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Cardiac MRI is a noninvasive diagnostic tool using nonionizing radiation that is widely used in patients with ST-segment elevation myocardial infarction (STEMI). Cardiac MRI depicts different prognosticating components of myocardial damage such as edema, intramyocardial hemorrhage (IMH), microvascular obstruction (MVO), and fibrosis. But how do cardiac MRI findings correlate to histologic findings? Shortly after STEMI, T2-weighted imaging and T2* mapping cardiac MRI depict, respectively, edema and IMH. The acute infarct size can be determined with late gadolinium enhancement (LGE) cardiac MRI. T2-weighted MRI should not be used for area-at-risk delineation because T2 values change dynamically over the first few days after STEMI and the severity of T2 abnormalities can be modulated with treatment. Furthermore, LGE cardiac MRI is the most accurate method to visualize MVO, which is characterized by hemorrhage, microvascular injury, and necrosis in histologic samples. In the chronic setting post-STEMI, LGE cardiac MRI is best used to detect replacement fibrosis (ie, final infarct size after injury healing). Finally, native T1 mapping has recently emerged as a contrast material-free method to measure infarct size that, however, remains inferior to LGE cardiac MRI. Especially LGE cardiac MRI-defined infarct size and the presence and extent of MVO may be used to monitor the effect of new therapeutic interventions in the treatment of reperfusion injury and infarct size reduction. (C) RSNA, 2021

Item does not contain fulltext Cardiac MRI is a noninvasive diagnostic tool using nonionizing radiation that is widely used in patients with ST-segment elevation myocardial infarction (STEMI). Cardiac MRI depicts different prognosticating components of myocardial damage such as edema, intramyocardial hemorrhage (IMH), microvascular obstruction (MVO), and fibrosis. But how do cardiac MRI findings correlate to histologic findings? Shortly after STEMI, T2-weighted imaging and T2* mapping cardiac MRI depict, respectively, edema and IMH. The acute infarct size can be determined with late gadolinium enhancement (LGE) cardiac MRI. T2-weighted MRI should not be used for area-at-risk delineation because T2 values change dynamically over the first few days after STEMI and the severity of T2 abnormalities can be modulated with treatment. Furthermore, LGE cardiac MRI is the most accurate method to visualize MVO, which is characterized by hemorrhage, microvascular injury, and necrosis in histologic samples. In the chronic setting post-STEMI, LGE cardiac MRI is best used to detect replacement fibrosis (ie, final infarct size after injury healing). Finally, native T1 mapping has recently emerged as a contrast material-free method to measure infarct size that, however, remains inferior to LGE cardiac MRI. Especially LGE cardiac MRI-defined infarct size and the presence and extent of MVO may be used to monitor the effect of new therapeutic interventions in the treatment of reperfusion injury and infarct size reduction. © RSNA, 2021 Online supplemental material is available for this article.

History An 8-year-old girl presented to our hospital with painful swelling of the left thigh and soft-tissue swelling in the right chest wall. The patient's history revealed that the swelling had been present since birth but had grown slowly. She had no history of relevant trauma. Her blood pressure was 145/95 mmHg (normal value

Background The American College of Radiology Dose Index Registry for CT enables evaluation of radiation dose as a function of patient characteristics and examination type. The hypothesis of this study was that academic pediatric CT facilities have optimized CT protocols that may result in a lower and less variable radiation dose in children. Materials and Methods A retrospective study of doses (mean patient age, 12 years; age range, 0-21 years) was performed by using data from the National Radiology Data Registry (year range, 2016-2017) (n = 239 622). Three examination types were evaluated: brain without contrast enhancement, chest without contrast enhancement, and abdomen-pelvis with intravenous contrast enhancement. Three dose indexes-volume CT dose index (CTDIvol), size-specific dose estimate (SSDE), and dose-length product (DLP)-were analyzed by using six different size groups. The unequal variance t test and the F test were used to compare mean dose and variances, respectively, at academic pediatric facilities with those at other facility types for each size category. The Bonferroni-Holm correction factor was applied to account for the multiple comparisons. Results Pediatric radiation dose in academic pediatric facilities was significantly lower, with smaller variance for all brain, 42 of 54 (78%) chest, and 48 of 54 (89%) abdomen-pelvis examinations across all six size groups, three dose descriptors, and when compared with that at the other three facilities. For example, abdomen-pelvis SSDE for the 14.5-18-cm size group was 3.6, 5.4, 5.5, and 8.3 mGy, respectively, for academic pediatric, nonacademic pediatric, academic adult, and nonacademic adult facilities (SSDE mean and variance P < .001). Mean SSDE for the smallest patients in nonacademic adult facilities was 51% (6.1 vs 11.9 mGy) of the facility's adult dose. Conclusion Academic pediatric facilities use lower CT radiation dose with less variation than do nonacademic pediatric or adult facilities for all brain examinations and for the majority of chest and abdomen-pelvis examinations. © RSNA, 2019 See also the editorial by Strouse in this issue.

To study T1 baseline signal intensity (SI) and contrast material enhancement kinetics of normal breast parenchyma by using dynamic contrast-enhanced (DCE) magnetic resonance (MR) mammography and to determine the influence of anthropometric measures and menopausal status on the variability of these features.Institutional review board approval and written informed consent were obtained. Between June 2008 and September 2011, 345 women (age range, 26-81 years; mean age, 51.3 years ± 11.6 [standard deviation]) underwent DCE MR mammography, with T1-weighted three-dimensional MR images (repetition time msec/echo time msec, 8.86/4.51; flip angle, 25°) acquired with a 1.5-T whole-body MR unit before and 1, 2, 3, 4, and 5 minutes after a gadobutrol bolus injection of 0.1 mmol per kilogram of body weight. Regions of interest were traced manually, and T1 SI of parenchyma was recorded. The influence of different predictors of T1 baseline SI and contrast enhancement was studied by using random-effects models.T1 baseline SI varied considerably between women, with a mean of 167.7 ± 49.2 (71.4-424.7 [range]) and 175.9 ± 48.9 (51.8-458.3) in the right and the left breast, respectively (P.01). T1 baseline SI increased linearly with age (P.0001) and body weight (P.0001). After contrast material delivery, relative percentage of enhancement was 8.1%, 13.8%, 18.2%, 22.1%, and 24.6% at 1, 2, 3, 4, and 5 minutes, respectively, but varied considerably between women. Contrast enhancement was 9.3% in the lowest quintile and 47.4% in the highest. Contrast enhancement increased with body weight (P.01) but decreased in postmenopausal women (P.01). Women with higher baseline T1 SI tended to have a higher contrast enhancement slope.Anthropometric measures and menopausal status contribute to a large variability in contrast enhancement of normal breast parenchyma. This might influence the interpretation of contrast enhancement kinetics of breast lesions and current strategies for determining contrast medium dose for breast MR imaging.

The continuing advances in computed tomographic (CT) technology in the past decades have provided ongoing opportunities to improve CT image quality and clinical practice and discover new clinical CT imaging applications. New CT technology, however, has introduced new challenges in clinical radiology practice. One of the challenges is with intravenous contrast medium administration and scan timing. In this article, contrast medium pharmacokinetics and patient, contrast medium, and CT scanning factors associated with contrast enhancement and scan timing are presented and discussed. Published data from clinical studies of contrast medium and physiology are reviewed and interpreted. Computer simulation data are analyzed to provide an in-depth analysis of various factors associated with contrast enhancement and scan timing. On the basis of basic principles and analysis of the factors, clinical considerations and modifications to protocol design that are necessary to optimize contrast enhancement for common clinical CT applications are proposed.

To describe and determine the reproducibility of a simplified model to quantitatively measure heterogeneous intralesion contrast agent diffusion in colorectal liver metastases.This HIPAA-compliant retrospective study received institutional review board approval, and written informed consent was obtained from 14 patients (mean age, 61 years +/- 9 [standard deviation]; range, 41-78 years), including 10 men (mean age, 65 years +/- 8; range, 47-78 years) and four women (mean age, 54 years +/- 9; range, 41-59 years), with colorectal liver metastases. Magnetic resonance (MR) imaging was performed twice (first baseline MR image [B(1)] and second baseline MR image [B(2)]) in a single target lesion prior to therapy. Dynamic contrast material-enhanced MR imaging was performed by using a saturation-recovery fast gradient-echo sequence. A simplified contrast agent diffusion model was proposed, and a contrast agent diffusion coefficient (CDC) was calculated. The reproducibility of the CDC measurement was evaluated by using the Bland-Altman plot and a linear regression model.The mean CDC was 0.22 mm(2)/sec (range, 0.01-0.73 mm(2)/sec) on B(1) and 0.24 mm(2)/sec (range, 0.01-0.71 mm(2)/sec) on B(2), with an intraclass correlation coefficient of 0.91 (P.0001). Bland-Altman plot showed good agreement, with a mean difference in measurement pairs of 0.017 mm(2)/sec +/- 0.096. The slope from the linear regression model was 0.89 (95% confidence interval: 0.63, 1.15) and the intercept was 0.01 (95% confidence interval: -0.08, 0.09).The CDC enables a quantitative description of contrast enhancement heterogeneity in lesions. Given the high reproducibility of the CDC metric, CDC appears promising for further qualification as an imaging biomarker of change measurement in response assessment.http://radiology.rsnajnls.org/cgi/content/full/248/3/901/DC1.

To retrospectively determine and compare the sensitivity and specificity of unenhanced and contrast material-enhanced computed tomography (CT) (reference standard) in the diagnosis of brain abnormalities and to evaluate any change in diagnosis that resulted from the contrast-enhanced study.This study was approved by the local research ethics board; the requirement for informed consent was waived. The authors reviewed the unenhanced and contrast-enhanced CT scans of the brain obtained in 353 children for indications other than trauma. There were 196 boys and 157 girls aged 0 months to 17.8 years. Scans were read independently by two pediatric neuroradiologists who were blinded to clinical information. The diagnosis for each scan was recorded according to the anatomic section (supratentorial, infratentorial, ventricles, and skull). The final diagnosis was classified as normal, abnormal, or equivocal. kappa Statistics, with 95% confidence intervals, were reported, and the sensitivity, specificity, positive predictive value, and negative predictive value were calculated.Interreader agreement for different anatomic regions varied between good (kappa coefficient, 0.63) and very good (kappa coefficient, 0.88) for unenhanced and contrast-enhanced scans. Sensitivity, specificity, positive predictive value, and negative predictive value for unenhanced scans were 97%, 89%, 87%, and 97%, respectively. The use of contrast material led to a change in the original normal or equivocal diagnosis to an abnormal diagnosis for only five (2.7%) of the 183 normal unenhanced scans.Unenhanced CT of developing brains has high sensitivity and specificity in the diagnosis of pathologic findings. The use of intravenous contrast material after unenhanced CT of the brain in children did not change the diagnosis frequently.

To determine whether changes in diffusion and/or contrast enhancement are of prognostic value in the early stage of Legg-Calvé-Perthes disease (LCPD).This study was approved by the institutional review board, and written informed consent was obtained from patient parents. Diffusion and contrast agent-enhanced magnetic resonance (MR) imaging studies were performed in 46 children (37 boys and nine girls; mean age, 7.5 years [age range, 3.3-11.9 years]) with unilateral LCPD at the early stage before development of extensive femoral head deformity. The degree of contrast enhancement was measured on the contrast-enhanced MR images, and the apparent diffusion coefficient (ADC) value was measured on the ADC map at various regions of interest in the proximal femur. The association of the MR imaging parameters that compared the affected side with the contralateral normal side with the femoral head deformity index value above 0.3 at 2 years was investigated.Increased diffusion in the metaphysis (P = .003) and decreased contrast enhancement in the central epiphysis (P = .034) were the significant prognostic indicators of subsequent femoral head deformation. ADC in the metaphysis 45% higher and a contrast enhancement in the central epiphysis 37% lower than those of the contralateral normal side are associated with a nonfavorable prognosis. For diffusion MR imaging, sensitivity was 83% (15 of 18), specificity was 86% (24 of 28), positive predictive value was 79% (15 of 19), negative predictive value was 89% (24 of 27), and accuracy was 85% (39 of 46). For contrast-enhanced MR imaging, sensitivity was 78% (14 of 18), specificity was 64% (18 of 28), positive predictive value was 58% (14 of 24), negative predictive value was 82% (18 of 22), and accuracy was 70% (32 of 46).Diffusion and contrast-enhanced MR imaging are potentially useful to assess risk of later development of femoral head deformity.

To establish a preoperative protocol for ultrasonographically guided percutaneous radiofrequency (RF) ablation of large liver tumors that is based on mathematic models and clinical experience and to evaluate the role of this protocol in RF ablation.A regular prism and a regular polyhedron model were used to develop a preoperative protocol for liver tumor ablation. This protocol enabled the authors to minimize the number of ablation spheres, optimize the overlapping mode, and determine the electrode placement process. One hundred ten patients with 121 liver tumors were treated by using this protocol. Sixty-nine patients had 74 hepatocellular carcinomas (HCCs), and 41 had 47 metastases to the liver (ie, metastatic liver carcinomas [MLCs]). Patients underwent follow-up helical computed tomography (CT) 1 month and every 2-3 months after RF ablation. Ablation was considered a success if no contrast enhancement was detected in the treated area on the CT scan obtained at 1 month.A total of 536 ablations were performed in the 121 tumors. The ablation success rate was 87.6% (106 of 121 tumors); the local recurrence rate, 24.0% (29 of 121 tumors); and the estimated mean recurrence-free survival, 17.1 months. Twenty-five patients underwent 38 re-treatments for local tumor recurrence. Major complications occurred in seven patients. Of these patients, only one, who had a tumor close to the colon, had a colon perforation 1 week after RF and required surgical intervention.The described protocol for treatment of large tumors had a success rate of 87.6% and a local recurrence rate of 24.0%.

Cataloged from PDF version of article. The purpose of this study was to demonstrate the use of a transrectal system that enables precise magnetic resonance (MR) image guidance and monitoring of prostate interventions. The system used a closed-bore 1.5-T MR imaging unit and enables one to take advantage of the higher signal-to-noise ratio achieved with traditional magnet designs, which is crucial for accurate targeting and monitoring of prostate interventions. In the first of the four canine studies, reliable needle placement, with all needles placed within 2 mm of the desired target site, was achieved. In two other studies, MR imaging was used to monitor distribution of injected contrast agent solution (gadopentetate dimeglumine mixed with trypan blue dye) in and around the prostate, thereby confirming that solution had been delivered to the desired tissue and also detecting faulty injections. In the final study, accurate placement and MR imaging of brachytherapy seeds in the prostate were demonstrated. The described system provides a flexible platform for a variety of minimally invasive MR image-guided therapeutic and diagnostic prostate interventions.

Magnetic resonance (MR) images of coronary arteries were acquired with an inversion recovery–prepared technique after intraarterial injection of contrast material in five dogs. Real-time two-dimensional projection images were obtained with a temporal resolution of 3 frames per second. Three-dimensional electrocardiographically triggered high-spatial-resolution images were obtained with a fraction of the contrast agent required for intravenous injections. Background tissues were adequately suppressed in all images. On the basis of this experimental data, the optimal contrast agent concentration for two-dimensional real-time projection imaging was 6%. This preliminary work shows that contrast material–enhanced MR angiography with intraarterial injections is feasible with the proposed techniques. © RSNA, 2002

To establish a quantitative magnetic resonance (MR) imaging contrast enhancement criterion for distinguishing cysts from solid renal lesions.Regions of interest were measured in 74 patients with renal lesions evaluated by means of dynamic contrast material-enhanced MR imaging with serial breath-hold spoiled gradient-echo acquisitions. Sensitivity for renal tumors and specificity for renal cysts were established by using percentage of enhancement thresholds that varied between 5% and 35%.The mean percentage of enhancement at MR imaging for the 50 renal cysts was less than 5%; for the 50 renal tumors, it was 97% or higher. With use of a threshold percentage of enhancement of 15% and results obtained between 2 and 4 minutes after administration of contrast material, all malignancies (sensitivity for tumor, 100%) were diagnosed, and there were 6% or fewer false-positive tumor diagnoses. Lower thresholds resulted in unacceptably high false-positive rates (ie, cysts that appeared to enhance-pseudoenhancement), whereas higher threshold values (20%) resulted in an unacceptably lower sensitivity for tumors.The optimal percentage of enhancement threshold for distinguishing cysts from malignancies with the imaging technique prescribed was 15%, and the optimal timing for measurement was 2-4 minutes after administration of contrast material.

This review recounts the history of brain tumor diagnosis from antiquity to the present and, indirectly, the history of neuroradiology. Imaging of the brain has from the beginning held an enormous interest because of the inherent difficulty of this endeavor due to the presence of the skull. Because of this, most techniques when newly developed have always been used in neuroradiology and, although some have proved to be inappropriate for this purpose, many were easily incorporated into the specialty. The first major advance in modern neuroimaging was contrast agent-enhanced computed tomography, which permitted accurate anatomic localization of brain tumors and, by virtue of contrast enhancement, malignant ones. The most important advances in neuroimaging occurred with the development of magnetic resonance imaging and diffusion-weighted sequences that allowed an indirect estimation of tumor cellularity; this was further refined by the development of perfusion and permeability mapping. From its beginnings with indirect and purely anatomic imaging techniques, neuroradiology now uses a combination of anatomic and physiologic techniques that will play a critical role in biologic tumor imaging and radiologic genomics.

To evaluate the effects of breast compression on breast cancer masses, contrast material enhancement of glandular tissue, and quality of magnetic resonance (MR) images in the identification and characterization of breast lesions.This was a HIPAA-compliant, institutional review board-approved retrospective study, with waiver of informed consent. Images from 300 MR imaging examinations in 149 women (mean age ± standard deviation, 51.5 years ± 10.9; age range, 22-76 years) were evaluated. The women underwent diagnostic MR imaging (no compression) and MR-guided biopsy (with compression) between June 2008 and February 2013. Breast compression was expressed as a percentage relative to the noncompressed breast. Percentage enhancement difference was calculated between noncompressed- and compressed-breast images obtained in early and delayed contrast-enhanced phases. Breast density, lesion type (mass vs non-masslike enhancement [NMLE]), lesion size, percentage compression, and kinetic curve type were evaluated. Linear regression, receiver operating characteristic (ROC) curve analysis, and κ test were performed.Mean percentage compression was 31.3% ± 9.2 (range, 5.8%-53.2%). Percentage enhancement was higher in noncompressed- versus compressed-breast studies in early (146% ± 66 vs 107% ± 42, respectively; P.001) and delayed (158% ± 68 vs 107% ± 42, respectively; P = .1) phases. Among breast lesions, 12% (seven of 59) were significantly smaller when compressed, which led to underestimation of TNM classification (P.001). Breast masses (n = 35) showed significantly higher early percentage enhancement (157% ± 71) than lesions with NMLE (n = 15, 120% ± 40; P = .02) and a percentage enhancement difference (47.5% ± 64 vs 17% ± 28, respectively; P = .023). Kinetic curve performance for identifying invasive cancer decreased after compression (area under ROC curve = 0.53 vs 0.71, respectively; P = .02). Breast compression resulted in complete loss of enhancement of nine of 210 lesions (4%).Breast compression during biopsy affected breast lesion detection, lesion size, and dynamic contrast-enhanced MR imaging interpretation and performance. Limiting the application of breast compression is recommended, except when clinically necessary.

The standardized enhancement value and standardized perfusion value allow comparison between different methods for quantification of contrast enhancement during computed tomography (CT). Standard perfusion values calculated from CT measurements of perfusion within pulmonary nodules compared favorably with those derived from previously reported enhancement data and correlated with standardized uptake values obtained from positron emission tomographic images (r = 0.8, P < .01).

The authors developed a free-breathing black-blood coronary magnetic resonance (MR) angiographic technique with a potential for exclusive visualization of the coronary blood pool. Results with the MR angiographic technique were evaluated in eight healthy subjects and four patients with coronary disease identified at conventional angiography. This MR angiographic technique accurately depicted luminal disease in the patients and permitted visualization of extensive continuous segments of the native coronary tree in both the healthy subjects and the patients. Black-blood coronary MR angiography provides an alternative source of contrast enhancement.

To determine if intravenously administered contrast material improves overall reader confidence in the assessment of the colon, large-bowel wall conspicuity, and diagnostic accuracy in the detection of colorectal polyps and cancers at computed tomographic (CT) colonography.Two hundred patients underwent CT colonography in both supine and prone positions. A five-point scale was used to assess the effect of contrast enhancement on overall reader confidence and bowel wall conspicuity. Eighty-one patients underwent CT colonography with complete colonoscopic or surgical correlation; diagnostic accuracy was compared in 48 patients who received contrast material and 33 who did not.Bowel preparation was ideal in 38 (19%) of 200 patients. Enhanced prone CT images had significantly better scores for reader confidence (4.9 +/- 0.1 vs 4.6 +/- 0.1, P:.005) and bowel wall conspicuity (4.6 +/- 0.2 vs 4.2 +/- 0.2, P:.005) compared with those of nonenhanced prone images despite no significant difference in bowel distention (3.8 +/- 0.2 vs 3.9 +/- 0. 1, P: =.8). Enhancement significantly improved the ability to depict medium (6-9-mm) polyps (75% vs 58%, P:.05). Three large (10-19-mm) polyps were detected only with contrast enhancement; two remained submerged despite dual positioning.The use of intravenously administered contrast material significantly improved reader confidence in the assessment of bowel wall conspicuity and the ability of CT colonography to depict medium polyps in suboptimally prepared colons.

The effect of contrast material on fast fluid-attenuated inversion-recovery (FLAIR) magnetic resonance images was evaluated for 16 patients with enhancing gliomas and 12 patients with cerebral metastases. Because of a marked T1 effect, fast FLAIR imaging provided a marked contrast enhancement, resulting in the highest tumor-to-background contrast ratio compared with standard imaging techniques.

To evaluate perflenapent emulsion as a contrast agent for ultrasound (US) of the liver, kidneys, and vasculature.A randomized, double-blind, placebo-controlled, multicenter trial of 151 patients was performed. Investigators and blinded readers compared sonograms obtained after intravenous administration of perflenapent emulsion (0.05 mL/kg) and of a placebo with baseline sonograms.Contrast enhancement occurred in 140 of 149 patients (94%) after perflenapent administration and in 12 patients (8%) after placebo administration (P.001). Enhancement lasted 5.0-15.4 minutes with perflenapent and 0.1-1.7 minutes with the placebo (P.001). Perflenapent enhanced or facilitated visualization of blood flow, abnormal structures, masses, and lesions in 138 of 147 patients (94%) versus 12 of 147 (8%) for the placebo (P.001). Improved visualization assisted in the diagnosis in 105 of 143 perflenapent studies (73%) compared with five of 143 placebo studies (3%) (P.001). Diagnostic information affected case management in 71 of 148 patients (48%) after perflenapent administration and in nine of 148 patients (6%) after placebo administration (P.001). Adverse effects associated with perflenapent were few and mostly mild, occurred within 30 minutes, and resolved without treatment.Perflenapent emulsion is a safe and effective contrast agent for US of the liver, kidneys, and vasculature.

To evaluate whether very early magnetic resonance (MR) imaging enables distinction of residual tumor from benign postoperative change in children.Forty-six postoperative MR examinations were performed in 43 children with intracranial tumors within 24 hours of the completion of surgery during a 2-year period. These examinations were categorized according to whether residual tumor could be definitely identified or excluded, or whether the diagnosis was uncertain.Contrast enhancement occurred in 33 of 46 MR examinations performed within 24 hours of surgery. In 18 instances, this was associated with obvious residual tumor. In 15 patients, only small amounts of linear or patchy enhancement were seen. Of these, seven patients (46%) were disease-free for an average of 4.5 years. Assessment for postoperative enhancement was hampered in seven patients because of the presence of methemoglobin in the tumor bed. Contrast enhancement was not observed in two patients before surgery.Surgically induced, MR-detectable contrast enhancement and extracellular methemoglobin formation occurs within 24 hours of the completion of intracranial surgery. This can interfere with the detection of small amounts of residual tumor.

To determine characteristic features of peripheral cholangiocarcinoma on two-phase spiral computed tomographic (CT) scans.Thirty-four patients with peripheral cholangiocarcinoma underwent two-phase spiral CT. Hepatic arterial phase and portal venous phase images were obtained 30 and 65 seconds, respectively, after the start of contrast material infusion.Thin, mild, incomplete rimlike contrast enhancement at the tumor periphery was seen on CT scans from both phases in 23 patients. Thick, continuous rimlike contrast enhancement and marked homogeneous contrast enhancement were present on scans in four patients and one patient, respectively. No definite contrast enhancement pattern was seen on scans in six patients. Other findings included increased lobar or segmental hepatic attenuation in adjacent normal liver during the arterial phase (n = 10), markedly low attenuation with amorphous areas of slightly high attenuation in the tumor during both phases (n = 33), internal septumlike linear structures (n = 8), narrowing or obstruction of the portal vein as it traversed the tumor (n = 16), and a patent hepatic vein (n = 4).Thin, mild, incomplete rimlike contrast enhancement at the tumor periphery and markedly low intratumoral attenuation with amorphous areas of slightly high attenuation during both scanning phases are typical findings of peripheral cholangiocarcinoma.

To evaluate the usefulness of contrast material-enhanced magnetic resonance (MR) imaging in objective assessment of prostatic cryosurgery and the role of MR imaging in the modification of prostatic cryosurgical technique.Thirty-eight consecutive patients with localized (T1-3, N0, M0) prostatic adenocarcinoma treated with prostatic cryosurgery underwent MR imaging without contrast enhancement before cryosurgery and unenhanced and gadolinium-enhanced MR imaging within 1-3 weeks after cryosurgery. The first 20 patients also underwent MR imaging at 3 months after cryosurgery. MR imaging findings were correlated with those from transrectal ultrasound-directed prostatic staging biopsy.Cryonecrotic prostate was identified as avascular regions characterized by absolute signal void on contrast-enhanced images. With progressive modification of cryosurgical technique, complete cryoablation of the prostate was achieved in the latter nine of the 38 patients. When cryoablation was considered complete according to MR imaging criteria, findings invariably correlated with those at biopsy, with no residual prostate tissue or tumor.Gadolinium-enhanced MR imaging of the prostate after cryosurgery provides a highly accurate means of monitoring success. Objective MR imaging findings allow modifications to the technology and technique, resulting in optimal therapeutic results with prostatic cryosurgery.

To determine the usefulness of delayed post-equilibrium-phase contrast material-enhanced images in evaluation of intrahepatic cholangiocarcinoma.Review of surgical, pathologic, and radiologic records revealed 47 patients with proved cholangiocarcinoma with delayed (6-36 minutes) post-equilibrium-phase contrast-enhanced computed tomographic (CT) scans. Unenhanced, dynamic contrast-enhanced, and delayed images were retrospectively reviewed, and enhancement patterns for cholangiocarcinoma lesions were recorded. Degree of delayed enhancement was compared with that of surrounding liver parenchyma. Patterns of delayed enhancement were characterized as homogeneous or heterogeneous. Enhancement characteristics were correlated with histologic findings.Thirty-five (74%) of 47 patients had tumors with mild or marked hyperattenuating delayed contrast enhancement, of which 18 had tumors with homogeneous hyperattenuating enhancement. In three patients, the only evidence of tumor was on the delayed images. In one patient, the tumor was not definable at any imaging phase. Tumors with delayed enhancement tended to be fibrous; however, degree of contrast material retention did not always correlate with the fibrous content of tumors at histopathologic analysis.Delayed tumoral contrast enhancement is a typical feature of intrahepatic cholangiocarcinoma and may aid in the detection and characterization of such lesions at CT.

To assess the attenuation of the adrenal gland with computed tomography (CT) before and after multiple phases of contrast enhancement in both control subjects and patients with adenomas and nonadenomas.Seventy-two patients with 78 adrenal masses (41 adenomas, 37 nonadenomas) underwent helical CT. Forty subjects served as controls. Unenhanced CT was performed followed by enhanced CT at 30, 60, 90, and 180 seconds and 30 minutes.At unenhanced CT, mean attenuation was 4 HU +/- 16 for adenomas compared with 37 HU +/- 12 for the nonadenomas (P.001) and 24 HU +/- 3 for normal glands. Although the mean attenuation of nonademonas was significantly greater than that of adenomas on 60- and 90-second scans (P.001), there was greater overlap in attenuation of the adenomas and nonadenomas than on unenhanced images. At 180 seconds, nonadenomas had higher attenuation than adenomas (73 HU +/- 17 vs 41 HU +/- 18; P.001). At 30 minutes, all adenomas had attenuation less than 37 HU, whereas all nonadenomas had attenuation greater than 41 HU.Delayed-enhanced CT scans obtained 30 minutes after administration of contrast material can enable differentiation of adenomas and nonadenomas.

Parathyroid four-dimensional (4D) computed tomography (CT) is an imaging technique for preoperative localization of parathyroid adenomas that involves multidetector CT image acquisition during two or more contrast enhancement phases. Four-dimensional CT offers an alternative or additional tool in the evaluation of primary hyperparathyroidism. The purpose of this article is to describe the 4D CT technique and provide a practical guide to the radiologist for imaging interpretation. The article will discuss the rationale for imaging, approach to interpretation, imaging findings, and pitfalls.

In a retrospective study, 123 patients with tumors (the majority were recurrent pelvic or breast neoplasms) underwent 376 cycles of intraarterial chemotherapy. Contrast material-enhanced computed tomography was performed to check the position of the catheter during 221 cycles. On the basis of findings, the catheter was repositioned 46 (20.8%) times because of weak contrast enhancement in the tumor region (n=24[10.9%]), involvement of neighboring healthy tissue (n=15[6.8%]), or both (n=7[3.2%]).

To evaluate the effect of a reduction in iodine dose by altering volume and/or concentration of contrast material on hepatic contrast enhancement (HCE) values during hepatic helical computed tomography (CT).One hundred eleven patients were randomized into four contrast material protocols according to concentration (in milligrams of iodine per milliliter)/volume (in milliliters)/grams of iodine: group 1, ioversol, 320/150/48; group 2, ioversol, 320/100/32; group 3, iohexol, 300/150/45; group 4, ioversol, 300/100/30. Helical CT protocols were identical for the four groups. Time-attenuation curves were constructed; the mean HCE, contrast enhancement index (CEI), and optimal liver scanning interval (OLSI) were calculated; and the results were compared statistically. RESULTS;: Time-attenuation curves, mean HCE, CEI, and OLSI of groups 1 and 3 were significantly superior to those for groups 2 and 4. Decrease in volume from 150 to 100 mliters decreased mean HCE by 27%, CEI by 69%, and OLSI from 80%-100% to 0%-43% at threshold levels of 40-60 HU.Decrease in iodine dose from 45-48 g to 30-32 g significantly decreases all HCE values, which potentially decreases detection of focal hypovascular hepatic lesions.

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 (MAX50 HU, CEI at 30 HU300 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.

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.

To develop and compare contrast material injection protocols suitable for hepatic helical computed tomography (CT).Monophasic and biphasic helical CT were performed with contrast material with an iodine load of 50 g at 3 mL/sec for 60 seconds or at 5 mL/sec for 10 seconds and 2 mL/sec for 65 seconds, respectively. In 58 men and 51 women, aged 22-77 years, aortic and hepatic enhancement curves were constructed from a cluster acquisition with a slip-ring scanner operating in a nonhelical mode.The monophasic protocol produced a higher peak aortic enhancement (180 HU +/- 47 [+/- 1 standard deviation]) than the biphasic protocol (150 HU +/- 24). Peak hepatic enhancement (63-64 HU +/- 15) was equivalent. Calculated equilibrium time for the monophasic protocol was 95.1 seconds and for the biphasic protocol was 101.4 seconds. The contrast enhancement index differed only marginally between the two protocols (P.4).Monophasic and biphasic protocols produced equivalent results when tailored for the shorter temporal window of a rapid-sequence helical acquisition.

To evaluate use of magnetic resonance (MR) imaging with saline solution as contrast agent in diagnosis of perianal fistulous disease.Spin-echo intermediate-, T2-, and T1-weighted images were obtained before and after instillation of saline solution into anal fistulas in 12 of 16 consecutive patients. In four patients without secretory fistulas, images were obtained without contrast enhancement.Fistulous tracts were found in 13 patients, fluid cavities in 13, secondary fibrotic tracts in two, and normal perirectal tissue in one. The extent of fistulas and fluid collections was better delineated or more conspicuous on contrast-enhanced images in eight and 10 examinations, respectively, in part due to expansion of collapsed portions of the fistulous system. T2-weighted images were sufficient for diagnosis.MR imaging with saline solution as contrast agent may improve visualization of fistulas and their relationship to normal anatomic structures in patients with complex fistulous systems with relatively sparse secretion.

To prospectively evaluate stepping digital subtraction angiography (S-DSA), which enables peripheral digital subtraction angiography (DSA) of both lower extremities after one injection of contrast material, in comparison with conventional screen-film angiography (SFA) for evaluation of lower-extremity vascular disease.Fifty consecutive patients were prospectively examined. Each study was performed without knowledge of the findings in the other. Additional stationary DSA images were obtained whenever necessary. All studies were individually evaluated for diagnostic adequacy and then side by side for vascular opacification, timing of contrast enhancement, ease of reading, and overall superiority.The diagnostic adequacy of S-DSA was not statistically different from that of SFA (P.30). SFA was subjectively considered superior in opacification (P.003), ease of reading (P.003), and subjective overall superiority (P.005). S-DSA was superior in timing of contrast enhancement (P.001).The advantages of S-DSA can be achieved while the diagnostic adequacy of SFA is maintained. However, SFA was considered superior in three of four subjective characteristics.

To determine contrast enhancement after cerebral infarction at T1-weighted magnetic resonance (MR) imaging with delayed, gadolinium-enhanced, and magnetization transfer (MT) techniques.Ten patients aged 40-81 years with recent infarctions (7 days) were prospectively studied at MR imaging. Gadoteridol (0.1 mmol/kg [standard dose] and an additional 0.2 mmol/kg [high dose]) was administered before imaging with and without MT saturation and after a 15-minute delay. Two neuroradiologists ranked enhancement conspicuity.interobserver concordance was excellent (kappa = .86). Pairwise comparisons revealed high-dose MT images were ranked highest, followed by high-dose delayed non-MT images (P.01). Standard-dose MT images and initial high-dose non-MT images were ranked intermediately but were not distinguishable from each other (P.05). Initial and delayed standard-dose MT images were ranked lowest (P.01) and were not distinguishable from each other.MT saturation and high-dose gadoteridol individually and synergistically improve the depiction of contrast enhancement.

To investigate the prevalence, fate, and effect of focal contrast enhancement lesion within the hematoma on contrast material-enhanced computed tomographic (CT) images in patients with distal aortic intramural hematoma (IMH).This retrospective study was approved by the institutional review board; informed consent was waived. Clinical and CT data in 107 patients with distal IMH who received medical treatment were analyzed, including remodeling processes of IMH at follow-up CT. IMH progression was defined as development of aortic dissection (AD) and aneurysm or hematoma increase.The frequency of focal contrast enhancement was 39.3%, and hematoma was thicker in patients with focal contrast enhancement than in those without (12.3 mm ± 3.6 [standard deviation] vs 10.1 mm ± 4.1, P = .006). Although development of AD occurred more frequently in patients with focal contrast enhancement (21% vs 3%, P = .006), hematoma resorption (57% vs 71%) was the most common pattern of remodeling in both groups without any significant difference (P = .148). The frequency of development of aortic aneurysm (17% vs 14%, P = .690) and increase of hematoma (0% vs 5%, P = .278) was not significantly different between groups. The 1-, 3-, 5-, and 7-year survival rates were 96.3% ± 1.8, 95.2% ± 2.1, 87.9% ± 3.4, and 80.7% ± 4.4, respectively. Patients with IMH progression showed lower survival rates than those without (P = .028). While no significant difference in the overall survival rates could be demonstrated in patients with and those without focal contrast enhancement (P = .442), our study had only 17% power to detect a difference of 10%. Initial maximal aortic diameter was the only factor associated with survival rates (hazard ratio = 1.129; 95% confidence interval: 1.063, 1.199). The optimal cutoff for prediction of mortality within 7 years was 41 mm.Urgent intervention for patients with focal contrast enhancement is not necessary during the acute stage, and long-term close monitoring with imaging is a better option considering diverse remodeling processes of distal IMH.

To evaluate the utility of hepatocyte-phase gadoxetate disodium-enhanced magnetic resonance (MR) imaging in staging hepatic fibrosis and to compare it with diffusion-weighted imaging.This retrospective study had institutional review board approval, and the requirement for informed consent was waived. Gadoxetate disodium-enhanced and diffusion-weighted MR images obtained in 114 consecutive patients (70 men, 44 women; age range, 37-91 years) were evaluated. Liver-to-muscle signal intensity (SI) ratio on hepatocyte-phase images (SI(post)), contrast enhancement index calculated as SI(post) /SI(pre), where SI(pre) is liver-to-muscle SI ratio on nonenhanced images, and apparent diffusion coefficient (ADC) of the liver were measured. Necroinflammatory activity grades and hepatic fibrosis stages were histopathologically determined in 99 patients. Multiple regressions of SI(post), contrast enhancement index, ADC, serum albumin concentration, serum total bilirubin level, prothrombin time, and Child-Pugh score were examined to determine correlation with hepatic necroinflammatory activity grades and fibrosis stages.Among the MR, hematologic, and clinical parameters, contrast enhancement index was most strongly correlated with fibrosis stage (r = -0.79, P.001). Multiple regression analysis showed that the contrast enhancement index, ADC, and prothrombin time were significantly correlated (r(2) = 0.66, P.05) with fibrosis stage and that the contrast enhancement index and serum total bilirubin level were weakly correlated (r(2) = 0.24, P.05) with the necroinflammatory activity grade.Gadoxetate disodium-enhanced MR imaging is more reliable for staging hepatic fibrosis than are diffusion-weighted MR imaging, hematologic, and clinical parameters.

To clarify the importance of imaging plane in evaluation of invasion by tumor into muscle, 50 patients with bladder tumors underwent examination with magnetic resonance (MR) imaging performed with an oblique plane and the early phase of contrast enhancement. After the ideal oblique plane was selected, an oblique T2-weighted image was obtained. Gadopentetate dimeglumine was then administered, and an oblique T1-weighted image was obtained. The staging based on oblique T2-weighted and oblique contrast material-enhanced T1-weighted MR images was then correlated with histopathologic staging. The respective accuracies of oblique contrast-enhanced T1-weighted and oblique T2-weighted images were 78% and 60% for overall staging (P.05), 90% and 74% for differentiation between (a) stage T1 and lower-stage tumors and (b) stage T2 and higher-stage tumors (P.05), and 92% and 88% for differentiation between (a) stage T2 and lower-stage tumors and (b) stage T3a and higher-stage tumors (P.05). Oblique MR imaging performed in conjunction with the early phase of contrast enhancement showed significantly high staging accuracy, especially in differentiation between superficial tumors and tumors with superficial muscle invasion.

The purpose of this study was to determine whether additional clinically useful information could be obtained from gadolinium-enhanced magnetic resonance (MR) imaging compared with the information obtained from nonenhanced MR imaging and computed tomography (CT). Therefore, the authors selected 41 patients, whose results at CT examinations demonstrated a variety of pathologic conditions of the paranasal sinuses, to undergo MR imaging both with and without the use of gadopentetate dimeglumine for contrast enhancement. In 22 of 35 cases of neoplasms and mucoceles occurring separately, the lesions were correctly differentiated by established MR signal criteria alone. However, 32 of these 35 cases were accurately differentiated when gadolinium-enhanced MR images were obtained. Six cases demonstrated co-existing neoplasm and mucocele: Gadolinium-enhanced MR enabled correct differentiation of five of these lesions, while unenhanced MR enabled correct differentiation of three. On the basis of these results, the authors conclude that the use of gadopentetate dimeglumine for contrast enhancement at MR imaging is useful for differentiating mucoceles from neoplasms in the sinonasal tract.

Gadopentetate dimeglumine (gadolinium diethylenetriaminepentaacetic acid [DTPA]) was prospectively administered to 15 consecutive neonates and young infants (less than 6 weeks old) referred for routine cranial magnetic resonance (MR) imaging. The goals of the study were (a) to provide preliminary safety and efficacy data concerning the use of this drug in neonates and (b) to determine whether the patterns and time course of normal contrast material enhancement were similar to those seen in older children and adults. Gd-DTPA-enhanced MR images revealed significant abnormalities not seen on the MR images obtained before administration of contrast material in four (27%) of 15 patients. The adult dose (0.1 mmol/kg) provided bright enhancement of normal intracranial structures. Because of significantly reduced glomerular filtration and renal clearance rates in newborns, vivid contrast enhancement of normal structures was seen to persist for several hours after injection. A prolonged window of time for imaging may therefore exist for neonates and young infants.

Owing to ongoing technical refinements and intense scientific and clinical evaluations, computed tomography (CT) of the heart has left the research realm and matured into a clinical application that is about to fulfill its promise to replace invasive cardiac catheterization in selected patient populations. CT coronary angiography is technically more challenging than other CT applications owing to the nature of its target, the continuously moving heart. Rapid technical developments in this field require constant adaptation of acquisition protocols. These challenges, however, are in no way insurmountable for users with knowledge of the general CT technique. The intent of this communication is to provide those interested in and involved with coronary CT angiography with a step-by-step "manual" describing the authors' approach to performing coronary CT angiography. Included are considerations regarding appropriate patient selection, patient medication, radiation protection, contrast enhancement, acquisition and reconstruction parameters, image display and analysis techniques, and the radiology report. The recommendations are based on the authors' experience, which spans the evolution of multi-detector row CT for cardiac applications, from its beginning to the advent of the most current generations of 64-section and dual-source CT technologies, which they believe herald the entrance of this examination into routine clinical practice.

To retrospectively evaluate the correlation between the degree of contrast enhancement on dynamic computed tomographic (CT) scans and the degree of neoangiogenesis and sinusoidal capillarization in hepatocellular carcinoma (HCC).The institutional review board did not require approval or informed patient's consent for the review of medical records or images. Dynamic CT scans of 97 nodular HCCs in 97 patients (79 men, 18 women; age range, 29-73 years; mean age, 54 years) were evaluated in terms of the attenuation change in the arterial, portal venous, and delayed phases, and the results were correlated with the number of unpaired arteries and the degree of sinusoidal capillarization at histopathologic examination. The mean attenuation value of the nodular HCCs on triple-phase helical CT scans was correlated with the number of unpaired arteries and the degree of sinusoidal capillarization. Statistical analysis was performed with the Spearman rank correlation test.The number of unpaired arteries in the nodular HCCs was found to correlate with the degree of contrast enhancement in the arterial phase (r = 0.225, P = .027), but did not correlate with the degree of contrast enhancement in the portal and delayed phases. The degree of sinusoidal capillarization did not correlate linearly with the mean attenuation of the nodular HCCs in any phase of contrast enhancement.The degree of contrast enhancement of the nodular HCCs in the arterial phase tended to correlate with the number of unpaired arteries, but no correlation was evident between the degree of contrast enhancement and sinusoidal capillarization in any phase of CT imaging.

The authors investigated the contrast enhancement characteristics of the coronary artery stent lumen to assess patency and then evaluated the accuracy of computed tomographic (CT) measurement of the in-stent luminal diameter. Nineteen patients (16 men and three women; mean age, 58.7 years) with 26 stents underwent cardiac-gated CT angiography with a 16-detector row scanner 1-3 weeks after stent placement. CT images depicted the lumina of 20 stents in 14 patients. CT attenuation measured in the treated lumen was higher than, and correlated highly (r/= 0.87) with, attenuation in the proximal and distal untreated lumen. Estimated values for in-stent luminal diameter were lower with CT than with conventional angiography (P.001), and the mean error (16.1%) that resulted from estimation based on sharp-kernel CT images was significantly smaller than that (27.3%) from estimation based on medium-smooth-kernel CT images (P.001). Visualization of the in-stent lumen at CT angiography with a 16-detector row scanner allows assessment of coronary artery stent patency on the basis of measured contrast enhancement.

To investigate in computed tomographic (CT) angiography whether an exponentially decelerated contrast medium injection, as compared with a standard constant-rate injection, can facilitate uniform vascular contrast enhancement with a reduced contrast material volume.CT angiography of the abdominal aorta was performed in 46 subjects by using an exponentially decelerated injection method: 134 mL of contrast medium was injected for 40 seconds, starting at 4.0 mL/sec and decreasing exponentially to 2.7 mL/sec by the end of the injection. Twenty-one of these subjects also underwent CT angiography with a constant-rate injection: 160 mL of contrast medium was injected for 40 seconds at a constant rate of 4 mL/sec. Time-enhancement curves and the magnitude of peak vascular enhancement were measured. Enhancement uniformity was evaluated by using three indexes: (a) duration of contrast enhancement achieved within 80% of the peak (80% DCE), (b) SD of the normalized contrast enhancement (SDNCE) measured from the beginning of spiral CT scanning to the time when the enhancement decreased to a level lower than the beginning level, and (c) slope of the enhancement curve calculated by using linear regression analysis.Exponentially decelerated injection resulted in more uniform enhancement. Mean values generated by using exponentially decelerated versus constant-rate injection in 21 paired comparisons were, respectively, 30.8 seconds +/- 5.0 versus 22.6 seconds +/- 7.6 for 80% DCE, 0.052 +/- 0.017 versus 0.086 +/- 0.031 for SDNCE, and 0.47 HU/sec +/- 0.70 versus 2.27 HU/sec +/- 0.87 for slope (P.001 for all indexes). Compared with the peak enhancement resulting from the constant-rate injection, that resulting from the exponentially decelerated injection was reduced by a mean of 17.2% +/- 10.0.Uniform vascular contrast enhancement and reduced contrast medium volume, which are desirable in CT angiography, can be achieved with exponentially decelerated injection.

A method for visualizing myocardial infarction with a three-dimensional (3D) breath-hold gated acquisition was examined. By using variable sampling in time, whole heart coverage with a single volume acquisition was achieved in 24 heart beats. In a study of 35 patients, in whom 3D volume acquisition was compared with a two-dimensional (2D) acquisition, all regions of myocardial infarction were correctly identified at 3D examination. The mean imaging time for 12 section locations was 8.0 minutes +/- 3.0 with a 2D approach compared with 22 seconds +/- 4 with a 3D approach (P.001). Advantages were also noted for infarct contrast-to-noise ratio: 60 +/- 37 for 3D versus 33 +/- 20 for 2D imaging (P.001). No significant differences (P.05) were noted at qualitative assessment of myocardial suppression, endocardial border visualization, respiratory and cardiac motion artifacts, or confidence of transmurality of the infarct.

From: Takamichi Murakami, MD, PhD,* Tonsok Kim, MD,* Masatoshi Hori, MD, PhD,* Michael P. Federle, MD Department of Radiology, Osaka University Graduate School of Medicine 2–2 Yamadaoka, Suita-city, Osaka 565-0871, Japan* Department of Radiology, University of Pittsburgh Medical Center, Pa e-mail: murakami@radiol.med.osaka-u.ac.jp Editor: Optimal timing for acquisition of the arterial dominant set of computed tomographic (CT) images can be influenced by numerous variables, such as patient size and cardiovascular status. The fast imaging ability of multi–detector row helical CT to scan the entire liver in 10 seconds or less gives us the opportunity to acquire two separate sets of CT images in the liver within the time period generally regarded as the hepatic arterial dominant phase (double arterial phase). The double arterial phase images were expected to cover optimal timing of the arterial dominant phase. In our previous study (1), we reported that the double arterial phase, including the early and late arterial phases, could improve the detection of hepatocellular carcinoma (HCC). However, Dr Laghi and colleagues (2) reported that the use of an early arterial phase did not result in any improvement. There were a few differences in scanning parameters between their study and ours. The amount of contrast medium used for test injection was 20 mL in their study and 15 mL in our study, and scanning time of the double arterial phase was 24 seconds in their study and 26 seconds in our study. These may be some causes of the discrepancy. Another possible explanation for this discrepancy was suspected by Dr Laghi and colleagues to be the different mean sizes of HCC nodules. We suspected that the main possible reason for this discrepancy depended on patient size in each study—in other words, total amount of contrast medium used for patients. In both studies, the volume of contrast agent delivered was 2 mL per kilogram of body weight. The volume of contrast agent administered in our study ranged from 82 to 182 mL (mean, 114.2 mL). This was less than that in their study, which ranged from 120 to 168 mL (mean, 128 mL), because the body weight of our patients was less than that of patients in their study. Time to aortic peak enhancement was reported to be proportional to the injection duration or injection rate at a given injection duration; therefore, time to peak enhancement is shorter with shorter injection duration (3). The magnitude of peak contrast enhancement increases linearly with the total mass (concentration of contrast medium times volume of iodine injected at a given injection rate) (3,4). The possibility existed that aortic peak enhancement in smaller patients in our study, such as those who weighed less than 50 kg (injection duration less than 20 seconds at an injection rate of 5 mL/sec, although scanning time of the double arterial phase was 26 seconds), was reached sooner, and aortic enhancement decreased more rapidly in the late arterial phase. Time to peak arterial enhancement of HCC nodules in such smaller patients was also shorter than that in larger patients, and hypervascular HCC nodules in such smaller patients might show peak enhancement on the early arterial phase images. Our recent data (unpublished data, 2002), obtained by using multi–detector row helical CT with 0.5-second scanning (which can be used to obtain double arterial phase images in about 20 seconds), showed that late arterial phase CT images have significantly superior sensitivity to that of early arterial phase CT images. Our data also showed that there is no significant difference between the late arterial and double arterial phase images for detection of HCC nodules

To investigate pharmacokinetic and physiologic factors that determine the time to peak intravenous contrast medium enhancement in computed tomographic (CT) and magnetic resonance (MR) angiography in the porcine mid-abdominal aorta.Four pigs were imaged repeatedly in seven to eight sets: For each set, 20 dynamic CT scans were obtained at a fixed aortic level after intravenous injection of contrast medium. From a physiologically based compartment model, aortic contrast enhancement curves were generated by varying contrast medium injection duration from 1 to 40 seconds. Contrast enhancement curves and times to peak aortic enhancement from the experiment and model were compared. Time to peak aortic enhancement obtained from the injection with the shortest duration was considered the time to peak test bolus contrast enhancement. Mathematic and pharmacokinetic analyses were performed to investigate factors that determine peak enhancement.Empiric and compartmental model times to peak aortic enhancement were in good agreement. Time to peak aortic enhancement corresponded to the weighted sum of injection duration and time to peak test bolus enhancement. With increasing injection duration, the relative contribution of injection duration to peak aortic enhancement time increased. When injection duration was longer than time to peak test bolus enhancement, time to peak aortic enhancement increased linearly with injection duration and occurred shortly after completion of injection. However, when injection duration was shorter than time to peak test bolus enhancement, time to peak aortic enhancement was determined predominantly by time to peak test bolus enhancement and only gradually increased with injection duration.Time to peak aortic enhancement is determined by the relative contributions of injection duration and contrast medium traveling time and may well be explained by contrast medium volumetric inflow and recirculation physiology.

To determine whether magnetic resonance (MR) imaging with MS-325, a recently developed blood pool contrast agent, can depict sexual arousal response in healthy women.Serial MR imaging of the external genitalia was performed in 12 healthy sexually functional women before and after administration of MS-325. MR images were obtained every 3 minutes during a 45-minute examination. During the examination, the subjects viewed neutral and erotic video material while they were in the magnet bore. MR image analysis at each interval consisted of vaginal wall, vaginal mucosa, and clitoris assessments; femoral vein signal intensity measurements; relative regional blood volume (rRBV) calculations; and clitoral volume measurements. Statistical analysis of the results was performed with a t test.On subjective questionnaires, all subjects in the test group reported being sexually aroused. MS-325-enhanced MR images showed strong contrast enhancement of the external genitalia. The rRBV in the glans clitoris of seven of 10 subjects and in the clitoral body of eight of these subjects increased significantly (P.05) during erotic visual stimulation. All 10 subjects had a significant (P.05) increase in clitoral size. There were no significant differences in any measures between the pre- and postmenopausal study groups.The sexual arousal response in healthy women can be monitored at serial MR imaging with MS-325. This examination holds promise for future studies of sexual arousal dysfunction in women.

To assess the capability of helical computed tomography (CT) to assist in the differentiation between mucinous and nonmucinous gastric carcinomas, with a focus on the thickened stomach wall itself.In 62 patients with pathologically proved mucinous (n = 21) or nonmucinous (n = 41) gastric carcinomas, contrast material-enhanced helical CT images were obtained. The gross appearance, contrast enhancement pattern, predominant thickened layer, and degree of enhancement were retrospectively evaluated. Statistical analyses were performed with Fisher exact, chi(2), and Student t tests. A P value of less than.05 was considered to indicate a statistically significant difference.The most common type of gross appearance in both carcinomas was fungating: It occurred in 71% of patients with mucinous carcinomas and in 59% of patients with nonmucinous carcinomas. The next most common gross appearance type was ulcerative (24% of patients) in nonmucinous carcinomas and diffusely infiltrative (29% of patients) in mucinous carcinomas (P =.009). The most common contrast enhancement pattern was homogeneous (61% of patients) in nonmucinous carcinomas and layered (62% of patients) in mucinous carcinomas (P =.001). These findings were significantly different. The predominantly affected thickened layer was the high-attenuating inner layer or the entire layer (88% of patients) in nonmucinous carcinomas and the low-attenuating middle or outer layer (57% of patients) in mucinous carcinomas. Only two mucinous tumors showed miliary punctate calcifications in infiltrative lesions.Helical CT may assist in distinguishing mucinous from nonmucinous gastric carcinoma, primarily on the basis of enhancement pattern, predominant layer of the thickened wall, gross appearance, and presence of calcifications.

To evaluate temporal changes in signal intensity (SI) and degree of contrast enhancement (CE) of bone marrow in lumbosacral vertebrae inside and outside the radiation therapy (RT) field.Twenty-three patients with advanced uterine cervical cancer who were treated with RT were prospectively evaluated. Each patient underwent four dynamic magnetic resonance (MR) studies: before RT, 2 and 4 weeks after initiation of RT, and 4 weeks after completion of RT. SI and CE were calculated in all four studies of each patient.Bone marrow inside the RT field showed steady and marked increase in precontrast SI and early and transient increase in CE at 2 weeks after initiation of RT followed by progressive and marked decrease in CE at 4 weeks after initiation of RT and 4 weeks after completion of RT. Bone marrow outside the RT field showed slight increase in precontrast SI and steady and moderate decrease in CE to a lesser degree without early increase as seen in bone marrow inside the RT field.RT causes an increase in precontrast SI predominantly in bone marrow inside the RT field. However, a decrease in CE is seen in bone marrow not only inside but also outside the RT field.

A magnetic resonance (MR) angiographic protocol was evaluated in the carotid bifurcation with use of a pulse sequence for time-resolved three-dimensional imaging of contrast material kinetics. The enhancement ratio, a quantitative measure of contrast enhancement, indicated that all studies included an image obtained near the peak of the intraarterial concentration of contrast agent (enhancement ratio, 90% +/- 9 [standard deviation]). Studies acquired at a higher frame rate (4.1-4.9 seconds) exhibited less venous enhancement (enhancement ratio, 25% +/- 16) than studies acquired with slower (6.0-9.6-second) frame rates (enhancement ratio, 46% +/- 25).