Focal Iodine Defects on Color-Coded Iodine Perfusion Maps of Dual-Energy Pulmonary CT Angiography Images: A Potential Diagnostic Pitfall
ABSTRACT 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.
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ABSTRACT: The purpose of this study was to evaluate the feasibility and diagnostic utility of lung perfused blood volume (LPBV) images generated by dual-energy computed tomography (CT), as compared with pulmonary perfusion scintigraphy, for patients with chronic thromboembolic pulmonary hypertension. Patients (n = 51) with chronic pulmonary thromboembolic embolism were examined by dual-source CT in dual-energy mode. Lung perfused blood volume images were generated by analysis of the iodine content of the lung parenchyma using dual-energy data. Pulmonary perfusion defects were evaluated on a segment-by-segment basis in images obtained by both LPBV and pulmonary scintigraphy. Findings suggestive of chronic thromboembolic pulmonary hypertension in CT pulmonary angiography were analyzed. All examinations were acquired without complications, and the contrast enhancement of the pulmonary artery was sufficient for diagnosis of vascular thromboses. In the LPBV images, in 76 (8.3%) of 918 segments, it was difficult to assess perfusion because of artifacts. The agreement between the 2 modalities was good (κ = 0.70). The sensitivity of LPBV in detecting perfusion defects was 96%; the specificity was 76%; the positive predictive value was 94%, and the negative predictive value was 29%. Lung perfused blood volume imaging by dual-energy CT is feasible for the evaluation of pulmonary perfusion and is comparable to pulmonary scintigraphy. It is possible to evaluate vessels and pulmonary perfusion with CT pulmonary angiography and LPBV images and to assess pulmonary perfusion more definitively in diagnosing chronic pulmonary thromboembolic embolism.Journal of computer assisted tomography 09/2011; 35(5):590-5. DOI:10.1097/RCT.0b013e318224e227 · 1.60 Impact Factor
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ABSTRACT: In morbidly obese patients, computed tomography frequently represents the only viable option for non-invasive imaging diagnostics. The aim of this study was to analyze the weight limits, dose and image quality with standard CT scanners and to determine the diagnostic value and dose with a dual source XXL mode.A total of 15 patients (average body weight 189.6 ± 42 kg) were retrospectively identified who had been examined with the XXL mode. Of these patients 7 (average body weight 176.4 ± 56 kg) had been examined using both the XXL and standard protocols allowing for an intraindividual comparison in this subcollective. Additionally 14 patients weighing between 90 and 150 kg (average 106.1 ± 19 kg) examined with standard protocols were included as references. Dose, image noise and subjectively assessed image quality (rating scale 1-4) were determined. Additionally, a large abdomen phantom of 48 cm diameter was examined with both protocols at equivalent tube current-time product in order to compare the dose efficiency.The patient groups differed significantly in dose (CTDI(vol) XXL 72.9 ± 23 versus standard 16.7 ± 11 mGy; intraindividual 64.1 ± 20 versus 27.0 ± 15 mGy). The image noise was generally somewhat higher in the XXL group but significantly lower in the intraindividual comparison (liver 24.2 ± 14 HU versus 36.3 ± 20 HU; p = 0.03; fat 15.5 ± 8 HU versus 26.2 ± 12 HU; p=0.02). With ratings of 1.9 ± 0.7 and 1.8 ± 0.7 image quality did not differ significantly in general, whereas there was a clear difference in the intraindividual comparison (1.8 ± 0.8 versus 3.0 ± 1.2) and only the XXL protocol achieved diagnostic quality in all cases, while 43% of the examinations with the standard protocol were rated as non-diagnostic. The quantification of dose efficiency in the phantom scans yielded no significant difference between the protocols.Up to 150 kg body weight, CT can be performed with the standard technique at 120 kVp with tube current modulation. In larger patients diagnostic image quality can only be achieved reliably with the dual source XXL mode, although at considerably increased calculated dose. However, standard conversion factors yield false high values so that the estimation of the biologically relevant equivalent dose is very difficult.Der Radiologe 03/2011; 51(5):366-71. · 0.41 Impact Factor
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ABSTRACT: Dual-energy dual source CT can almost simultaneously image patients using two different tube potentials, allowing material decomposition and creation of 'virtual unenhanced' (VU) images from post-contrast series. 75 patients undergoing triple-phase liver CT examinations were imaged using a second generation dual-source CT machine with tube potentials 140/100 kVp. Post-processing VU series were derived from arterial and portal phases. Regions-of-interest from liver parenchyma and within fat ('noise' assessment) were drawn to compare VU series to conventional unenhanced (CU) series. Subjective analysis assessed image quality and the suitability of VU to replace CU series. Mean Hounsfield unit (HU) values of liver were higher in the VU series: portal 51.9 (SD = 10.29), arterial 51.1 (SD = 10.05), compared to the CU series 49.2 (SD = 9.11); P<0.001. However, Pearson's correlation of the VU and CU series remained excellent: 0.838 (portal), 0.831 (arterial). Bland-Altman plots also showed good agreement between both VU and the CU datasets. Noise measurements were significantly lower in both VU series (P<0.001). For subjective analysis, image quality was rated as very good/excellent in 100% of CU images, 93.3% of portal VU and 88.7% of arterial VU series. Overall, portal VU and arterial VU images were acceptable replacements for the CU series in 97.4% and 96.1%, respectively. Post-processing was noted to create a number of artefacts in VU images--knowledge of these is essential for interpretation. Portal and arterial-derived VU images objectively correlate to CU images and demonstrate good image quality and acceptability. VU image sets could replace the conventional unenhanced images in the vast majority of cases, significantly reducing radiation dose.European journal of radiology 04/2011; 81(7):1438-45. DOI:10.1016/j.ejrad.2011.03.042 · 2.16 Impact Factor