Differences In Contrast Enhancement Research Articles

1.5 Harmonic Imaging Sonography with microbubble contrast agent improves characterization of hepatocellular carcinoma

To investigate the usefulness of 1.5 Harmonic Imaging Sonography with the use of the contrast agent Levovist for the diagnosis of hepatocellular carcinoma (HCC) and for the evaluation of therapeutic response. Phantom experiments were performed to compare the contrast effects of 2(nd) harmonic imaging and 1.5 Harmonic Imaging Sonography. 1.5 Harmonic Imaging Sonography was employed to examine 36 patients with HCC (42 nodules) before and after the treatment and to compare against the findings obtained using other diagnostic imaging modalities. In 1.5 Harmonic Imaging Sonography, the tumor vessels of HCCs were clearly identified during the early phase, and late-phase images clearly demonstrated the differences in contrast enhancement between the tumor and surrounding hepatic parenchyma. Blood flow within the tumor was detected in 36 nodules (85.7%) during the early phase and in all 42 nodules (100%) during the late phase using 1.5 Harmonic Imaging Sonography, in 38 nodules (90.5%) using contrast-enhanced CT, in 34 nodules (81.0%) using digital subtraction angiography (DSA), and in 42 nodules (100%) using US CO(2) angiography. Following transcatheter arterial embolization, 1.5 Harmonic Imaging Sonography detected blood flow and contrast enhancement within the tumors that were judged to contain viable tissue in 20 of 42 nodules (47.6%). However, 6 of these 10 cases were not judged in contrast-enhanced CT. 1.5 Harmonic Imaging Sonography was compared with the US CO(2) angiography findings as the gold standard, and the sensitivity and specificity of these images for discerning viable and nonviable HCC after transcatheter arterial embolization were 100% and 100%, respectively. 1.5 Harmonic Imaging Sonography permits the vascular structures of HCCs to be identified and blood flow within the tumor to be clearly demonstrated. Furthermore, 1.5 Harmonic Imaging Sonography is potentially useful for evaluating the therapeutic effects of transcatheter arterial embolization on HCC.

Microbubble responses to a similar mechanical index with different real-time perfusion imaging techniques.

The purpose of this study was to determine differences in contrast enhancement and microbubble destruction rates with current commercially available low-mechanical index (MI) real-time perfusion imaging modalities. A tissue-mimicking phantom was developed that had vessels at 3 cm (near field) and 9 cm (far field) from a real-time transducer. Perfluorocarbon-exposed sonicated dextrose albumin microbubbles (PESDA) were injected proximal to a mixing chamber, and then passed through these vessels while the region was insonified with either pulses of alternating polarity with pulse inversion Doppler (PID) or pulses of alternating amplitude by power modulation (PM) at MIs of 0.1, 0.2 and 0.3. Effluent microbubble concentration, contrast intensity and the slope of digital contrast intensity vs. time were measured. Our results demonstrated that microbubble destruction already occurs with PID at an MI of 0.1. Contrast intensity seen with PID was less than with PM. Therefore, differences in contrast enhancement and microbubble destruction rates occur at a similar MI setting when using different real-time pulse sequence schemes.

Cervical carcinoma: standard and pharmacokinetic analysis of time-intensity curves for assessment of tumor angiogenesis and patient survival.

Since detailed knowledge regarding the pathophysiological properties which in turn are responsible for differences in contrast enhancement--remain fairly undetermined, it was the aim of this study (i) to examine the association of standard and pharmacokinetic analysis of time-intensity curves in dynamic MRI with histomorphological markers of tumor angiogenesis (microvessel density [MVD]; vascular endothelial growth factor [VEGF]); and (ii) to determine the ultimate value of a histomorphological and a dynamic MRI approach by correlation of those data with disease outcome in patients with primary cancer of the uterine cervix. Pharmacokinetic parameters (amplitude A, exchange rate constant k21) and standard parameters (maximum signal intensity (SI)-increase [SI-I] over baseline and steepest SI-upslope per second [SI-U/s]) were calculated from contrast-enhanced dynamic MR imaging series in 37 patients with biopsy-proven primary cervical cancer. On the surgical whole mount specimens, histomorphological markers of tumor angiogenesis (MVD, VEGF) were compared with similar sized and positioned regions-of-interest (ROIs) on the MRI-derived parameters. For MRI and histomorphological data, Kaplan-Meier survival curves were calculated and compared using log-rank statistics. A significant association was found between MVD and amplitude A (P < 0.01) and SI-I (P < 0.05). No significant relationships were observed between the VEGF expression and all dynamic MRI parameters. Kaplan-Meier curves based on k21 and SI-U/s showed that tumors with high k21 and SI-U/s values had a significantly (P < 0.05, 0.001, respectively) worse disease outcome than tumors with low k2, and SI-U/s values. None of the histomorphological gold standard markers for assessing tumor angiogenesis (MVD, VEGF) had any significant power to predict patient survival. It is concluded that (1) the pathophysiological basis for differences in dynamic MRI is MVD but not VEGF-expression; (2) a functional, dynamic MRI approach (both standard and a pharmacokinetic analysis) may be better suited to assess angiogenic activity in terms of patient survival than current histomorphological-based markers of tumor angiogenesis; and [3] compared with standard analysis, a simple pharmacokinetic analysis of time-intensity curves is not superior to assess MVD or patient survival.

Pancreatic-phase versus portal vein-phase helical CT of the pancreas: optimal temporal window for evaluation of pancreatic adenocarcinoma.

Our objective was to use helical CT to compare the enhancement attenuation values of pancreatic adenocarcinoma, adjacent normal pancreas, and critical vascular structures during the pancreatic phase and portal vein phase. Forty-one patients with pathologically proven pancreatic adenocarcinoma underwent dual-phase thin-section dynamic helical CT using a pancreatic-phase and portal vein-phase protocol. The scan delay after initiation of the contrast bolus was 40 sec for the pancreatic phase and 70 sec for the portal vein phase. Attenuation values after i.v. contrast administration were calculated during both phases of scanning for normal pancreas, pancreatic tumor, celiac axis, superior mesenteric artery, superior mesenteric vein, splenic vein, and portal vein. Quantitative values were assessed using regions of interest. Mean differences of enhancement between tumor and normal pancreas were significantly greater in the pancreatic phase (57 H) than the portal vein phase (35 H) (p = .0001). Enhancement values of all the critical vascular structures were also significantly greater in the pancreatic phase than the portal vein phase (p < .001). With dynamic thin-section helical CT, pancreatic-phase scanning provides greater differences in contrast enhancement between normal pancreas and pancreatic tumor and between pancreatic tumors and surrounding critical vascular structures than does portal vein-phase scanning.

Cervical carcinoma: standard and pharmacokinetic analysis of time–intensity curves for assessment of tumor angiogenesis and patient survival

Since detailed knowledge regarding the pathophysiological properties—which in turn are responsible for differences in contrast enhancement—remain fairly undetermined, it was the aim of this study (i) to examine the association of standard and pharmacokinetic analysis of time–intensity curves in dynamic MRI with histomorphological markers of tumor angiogenesis (microvessel density [MVD]; vascular endothelial growth factor [VEGF]); and (ii) to determine the ultimate value of a histomorphological and a dynamic MRI approach by correlation of those data with disease outcome in patients with primary cancer of the uterine cervix. Pharmacokinetic parameters (amplitude A, exchange rate constant k21) and standard parameters (maximum signal intensity (SI)-increase [SI–I] over baseline and steepest SI-upslope per second [SI-U/s]) were calculated from contrast-enhanced dynamic MR imaging series in 37 patients with biopsy-proven primary cervical cancer. On the surgical whole mount specimens, histomorphological markers of tumor angiogenesis (MVD, VEGF) were compared with similar sized and positioned regions-of-interest (ROIs) on the MRI-derived parameters. For MRI and histomorphological data, Kaplan–Meier survival curves were calculated and compared using log-rank statistics. A significant association was found between MVD and amplitude A (P<0.01) and SI-I (P<0.05). No significant relationships were observed between the VEGF expression and all dynamic MRI parameters. Kaplan–Meier curves based on k21and SI-U/s showed that tumors with high k21 and SI-U/s values had a significantly (P<0.05, 0.001, respectively) worse disease outcome than tumors with low k21 and SI-U/s values. None of the histomorphological gold standard markers for assessing tumor angiogenesis (MVD, VEGF) had any significant power to predict patient survival. It is concluded that (1) the pathophysiological basis for differences in dynamic MRI is MVD but not VEGF-expression; (2) a functional, dynamic MRI approach (both standard and a pharmacokinetic analysis) may be better suited to assess angiogenic activity in terms of patient survival than current histomorphological-based markers of tumor angiogenesis; and [3] compared with standard analysis, a simple pharmacokinetic analysis of time–intensity curves is not superior to assess MVD or patient survival.

Hepatic spiral CT: reduction of dose of intravenous contrast material.

To assess the potential for reduction of contrast material dose in hepatic spiral computed tomography (CT). Four hundred eighty-seven outpatients were randomized prospectively into nine biphasic and eight uniphasic injection protocols: 75, 100, or 125 mL of 240, 300, or 350 mg of iodine per milliliter of iohexol (18-44 grams of iodine). Protocols were compared according to the maximum hepatic enhancement (MAX) and the contrast enhancement index (CEI). Uniphasic injection was superior to biphasic injection for all protocols. No statistically significant difference in contrast enhancement was present for 38-44 grams of iodine with the uniphasic technique. Adequate enhancement thresholds (MAX > 50 HU, CEI at 30 HU > 300 HU x sec) were exceeded in more than 70% of heavy patients ( > 183 lb [83 kg]) with uniphasic injection of 38 g. For thin patients ( < 183 lb [83 kg]), uniphasic injection of 26 g produced adequate enhancement. Contrast material dose may be reduced by up to 40% in thin patients undergoing hepatic spiral CT after uniphasic injection of contrast material; this may result in substantial cost savings.

Evaluation of solitary pulmonary nodules with dynamic contrast-enhanced MR imaging--a promising technique.

The evaluation of a solitary pulmonary nodule (SPN) is one of the most frequently encountered challenges in thoracic radiology. In addition to a "state-of-the-art" evaluation of SPNs with CT and biopsy techniques, recently the assessment of the enhancement characteristics with iodinized contrast agents has shown its potential to improve the characterization of SPNs. We investigated whether dynamic contrast-enhanced MRI is suitable to assess the degree and kinetics of MR contrast enhancement and whether this technique could help in the noninvasive specification of SPNs. We studied prospectively 21 patients with SPNs. T1-weighted and proton density-weighted spoiled gradient-echo breath-hold images (2D-FLASH) were obtained before and after the administration of Gd-DTPA in a standard dosage of 0.1 mmol/kg body weight. The maximum enhancement and the initial velocity of contrast uptake were assessed and correlated with pathohistological findings. To quantify contrast enhancement, we used the relative signal intensity increase (S(rel)) and the recently introduced enhancement factor (EF) and contrast uptake equivalent (CE). Dynamic contrast-enhanced MRI proved to be well suited for the assessment of the contrast enhancement characteristics of SPNs. Significant differences were found in the degree and kinetics of contrast enhancement for specific types of nodules. Malignant neoplastic SPNs enhanced stronger and faster than benign neoplastic SPNs. The strongest and fastest enhancement, however, was found in a benign type of nodules where histology revealed inflammatory/fibrous lesions. These differences in contrast enhancement between the different pathohistological groups were more significant when EF and CE rather than S(rel) was used for the quantification of contrast enhancement. The results of this study indicate a potential role for dynamic contrast-enhanced MRI in the preoperative noninvasive evaluation of SPNs using EF and CE as contrast uptake assessment parameters.

Optimizing CT portography: a prospective comparison of injection into the splenic versus superior mesenteric artery.

To evaluate whether computed tomographic arterial portography (CTAP) is best performed with injections in the superior mesenteric artery (SMA) or the splenic artery. Seventy-one studies were performed with injection into the SMA (n = 37) or splenic artery (n = 34) of 150 mL of contrast material at 1.5 mL/sec and 20-second delay for both groups. Images were reviewed for location and type of nontumoral perfusion abnormalities. The degree of liver parenchymal enhancement with each technique was compared. Fewer nontumoral perfusion defects were seen with splenic artery (65%) versus SMA (78%) injection. Visual differences in contrast enhancement with greater attenuation in dependent portions of the liver were seen with greater frequency with SMA (41%) than with splenic artery (24%) injection. Contrast enhancement that obscured detail in the right lobe was seen only with SMA injections (16%). Greater parenchymal enhancement (up to 18 HU) at all time intervals was seen with splenic artery injection. Because of greater parenchymal enhancement and fewer nontumoral perfusion abnormalities, splenic artery catheterization is the preferred technique for CTAP.

Differences in contrast enhancement between intra- and extra-axial lesions after two hours of iodine injection.

In order to try to improve discrimination between the brain lesions that produce damage to the brain-blood barrier and those which are irrigated by extracerebral vessels, the behavior of contrast enhancement up to two hours after iodine injection was studied in two groups of patients. Eight patients had extra-axial lesions (7 meningiomas, one acoustic neuroma) and eleven had intra-axial lesions (6 of astrocytic type, 3 metastases, 2 inflammatory). In the first group, mean values of the lesioned areas in HU decreased progressively with time. However, in many cases in the second group the values at the end of the study were equal to or higher than those observed immediately after contrast medium injection. Highly significant differences were observed between the two groups. The contrast medium in the intra-axial lesions conform to the behavior of all other fluids in a damaged barrier, remaining for a very long time in the interstitial space. In the extra-axial lesions, the contrast moved freely and the return from the interstitial to the intravascular space was also unobstructed, since values decayed immediately after injection. For these reasons, the observation of scans after two hours of contrast injection might be useful for differential diagnosis in those cases where doubt exists.

Contrast-Enhanced Computed Tomography in Carcinoma of the Urinary Bladder

Computed tomography (CT) scans of the urinary bladder were taken before and in combination with intravenous contrast medium injection in 30 patients with invasive bladder carcinoma. Three different ways of injecting the same amount of intravenous contrast material were used in three groups, each consisting of ten patients. In the first group the contrast medium was given during 90 seconds, in the second group during 40 seconds and in the third one, the first half during 20 seconds and the second half during 90 seconds. The attenuation in the tumors and in the bladder wall was measured in Hounsfield units. Independent of injection method, all tumors showed significantly higher contrast enhancement than the bladder wall when the injection was terminated. The difference in contrast enhancement was greatest in the group where the shortest injection time was used and greatest immediately after the conclusion of the injection. The difference in contrast enhancement between tumor and bladder wall was visible on ...

Contrast-Enhanced Computed Tomography in Carcinoma of the Urinary Bladder

Computed tomography (CT) scans of the urinary bladder were taken before and in combination with intravenous contrast medium injection in 30 patients with invasive bladder carcinoma. Three different ways of injecting the same amount of intravenous contrast material were used in three groups, each consisting of ten patients. In the first group the contrast medium was given during 90 seconds, in the second group during 40 seconds and in the third one, the first half during 20 seconds and the second half during 90 seconds. The attenuation in the tumors and in the bladder wall was measured in Hounsfield units. Independent of injection method, all tumors showed significantly higher contrast enhancement than the bladder wall when the injection was terminated. The difference in contrast enhancement was greatest in the group where the shortest injection time was used and greatest immediately after the conclusion of the injection. The difference in contrast enhancement between tumor and bladder wall was visible on the monitor in all cases.

PHARMACOKINETICS OF NEWER CONTRAST MEDIA IN CT SCANNING

A new non-ionic contrast medium lopamidol and a new monoacidic dimer Hexabrix (meglumine/sodium Ioxaglate) were compared to meglumine/sodium diatrizoate in patient's undergoing CT scanning. Utilizing a Sieman's Somatome, 4 second CT scanner, blood and tissue enhancement was measured in humans after a rapid intravenous bolus injection. CT scans were obtained at the end of the injection, 1,2, 3,5, and 15 minutes after injection. CT numbers were measured in the aorta, liver, spleen, and kidney periphery. In the first minute after injection, both Hexabrix and Iopamidol showed a higher blood level of iodine in the aorta. The contrast enhancement measured in the liver, spleen and kidney periphery were slightly higher within the first minute with the two new contrast media as compared to diatrizoate. After the first minute, and after equilbration of contrast media with the extracellular space, no significantly measurable difference in contrast enhancement was found in the aorta, spleen or liver. The contrast enhancement within the kidney continued to be higher with the two new contrast media, probably due to the higher tubular iodine concentrations. We postulate that the higher contrast enhancement within the first minute after rapid bolus intravenous injection may be due to a slower dilution of the contrast bolus due to the lower osmolality of the new contrast media. Because of the transiently higher blood level of iodine within the first minute after intravenous bolus injection, Iopamidol and Hexabrix may have advantages over currently available contrast media in dynamic CT scanning. After the first minute, however, the contrast enhancement of the organs studied were not significantly different than that of diatrizoate and would probably have no significance in the clinical setting during non-dynamic CT scanning. These agents may have advantages during renal CT scanning because of the higher urinary iodine concentrations obtained with these agents. Because of reduced side effects, these newer contrast media are desirable.

Contrast Enhancement

Contrast enhancement attenuation units were calculated from 13 tissues and organs of 20 rats at five different times after bolus 125I-diatrizoate administration. Percent distribution volume of diatrizoate was calculated from these results. The statistical significance of differences in contrast enhancement between each of 72 tissue pairs was determined at each of the five times. A similar treatment of percent distribution volume for 60 tissue pairs was determined. The time elapsed after contrast medium injection appears to be of pivotal importance in contrast enhancement diagnosis. Calculation of percent contrast distribution volume is of potential diagnostic importance, since it reveals contrast medium behavior not evident from a visual perusal of scans. The above methods can be readily adapted to computed tomography scanning.