Helical CT of the urinary organs Schreyer, H H; Uggowitzer, M M; Ruppert-Kohlmayr, A
European radiology
12, Številka:
3
Journal Article
Recenzirano
Despite of the diagnostic potential of conventional CT (CCT), limitations being inherent in this technology reduce its diagnostic confidence and limit clinical CT applications as 3D imaging. Helical ...CT (HCT) has far overcome the limitations of CCT and has become the standard CT technology. After a short overview on the technique of HCT and its advantages over CCT, the impact of HCT on the detection of disorders of the urinary organs is discussed. Due to the high quality of 3D reconstructions, vessels are visualized free of artefacts resulting in a dramatic improvement and acceptance of CT angiography, which has become a clinically important examination in the evaluation of obstructive renal artery disease. Fast HCT provides a precise assessment of the three phases of the nephrogram and it is a prerequisite for an improved depiction of abnormal vascular perfusion and impaired tubule transit of contrast material. Helical CT enables an improved characterization of cystic mass lesions reducing the diagnosis of indeterminate masses and thus facilitating a better therapeutic management. The diagnosis of renal cell carcinomas (RCC) has improved due to an increased sensitivity in detecting small RCCs, and an increased specificity in the diagnosis of neoplastic lesions. Improved staging of RCCs is the result of accurate assessment of venous tumour extension. When planning nephron-sparing surgery 3D display of the renal tumour helps to determine the resectability of the mass depicting its relation to major renal vessels and the renal collecting system. In the evaluation of renal trauma HCT provides shorter scanning time and thus fewer artefacts in the examination of traumatized patients who cannot cooperate adequately. Three-dimensional postprocessing modalities allow the assessment of the renal vascular pedicel by CT angiography and improve the demonstration of complex lacerations of the renal parenchyma. In the evaluation of the upper urinary tract unenhanced HCT has become the imaging method of choice in the diagnosis and differential diagnosis of acute flank pain since it is highly sensitive and specific in detecting calculus disease. Unenhanced HCT may furthermore demonstrate causes of flank pain unrelated to urolithiasis. Gapless volume scanning and improved resolution in the z-axis during the excretory phase enables improved visualization of the renal collecting systems and ureters, resulting in a better demonstration of intraluminal and extraluminal pathology.
Differences of attenuation and enhancement patterns in focal nodular hyperplasia and hepatocellular adenoma were evaluated and quantified using triphasic single-slice helical CT.
Forty-five ...histologically proven focal nodular hyperplasias in 27 patients and 18 hepatocellular adenomas in six patients were examined with helical CT. Quantitative evaluation included the following: attenuation of lesions, scar, and liver parenchyma during unenhanced, arterial (20 sec after injection), and portal venous phases (70 sec after injection); relative enhancement of lesions and liver (the ratio between attenuation in arterial phase and portal venous phase, respectively, and attenuation in unenhanced phase); and the prevalence of scar and its central vessel in focal nodular hyperplasia.
The study showed no significant difference between mean attenuation values of focal nodular hyperplasia (mean +/- SD, 51.2 +/- 5.9 H) and hepatocellular adenoma (mean +/- SD, 56.3 +/- 7.8 H) in the unenhanced phase. In the arterial phase attenuation values were significantly higher in focal nodular hyperplasia (mean +/- SD, 117.9 +/- 15.1 H) than in hepatocellular adenoma (mean +/- SD, 80.1 +/- 10.5 H). In the portal venous phase no significant differences in attenuation values were detected between focal nodular hyperplasia (mean +/- SD, 112.1 +/- 20.4 H) and hepatocellular adenoma (mean +/- SD, 110.2 +/- 12.9 H). For enhancement parameter thresholds separating focal nodular hyperplasia from hepatocellular adenoma, the following were found: the relative enhancement was higher in 100% of the focal nodular hyperplasias and lower than or equal to 1.6 (accuracy, 96%) in 87% of the hepatocellular adenomas.
Triphasic helical CT combined with quantitative evaluation of liver lesions offers the possibility of detecting differences in liver lesions that are visually similar on CT. The attenuation and relative enhancement in the arterial phase show significant differences that make accurate differentiation between focal nodular hyperplasia and hepatocellular adenoma possible.
To evaluate the potential of a saline solution flush after the contrast material bolus in abdominal multidetector row CT (MDCT) in contrast material dose and cost reduction.
Abdominal MDCT was ...performed in 78 patients who were assigned randomly to 2 groups receiving 120 mL nonionic contrast material (300 mgI/mL) alone or 100 mL of the same contrast material pushed with 40 mL of saline solution. Mean attenuation values for both groups were measured in the liver, the spleen, the pancreas, the portal vein, the inferior vena cava, and the abdominal aorta. Cost analyses were performed for both groups.
There was no significant difference in parenchymal and vascular enhancement between both groups. The difference of the enhancement was 2 HU for the liver (P = 0.11), 2 HU for the spleen (P = 0.44), 3 HU for the pancreas (P = 0.38), 9 HU for the portal vein (P = 0.11), 3 HU for the inferior vena cava (P = 0.55), and 10 HU for the aorta (P = 0.06). Taking the costs of contrast material, saline solution, and disposal material into account, 7.30 dollars was saved by the patient using a saline solution flush.
Using a saline flush after the contrast material bolus in abdominal MDCT allows an iodine dose reduction of approximately 6 g, or 17%, without impairing mean parenchymal and vascular enhancement and a cost reduction of 7.30 dollars per patient.
The aim of this study was to determine if a saline solution flush following low dose contrast material bolus improves parenchymal and vascular enhancement during abdominal multiple detector-row ...computed tomography (MDCT). Forty-one patients (24 men and 17 women; mean age 49 years, age range 27-86 years) underwent abdominal MDCT (collimation 4x5 mm, 15-mm table increment, reconstruction interval 5 mm, gantry rotation period 0.8 s) with a single- as well as with a double syringe power injector. Indication for examination were benign and malignant tumors and inflammatory diseases. Patients received 100 ml nonionic contrast material (300 mgI/ml) alone or pushed with 20 ml saline solution. Mean enhancement values for both protocols were measured in the liver, the spleen, the pancreas, the renal cortex, the portal vein, the inferior vena cava and the abdominal aorta. Double syringe power-injector protocol led to significantly higher parenchymal and vascular enhancement than single syringe power-injector protocol (p<0.05). The improvement in mean enhancement of the liver was 9 +/- 9 HU, of the spleen 8 +/- 10 HU, of the pancreas 7 +/- 9 HU, and of the renal cortex 8 +/- 20 HU. The improvement in mean enhancement of the portal vein was 10 +/- 17 HU of the inferior vena cava 8 +/- 13 HU and of the abdominal aorta 10 +/- 17 HU. The use of a double syringe power injector with saline flush following contrast material bolus significantly improves parenchymal and vascular enhancement during contrast-enhanced abdominal MDCT with low iodine doses.
Issue Title: ECR 2003, Vienna, Austria, March 7-9, 2003 Contrast optimization in MRI. Advances in vascular and cardiac MDCT imaging. Contrast ultrasound: A new modality for abdominal imaging When ...evaluating focal liver disease, a variety of imaging modalities and recent techniques can be used, depending on the patient's history, the clinical suspicion to be addressed, the probability of a certain disease, as well as the availability and the radiologist's personal knowledge of a certain imaging method. Because of these factors, no rigid diagnostic algorithm can be given. Nevertheless, specific contrast agents and tailored dynamic imaging protocols are prerequisites for obtaining optimal results.PUBLICATION ABSTRACT
Objective: To evaluate the potential of spiral computed tomography (CT) densitometry of the lung to assess segmental perfusion defects in patients with acute pulmonary embolism.
Materials and ...Methods: Ten patients with known segmental or lobar perfusion defects on ventilation/perfusion scintigraphy and with normal findings in the contralateral lung segment underwent spiral CT of the thorax before and after the administration of contrast material. Regions of interest were defined in 14 segments with normal perfusion and in 14 segments with reduced perfusion. Three consecutive densitometry measurements were performed in each segment.
Results: Those segments with reduced perfusion showed a significantly lower mean CT value on the enhanced scans (−813.4±57.1 Hounsfield units (HU) vs −794.0±44.8 HU,
P=0.01) and a significantly decreased contrast enhancement (12.3±18.2 HU vs 29.8±16.6 HU,
P<0.01) when compared to segments with normal perfusion. Measurements from the unenhanced CT scans were not statistically different between segments with reduced and normal perfusion.
Conclusions: Spiral CT densitometry allows the assessment of at least segmental perfusion defects in patients with acute pulmonary embolism.
The purpose of our study was to examine the clinical value of echo-enhanced transcranial power Doppler sonography (EE-TCD), including it ability to assess hemodynamic parameters of the intracranial ...vasculature, in patients with suspected cerebral arteriovenous malformations (AVMs) and to compare this method with angiography.
Sixteen patients with suspected cerebral AVMs were examined with EE-TCD and angiography. As an echo-enhancing agent, SHU 508A (Levovist) was administered intravenously by bolus injection in nine patients and by continuous infusion in seven. Sonograms were reviewed without knowledge of other imaging results and were correlated with angiographic findings.
Angiography showed AVMs in 12 of 16 patients. Eleven lesions were located in the anterior or middle fossa and one was in the posterior fossa. EE-TCD was slightly less sensitive in the detection of AVMs (92%, 11/12 lesions), since in one patient the lacking acoustic window did not allow a transcranial examination. EE-TCD slightly underestimated AVM size compared with angiographic findings but showed feeding arteries with sufficient acoustic properties. In seven patients (58%), angiography revealed a coincidental blood supply from another intracranial or extracranial vessel, which was missed by EE-TCD in all cases. Assessment of peak systolic velocities and resistive indexes resulted in a higher (mean, 191.1 cm/s) and a lower (mean, 45.7%) value, respectively, in the feeding arteries as compared with the contralateral arteries (mean, 101.8 cm/s and 55.6%, respectively). Side-to-side differences were significantly higher in patients with AVMs than in those without a malformation. Signal enhancement was markedly longer with continuous infusion (mean, 520 seconds +/- 28.2) than with bolus injection (mean, 145 seconds +/- 10.5) of the contrast agent.
In our limited study group, EE-TCD was a sensitive method for the detection of AVMs, and Levovist proved to be a safe and effective echo-enhancing substance.
Orbital Dirofilariasis: MR Findings Groell, Reinhard; Ranner, Gerhard; Uggowitzer, Martin M ...
American journal of neuroradiology : AJNR,
02/1999, Letnik:
20, Številka:
2
Journal Article
Recenzirano
Dirofilariasis is a helminthic zoonosis occurring in many parts of the world. We report the findings in a 61-year-old woman who had painless right exophthalmos caused by orbital dirofilariasis. A ...vivid worm was embedded inside an inflammatory nodule in the right orbit. On T1-weighted MR images, the parasite was visible as a discrete, low-intensity, tubular signal in the center of the nodule surrounded by contrast-enhancing inflammatory tissue.
