Hepatic CT enhancement: effect of the rate and volume of contrast medium injection in an animal model.

BACKGROUND: To evaluate the relative effect of rate of injection and volume of contrast medium on aortic, portal, and hepatic enhancement during computed tomography (CT). METHODS: Thirty-eight nonincremental CT examinations were performed in three mini-pigs by using a combination of three different volumes (1.5, 2, and 3 mL/kg) and five different rates (1.5, 3, 4.5, 6, and 7.5 mL/s) of contrast material injection. Time-density enhancement curves of the aorta, portal vein, and liver were plotted over time for each rate of injection, each volume of contrast, and each volume-rate combination. In addition, aortic, portal, and liver peak enhancements, time-to-peak enhancements, optimal scanning intervals, and contrast enhancement indices were calculated for each volume-rate combination. RESULTS: Higher rates of injection increased peak aortic enhancement but had no effect on peak portal or hepatic enhancement. This result may be explained by the dilution of the bolus of contrast medium in the splanchnic circulation. When the results of a 6-mL/s injection of 1.5 mL/kg of contrast material were compared with a 3-mL/s injection of 2 mL/kg, maximum aortic enhancement increased by 32%, whereas maximum liver enhancement decreased by 35%. CONCLUSION: An increase in the rate of contrast injection results in an increase of peak aortic enhancement even when the total iodine load is decreased. However, an increase of the rate of contrast injection does not increase maximum liver enhancement, which is related to the total iodine dose injected. Therefore, one cannot compensate a decrease in the iodine load by an increase in injection rate in contrast-enhanced CT of the liver.

Enhancement patterns of renal masses during multiphase helical CT acquisitions.

BACKGROUND: To describe the appearance of renal masses during multiphase helical computed tomography (CT) acquisition and evaluate the impact of a cortical nephrographic phase on diagnosis. METHODS: The CT examinations of 33 patients with 37 lesions [18 renal cell carcinomas (RCC), nine solid tumors, 10 cystic lesions] were reviewed to characterize renal masses during four phases of CT scanning: plain, cortical nephrographic, tubular nephrographic, and pyelographic. Two reviewers analyzed all lesions on the complete data set, and a third reviewer analyzed three combinations of images separately: (1) plain and tubular nephrographic phases, (2) plain and cortical nephrographic phases, and (3) three phases combined. Receiver operating characteristics (ROC) curves were generated to determine the respective value of each combination in lesion characterization. RESULTS: During the cortical nephrographic phase, hyperdensity of solid renal masses was 100% specific and 22% sensitive for RCC, whereas combining hyperdense and isoattenuating heterogeneous masses was 91% specific and 56% sensitive. ROC curves demonstrated a sensitivity of 85%, 90%, 100% for the three combinations, respectively, with a constant specificity of 88% for diagnosing RCC. CONCLUSION: The cortical nephrographic phase is useful to characterize renal masses and should be included in the routine helical CT protocol.

Helical CT of the pancreas: a comparison of cine display and film-based viewing.

OBJECTIVE: Radiologists must manage a tremendous number of helical CT images daily. Hence, the use of cine display review is increasing. Our aim was to compare cine display of helical CT examinations of the pancreas with conventional film-based viewing. SUBJECTS AND METHODS: Forty-eight consecutive patients undergoing helical CT of the pancreas were prospectively included in the study. Five-millimeter-thick contrast-enhanced helical CT sections of the pancreas were reconstructed in 1-mm increments for cine display review and in 5-mm-thick increments for film-based review. Two radiologists reviewed the two sets of data independently. Review of the cine display images was followed by review of the film-based images 2 months later. For both the cine display and the film-based images, reviewers used a four-point scale to grade vascular anatomy (splenic vein and artery, superior mesenteric vein and artery, portal confluence, dorsal pancreatic artery, and gastroduodenal artery); ductal anatomy (common bile duct in its hilar, suprapancreatic, and intrapancreatic portions and pancreatic duct in its caudal, corporeal, and cephalic portions); sharpness of the pancreatic and lesion contours; and overall image quality. RESULTS: The conspicuity of pancreatic contours was graded better on cine display (p = .0035). All venous and arterial landmarks were graded significantly better on cine display. Likewise, visibility of the common bile ducts and pancreatic ducts was scored significantly better with cine display. In three patients, cine display images revealed the pancreatic duct, and the film-based images did not. Although 21 lesions were shown on both sets of images, the lesions were better seen on cine display (p < .005). CONCLUSION: Vascular and ductal anatomy is better delineated on cine images generated from overlapped sections than on conventional film-based images. Lesions are also more sharply delineated on cine display images.

Discursive strategies of subjects with high altitude hypoxia: extreme environment.

A discourse analysis was carried out on nine European lowlanders during a 2-month scientific expedition at high altitude including a 3-week stay in extreme survival conditions at the summit of Mt. Sajama (6542 m), in order to contribute to the understanding of psychological adaptation to extreme environments. This discourse analysis was part of a wide-ranging scientific investigation involving 12 scientific and medical research protocols which targeted human adaptation to high altitude chronic hypoxia. The objective of this study is to better understand the presence of linguistic markers capable of translating the subject's psychological state when faced with a threatening environment. This study was based on a method of propositional speech analysis developed by Ghiglione and Blanchet which emphasizes the cognitive function of verb categories, modalizers and adjuncts used by subjects. The method was developed in conjunction with psychopathological studies of the depressive state. Speech was recorded at time T1, 4 days after reaching the summit of Mt Sajama, and at time T2, 2 days before descending the mountain peak. These results revealed that in the absence of depression in any psychopathological sense of the word, normal subjects would react to their environment with a depressive component. However, the results of this study equally illustrate for some subjects a correspondence between those states with a depressive component and a physiological incomplete adaptation to high altitude. This correspondence could reflect the pathogenic effect of an adaptation deficit or could be in keeping with the literature concerning an incomplete adaptation effect induced by a latent depressive state.

Effect of portal venous flow augmentation on liver enhancement with CT.

BACKGROUND: The purpose of this study was to evaluate the effect of portal flow augmentation on hepatic computed tomographic (CT) enhancement. METHODS: Thirteen patients undergoing follow-up CT of the liver within 6 months of initial study ingested 470 mL of Ensure 30 min before the second examination. Contrast medium injection and scanning parameters were identical for both studies. RESULTS: The time to peak and the maximum and mean liver enhancements were 68 s, 56 HU, and 46 HU, respectively, for the examinations without Ensure and 68 s, 53 HU, and 44 HU for the examinations with Ensure. No significant difference was found between the two groups when mean liver enhancement was calculated over 3-s time intervals. CONCLUSION: Portal venous flow augmentation induced by a meal had no effect on liver enhancement.

[Parameters influencing hepatic parenchyma enhancement in x-ray computed tomography after intravenous injection of iodinated contrast medium]. / Paramèters influençant le rehaussement parenchymateux hépatique en tomodensitométrie après injection intraveineuse de produit de contraste iodé.

With the widespread use of spiral CT, a complete reassessment of intravenous injection of contrast material for body computed tomography is necessary. An optimal administration of contrast material with respect to scan timing is indeed more critical with spiral CT. Numerous factors affect hepatic contrast enhancement time-attenuation curves after injection of contrast material into a peripheral vein. Some are patient related, while other result from the modalities of administration of the iodinated agent. The objective of this article is to review the most contributive factors in liver enhancement after iodine injection. Knowledge of these factors can optimize the use of spiral CT, with the expected benefit of saving costs in contrast material.

Correlative imaging and pattern approach in ultrasonography of bone lesions: a pictorial essay.

The purpose of this paper is to sensitize musculoskeletal and general sonographers to a wide variety of bony abnormalities that may be noted adjacent to soft tissues of interest. The authors gathered sonographic images displaying abnormalities involving the periosseous, periosteal and cortical tissues from numerous patients who underwent imaging in their department. When available, correlative imaging or the pathological diagnosis (or both) is provided. The authors conclude that musculoskeletal ultrasonography, when used to its full potential, can reveal corroborative and occasionally unsuspected evidence of underlying bony abnormalities, so that correlative imaging (e.g., plain radiography, computed tomography, magnetic resonance imaging or bone scanning) can be performed as appropriate.

Tophaceous gout of the lumbar spine mimicking an epidural abscess: MR features.

We present the MR findings in a case of tophaceous gout of the lumbar spine with cauda equina compression, mimicking an epidural abscess. The diagnosis was clinically unsuspected and confirmed at laminectomy. Tophus material in the paraspinal soft tissues appeared intermediate in signal intensity and showed heterogeneous contrast enhancement.

[Spiral X-ray computed tomography: a new modality of scanner imaging]. / Tomodensitométrie hélicoïdale: une nouvelle modalité d'imagerie scanographique.

Spiral computed tomography is a new imaging modality that presents several advantages when compared to conventional and dynamic computed tomography. It consists in a continuous rotation of the X-Ray tube around the anatomical area to be explored, simultaneously with a move of the examination table at a constant speed. Advantages are the short acquisition time (below one minute), optimization of the intravenous injection of the iodinated contrast material, acquisition of a gapless volume of data which can be post-processed, permitting axial reconstructed sections which are perfectly contiguous, as well as an easy access to 2D multiplanar and 3D reconstructions, with the benefit of a substantial decrease in patients' radiation. This paper will review the prominent advantages, as well as the current limitations, of this new imaging modality.

A comparison of two injection protocols using helical and dynamic acquisitions in CT examinations of the pancreas.

OBJECTIVE: The patterns of pancreatic enhancement and their relation to various injection parameters remain largely unknown. The purpose of this study was twofold: to compare pancreatic enhancement obtained after high and low rates of i.v. injection of contrast medium and to compare image quality between helical and dynamic sequential CT examinations of the pancreas using optimized scanning parameters. SUBJECTS AND METHODS: One hundred patients were randomly allocated to undergo either a helical CT (HC) acquisition after contrast injection at 6 ml/sec or a dynamic sequential CT (DS) acquisition after contrast injection at 2 ml/sec. Both ionic and nonionic contrast material were used in each group. Pancreatic attenuation values were measured on each section in each patient and averaged for each group. Image quality and visualization of anatomic landmarks were scored by two independent reviewers who were blinded to the acquisition technique. RESULTS: Mean pancreatic enhancement was higher in the HC (61 +/- 17 H) than in the DS group (54 +/- 17 H) (p < .05). Peak pancreatic enhancement was similar in the HC (74 +/- 19 H) and DS (74 +/- 17 H) groups. In the HC group, the optimal pancreatic enhancement index was 47% versus 35% for the DS group. The time to peak enhancement was 39 sec in the HC group and 71 sec in the DS group. The optimal scanning interval was 13 sec in the HC group versus 21 sec in the DS group. Image quality was not significantly different between the protocols, but misregistration and motion artifacts were fewer on HC examinations. CONCLUSION: Overall pancreatic enhancement was higher in the HC group, but the faster rate of injection did not increase the peak pancreatic enhancement and decreased the optimal scanning interval (the interval of time during which pancreatic enhancement was greater than 60 H). Image quality was similar with both protocols.

Effect of rate of contrast medium injection on hepatic enhancement at CT.

PURPOSE: To determine the effect of the rate of contrast medium injection on liver enhancement at computed tomography (CT). MATERIALS AND METHODS: Forty-five patients who underwent a follow-up CT examination of the liver were included in five different groups according to the compared rates of contrast material delivery: group A, 2 versus 3 mL/sec; group B, 2 versus 4.5 mL/sec; group C, 3 versus 4.5 mL/sec; group D, 3 versus 6 mL/sec; and group E, 4.5 versus 6 mL/sec. RESULTS: Time to peak enhancement was shorter for the faster rates of injection. In each group, maximum enhancement was nearly identical for the paired examinations (group A, 57 vs 58 HU; group B, 48 vs 47 HU; group C, 55 vs 58 HU; group D, 55 vs 54 HU; group E, 62 vs 61 HU, respectively). Mean enhancement in each group was similar when calculated at 3-second intervals. CONCLUSION: Higher rates of injection shorten the time to peak liver enhancement but have no effect on maximum liver enhancement.

Comparison of helical and conventional computed tomography of the liver.

OBJECTIVE: To compare helical and conventional computed tomography (CT) of the liver in terms of enhancement (with different contrast media) and image quality, using optimal technique for each type of acquisition. PATIENTS AND METHODS: Of 218 consecutive patients referred to a tertiary-care hospital for CT of the liver, 166 were randomly assigned to undergo helical (79 patients) or conventional (87) CT. Fifty patients were excluded from the study because they were unable to hold their breath or were unable to cooperate or because they weighted more than 120 kg. Two other patients were excluded at the time of scanning because of a technical problem. Monophasic injections of contrast agent at 3 mL/second were given to patients undergoing helical CT and biphasic injections at 2 and 0.7 mL/second to patients undergoing conventional CT. The contrast media used were iothalamate meglumine, ioversol, iopamidol and iohexol. For each patient, liver enhancement over baseline attenuation was calculated for every slice, and time to peak enhancement was calculated. In addition, visualization of anatomic landmarks and image quality were scored by two independent reviewers. RESULTS: Minimum, maximum and mean liver enhancement were significantly greater in the group that underwent helical imaging (49, 62 and 55 Hounsfield units [HU] respectively) than in the group that underwent conventional imaging (36, 51 and 44 HU respectively) (Student's t-test, p < 0.0001). Similar differences were obtained when the results were analysed separately for each contrast medium. Image quality was not significantly different between the two acquisition modes. CONCLUSIONS: For computed tomography of the liver, monophasic injection of contrast medium at a high rate and helical acquisition (rather than biphasic injection and conventional acquisition) resulted in significantly better enhancement, without compromising image quality.

Helical CT of the liver: value of an early hepatic arterial phase.

PURPOSE: To prospectively evaluate a dual-phase helical acquisition in computed tomography (CT) of the liver. MATERIALS AND METHODS: Two helical CT acquisitions were performed in 103 patients: hepatic arterial phase (HAP) 15 seconds after injection of 2 mL/kg contrast material at a rate of 6 mL/sec and the portal venous phase (PVP) 90 seconds after injection. Detection of focal liver lesions, vascular anatomic features, and perfusion abnormalities were assessed by two reviewers. Liver enhancement was also calculated on every section. RESULTS: Of 119 detected focal liver lesions, nine were seen during HAP only and 40 during PVP only. According to a 0-3 score, visualization of the arterial anatomic landmarks was better during HAP (P < .0001). Five right replaced and two left replaced hepatic arteries were visualized only during HAP. Parenchymal perfusion abnormalities were found in 32 patients during HAP and in four patients during PVP. CONCLUSION: A dual-phase acquisition depicted 8% additional focal liver lesions and outlined the entire vasculature of the liver.

[MRI and chronic osteoarticular infections. Contribution of inversion-recuperation sequence with fat signal cancellation in the follow-up of chronic osteitis under medical treatment. Apropos of 14 cases]. / IRM et infections ostéo-articulaires chroniques. Apport de la séquence inversion-récupération avec annulation des graisses dans le suivi des ostéites chroniques sous traitement médical. A propos de 14 cas.

MR Imaging was performed with T1 weighted, Rho T2* (Grass) and S.T.I.R. sequences on medically treated chronic osteomyelitis patients. MR Imaging is definitely the best tool available in thorough evaluation of the extent of lesions. It allows the evolution or remission of focal inflammatory lesions to be traced for follow up. Bone sequestra needing surgery can be identified and soft tissue abcesses differentiated from cellulitis. In future, MR Imaging could replace tomography and fistulography, while scintigraphy would be more useful in cases of recent acute infections and their differential diagnoses.