments with a PE-related defect only depicted on Lung Mono images. Among the 28 PE patients, the distribution of gradient of attenuation between perfused areas and defects was significantly higher on Lung Mono images compared to Lung PBV (median= 73.5 HU (QI=65.0; Q3=86.0) vs 24.5 HU (22.0; 30.0); p<0.0001). In all patients, fissures were precisely identified in 77.6% of patients (45/58) on Lung Mono images while blurred (30/58; 51.7%) or not detectable (28/58; 48.3%) on Lung PBV images.

CONCLUSION

Lung Mono perfusion imaging allows significant improvement in the overall image quality and improved detectability of PE-type perfusion defects.

Dual-energy CT quantification of fractional extracellular space in cirrhotic patients: comparison between early and delayed equilibrium phases and correlation with oesophageal varices

OBJECTIVE

Fractional extracellular space has been validated as a marker of hepatic fibrotic in cirrhotic patients at CT-scan as well as on dual-energy CT, which takes advantage from iodine uptake. Since no consensus still exists between equilibrium phases performed at 3 or 10 min, the first aim of this work is to evaluate performances at the two different time points. Moreover, correlation between fractional extracellular space and oesophageal varices, directly related to liver fibrosis, has been assessed.

MATERIALS AND METHODS

Dual-Energy equilibrium phases at 3 and 10 min were performed within a follow-up CT-protocol scan in cirrhotic patients. Oesophageal varices were endoscopically assessed according to their size. At the two different time points, correlation between iodine density of the right and left liver lobes and correlation between the fractional extracellular space values were assessed. Correlation between fractional extracellular space and endoscopic grade of oesophageal varices was calculated.

RESULTS

No statistical differences were found between the iodine density values from the two liver lobes at the two time points (p = 0.8 at 3'; p = 0.5 at 10'). No statistical difference about fractional extracellular space estimation was found between the two time points (p = 0.17). Correlation between fractional extracellular space values and oesophageal varices was moderate (ρ = 0.45, IC 0.08-0.71, p < 0.05).

CONCLUSION

Fractional extracellular space assessed on dual-energy CT at equilibrium phases with different timing was substantially similar. The moderate correlation found between fractional extracellular space and endoscopic grade of oesophageal varices confirms that CT-scan is not currently reliable as endoscopy.

EXPERIMENTAL EXAMINATION OF RADIATION DOSES OF DUAL- AND SINGLE-ENERGY COMPUTED TOMOGRAPHY IN CHEST AND UPPER ABDOMEN IN A PHANTOM STUDY

The aim of this phantom study is to examine radiation doses of dual- and single-energy computed tomography (DECT and SECT) in the chest and upper abdomen for three different multi-slice CT scanners. A total of 34 CT protocols were examined with the phantom N1 LUNGMAN. Four different CT examination types of different anatomic regions were performed both in single- and dual-energy technique: chest, aorta, pulmonary arteries for suspected pulmonary embolism and liver. Radiation doses were examined for the CT dose index CTDIvol and dose-length product (DLP). Radiation doses of DECT were significantly higher than doses for SECT. In terms of CTDIvol, radiation doses were 1.1-3.2 times higher, and in terms of DLP, these were 1.1-3.8 times higher for DECT compared with SECT. The third-generation dual-source CT applied the lowest dose in 7 of 15 different examination types of different anatomic regions.

Dual energy imaging in cardiothoracic pathologies: A primer for radiologists and clinicians

Recent advances in dual-energy imaging techniques, dual-energy subtraction radiography (DESR) and dual-energy CT (DECT), offer new and useful additional information to conventional imaging, thus improving assessment of cardiothoracic abnormalities. DESR facilitates detection and characterization of pulmonary nodules. Other advantages of DESR include better depiction of pleural, lung parenchymal, airway and chest wall abnormalities, detection of foreign bodies and indwelling devices, improved visualization of cardiac and coronary artery calcifications helping in risk stratification of coronary artery disease, and diagnosing conditions like constrictive pericarditis and valvular stenosis. Commercially available DECT approaches are classified into emission based (dual rotation/spin, dual source, rapid kilovoltage switching and split beam) and detector-based (dual layer) systems. DECT provide several specialized image reconstructions. Virtual non-contrast images (VNC) allow for radiation dose reduction by obviating need for true non contrast images, low energy virtual mono-energetic images (VMI) boost contrast enhancement and help in salvaging otherwise non-diagnostic vascular studies, high energy VMI reduce beam hardening artifacts from metallic hardware or dense contrast material, and iodine density images allow quantitative and qualitative assessment of enhancement/iodine distribution. The large amount of data generated by DECT can affect interpreting physician efficiency but also limit clinical adoption of the technology. Optimization of the existing workflow and streamlining the integration between post-processing software and picture archiving and communication system (PACS) is therefore warranted.

Principles and applications of dual source CT

This article describes the technical principles and clinical applications of dual source CT. A dual source CT (DSCT) is a CT system with two x-ray tubes and two detectors at an angle of approximately 90°. Both measurement systems acquire CT scan data simultaneously at the same anatomical level of the patient (same z-position). DSCT provides temporal resolution of approximately a quarter of the gantry rotation time for cardiac, cardio-thoracic and pediatric imaging. Successful imaging of the heart and the coronary arteries at high and variable heart rates has been demonstrated. DSCT systems can be operated at twice the spiral pitch of single source CT systems (up to pitch 3.2). The resulting high table speed is beneficial for pediatric applications and fast CT angiographic scans, e. g. of the aorta or the extremities. Operating both X-ray tubes at different tube potential (kV) enables the acquisition of dual energy data and the corresponding applications such as monoenergetic imaging and computation of material maps. Spectral separation can be improved by different filtration of the X-ray beams of both X-ray tubes. As a downside, DSCT systems have to cope with some challenges, among them the limited size of the second measurement system, and cross-scattered radiation.

Comparison of Dual- and Single-Source Dual-Energy CT for Diagnosis of Acute Pulmonary Artery Embolism

PURPOSE

 Comparison of dual-source dual-energy CT (DS-DECT) and split-filter dual-energy CT (SF-DECT) regarding image quality and radiation dose in patients with suspected pulmonary embolism.

MATERIALS AND METHODS

 We retrospectively analyzed pulmonary dual-energy CT angiography (CTPA) scans performed on two different CT scanners in 135 patients with suspected pulmonary embolism (PE). Scan parameters for DS-DECT were 90/Sn150 kV (n = 68 patients), and Au/Sn120 kV for SF-DECT (n = 67 patients). The iodine delivery rate was 1400 mg/s in the DS-DECT group vs. 1750 mg/s in the SF-DECT group. Color-coded iodine distribution maps were generated for both protocols. Objective (CT attenuation of pulmonary trunk [HU], signal-to-noise ratio [SNR], contrast-to-noise ratio [CNR]) and subjective image quality parameters (two readers [R], five-point Likert scale), as well as radiation dose parameters (effective radiation dose, size-specific dose estimations [SSDE]) were compared.

RESULTS

 All CTPA scans in both groups were of diagnostic image quality. Subjective CTPA image quality was rated as good or excellent in 80.9 %/82.4 % (R1 / R2) of DS-DECT scans, and in 77.6 %/76.1 % of SF-DECT scans. For both readers, the image quality of split-filter iodine distribution maps was significantly lower (p < 0.05) with good or excellent ratings in only 43.3 %/46.3 % (R1 / R2) vs. 83.8 %/88.2 % for maps from DS-DECT. The HU values of the pulmonary trunk did not differ between the two techniques (p = n. s.), while both the SNR and CNR were significantly higher in the split-filter group (p < 0.001; p = 0.003). Both effective radiation dose (2.70 ± 1.32 mSv vs. 2.89 ± 0.94 mSv) and SSDE (4.71 ± 1.63 mGy vs. 5.84 ± 1.11 mGy) were significantly higher in the split-filter group (p < 0.05).

CONCLUSION

 The split-filter allows for dual-energy imaging of suspected pulmonary embolism but is associated with lower iodine distribution map quality and higher radiation dose.

KEY POINTS

  · The split-filter allows for dual-energy data acquisition from single-source single-layer CT scanners.. · Compared to the assessed dual-source dual-energy system, split-filter dual-energy imaging of a suspected pulmonary embolism is associated with lower iodine distribution map quality and higher radiation dose.. · Both the split-filter and the dual-source scanner provide diagnostic image quality in CTPA..

CITATION FORMAT

· Petritsch B, Pannenbecker P, Weng AM et al. Comparison of Dual- and Single-Source Dual-Energy CT for Diagnosis of Acute Pulmonary Artery Embolism. Fortschr Röntgenstr 2021; 193: 427 - 436.

CTPA with a conventional CT at 100 kVp vs. a spectral-detector CT at 120 kVp: Comparison of radiation exposure, diagnostic performance and image quality

•

With SD-CT, increased radiation exposure is not present.

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In the current study, CTDI_vol was lower with SD-CT than with C-CT, even when 100 kVp was used for the latter.

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With SD-CT, higher levels of diagnostic performance and image quality can be achieved.

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SD-CT may be the system of choice due to the availability of spectral data and thus additional image information.

Purpose

To compare CT pulmonary angiographies (CTPAs) as well as phantom scans obtained at 100 kVp with a conventional CT (C-CT) to virtual monochromatic images (VMI) obtained with a spectral detector CT (SD-CT) at equivalent dose levels as well as to compare the radiation exposure of both systems.

Material and Methods

In total, 2110 patients with suspected pulmonary embolism (PE) were examined with both systems. For each system (C-CT and SD-CT), imaging data of 30 patients with the same mean CT dose index (4.85 mGy) was used for the reader study. C-CT was performed with 100 kVp and SD-CT was performed with 120 kVp; for SD-CT, virtual monochromatic images (VMI) with 40, 60 and 70 keV were calculated. All datasets were evaluated by three blinded radiologists regarding image quality, diagnostic confidence and diagnostic performance (sensitivity, specificity). Contrast-to-noise ratio (CNR) for different iodine concentrations was evaluated in a phantom study.

Results

CNR was significantly higher with VMI at 40 keV compared to all other datasets. Subjective image quality as well as sensitivity and specificity showed the highest values with VMI at 60 keV and 70 keV. Hereby, a significant difference to 100 kVp (C-CT) was found for image quality. The highest sensitivity was found using VMI at 60 keV with a sensitivity of more than 97 % for all localizations of PE. For diagnostic confidence and subjective contrast, highest values were found with VMI at 40 keV.

Conclusion

Higher levels of diagnostic performance and image quality were achieved for CPTAs with SD-CT compared to C-CT given similar dose levels. In the clinical setting SD-CT may be the modality of choice as additional spectral information can be obtained.

Single- and dual-energy CT pulmonary angiography using second- and third-generation dual-source CT systems: comparison of radiation dose and image quality

OBJECTIVES

To evaluate radiation exposure and image quality in matched patient cohorts for CT pulmonary angiography (CTPA) acquired in single- and dual-energy mode using second- and third-generation dual-source CT (DSCT) systems.

METHODS

We retrospectively included 200 patients (mean age, 65.5 years ± 15.7 years) with suspected pulmonary embolism-equally divided into four study groups (n = 50) and matched by gender and body mass index. CTPA was performed with vendor-predefined second-generation (group A, 100-kV single-energy computed tomography (SECT); group B, 80/Sn140-kV dual-energy computed tomography (DECT)) or third-generation DSCT (group C, 100-kV SECT; group D, 90/Sn150-kV DECT) devices. Radiation metrics were assessed using a normalized scan range of 27.5 cm. For objective image quality evaluation, dose-independent figure-of-merit (FOM) contrast-to-noise ratios (CNRs) were calculated. Subjective image analysis included ratings for overall image quality, reader confidence, and image artifacts using five-point Likert scales.

RESULTS

Calculations of the effective dose (ED) of radiation for a normalized scan range of 27.5 cm showed nonsignificant differences between SECT and DECT acquisitions for each scanner generation (p ≥ 0.253). The mean effective radiation dose was lower for third-generation groups C (1.5 mSv ± 0.8 mSv) and D (1.4 mSv ± 0.7 mSv) compared to second-generation groups A (2.5 mSv ± 0.9 mSv) and B (2.3 mSv ± 0.6 mSv) (both p ≤ 0.013). FOM-CNR measurements were highest for group D. Qualitative image parameters of overall image quality, reader confidence, and image artifacts showed nonsignificant differences among the four groups (p ≥ 0.162).

CONCLUSIONS

Third-generation DSCT systems show lower radiation dose parameters for CTPA compared to second-generation DSCT. DECT can be performed with both scanner generations without radiation dose penalty or detrimental effects on image quality compared to SECT.

KEY POINTS

• Radiation exposure showed nonsignificant differences between SECT and DECT for both DSCT scanner devices. • Dual-energy CTPA provides equivalent image quality compared to standard image acquisition. • Subjective image quality assessment was similar among the four study groups.

In Vivo Analysis of Urinary Stones With Dual-Energy Computed Tomography

OBJECTIVE

Formation mechanisms and treatment of the urinary stones are different, depending on their chemical structure. Therefore, determining the stone type plays a key role in planning treatment and preventive measures. Computed tomography (CT), with the use of dual-energy technology in recent years, has made it possible to do in vivo analysis of urinary stones. In this study, we aimed to evaluate the diagnostic efficacy of dual-energy CT (DECT) and compare its results with in vitro analysis, which is accepted as a gold standard for analysis of urinary stones.

MATERIALS AND METHODS

The DECT examinations were performed on 373 patients using 128-slice dual-source CT scanner. Analysis of attenuation ratios in the high and low kilovoltage peak values of the stone was performed at workstation, and stones were classified as hydroxyapatite, calcium oxalate, cystine, and uric acid. On follow-up, the stone was obtained in 35 patients as a result of surgery or passed spontaneously. The DECT analysis and in vitro analysis results were compared and statistically evaluated.

RESULTS

In all patients, 136 hydroxyapatite, 160 calcium oxalate, 57 uric acid, and 20 cystine stones were detected with DECT. In vitro analyses of the stones were performed in 35 patients, and 8 hydroxyapatite, 18 calcium oxalate, 6 uric acid, and 3 cystine stones were revealed. When DECT analysis results were compared with in vitro analysis results, stone types were detected correctly in 32 (91.4%) patients and incorrectly in 3 (8.6%) patients. Especially all uric acid and cystine stones were correctly detected with DECT.

CONCLUSIONS

With advanced postprocess analysis methods, DECT is able to analyze urinary stones. The DECT is found superior especially in detecting uric acid and cystine stones. Its success in detecting hydroxyapatite and calcium oxalate stones is also high. When in vivo analyses of the stones are performed with DECT, it will be possible to make a contribution to the personalization and optimization of the treatment.

Thoracic-abdominal imaging with a novel dual-layer spectral detector CT: intra-individual comparison of image quality and radiation dose with 128-row single-energy acquisition

BACKGROUND

A novel, multi-energy, dual-layer spectral detector computed tomography (SDCT) is commercially available now with the vendor's claim that it yields the same or better quality of polychromatic, conventional CT images like modern single-energy CT scanners without any radiation dose penalty.

PURPOSE

To intra-individually compare the quality of conventional polychromatic CT images acquired with a dual-layer spectral detector (SDCT) and the latest generation 128-row single-energy-detector (CT128) from the same manufacturer.

MATERIAL AND METHODS

Fifty patients underwent portal-venous phase, thoracic-abdominal CT scans with the SDCT and prior CT128 imaging. The SDCT scanning protocol was adapted to yield a similar estimated dose length product (DLP) as the CT128. Patient dose optimization by automatic tube current modulation and CT image reconstruction with a state-of-the-art iterative algorithm were identical on both scanners. CT image contrast-to-noise ratio (CNR) was compared between the SDCT and CT128 in different anatomic structures. Image quality and noise were assessed independently by two readers with 5-point-Likert-scales. Volume CT dose index (CTDI_vol), and DLP were recorded and normalized to 68 cm acquisition length (DLP₆₈).

RESULTS

The SDCT yielded higher mean CNR values of 30.0% ± 2.0% (26.4-32.5%) in all anatomic structures ( P < 0.001) and excellent scores for qualitative parameters surpassing the CT128 (all P < 0.0001) with substantial inter-rater agreement (κ ≥ 0.801). Despite adapted scan protocols the SDCT yielded lower values for CTDI_vol (-10.1 ± 12.8%), DLP (-13.1 ± 13.9%), and DLP₆₈ (-15.3 ± 16.9%) than the CT128 (all P < 0.0001).

CONCLUSION

The SDCT scanner yielded better CT image quality compared to the CT128 and lower radiation dose parameters.

Dual-Energy CT Angiography for Detection of Pulmonary Emboli: Incremental Benefit of Iodine Maps

Purpose To determine if there is added benefit of using iodine maps from dual-energy (DE) CT in addition to conventional CT angiography images to diagnose pulmonary embolism (PE). Materials and Methods In this retrospective analysis, 1144 consecutive dual-energy CT angiography examinations performed from January through September 2014 at an oncologic referral center to evaluate for PE were reviewed. The 1144 examinations included 1035 patients (mean age, 58.7 years; range, 15-99 years). First, the location, level, and type (occlusive vs nonocclusive) of PEs on conventional CT angiograms were recorded. Iodine maps were then reviewed for defects suggestive of PE. Last, CT angiograms were rereviewed to detect additional PEs suggested by the iodine map. Consensus reviews were performed for examinations with PEs. The confidence interval of percentages was calculated by using the Clopper-Pearson method. Results On 147 of 1144 (12.8%) CT angiograms, a total of 372 PEs were detected at initial review. After review of the DE CT iodine map, 27 additional PEs were found on 26 of 1144 CT angiograms (2.3%; 95% confidence interval [CI]: 1.5%, 3.3%). Of the 27 additional PEs, six (22.2%) were segmental, 21 (77.8%) were subsegmental, 24 (88.9%) were occlusive, and three (11.1%) were nonocclusive. Eleven of 1144 (1.0%; 95% CI: 0.5%, 1.7%) CT angiograms had a new diagnosis of PE after review of the DE CT iodine maps. Conclusion Dual-energy CT iodine maps show a small incremental benefit for the detection of occlusive segmental and subsegmental pulmonary emboli. © RSNA, 2018.

Dual-Energy Computed Tomography: Dose Reduction, Series Reduction, and Contrast Load Reduction in Dual-Energy Computed Tomography

Evolution in computed tomography technology and image reconstruction have significantly changed practice. Dual energy computed tomography is being increasingly adopted owing to benefits of material separation, quantification, and improved contrast-to-noise ratio. The radiation dose can match that from single energy computed tomography. Spectral information derived from a polychromatic x-ray beam at different energies yields in image reconstructions that reduce the number of phases in a multiphasic examination and decrease the absolute amount of contrast media. This increased analytical and image processing capability provides new avenues for addressing radiation dose and iodine exposure concerns.

90-kVp low-tube-voltage CT pulmonary angiography in combination with advanced modeled iterative reconstruction algorithm: effects on radiation dose, image quality and diagnostic accuracy for the detection of pulmonary embolism

OBJECTIVE

To evaluate low-tube-voltage 90-kVp CT pulmonary angiography (CTPA) with advanced modeled iterative reconstruction algorithm (Admire) compared to 120-kVp equivalent dual-energy (DE) acquisition with regards to radiation exposure, image quality and diagnostic accuracy for pulmonary embolism (PE) assessment.

METHODS

CTPA studies of 40 patients with suspected PE (56.7 ± 16.3 years) performed on a third-generation 192-slice dual-source CT scanner were retrospectively included. 120-kVp equivalent linearly-blended (60% 90-kVp, 40% 150-kVp) and 90-kVp images were reconstructed. Attenuation and noise of the pulmonary trunk were measured to calculate contrast-to-noise ratios (CNR). Three radiologists assessed the presence of central and segmental PE and diagnostic confidence. Interobserver agreement was calculated using intraclass correlation coefficient (ICC). Radiation exposure was assessed as effective dose (ED).

RESULTS

Pulmonary trunk CNR values were significantly increased in 90-kVp compared to linearly-blended series (15.4 ± 6.3 vs 11.3 ± 4.6, p < 0.001). Diagnostic accuracy for PE assessment was similar in both series with excellent interobserver agreement (p = 0.48; ICC, 0.83; p = 0.48). Overall confidence for PE assessment was rated excellent for both series with a significant advantage for linearly-blended series (p < 0.001; 4.1 vs 3.8). ED was reduced by 37.2% with 90-kVp compared to 120-kVp equivalent image series (1.1 ± 0.6 vs 1.7 ± 0.7 mSv, p < 0.001).

CONCLUSION

90-kVp CTPA with Admire provided increased quantitative image quality with similar diagnostic accuracy and confidence for PE assessment compared to 120-kVp equivalent acquisition, while radiation dose was reduced by 37.2%. Advances in knowledge: 90-kVp CTPA with an advanced iterative reconstruction algorithm results in excellent image quality and reduction of radiation exposure without limiting diagnostic performance.

Dual Energy Computed Tomography Applications for the Evaluation of the Spine

Capturing the energy-dependent x-ray attenuation of different tissues, dual-energy computed tomography offers multiple benefits in the imaging of the spine, such as bone and iodinated contrast removal, monosodium urate imaging, and robust reduction of beam-hardening artifacts. The emerging new applications of this technique include bone marrow imaging in acute trauma and myeloinfiltrative disorders, improved bone density determination, and noninvasive assessment of spinal gout.

Comparison of the effect of radiation exposure from dual-energy CT versus single-energy CT on double-strand breaks at CT pulmonary angiography

PURPOSE

To compare the effect of dual-source dual-energy CT versus single-energy CT on DNA double-strand breaks (DSBs) in blood lymphocytes at CT pulmonary angiography (CTPA).

METHODS AND MATERIALS

Sixty-two patients underwent either dual-energy CTPA (Group 1: n = 21, 80/Sn140 kVp, 89/38 mAs; Group 2: n = 20, 100/Sn140 kVp, 89/76 mAs) or single-energy CTPA (Group 3: n = 21, 120 kVp, 110 mAs). Blood samples were obtained before and 5 min after CTPA. DSBs were assessed with fluorescence microscopy and Kruskal-Walls tests were used to compare DSBs levels among groups. Volume CT dose index (CTDIvol), dose length product (DLP) and organ radiation dose were compared using ANOVA.

RESULTS

There were increased excess DSB foci per lymphocyte 5 min after CTPA examinations in three groups (Group 1: P = .001; Group 2: P = .001; Group 3: P = .006). There were no differences among groups regarding excess DSB foci/cell and percentage of excess DSBs (Group 1, 23%; Group 2, 24%; Group 3, 20%; P = .932). CTDIvol, DLP and organ radiation dose in Group 1 were the lowest among the groups (all P < .001).

CONCLUSION

DSB is increased following dual-source and single-source CTPA, while dual-source dual-energy CT protocols do not increase the estimated radiation dose and also do not result in a higher incidence of DNA DSBs in patients undergoing CTPA.

Evaluation of a proper cutoff value on quantitative dual-energy perfusion CT for the assessment of acute pulmonary thromboembolism

Background The cutoff value for assessing the severity of acute pulmonary thromboembolism (PTE) using relative volumetric evaluations of dual-energy perfusion computed tomography (DEpCT) is unclear. Purpose To determine the proper cutoff value for determining the severity of PTE using DEpCT volumetry. Material and Methods A total of 185 patients with venous thromboembolism were included in this study, of whom 61 were diagnosed with acute PTE. DEpCT images were three-dimensionally reconstructed at the following attenuation ranges: 1-2 HU (V2), 1-10 HU (V10), and 1-120 HU (V120). The ratios of low perfusion areas associated with each threshold range per V120 were also calculated, and the relative ratios were expressed as %V2 to %V10. These values were compared with factors indicating the severity of PTE, including the pulmonary arterial pressure, heart rate, CT angiographic obstruction index (CTOI), and right/left ventricular diameter ratio (RV/LV). Results The area under the curve (AUC) of %V2 was highest (0.783) among these values (95% confidence interval, 0.710-0.856) based on the presence of IPCs. The %V2 showed moderate correlations with CTOI (r = 0.36, P = 0.005) and RV/LV (r = 0.36, P = 0.004) in the patients with acute PTE. Conclusion Volumetric evaluations of DEpCT images using the lowest attenuation threshold range (1-2 HU) exhibit the best correlation with factors suggesting the severity of acute PTE.

Radiation Optimized Dual-source Dual-energy Computed Tomography Pulmonary Angiography: Intra-individual and Inter-individual Comparison

OBJECTIVES

This study aimed to intra-individually and inter-individually compare image quality, radiation dose, and diagnostic accuracy of dual-source dual-energy computed tomography pulmonary angiography (CTPA) protocols in patients with suspected pulmonary embolism (PE).

METHODS

Thirty-three patients with suspected PE underwent initial and follow-up dual-energy CTPA at 80/Sn140 kVp (group A) or 100/Sn140 kVp (group B), which were assigned based on tube voltages. Subjective and objective CTPA image quality and lung perfusion map image quality were evaluated. Diagnostic accuracies of CTPA and perfusion maps were assessed by two radiologists independently. Effective dose (ED) was calculated and compared.

RESULTS

Mean computed tomography (CT) values of pulmonary arteries were higher in group A than group B (P = .006). There was no difference in signal-to-noise ratio and contrast-to-noise ratio between the two groups (both P > .05). Interobserver agreement for evaluating subjective image quality of CTPA and color-coded perfusion images was either good (κ = 0.784) or excellent (κ = 0.887). Perfusion defect scores and diagnostic accuracy of CTPA showed no difference between both groups (both P > .05). Effective dose of group A was reduced by 45.8% compared to group B (P < .001).

CONCLUSIONS

Second-generation dual-source dual-energy CTPA with 80/Sn140 kVp allows for sufficient image quality and diagnostic accuracy for detecting PE while substantially reducing radiation dose.

Dual-Energy CT: Spectrum of Thoracic Abnormalities

Recent studies have demonstrated that dual-energy computed tomography (CT) can provide useful information in several chest-related clinical indications. Compared with single-energy CT, dual-energy CT of the chest is feasible with the use of a radiation-dose-neutral scanning protocol. This article highlights the different types of images that can be generated by using dual-energy CT protocols such as virtual monochromatic, virtual unenhanced (ie, water), and pulmonary blood volume (ie, iodine) images. The physical basis of dual-energy CT and material decomposition are explained. The advantages of the use of virtual low-monochromatic images include reduced volume of intravenous contrast material and improved contrast resolution of images. The use of virtual high-monochromatic images can reduce beam hardening and contrast streak artifacts. The pulmonary blood volume images can help differentiate various parenchymal abnormalities, such as infarcts, atelectasis, and pneumonias, as well as airway abnormalities. The pulmonary blood volume images allow quantitative and qualitative assessment of iodine distribution. The estimation of iodine concentration (quantitative assessment) provides objective analysis of enhancement. The advantages of virtual unenhanced images include differentiation of calcifications, talc, and enhanced thoracic structures. Dual-energy CT has applications in oncologic imaging, including diagnosis of thoracic masses, treatment planning, and assessment of response to treatment. Understanding the concept of dual-energy CT and its clinical application in the chest are the goals of this article.

Getting the Most From Your Dual-Energy Scanner: Recognizing, Reducing, and Eliminating Artifacts

OBJECTIVE

Dual-energy CT (DECT) is an innovative imaging modality that allows superior detection of pulmonary embolism, enhanced detection of urate in gout, and improved assessment of metal prostheses when compared with conventional CT.

CONCLUSION

The primary aim of this review is to describe these DECT protocols and compare each to its respective diagnostic reference standards. Moreover, this review will describe how to recognize, reduce, and eliminate DECT artifacts, thereby maximizing its diagnostic capabilities.

Systematic Comparison of Reduced Tube Current Protocols for High-pitch and Standard-pitch Pulmonary CT Angiography in a Large Single-center Population

RATIONALE AND OBJECTIVES

Benefits of iterative reconstruction (IR) algorithms combined with dose-reduction techniques have been shown at computed tomography pulmonary angiography (CTPA) in several medium to small patient collectives. In this study, we performed a systematic comparison of image quality to combinations of reduced tube current (RC) and IR for both standard-pitch (SP) single-source and high-pitch (HP) dual-source CTPA in a large, single-center population.

MATERIALS AND METHODS

Three hundred eighty-two consecutive patients (October 2010 through December 2012) received clinically indicated CTPA with one of four consecutively changed protocols: (1) HPSC: 180 mAs, weighted filtered back projection, pitch = 3; (2) HPRC: 90 mAs, IR, pitch = 3; (3) SPSC: 180 mAs, weighted filtered back projection, pitch = 1.2; and (4) HPRC: 90 mAs, IR, pitch = 1.2. Tube potential was 100 kV. Vascular attenuation and standardized signal-to-noise ratio (sSNR) were measured in the pulmonary trunk (sSNRPT) and on segmental artery level (sSNRS1, sSNRS10). Dose-length-product was recorded per series. Two independent investigators rated image quality. Kolmogorov-Smirnov test, Kruskal-Wallis test, and kappa statistics were used for statistical analysis. Median values are presented per group.

RESULTS

Image quality was consistent between all groups (observer 1: P = 0.118; observer 2: P = 0.122). Inter-reader consistency was very good (κ = 0.866, P < 0.001). Dose-length-product was significantly reduced in HP and RC groups (P < 0.001 for each; SPSC: 139.5 mGycm; HPRC: 92 mGycm; SPSC: 211 mGycm; HPRC: 137 mGycm). sSNR was comparable (sSNRPT overall: P = 0.052; sSNRS1 overall: P = 0.161; and sSNRS10 overall: P = 0.259).

CONCLUSIONS

Substantial dose reduction can be within a routine clinical setting without quantifiable loss of image quality either by HP pulmonary angiography or by a combination of IR and RC in either HP or SP acquisition.

Advances in Multidetector CT Diagnosis of Pediatric Pulmonary Thromboembolism

Although pediatric pulmonary thromboembolism is historically believed to be rare with relatively little information available in the medical literature regarding its imaging evaluation, it is more common than previously thought. Thus, it is imperative for radiologists to be aware of the most recent advances in its imaging information, particularly multidetector computed tomography (MDCT), the imaging modality of choice in the pediatric population. The overarching goal of this article is to review the most recent updates on MDCT diagnosis of pediatric pulmonary thromboembolism.

70-kVp High-pitch Computed Tomography Pulmonary Angiography with 40 mL Contrast Agent: Initial Experience

RATIONALE AND OBJECTIVES

To assess image quality, radiation dose, and diagnostic accuracy of 70-kVp high-pitch computed tomography pulmonary angiography (CTPA) using 40 mL contrast agent and sinogram affirmed iterative reconstruction (SAFIRE) compared to 100-kVp CTPA using 60 mL contrast agent and filtered back projection.

MATERIALS AND METHODS

Eighty patients underwent CTPA at either 70 kVp (group A, n = 40; 3.2 pitch, 40 mL contrast medium, and SAFIRE) or 100 kVp (group B, n = 40; 1.2 pitch, 60 mL contrast medium, and filtered back projection). Signal-to-noise ratio and contrast-to-noise ratio were calculated. Subjective image quality was evaluated using a five-grade scale, and diagnostic accuracy was assessed. Radiation doses were compared.

RESULTS

Computed tomography values, signal-to-noise ratio, and contrast-to-noise ratio of pulmonary arteries were higher in group A compared to group B (all P < 0.001). Subjective image quality showed no difference between the two groups (P = 0.559) with good interobserver agreement (κ = 0.647). No difference was found regarding diagnostic accuracy between the two groups (P > 0.05). The effective dose for group A was lower by 80% compared to group B (P < 0.001).

CONCLUSIONS

70-kVp high-pitch CTPA with reduced contrast media and SAFIRE provides comparable image quality and substantial radiation dose savings compared to a routine CTPA protocol.

Pediatric Pulmonary Hypertension: Guidelines From the American Heart Association and American Thoracic Society

Pulmonary hypertension is associated with diverse cardiac, pulmonary, and systemic diseases in neonates, infants, and older children and contributes to significant morbidity and mortality. However, current approaches to caring for pediatric patients with pulmonary hypertension have been limited by the lack of consensus guidelines from experts in the field. In a joint effort from the American Heart Association and American Thoracic Society, a panel of experienced clinicians and clinician-scientists was assembled to review the current literature and to make recommendations on the diagnosis, evaluation, and treatment of pediatric pulmonary hypertension. This publication presents the results of extensive literature reviews, discussions, and formal scoring of recommendations for the care of children with pulmonary hypertension.

Quantification of the Iodine Content of Perigastric Adipose Tissue by Dual-Energy CT: A Novel Method for Preoperative Diagnosis of T4-Stage Gastric Cancer

This study investigated the utility of quantifying iodine concentration (IC) in perigastric adipose tissue, using dual-energy computed tomography (DECT), for the detection of T4a-stage gastric cancer. Fifty-four patients with gastric cancer were enrolled at the Fourth Hospital of Hebei Medical University between January and June 2013. Patients were imaged preoperatively with conventional computed tomography (CT) scans and DECT, and the IC in perigastric fat adjacent to the tumor calculated from arterial phase (AP) and portal venous phase (PVP) images. The patients subsequently received surgical treatment (gastrectomy), and histologic analysis of resected specimens was used as a ‘gold standard’ reference for cancer staging. Receiver operating characteristic (ROC) curve analysis was employed to assess the utility of DECT for identifying T4a-stage gastric cancer, with optimal IC thresholds determined from the area under the ROC curve (AUC). Postoperative histology revealed that 32 patients had serosal invasion (group A), and 22 did not (group B). The accuracy of conventional CT for distinguishing stage T4 from non-T4 stages was 68.5% (37/54). IC was significantly higher in group A than in group B (AP: 0.60±0.34 vs. 0.09±0.19 mg/mL, p<0.001; PVP: 0.83±0.41 vs. 0.27±0.21 mg/mL, p<0.001). The sensitivity, specificity and AUC for detecting serosal invasion were 77.1%, 79.2% and 0.89 at an IC threshold of 0.25 mg/mL for AP images; and 80.0%, 79.2% and 0.90 at an IC threshold of 0.45 mg/mL for PVP images. These results indicated that Iodine quantification in perigastric fat using DECT is an accurate method for detecting serosal invasion by gastric cancer.

70 kVp computed tomography pulmonary angiography: potential for reduction of iodine load and radiation dose

PURPOSE

The purpose of the study was to evaluate 70 kVp dual-source computed tomography pulmonary angiography (CTPA) with reduced iodine load in comparison with single-source 70 and 100 kVp CTPA with standard iodine load regarding image quality and radiation dose.

MATERIALS AND METHODS

Three groups with 40 consecutive patients each underwent either standard single-source 100 kVp (120 mAs; group A), single-source 70 kVp (208 mAs; group B), or dual-source 70 kVp CTPA (416 mAs; group C). A volume of 70 mL of contrast material with 400 mg I/mL (groups A, B) or 300 mg I/mL (group C) was administered. Chest diameter, dose-length product, intravascular signal attenuation, image noise, signal to noise ratio (SNR), and contrast to noise ratio (CNR) were compared. Two observers rated subjective image quality regarding intravascular enhancement and image noise using 5-point scales.

RESULTS

Chest diameter and age were similar (P ≥ 0.28) for all groups. Compared with group A, the average dose-length product was 59% lower in group B (67.3 ± 11.8 vs. 164.7 ± 50.6 mGy cm, P<0.001) and similar between groups A and C (167.7 ± 41.2 mGy cm, P = 0.39). Average SNR and CNR were significantly higher for group C (21.5 ± 4.7 and 19.0 ± 4.5, respectively) compared with groups A (18.3 ± 3.5 and 15.8 ± 3.4, respectively) and B (17.3 ± 5.8 and 15.6 ± 5.5, respectively; all Ps ≤ 0.001). Subjective image quality ratings regarding enhancement and noise were highest for group C (1.73 ± 0.62 and 2.03 ± 0.66, respectively).

CONCLUSIONS

Compared with standard 100 kVp CTPA, single-source 70 kVp CTPA allows for significant radiation dose savings with comparable SNR and CNR, whereas dual-source 70 kVp CTPA results in a superior objective image quality albeit a reduction of iodine concentration.

In vivo characterization of urinary calculi on dual-energy CT: going a step ahead with sub-differentiation of calcium stones

BACKGROUND

The role of dual-energy computed tomography (DECT) in characterization of urinary calculi is evolving and literature regarding differentiation of calcium calculi is sparse and confounding.

PURPOSE

To evaluate the capability of DECT in assessing the urinary calculi composition in vivo, especially in differentiating various types of calcium calculi.

MATERIAL AND METHODS

One hundred and twenty patients underwent DECT for characterization of urinary calculi. Seventy patients with 114 calculi, including 93 calcium stones, were retrospectively analyzed. DE ratios and attenuation differences were compared using ANOVA and receiver-operating-characteristic (ROC) analysis was done to predict cut-off values, in particular for detecting calcium-oxalate-monohydrate (COM) stones.

RESULTS

DE ratio ≤1.14 accurately detected uric acid calculi, ≥1.29 was definitive for calcium and intermediate values were characteristic of cystine stones. DE ratios were significantly different between group 1 (COM [n = 32]; mean 1.376 ± 0.041), group 2 ([calcium oxalate dihydrate (COD) + COM] [n = 51]; 1.416 ± 0.048), and group 3 ([carbonate apatite (CaP) + COD + COM] [n = 10]; 1.468 ± 0.038) (group 1 vs. 2, P = 0.001; 1 vs. 3, P = 0.000; 2 vs. 3, P = 0.004). More importantly, pure COM calculi (group 1) had significantly lower DE ratio compared with mixed calcium calculi (groups 2 and 3) (P = 0.000). Attenuation differences (between low and high kV images) could not distinguish between COM and mixed calculi. ROC analysis for detection of COM calculi yielded AUC of 0.770 with cut-off DE ratio 1.385 (sensitivity 65.6%, specificity 82%) and value <1.335 was seen only with COM calculi (100% specificity).

CONCLUSION

DECT can be employed for in vivo differentiation of various types of calculi and for detection of relatively lithotripsy-resistant COM calculi.

Evaluation of monoenergetic imaging to reduce metallic instrumentation artifacts in computed tomography of the cervical spine

OBJECT

Monoenergetic imaging with dual-energy CT has been proposed to reduce metallic artifacts in comparison with conventional polychromatic CT. The purpose of this study is to systematically evaluate and define the optimal dual-energy CT imaging parameters for specific cervical spinal implant alloy compositions.

METHODS

Spinal fixation rods of cobalt-chromium or titanium alloy inserted into the cervical spine section of an Alderson Rando anthropomorphic phantom were imaged ex vivo with fast-kilovoltage switching CT at 80 and 140 peak kV. The collimation width and field of view were varied between 20 and 40 mm and medium to large, respectively. Extrapolated monoenergetic images were generated at 70, 90, 110, and 130 kiloelectron volts (keV). The standard deviation of voxel intensities along a circular line profile around the spine was used as an index of the magnitude of metallic artifact.

RESULTS

The metallic artifact was more conspicuous around the fixation rods made of cobalt-chromium than those of titanium alloy. The magnitude of metallic artifact seen with titanium fixation rods was minimized at monoenergies of 90 keV and higher, using a collimation width of 20 mm and large field of view. The magnitude of metallic artifact with cobalt-chromium fixation rods was minimized at monoenergies of 110 keV and higher; collimation width or field of view had no effect.

CONCLUSIONS

Optimization of acquisition settings used with monoenergetic CT studies might yield reduced metallic artifacts.

CT angiography in the diagnosis of cardiovascular disease: a transformation in cardiovascular CT practice

Computed tomography (CT) angiography represents the most important technical development in CT imaging and it has challenged invasive angiography in the diagnostic evaluation of cardiovascular abnormalities. Over the last decades, technological evolution in CT imaging has enabled CT angiography to become a first-line imaging modality in the diagnosis of cardiovascular disease. This review provides an overview of the diagnostic applications of CT angiography (CTA) in cardiovascular disease, with a focus on selected clinical challenges in some common cardiovascular abnormalities, which include abdominal aortic aneurysm (AAA), aortic dissection, pulmonary embolism (PE) and coronary artery disease. An evidence-based review is conducted to demonstrate how CT angiography has changed our approach in the diagnosis and management of cardiovascular disease. Radiation dose reduction strategies are also discussed to show how CT angiography can be performed in a low-dose protocol in the current clinical practice.

70 kV computed tomography of the thorax: valence for computer-assisted nodule evaluation and radiation dose - first clinical results

BACKGROUND

Computed tomography (CT) is the gold standard for evaluation of pulmonary nodules and is at the same time responsible for the majority of the collective effective dose.

PURPOSE

To evaluate radiation dose and efficacy of computer-assisted detection (CAD) for solid pulmonary nodules in low dose chest CT performed at 70 kV.

MATERIAL AND METHODS

CAD was performed upon chest CT with 70 kV and 100 kV (gold standard) at manufacture's recommended tube current of 87 mAs (collimation, 64 × 0.6 mm). Detection rate for pulmonary nodules and size measurements of both techniques were compared to each other. Radiation dosage in terms of effective dose (E) was measured using an Alderson-Rando Phantom.

RESULTS

Seventy-four patients with 301 solid nodules were included in the study. CAD detection rate was similar for 70 kV (94.7%) and 100 kV (92.4%). Mean transversal nodule diameter was 5.5 mm for 70 kV and 5.7 mm for 100 kV with an average volume of 0.12 mL (both techniques). Derived from the phantom measurements patient examinations resulted in an E of 0.51 mSv (70 kV) versus 2.02 mSv (100 kV).

CONCLUSION

70 kV low-dose chest CT is suitable for CAD based lung nodule analysis at a fraction of the radiation burden of the standard technique. Since the measurements are highly accurate, 70 kV CT could be used for detection of pulmonal lesions as well as follow-up studies.

Second-generation dual-energy computed tomography of the abdomen: radiation dose comparison with 64- and 128-row single-energy acquisition

PURPOSE

This study was designed to compare the radiation dose in abdominal dual-energy (DE) and single-energy (SE) acquisitions obtained in clinical practice with a second-generation DE computed tomography (DECT) and to analyze the dose variation in comparison with an SE acquisition performed with a 64-row SECT (SECT).

METHODS

A total of 130 patients divided into 2 groups underwent precontrast and portal abdominal 128-row CT examination. In group A, DE portal acquisition was performed using a detector configuration of 2 × 40 × 0.6 mm, tube A at 80 kVp and a reference value of 559 mAs, tube B at 140 kVp and a reference value of 216 mAs, pitch 0.6, and online dose modulation; group B underwent SE portal acquisition using a detector configuration of 64 × 0.6 mm, 120 kVp and a reference value of 180 mAs, pitch 0.75, and online dose modulation. Group C consisted of 32 subjects from group A previously studied with 64-row SECT using the following parameters: detector configuration 64 × 0.6 mm, 120 kVp and a reference value of 180 mAs, pitch 0.75, and online dose modulation. In each group, the portal phase dose-length product and radiation dose (mSv) were calculated and normalized for a typical abdominal acquisition of 40 cm.

RESULTS

After normalization to standard 40-cm acquisition, a dose-length product of 599.0 ± 133.5 mGy · cm (range, 367.5 ± 1231.2 mGy · cm) in group A, 525.9 ± 139.2 mGy · cm (range, 215.7-882.8 mGy · cm) in group B, and 515.9 ± 111.3 mGy · cm (range, 305.5-687.2 mGy · cm) in group C was calculated for portal phase acquisition.A significant radiation dose increase (P < 0.05) was observed in group A (10.2 ± 2.3 mSv) compared with group B (8.9 ± 2.4) and group C (8.8 ± 1.9 mSv). No significant difference (P > 0.05) was reported between SE 64- and 128-row acquisitions. A significant positive correlation between radiation dose and body mass index was observed in each group (group A, r = 0.59, P < 0.0001; group B, r = 0.35, P < 0.0001; group C, r = 0.20, P = 0.0098).

CONCLUSIONS

In clinical practice, abdominal DECT acquisition shows a significant but minimal radiation dose increase, on the order of 1 mSv, compared with 64- and 128-row SE acquisition. The slightly increased radiation dose can be justified if the additional information obtained using a spectral imaging approach directly impacts on patient management or reduce the overall radiation dose with the generation of virtual unenhanced images, which can replace the precontrast acquisition.

Volumetric evaluation of dual-energy perfusion CT for the assessment of intrapulmonary clot burden

AIM

To evaluate the volumetric values of intrapulmonary clots (IPCs) using 64-section dual-energy perfusion computed tomography (DEpCT).

MATERIALS AND METHODS

A total of 174 patients suspected of having acute pulmonary embolism (PE) underwent DEpCT, and acute PE was diagnosed in 48 of these patients. DEpCT images were three-dimensionally reconstructed with four threshold ranges: 1-120 HU (V₁₂₀), 1-15 HU (V₁₅), 1-10 HU (V₁₀), and 1-5 HU (V₅). Each relative value per V₁₂₀ was expressed as %V₁₅, %V₁₀ and %V₅. These values were compared with the d-dimer, pulmonary arterial (PA) pressure, right ventricular (RV) diameter, RV/left ventricular diameter ratio, PA diameter, and CT angiographic obstruction index (CTOI).

RESULTS

In patients with IPCs, PA pressure, d-dimer and volumetric values of DEpCT were significantly higher (p < 0.001). Relative volumetric values at DEpCT had better correlations with the PA pressure, PA diameter, and CTOI than absolute ones, and %V₅ especially had good correlations with PA pressure (r = 0.44, p = 0.02), PA diameter (r = 0.40, p = 0.005), and CTOI (r = 0.38, p = 0.009).

CONCLUSION

The relative volumetric evaluation of DEpCT images with a lower attenuation threshold range may be helpful for assessing right heart strain, because these values had good correlation with CTOI, pulmonary pressure, and diameter in suggesting right heart load.

Impact of iodine delivery rate with varying flow rates on image quality in dual-energy CT of patients with suspected pulmonary embolism

RATIONALE AND OBJECTIVES

To prospectively compare four contrast material injection protocols for dual-energy computed tomography (CT) pulmonary angiography (DE-CTPA) in patients with suspected pulmonary embolism (PE).

MATERIALS AND METHODS

One hundred twenty consecutive patients were randomized to contrast material injection protocols defined by different iodine concentrations and iodine delivery rates (IDRs): (A) 80 mL iopromide 370/4 mL/sec = IDR 1.4 gI/sec; (B) 80 mL iopromide 370 at 3 mL/sec = IDR 1.1 gI/sec; (C) 98 mL iopromide 300 at 4.9 mL/sec = IDR 1.4 gI/sec; and (D) 98 mL iopromide 300 at 3.7 mL/sec = IDR 1.1 gI/sec. Attenuation values were measured in the inflow tract (subclavian vein-superior vena cava-right atrium), target tract (right ventricle-pulmonary trunk-pulmonary arteries), and outflow tract (left atrium-left ventricle-ascending aorta). Two readers assessed subjective image quality of CTPA images and iodine perfusion maps. The number of artifacts due to hyperdense contrast material on iodine perfusion maps was recorded.

RESULTS

Target tract attenuation was highest for protocol A with 374 ± 98 Hounsfield units (HU) (highly concentrated contrast material/high IDR). This was significant compared to protocols B and D (P = .0118, P = .0427) but not compared to protocol C (P = .3395). No significant difference in target tract attenuation was found between protocols B (309 ± 80 HU), protocol C (352 ± 119 HU), and D (325 ± 74 HU). CTPA and iodine perfusion map image quality for protocol A was rated significantly higher compared to all other protocols (median score = 5/4; P < .0001 for both) with moderate interreader agreement (κ = 0.58/0.47). Protocols A and B displayed increased artifacts on iodine perfusion maps compared to protocols C and D (3 versus 2).

CONCLUSION

Despite increased artifacts on iodine perfusion maps, highly concentrated iodinated contrast material combined with high flow rates provides improved diagnostic image quality and has the highest target-tract attenuation for DE-CTPA protocols.

Dual-energy lung perfusion and ventilation CT in children

Dual-energy thoracic CT provides two key insights into lung physiology, i.e. regional perfusion and ventilation, and has been actively investigated to find clinically relevant applications since the introduction of dual-source CT. This functional information provided by dual-energy thoracic CT is supplementary because high-resolution thoracic anatomy is entirely preserved on dual-energy thoracic CT. In addition, virtual non-contrast imaging can omit pre-contrast scanning. In this respect, dual-energy CT imaging technique is at least dose-neutral, which is a critical requirement for paediatric imaging. In this review, imaging protocols, analysis methods, clinical applications and diagnostic pitfalls of dual-energy thoracic CT for evaluating lung perfusion and ventilation in children are described.

Dual-energy CT applications in the abdomen

OBJECTIVE

The purpose of this article is to give a brief overview of the technical background of dual-energy CT (DECT) imaging and to review various DECT applications in the abdomen that are currently available for clinical practice. In a review of the recent literature, specific DECT applications available for abdominal organs, liver, pancreas, kidneys including renal stones, and adrenal glands, will be discussed in light of reliability and clinical usefulness in replacing true unenhanced imaging, increased lesion conspicuity, iodine extraction, and improved tissue/material characterization (e.g., renal stone composition). Radiation dose considerations will be addressed in comparison with standard abdominal imaging protocols.

CONCLUSION

Modern DECT applications for the abdomen expand the use of CT and enable advanced quantitative methods in the clinical routine on the basis of differences in material attenuation observed by imaging at two different distinct photon energies.

Dual-energy CT: radiation dose aspects

OBJECTIVE

Various applications for dual-energy CT (DECT) have been investigated and have shown substantial clinical benefits. However, only limited data are available regarding the radiation dose associated with DECT imaging. The purpose of this article is to review the available literature regarding the radiation dose associated with DECT imaging applications in comparison with conventional single-energy CT techniques.

CONCLUSION

The rediscovery of DECT and the increasing availability of this technique on clinical CT systems have opened new dimensions for CT. The advanced spectral differentiation of materials within the human body as well as the selective visualization or subtraction of iodinated contrast material or xenon provides both advanced visualization of disease-specific molecular substrates as well as additional functional information within a single scan.

Pulmonary embolism detection and characterization through quantitative iodine-based material decomposition images with spectral computed tomography imaging

OBJECTIVES

To assess the diagnostic value of pulmonary embolism (PE) detection and characterization through quantitative iodine-based material decomposition images with spectral computed tomography (CT) imaging.

MATERIALS AND METHODS

Fifty-three patients underwent CT pulmonary angiography (CTPA) with spectral imaging mode with the simultaneous acquisition of 80 kVp and 140 kVp on a GE Discovery CT750HD scanner to generate monochromatic CTPA and material decomposition images. CTPA images were reviewed for the presence, localization, and degree (occlusive or nonocclusive) of PE. The iodine distribution in the lung parenchyma on the iodine-based material decomposition images was used to identify perfusion defects, which were then correlated to the CTPA findings. The iodine densities for the perfusion defects and the normal lung parenchyma were measured and statistically compared. Twelve PE patients underwent anticoagulation, and the iodine densities for the perfusion defects before and after the treatment were also measured and compared. The receiver operating characteristics curve was generated to assess the differential diagnostic performances of iodine density in distinguishing the presence or absence of PE and the occlusive or nonocclusive PE.

RESULTS

A total of 93 clots (51 occlusive and 42 nonocclusive) were found in 19 patients with lobar (26), segmental (54), or subsegmental (13) distribution. CTPA identified 88 clots initially and 5 more retrospectively with the help of iodine mapping. Thirty-three of 34 normal CTPA patients had symmetric iodine distribution. All occlusive clots and 11 nonocclusive clots showed clear evidence of iodine distribution defects. There was a significant difference for the iodine density among normal lung parenchyma (1.89 mg/mL [0.85-3.29 mg/mL]), nonocclusive perfusion defects (0.83 mg/mL [0.44-1.26 mg/mL]), and occlusive perfusion defects (0.27 mg/mL [0.00-0.62 mg/mL]) (P < 0.001). The iodine densities of perfusion defects before and after anticoagulation were significantly different (P < 0.001). Receiver operating characteristics analyses showed high discriminatory power for using the quantification of iodine density in distinguishing the presence or absence of PE and the occlusive or nonocclusive PE.

CONCLUSIONS

Spectral CT imaging generated both monochromatic CTPA images for morphologic analysis of PE and material decomposition images for quantitative depiction of pulmonary blood flow and perfusion defects. Quantification of iodine density may be used as a predictor in distinguishing the presence or absence of PE and the severity of PE.