Dual-energy CT Pulmonary Angiography Research Articles

Dual Energy CT lung perfusion imaging—Correlation with SPECT/CT

Aims were (1) to determine the diagnostic accuracy of Dual Energy CT (DECT) in the detection of perfusion defects and (2) to evaluate the potential of DECT to improve the sensitivity for PE. 15 patients underwent Dual Energy pulmonary CT angiography (DE CTPA) and a combination of lung perfusion SPECT/CT and ventilation scintigraphy. CTPA and DE iodine distribution maps as well as perfusion SPECT/CT and inhalation scintigrams were reviewed for pulmonary embolism (PE) diagnosis. DECT and SPECT perfusion images were assessed regarding localization and extent of perfusion defects. Diagnostic accuracy of DE iodine (perfusion) maps was determined with reference to SPECT/CT. Diagnostic accuracies for PE detection of DECT and of SPECT/CT with ventilation scintigraphy were calculated with reference to the consensus reading of all modalities. DE CTPA had a sensitivity/specificity of 100%/100% for acute PE, while the combination of SPECT/CT and ventilation scintigraphy had a sensitivity/specificity of 85.7%/87.5%. For perfusion defects, DECT iodine maps had a sensitivity/specificity of 76.7% and 98.2%. DECT is able to identify pulmonary perfusion defects with good accuracy. This technique may potentially enhance the diagnostic accuracy in the assessment of PE.

Feasibility of gadolinium-enhanced dual energy CT pulmonary angiography: a pilot study in rabbits

The purpose of this study was to evaluate the feasibility of gadolinium-enhanced dual energy CT pulmonary angiography (CTPA) to detect pulmonary embolism (PE) in rabbits. Dual energy CT was performed on phantoms composed of different dilution of gadolinium and iodinated contrast agents, CT numbers of the phantoms were measured at different tube voltages. Ten rabbits, which were subdivided into two groups receiving 3 or 5ml/kg of gadolinium based contrast agent (n=5 for each group), underwent baseline gadolinium-enhanced dual energy CTPA. The CT numbers of pulmonary arteries were measured. The following day, sponge gelatin was injected into femoral vein of 6 rabbits to create pulmonary emboli. The rabbit were re-imaged 2h after sponge gelatin injection. Histopathology analysis of the lung lobes was performed. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Serum creatinine levels were measured on day 1 before gadolinium contrast media injection, and on day 2 prior to PE creation. The phantoms and animal study showed that the CT numbers of gadolinium-based contrast agent and pulmonary arteries at 80kVp were higher than those at 140kVp and average weighted 120kVp. In 6 rabbits, CTPA showed bilateral pulmonary artery emboli, and the reconstructed gadolinium maps showed decreased pulmonary perfusion in the corresponding lung lobes. With the histopathology results as the reference standards, CTPA and Blood flow imaging (BFI) detected PE in 14 and 14 of the 14 pulmonary lobes, 26, 24 lobes without PE, respectively, corresponding to sensitivities of 100 and 100%, and specificities of 100 and 92%, respectively. Serum creatinine level increased by 6.7 and 20.6% in the rabbits receiving 3 and 5ml/kg gadolinium based contrast medium respectively. Histopathological analysis found no significant tubular necrosis at either gadolinium dose. Gadolinium-enhanced dual energy CT pulmonary angiography is feasible and it can simultaneously provide information on pulmonary artery and lung perfusion in a rabbit model of PE.

Focal Iodine Defects on Color-Coded Iodine Perfusion Maps of Dual-Energy Pulmonary CT Angiography Images: A Potential Diagnostic Pitfall

The purpose of this article is to systematically investigate focal iodine defects found in patients without other CT evidence for pulmonary embolism on color-coded iodine perfusion maps of dual-energy pulmonary CT angiography scans. Forty-three patients (mean age, 56.9 years; range, 29-88 years) who underwent pulmonary CT angiography using dual-energy CT from November 2007 to February 2008 but who had no pulmonary embolism were included in our study. Dark orange- or black-colored areas on color-coded iodine perfusion maps were interpreted as focal iodine defects. Two radiologists recorded the presence, location, and characteristics of the focal iodine defects in consensus and evaluated the examinations with regard to the causes of the focal iodine defects. Focal iodine defects were found in 41 patients (95%). The most commonly involved segments were the anterior segment of the right upper lobe (33/38, 86.8%), the apical segment of the right upper lobe (32/38, 84.2%), the medial segment of the right middle lobe (32/38, 84.2%), the apicoposterior segment of the left upper lobe (35/42, 83.3%), the superior and inferior lingular segments of the left upper lobe (23/42, 54.8%), and the medial-basal segment of the right lower lobe (11/32, 34.4%). Beam-hardening artifacts caused by contrast material in the superior vena cava accounted for nearly all defects in the apices of both upper lobes. Cardiac motion was the most common cause of defects in right middle lobe and left upper lobe lingular segments, and diaphragmatic motion was the most common cause in the lung bases. Knowledge of the focal iodine defects not related to pulmonary embolism leads to more accurate interpretation of dual-energy pulmonary CT angiography scans.

Triphasic contrast injection improves evaluation of dual energy lung perfusion in pulmonary CT angiography

Lung perfusion analysis at dual energy CT (DECT) is sensitive to beam hardening artifacts from dense contrast material (CM). We compared two scan and four CM injection protocols in terms of severity of artifacts and attenuation levels in the thoracic vessels. Data of 120 patients who had undergone dual source dual energy CT pulmonary angiography for suspected acute pulmonary embolism were evaluated. Group 1 (n=30) was scanned in craniocaudal direction using 64×0.6 mm collimation; groups 2-4 (n=30 each) were scanned in caudocranial direction using 14×1.2 mm collimation. In groups 1-3 biphasic injection protocols with different amounts of CM and NaCl were investigated. In group 4 a split-bolus protocol with an initial CM bolus of 50 ml followed by 30 ml of a 70%:30% NaCl/CM mixture and a 50 ml NaCl chaser bolus was used. CT density values in the subclavian vein (SV), superior vena cava (SVC), pulmonary artery tree (PA), and the descending aorta (DA) were measured. Artifacts arising from the SV and SVC on DE pulmonary iodine distribution map were rated on a scale from 1 to 5 (1=fully diagnostic; 5=non-diagnostic) by two blinded readers. In protocol 4 mean attenuation in the SV (645±158 HU) and SVC (389±114 HU) were significantly lower compared to groups 1-3 (p<0.002). Artifacts in group 4 (1.1±0.4 and 1.5±0.7 for the SV and SVC, respectively) were rated significantly less severe compared to group 1 (3.2±1.0 and 3.0±1.1), 2 (2.6±1.1 and 2.3±1.0) and 3 (1.9±0.9 and 1.9±0.7) (p<0.01 for all), whereas no significant difference was found between groups 1 and 2 for the subclavian vein (p=0.07). Attenuation in the PA was also significantly lower in group 4 (282±116 HU) compared to group 1 (397±137 HU), group 2 (376±115 HU) and group 3 (311±104 HU), but still on a diagnostic level. Split-bolus injection provides sufficient attenuation for pulmonary DECT angiography while beam hardening artifacts arising from high density contrast material in the thoracic vessels can be reduced significantly.

Comparative study of dual-energy CT pulmonary angiography and lung perfusion with pulmonary perfusion scintigraphy in the diagnosis of pulmonary embolism

Objective To investigate the diagnostic value of dual-energy CT pulmonary angiography (DE-CTPA) and dual-energy CT lung perfusion (DE-CTLP) in the assessment of pulmonary embolism comparing with pulmonary ventilation-perfusion scintigraphy. Methods Fifty patients suspected of PE (26 males, 24 females) underwent both DE-CTPA, DE-CTLP and pulmonary ventilation-perfusion scintigraphy. The results were compared and the correlation between the intravascular clots in DE-CTPA and the perfusion defects in DE-CTLP was analyzed. The sensitivity, specificity and accuracy of DE-CTLP for PE were assessed according to scintigraphic results which was considered as a gold standard. Result ( 1 ) Of 50 cases,920 segments in 46 cases were diagnostable, 4 cases were not included because of the poor image quality. lntravascular clots were found in 262 segments on DE-CTPA and perfusion defects in 266 segments were identified on DE-CTLP, while 268 segments were positive on scintigraphy. (2) The perfusion defects on DE-CTLP were correlated well with the clots on CTPA ( r = 0. 883, P < 0. 01 ). The Dual energy CT Lung perfusion imaging had a good consistence with scintigraphy (Kappa = 0. 940, P <0. 01 ). The sensitivity, specificity, positive and negative predictive value were 96. 2% (279/290), 98.0%(641/654), 95. 5% (279/292) and 98. 3% (641/652), respectively. (3)The radiation dose of DE-CTPA and CE-CTLP scan was(4. 37 ± 0. 47) mSv by using CareDose 4D technique. Conclusion DE-CTPA and CE-CTLP can provide pulmonary vascular morphology and parenchyma perfusion information which are useful and valuable for the diagnosis of PE. Key words: Pulmonary embolism; Tomography,X-ray computed; Perfusion; Radionuclide imaging

Evaluation of computer-aided detection and dual energy software in detection of peripheral pulmonary embolism on dual-energy pulmonary CT angiography

To evaluate the sensitivity of computer-aided detection(CAD) and dual-energy software('Lung PBV', 'Lung Vessels') for detecting peripheral pulmonary embolism(PE). Between Jan-2007 and Jan-2008, 309 patients underwent dual-energy CT angiography(DECTA) for the evaluation of suspected PE. Among them, 37 patients were retrospectively selected; 21 with PE at segmental-or-below levels and 16 without PE according to clinical reports. A standard computer assisted detection (CAD) package and two new types of software('Lung PBV', 'Lung Vessels') were applied on a dedicated workstation. This resulted in four alternative tests for detecting PE: DECTA alone and DECTA with CAD, 'Lung Vessels' and 'Lung PBV'. Two radiologists independently read all cases at different reading sessions. Two thoracic radiologists set the reference standard by combining all information from DECTA and software. The sensitivity of detection for all, segmental and subsegmental-or-below PE were assessed. The reference standard contained 136 PE(segmental 65, subsegmental-or-below 71). With DECTA alone, the sensitivity of detection for all, segmental and subsegmental-or-below pulmonary arteries was 54.5%/73.7%/34.4%; DECTA with CAD, 57.8%/76.8%/37.9%; DECTA with 'Lung PBV', 61.1%/79.9%/41.4%; DECTA with 'Lung Vessels', 64.0%/78.3%/48.5% respectively. The use of CAD, Lung Vessels and Lung PBV shows improved capability to detect peripheral PE.

Dual-Energy Computed Tomographic Pulmonary Angiography

The aim of this study was to assess if dual-energy computed tomographic pulmonary angiography (DE-CTPA) protocol performed on a dual-source CT scanner can improve image quality and diagnostic confidence compared with 80- and 140-kilovolt (peak) (kVp) image data sets. In an international review board-approved study, 22 patients (women-men, 12:10; mean [SD] age, 58.5 [16.5] years; age range, 18-85 years) underwent DE-CTPA on a dual-source CT for assessing pulmonary embolism. Scan parameters comprised reference milliampere-second of 140 at 140 kVp and 400 at 80 kVp with a pitch of 1.1- and 1.25-mm reconstructed slice thicknesses, respectively. Two radiologists analyzed the 140-kV, 80-kV, and dual-kilovolt images for vessel contrast, subjective image noise, presence of motion, artifacts, and diagnostic confidence at the level of main, lobar, and segmental or subsegmental pulmonary arteries on a 5-point scale (1, uninterpretable; 5, excellent). Computed tomographic numbers and objective noise were measured in these arteries. Data were analyzed using Student t test, Friedman chi2 analysis of variance, and Wilcoxon rank sum test (with Bonferroni correction). At 80 kVp, regardless of motion artifacts, there was a 104% increase in intravascular CT numbers, (mean [SD], 257 [104] Hounsfield units [HU] at 140 kVp and 525 [214] HU at 80 kVp) and 75% increase in objective noise (20 HU at 140 kVp and 35 HU at 80 kVp). Improvement in subjective contrast opacification and CT numbers with 80 kVp compared with 140 kVp was most marked in interlobar, segmental, and subsegmental arteries. Effective radiation dose decrease approximately 28% from a CTDI vol of 26.7 mGy to 20.1 mGy between dual-energy (case) and single-energy (control) groups. In conclusion, DE-CTPA has potential advantages for evaluations of pulmonary embolism and regarding improved image noise, vessel contrast, and diagnostic confidence compared with single higher-kilovolt (peak) protocols.

Detection of pulmonary embolism by dual energy CT: correlation with perfusion scintigraphy and histopathological findings in rabbits

The purpose of the study was to compare the ability of dual energy CT (DECT) and perfusion scintigraphy (PS) to detect pulmonary embolism (PE) in a rabbit model. Gelfoam (n = 20) or saline (n = 4) was injected into the femoral vein of rabbits. After 2 h, DECT pulmonary angiography (CTPA) was used to create blood flow imaging (BFI) and fusion images. The rabbits then underwent PS. Pathological determination of locations and numbers of lung lobes with PE was recorded. The sensitivity and specificity for BFI, CTPA, fused images and PS were calculated using the pathological results as reference standards. Compared with pathological evaluation, CTPA correctly identified PE in 40 lobes and absence of emboli in 80 lobes, corresponding to a sensitivity and specificity of 100%. BFI and fused images correctly identified PE in 40 lobes and the absence of emboli in 78 lobes, corresponding to a sensitivity and specificity of 100% and 98%, respectively. PS correctly detected 27 lobes with PE and 65 lobes without PE, corresponding to a sensitivity and specificity of 68% and 81%, respectively. BFI, CTPA and fused images derived from a single contrast-enhanced DECT provide a higher diagnostic accuracy of detecting PE than PS in a rabbit model.

Dual-Energy CT Pulmonary Angiography: A New Horizon in the Imaging of Acute Pulmonary Thromboembolism

Dual-Energy CT Pulmonary Angiography: A New Horizon in the Imaging of Acute Pulmonary ThromboembolismEdward T. D. Hoey, Deepa Gopalan and Nicholas J. ScreatonAudio Available | Share

Dual-energy CT pulmonary angiography: a novel technique for assessing acute and chronic pulmonary thromboembolism

Dual-energy computed tomography (DECT) involves the acquisition of CT datasets using two different photon spectra. Recent advances in CT technology, particularly the introduction of dualsource CT systems, have led to renewed interest in the application of DECT techniques. A dual-source CT system (Somatom Definition, Siemens Medical Solutions, Forchheim, Germany) has two x-ray tubes and two detectors that are mounted on the gantry at a 90 angular offset. The tubes can be operated at identical kilovoltage exposures to provide high temporal resolution (83 ms) for cardiac imaging or alternatively, they can be operated at two different energies. Hounsfield unit values for low atomic number materials (such as soft tissues) do not vary much with the kilovoltage exposure; however, materials with high atomic numbers, such as iodine, exhibit very differing degrees of attenuation at 80 kV compared with 140 kV. This effect can be exploited to obtain spectral information and differentiate iodine from other materials by acquiring datasets at two different energy levels. The ability of a dual-source system to simultaneously acquire two spiral acquisitions during the same phase of contrast enhancement excludes temporal changes in enhancement between acquisitions and spatial misregistration, which are the major limiting factors when attempting to apply this technique using a single-source system.