Assessment of a technology that permits individualized scan delays on helical hepatic CT: a technique to improve efficiency in use of contrast material.

Silverman, Paul M.; Roberts, Suzanne; Dučić, Ivica; Tefft, M C; Olson, Mary; Cooper, Cirrelda; Zeman, R K

doi:10.2214/ajr.167.1.8659426

Cited by 57 publications

(33 citation statements)

References 7 publications

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“…In our studies we performed the automatic bolus tracking technique in all patients without any technical or user-dependent problems. The time between the exceeding of the enhancement threshold value and the actual start of the spiral scan was relatively constant between 7.1 and 8.9 s. Other authors report a much higher variance of this delay between 5 and 15 s [20,21,22]. We assume that the more constant performance in our series depends on the fact that we could use a newer, more reliable version of the automatic bolus tracking software.…”

Section: Discussionmentioning

confidence: 75%

Biphasic spiral CT of the liver: automatic bolus tracking or time delay?

et al. 2001

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The aim of this study was to evaluate the value of automatic bolus tracking for biphasic spiral CT of the liver in comparison with time delay examinations. Forty patients scheduled for a biphasic spiral CT of the liver randomly were examined either with time delay of 25 s for the arterial phase and 55 s for the portal-venous phase (n = 20), or with an automatic scan start triggered by contrast enhancement in the aorta (n = 20). Examinations were performed with 120 ml of contrast material and a flow rate of 4.0 ml/s. Density measurements of the aorta, of the liver parenchyma, and of the spleen were obtained by means of regions of interest (ROI). The end of the arterial phase was considered when hepatic parenchymal enhancement was greater than 20 HU. In all patients of the group with automatic bolus tracking arterial scanning was completed in the arterial phase of the liver. In 25 % of patients with fixed time delay, however, an enhancement of liver parenchyma during arterial phase greater than 20 HU was observed. During the portal-venous phase there was no significant difference in parenchymal enhancement between both groups. Automatic bolus tracking allows an individualized timing of the arterial phase in biphasic spiral CT of the liver. The timing is more accurate than in time delay scanning.

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Section: Discussionmentioning

confidence: 75%

Biphasic spiral CT of the liver: automatic bolus tracking or time delay?

et al. 2001

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“…Sil verman et al [6][7][8] and Kopka et al [9,10] evaluated a system in which this rapid recon struction process allowed monitoring of hepatic contrast enhancement by near real-time graphic and numeric display ofhepatic density in a pre determined region of interest (ROl). Their sys tem allowed the operator to initiate helical CT imaging when hepatic density reached a preset numeric threshold (automated ROI threshold triggering).…”

Section: Discussionmentioning

confidence: 99%

“…Not surpris ingly, we have observed that hepatic vessels are easier to visualize during visual cue trig Mean hepatic enhancement obtained during the experimental portion of our study is difficult to compare with that reported in prior studies that evaluated RU! threshold triggering to opti mize hepatic contrast enhancement, because in those studies, patients weighed less and received higher doses of contrast agent, and different methods were used to subjectively evaluate scans [7][8][9][10]. Despite these differences, our re sults, using continuous imaging to individualize helical CT scanning delay time with visual cue triggering or RU!…”

Section: Rol By Patient Motionmentioning

confidence: 98%

“…Their sys tem allowed the operator to initiate helical CT imaging when hepatic density reached a preset numeric threshold (automated ROI threshold triggering). These investigators reported an im provement in the quality of hepatic contrast en hancement when compared with that of standard helical examinations using a fixed scanning delay time and suggested that the amount of contrast material could be reduced without compromising scan quality [8,10].…”

mentioning

confidence: 99%

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Optimizing contrast enhancement during helical CT of the liver: a comparison of two bolus tracking techniques.

Schweiger

Chang²,

Brown³

1998

American Journal of Roentgenology

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OBJECTIVE. The purposeof this studywas to evaluatea recentlydevelopedhardware and software system for CT scanning that generates images in real time and switches to heli cal CT scanning by either a visual cue or a region of interest (ROI) amplitude threshold. SUBJECTS AND METHODS. We randomlyandprospectivelydivided 120 abdominalCT examinations into three groups. Two groups received 75 ml of contrast agent at 1.5 ml/sec.Helical CT scanning began after visualization of the contrast bolus arrival in the hepatic veins (visual cue triggering) (39 patients) or after reaching an ROI threshold (automated ROI threshold triggering) (39 patients). A third group served as a control group (42 patients) and received 150 ml of contrast agent at I mllsec. Quality of hepatic enhancement was assessed objectively and subjectively. Comparisons were made after stratifying each group into three weight classes. RESULTS. Errorsoccurredin 12 (31%) of 39 examinationsin the groupwith automatedROl threshold triggering. In that group, we found a significantly (p < .04) lower mean hepatic enhancement in two of three weight categories, and a significantly (p < .04) lower mean sub jective scan quality in one of three weight categories, than we found in the group with visual cue triggering. CONCLUSION.Optimizing portalvenousphasehelicalCT of the liver after a low-vol ume bolus of contrast agent and an injection rate of 1.5 mI/sec is best achieved by initiating helical CT scanning after visualizing the contrast bolus arrival within the liver rather than af ter reaching a preset attenuation threshold.T he use of helical CT, with its abil ity to image a target organ rap idly, can greatly improve the probability of seeing all desired anatomy in a short time [1â€"5]. However, the rapid scan ning time of helical CT can increase the diffi culty of optimizing the delay time between the beginning of contrast material injection and the acquisition of images [2â€"4].Recent advances in reconstructionspeed al low helical CT scanning delay time to be individualizedon a case-by-case basis by mon itoring contrast enhancement with rapidly re constructed CT images obtained at a stationary level within or near the organ of interestduring the bolus injection of IV contrast material. Sil verman et al. [6][7][8] and Kopka et al. [9,10] evaluated a system in which this rapid recon struction process allowed monitoring of hepatic contrast enhancement by near real-time graphic and numeric display ofhepatic density in a pre determined region of interest (ROl). Their sys tem allowed the operator to initiate helical CT imaging when hepatic density reached a preset numeric threshold (automated ROI threshold triggering). These investigators reported an im provement in the quality of hepatic contrast en hancement when compared with that of standard helical examinations using a fixed scanning delay time and suggested that the amount of contrast material could be reduced without compromising scan quality [8, 10].A recently developed hardware and soft ware system devised for bol...

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“…Detection of liver lesions is not only dependent on scanning during the phase that optimally distinguishes normal from abnormal tissue as discussed [15][16][17][18][19][20][21][22][23][24] . Optimized imaging requires using adequate amounts of contrast, i.e.…”

Section: Higher Concentration Contrast In Msctmentioning

confidence: 99%

Liver metastases: imaging considerations for protocol development with Multislice CT (MSCT)

Silverman¹

2006

Cancer Imaging

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Conventional, single-slice helical computed tomography (SSCT) allowed for scanning the majority of the liver during the critical portal venous phase. This was often referred to as the 'optimal temporal window'. The introduction of current day multislice CT (MSCT) now allows us to acquire images in a much shorter time and more precisely than ever before. This yields increased conspicuity between low attenuation lesions and the enhanced normal liver parenchyma and optimal imaging for the vast majority of hepatic hypovascular metastases. Most importantly, these scanners, when compared to conventional non-helical scanners, avoid impinging upon the 'equilibrium' phase when tumors can become isodense/invisible. MSCT also allows for true multiphase scanning during the arterial and late arterial phases for detection of hypervascular metastases. The MSCT imaging speed has increased significantly over the past years with the introduction of 32-and 64-detector systems and will continue to increase in the future volumetric CT. This provides a number of important gains that are discussed in detail.

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Assessment of a technology that permits individualized scan delays on helical hepatic CT: a technique to improve efficiency in use of contrast material.

Cited by 57 publications

References 7 publications

Biphasic spiral CT of the liver: automatic bolus tracking or time delay?

Biphasic spiral CT of the liver: automatic bolus tracking or time delay?

Optimizing contrast enhancement during helical CT of the liver: a comparison of two bolus tracking techniques.

Liver metastases: imaging considerations for protocol development with Multislice CT (MSCT)

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