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Gadolinium as a CT Contrast Agent: Assessment in a Porcine Model

¹ Mallinckrodt Institute of Radiology, Washington University School of Medicine, Barnes-Jewish Hospital, 216 S Kingshighway Blvd, St Louis, MO 63110.

View larger version (23K): [in a new window]   Figure 1. Graph of gadodiamide and ioversol concentrations plotted against attenuation shows that at the manufactured concentrations, gadodiamide produces less attenuation. However, note that an iodine concentration equimolar to the gadolinium concentration in undiluted gadodiamide (0.5 mol/L = 64 mg of iodine per milliliter = ioversol dilution factor of 0.20) produces lower attenuation (1,907 HU) than undiluted gadodiamide (3,069 HU). The lines are regression lines. For ioversol, the slope is 8,971 HU (28 HU per mg of iodine per milliliter), and the y intercept is 113 HU. For gadodiamide, the slope is 2,972 HU (38 HU per milligram of gadolinium per milliliter), and the y intercept is 97 HU. Because the maximum scanner attenuation measurement could not exceed 3,071 HU, ioversol concentrations greater than a 0.3 dilution were not included in the regression analysis.

View larger version (119K): [in a new window]   Figure 2a. Peak enhancement at the three levels studied. (a) Intense enhancement is seen in the lower lobe pulmonary arteries (solid arrows), aorta (arrowhead), inferior vena cava (open arrow), atrium (a), and ventricle (v) on this CT scan obtained 18 seconds after the start of injection in pig 2. Enhancement in the pulmonary arteries is 227 HU. Enhancement in the aorta is 146 HU, which is lower than the peak aortic enhancement of 192 HU measured at this level 6 seconds later. (b) Enhancing hepatic parenchyma and vessels can be distinguished on this CT scan obtained in pig 3 at the time of peak hepatic enhancement, which occurred 57 seconds after the start of injection and was 23 HU. Aortic enhancement (small solid arrow) on this image is 30 HU; peak aortic enhancement had occurred at 21 seconds and was 134 HU. Also, note the visible enhancement of the stomach (S) wall. L = liver, large solid arrow = main portal vein, open arrow = inferior vena cava, arrowheads = enhancing hepatic vessels. (c) CT scan obtained in pig 3 at 32 seconds after the start of injection through the kidneys shows the peak enhancement of the renal parenchyma (small arrowheads), which is 63 HU. Enhancement of the aorta (solid arrow) is 78 HU, a decrease from the peak aortic enhancement of 134 HU at 21 seconds. The enhancing left renal vein (open arrow) emptying into the inferior vena cava is also seen. Note the enhancing mesenteric vessels (large arrowheads).

View larger version (115K): [in a new window]   Figure 2b. Peak enhancement at the three levels studied. (a) Intense enhancement is seen in the lower lobe pulmonary arteries (solid arrows), aorta (arrowhead), inferior vena cava (open arrow), atrium (a), and ventricle (v) on this CT scan obtained 18 seconds after the start of injection in pig 2. Enhancement in the pulmonary arteries is 227 HU. Enhancement in the aorta is 146 HU, which is lower than the peak aortic enhancement of 192 HU measured at this level 6 seconds later. (b) Enhancing hepatic parenchyma and vessels can be distinguished on this CT scan obtained in pig 3 at the time of peak hepatic enhancement, which occurred 57 seconds after the start of injection and was 23 HU. Aortic enhancement (small solid arrow) on this image is 30 HU; peak aortic enhancement had occurred at 21 seconds and was 134 HU. Also, note the visible enhancement of the stomach (S) wall. L = liver, large solid arrow = main portal vein, open arrow = inferior vena cava, arrowheads = enhancing hepatic vessels. (c) CT scan obtained in pig 3 at 32 seconds after the start of injection through the kidneys shows the peak enhancement of the renal parenchyma (small arrowheads), which is 63 HU. Enhancement of the aorta (solid arrow) is 78 HU, a decrease from the peak aortic enhancement of 134 HU at 21 seconds. The enhancing left renal vein (open arrow) emptying into the inferior vena cava is also seen. Note the enhancing mesenteric vessels (large arrowheads).

View larger version (121K): [in a new window]   Figure 2c. Peak enhancement at the three levels studied. (a) Intense enhancement is seen in the lower lobe pulmonary arteries (solid arrows), aorta (arrowhead), inferior vena cava (open arrow), atrium (a), and ventricle (v) on this CT scan obtained 18 seconds after the start of injection in pig 2. Enhancement in the pulmonary arteries is 227 HU. Enhancement in the aorta is 146 HU, which is lower than the peak aortic enhancement of 192 HU measured at this level 6 seconds later. (b) Enhancing hepatic parenchyma and vessels can be distinguished on this CT scan obtained in pig 3 at the time of peak hepatic enhancement, which occurred 57 seconds after the start of injection and was 23 HU. Aortic enhancement (small solid arrow) on this image is 30 HU; peak aortic enhancement had occurred at 21 seconds and was 134 HU. Also, note the visible enhancement of the stomach (S) wall. L = liver, large solid arrow = main portal vein, open arrow = inferior vena cava, arrowheads = enhancing hepatic vessels. (c) CT scan obtained in pig 3 at 32 seconds after the start of injection through the kidneys shows the peak enhancement of the renal parenchyma (small arrowheads), which is 63 HU. Enhancement of the aorta (solid arrow) is 78 HU, a decrease from the peak aortic enhancement of 134 HU at 21 seconds. The enhancing left renal vein (open arrow) emptying into the inferior vena cava is also seen. Note the enhancing mesenteric vessels (large arrowheads).

View larger version (28K): [in a new window]   Figure 3. Graph shows time-enhancement curves obtained by using data from pig 3. Enhancement peaks first in the pulmonary arteries and shortly thereafter in the aorta, then in the kidneys, and then in the liver. Enhancement in the pulmonary arteries and aorta of more than 75 HU above baseline and more than 40 HU above equilibrium levels persists for 20-30 seconds.