Aortic and hepatic enhancement and tumor-to-liver contrast: analysis of the effect of different concentrations of contrast material at multi-detector row helical CT

Feasibility of a single-phase portal venous CT protocol using bolus tracking technique and lean body weight-based contrast media dose

PURPOSE

To evaluate the impact of the use of lean body weight (LBW)-based contrast material (CM) dose and bolus tracking technique on portal venous phase abdominal CT image quality.

MATERIALS AND METHODS

IRB-approved prospective study; informed consent was acquired. In the period July-November 2023, we randomly selected 105 oncologic patients scheduled for a portal venous phase abdominal CT to undergo our experimental protocol (i.e., 0.7 gI/Kg of LBW CM administration and bolus tracking on the liver). Included patients had performed a "standard" portal venous phase abdominal CT (i.e., 0.6 gI/Kg of total body weight (TBW) contrast material administration and 70 s fixed delay) on the same scanner within the previous 12 months. One reader evaluated CT images measuring liver, portal vein, kidney cortex, and spleen attenuation; values were normalized to paraspinal muscles.

RESULTS

Median administered contrast dose (350 mgI/mL CM) was 99 mL (IQR: 81-115 mL) using the experimental protocol and 110 mL (IQR: 100-120 mL) using the standard one (p < 0.0001). Median acquisition delay using the experimental protocol was 65" (IQR 59-73"). Median normalized hepatic enhancement was significantly higher using the experimental protocol (1.97, IQR: 1.83-2.47 vs. 1.86, IQR: 1.58-2.11; p < 0.0001). Median normalized portal vein enhancement was significantly higher using the experimental protocol (3.43, IQR: 2.73-4.04 vs. 2.91, IQR: 2.58-3.41; p < 0.0001). No statistically significant differences were found in the kidneys' cortex and aorta normalized enhancement (p > 0.05).

CONCLUSION

The combination of LBW-based CM dose administration and bolus tracking allows a significant CM dose reduction and a significant liver and portal vein enhancement increase.

CLINICAL RELEVANCE STATEMENT

Lean body weight-based contrast material (CM) dose administration and bolus tracking technique in portal venous phase CT scans overcome differences in body composition and hemodynamics, improving reproducibility. It allows a significant CM dose reduction with increased liver and portal vein enhancement.

KEY POINTS

Lean body weight (LBW)-based contrast material (CM) dosing could be superior to total body weight dosing. Portal venous phase CT with a liver bolus tracking technique improved liver and spleen enhancement with a reduced contrast dose. The combination of LBW-based CM dosing and liver bolus tracking technique enables more "customized" CT examinations.

The Image Quality and Diagnostic Performance of CT with Low-Concentration Iodine Contrast (240 mg Iodine/mL) for the Abdominal Organs

Purpose: To evaluate the difference between CT examinations using 240 mgI/mL contrast material (CM) and 320 mgI/mL CM in the contrast enhancement of the abdominal organs and the diagnostic performance for focal hepatic lesions. Materials and methods: This retrospective study included 422 CT examinations, using 240 mgI/mL iohexol (Group A, 206 examinations) and 320 mgI/mL ioversol (Group B, 216 examinations), performed between April 2019 and May 2020. Two CT scanners (single-source CT (machine A) and dual-source CT (machine B)) were used to obtain CT images. Two radiologists independently drew regions of interest (ROIs) in the liver, pancreas, spleen, kidney, aorta, portal vein, and paraspinal muscle. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for each organ. They evaluated the degree of subjective enhancement of the organs and detected/differentiated focal hepatic lesions. Results: The SNR, CNR, and subjective enhancement of most organs were significantly higher in Group B than in Group A (p < 0.05). The sensitivity and specificity for cysts and malignancy were higher than 85.0% in both groups. The sensitivity for hemangioma was lower in Group B (<75%) than in Group A. In Group A, the SNR and CNR were significantly higher in most organs with machine B than with machine A. Conclusion: Although the SNR and CNR of the abdominal organs were lower with 240 mgI/mL CM than with 320 mgI/mL CM, 240 mgI/mL CM was feasible for evaluating the liver. A CT scanner with more advanced specifications may be beneficial for examinations with 240 mgI/mL CM by using lower tube voltage.

Comparison of the Value of Color Doppler Ultrasound and Multislice Spiral CT in the Differential Diagnosis of Benign and Malignant Nodules in the Liver

Objective

This study aimed to explore the value of color Doppler ultrasound and multislice spiral CT (MSCT) in the differential diagnosis of benign and malignant nodules in the liver.

Methods

The clinical imaging data of 102 patients with nodular hepatocellular carcinoma (hepatocellular carcinoma group) and 50 patients with focal nodular hyperplasia (FNH) of the liver (FNH group) admitted to our hospital were collected, and their color Doppler ultrasound and MSCT imaging features were retrospectively analyzed to explore the value of their clinical application in the differential diagnosis of benign and malignant nodules in the liver.

Results

The sensitivity, accuracy, and negative predictive value of MSCT in the diagnosis of nodular liver cancer were 94.12%, 92.76%, and 88.24%, respectively, which were significantly higher than those of color Doppler ultrasound 79.41%, 84.21%, and 69.12%, and the difference was statistically significant (P < 0.05).

Conclusion

In conclusion, the value of MSCT in the differential diagnosis of benign and malignant liver nodules was significantly better than color Doppler ultrasound.

Comparison of low kVp CT and dual-energy CT for the evaluation of hypervascular hepatocellular carcinoma

PURPOSE

To compare lesion conspicuity and image quality of arterial phase images obtained from low kVp (90-kVp) and dual-energy (DE) scans for the evaluation of hypervascular hepatocellular carcinoma (HCC).

METHODS

This retrospective study included 229 patients with HCC who underwent either 90 kVp (n = 106) or DE scan (80- and 150-kVp with a tin filter) (n = 123) during the arterial phase. DE scans were reconstructed into a linearly blended image with a mixed ratio of 0.6 (60% 80kVp and 40% 150 kVp) and post-processed for 40 keV and 50 keV images. The contrast-to-noise ratio (CNR) of HCC to the liver and image noise was measured. Lesion conspicuity, liver parenchymal image quality, and overall image preference were assessed qualitatively by three independent radiologists.

RESULTS

DE 40 keV images had the highest CNR of HCC, and DE blended images had the lowest image noise among four image sets (p = 0.01 and p < 0.001, respectively). There was no significant difference in mean volume CT dose index and dose-length product between DE and low kVp scan (ps > 0.05). For qualitative analyses, DE blended images had the highest scores for image quality and overall image preference (ps < 0.001).

CONCLUSION

At an equal radiation dose, DE 40 keV showed higher CNR of HCC and DE blended image showed higher image quality and image preference compared with low kVp CT.

Image quality improvement with deep learning-based reconstruction on abdominal ultrahigh-resolution CT: A phantom study

Purpose

In an ultrahigh‐resolution CT (U‐HRCT), deep learning‐based reconstruction (DLR) is expected to drastically reduce image noise without degrading spatial resolution. We assessed a new algorithm's effect on image quality at different radiation doses assuming an abdominal CT protocol.

Methods

For the normal‐sized abdominal models, a Catphan 600 was scanned by U‐HRCT with 100%, 50%, and 25% radiation doses. In all acquisitions, DLR was compared to model‐based iterative reconstruction (MBIR), filtered back projection (FBP), and hybrid iterative reconstruction (HIR). For the quantitative assessment, we compared image noise, which was defined as the standard deviation of the CT number, and spatial resolution among all reconstruction algorithms.

Results

Deep learning‐based reconstruction yielded lower image noise than FBP and HIR at each radiation dose. DLR yielded higher image noise than MBIR at the 100% and 50% radiation doses (100%, 50%, DLR: 15.4, 16.9 vs MBIR: 10.2, 15.6 Hounsfield units: HU). However, at the 25% radiation dose, the image noise in DLR was lower than that in MBIR (16.7 vs. 26.6 HU). The spatial frequency at 10% of the modulation transfer function (MTF) in DLR was 1.0 cycles/mm, slightly lower than that in MBIR (1.05 cycles/mm) at the 100% radiation dose. Even when the radiation dose decreased, the spatial frequency at 10% of the MTF of DLR did not change significantly (50% and 25% doses, 0.98 and 0.99 cycles/mm, respectively).

Conclusion

Deep learning‐based reconstruction performs more consistently at decreasing dose in abdominal ultrahigh‐resolution CT compared to all other commercially available reconstruction algorithms evaluated.

Towards Personalised Contrast Injection: Artificial-Intelligence-Derived Body Composition and Liver Enhancement in Computed Tomography

In contrast-enhanced computed tomography, total body weight adapted contrast injection protocols have proven successful in achieving a homogeneous enhancement of vascular structures and liver parenchyma. However, because solid organs have greater perfusion than adipose tissue, the lean body weight (fat-free mass) rather than the total body weight is theorised to cause even more homogeneous enhancement. We included 102 consecutive patients who underwent a multiphase abdominal computed tomography between March 2016 and October 2019. Patients received contrast media (300 mgI/mL) according to bodyweight categories. Using regions of interest, we measured the Hounsfield unit (HU) increase in liver attenuation from unenhanced to contrast-enhanced computed tomography. Furthermore, subjective image quality was graded using a four-point Likert scale. An artificial intelligence algorithm automatically segmented and determined the body compositions and calculated the percentages of lean body weight. The hepatic enhancements were adjusted for iodine dose and iodine dose per total body weight, as well as percentage lean body weight. The associations between enhancement and total body weight, body mass index, and lean body weight were analysed using linear regression. Patients had a median age of 68 years (IQR: 58–74), a total body weight of 81 kg (IQR: 73–90), a body mass index of 26 kg/m² (SD: ±4.2), and a lean body weight percentage of 50% (IQR: 36–55). Mean liver enhancements in the portal venous phase were 61 ± 12 HU (≤70 kg), 53 ± 10 HU (70–90 kg), and 53 ± 7 HU (≥90 kg). The majority (93%) of scans were rated as good or excellent. Regression analysis showed significant correlations between liver enhancement corrected for injected total iodine and total body weight (r = 0.53; p < 0.001) and between liver enhancement corrected for lean body weight and the percentage of lean body weight (r = 0.73; p < 0.001). Most benefits from personalising iodine injection using %LBW additive to total body weight would be achieved in patients under 90 kg. Liver enhancement is more strongly associated with the percentage of lean body weight than with the total body weight or body mass index. The observed variation in liver enhancement might be reduced by a personalised injection based on the artificial-intelligence-determined percentage of lean body weight.

Imaging Characteristics of Liver Metastases Overlooked at Contrast-Enhanced CT

OBJECTIVE

The purpose of this study was to evaluate the imaging characteristics of liver metastases overlooked at contrast-enhanced CT.

MATERIALS AND METHODS

The records of 746 patients with a diagnosis of liver metastases from colorectal, breast, gastric, or lung cancer between November 2010 and September 2017 were reviewed. Images were reviewed when liver metastases were first diagnosed, and images from prior contrast-enhanced CT examinations were checked if available. These lesions were classified into two groups: missed lesions (those missed on the prior images) and detected lesions (those correctly identified and invisible on the prior images or there were no prior images). Tumor size, contrast-to-noise ratio, location, presence of coexisting liver cysts and hepatic steatosis, and indications for examination were compared between the groups. The t test and Fisher exact test were used to analyze the imaging characteristics of previously overlooked lesions.

RESULTS

The final analysis included 137 lesions, of which 68 were classified as missed. In univariate analysis, contrast-to-noise ratio was significantly lower in missed lesions (95% CI, 2.65 ± 0.24 vs 3.90 ± 0.23; p < 0.001). The proportion of subcapsular lesions (odds ratio, 3.44; p < 0.001), hepatic steatosis (odds ratio, 6.35; p = 0.007), and examination indication other than survey of malignant tumors (odds ratio, 9.07; p = 0.02) were significantly higher for missed lesions.

CONCLUSION

Liver metastases without sufficient contrast enhancement, those in patients with hepatic steatosis, those in subcapsular locations, and those found at examinations for indications other than to assess for tumors were significantly more likely to be overlooked.

Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula

Purpose

To prospectively compare the performance of James and Boer formula in contrast media (CM) administration, in terms of image quality and parenchymal enhancement in obese patients undergoing CT of the abdomen.

Materials and Methods

Fifty-five patients with a body mass index (BMI) greater than 35 kg/m² were prospectively included in the study. All patients underwent 64-row CT examination and were randomly divided in two groups: 26 patients in Group A and 29 patients in Group B. The amount of injected CM was computed according to the patient's lean body weight (LBW), estimated using either Boer formula (Group A) or James formula (Group B). Patient's characteristics, CM volume, contrast-to-noise ratio (CNR) of liver, aorta and portal vein, and liver contrast enhancement index (CEI) were compared between the two groups. For subjective image analysis readers were asked to rate the enhancement of liver, kidneys, and pancreas based on a 5-point Likert scale.

Results

Liver CNR, aortic CNR, and portal vein CNR showed no significant difference between Group A and Group B (all P ≥ 0.177). Group A provided significantly higher CEI compared to Group B (P = 0.007). Group A and Group B returned comparable overall subjective enhancement values (3.54 and vs 3.20, all P ≥ 0.199).

Conclusions

Boer formula should be the method of choice for LBW estimation in obese patients, leading to an accurate CM amount calculation and an optimal liver contrast enhancement in CT.

LI-RADS technical requirements for CT, MRI, and contrast-enhanced ultrasound

Accurate detection and characterization of liver observations to enable HCC diagnosis and staging using LI-RADS requires a technically adequate imaging exam. To help achieve this objective, LI-RADS has proposed technical requirements for CT, MR, and contrast-enhanced ultrasound of liver. This article reviews the technical requirements for liver imaging, including the description of minimum acceptable technical standards, such as the scanner hardware requirements, recommended dynamic imaging phases, and common technical challenges of liver imaging.

MDCT of the liver in obese patients: evaluation of a different method to optimize iodine dose

PURPOSE

To prospectively compare two different approaches for estimating the amount of intravenous contrast media (CM) needed for multiphasic MDCT of the liver in obese patients.

MATERIALS AND METHODS

This single-center, HIPAA-compliant prospective study was approved by our Institutional Review Board. Ninety-six patients (55 men, 41 women), with a total of 42 hypovascular liver lesions, underwent MDCT of the liver. The amount of contrast medium injected was computed according to the patient's lean body weight which was estimated using either a bioimpedance device (Group A) or the James formula (Group B). The following variables were compared between the two groups: the amount of contrast medium injected (in grams of Iodine, gI), the contrast enhancement index (CEI) and the lesion-to-liver contrast-to-noise ratio.

RESULTS

Protocols A and B yielded significant differences in the amount of CM injected (mean values 41.9 ± 4.41 gI in Group A vs. 35.9 ± 5.75 gI in Group B; P = 0.021). The mean CEI value and lesion-to-liver contrast-to-noise ratio measured on the portal phase were significantly higher with protocol A than with protocol B (P < 0.05).

CONCLUSIONS

Our study shows that the adoption of a bioimpedance device in obese patients improves liver parenchymal enhancement and lesion conspicuity.

Selection of peripheral intravenous catheters with 24-gauge side-holes versus those with 22-gauge end-hole for MDCT: A prospective randomized study

PURPOSE

To compare the 24-gauge side-holes catheter and conventional 22-gauge end-hole catheter in terms of safety, injection pressure, and contrast enhancement on multi-detector computed tomography (MDCT).

MATERIALS & METHODS

In a randomized single-center study, 180 patients were randomized to either the 24-gauge side-holes catheter or the 22-gauge end-hole catheter groups. The primary endpoint was safety during intravenous administration of contrast material for MDCT, using a non-inferiority analysis (lower limit 95% CI greater than -10% non-inferiority margin for the group difference). The secondary endpoints were injection pressure and contrast enhancement.

RESULTS

A total of 174 patients were analyzed for safety during intravenous contrast material administration for MDCT. The overall extravasation rate was 1.1% (2/174 patients); 1 (1.2%) minor episode occurred in the 24-gauge side-holes catheter group and 1 (1.1%) in the 22-gauge end-hole catheter group (difference: 0.1%, 95% CI: -3.17% to 3.28%, non-inferiority P=1). The mean maximum pressure was higher with the 24-gauge side-holes catheter than with the 22-gauge end-hole catheter (8.16±0.95kg/cm² vs. 4.79±0.63kg/cm², P<0.001). The mean contrast enhancement of the abdominal aorta, celiac artery, superior mesenteric artery, and pancreatic parenchyma in the two groups were not significantly different.

CONCLUSION

In conclusion, our study showed that the 24-gauge side-holes catheter is safe and suitable for delivering iodine with a concentration of 300mg/mL at a flow-rate of 3mL/s, and it may contribute to the care of some patients, such as patients who have fragile and small veins. (Trial registration: UMIN000023727).

Comparison of enhancement and image quality: different iodine concentrations for liver on 128-slice multidetector computed tomography in the same chronic liver disease patients

BACKGROUND/AIMS

The objective of this study was to compare the degree of hepatic enhancement and image quality using contrast media of different iodine concentrations with the same iodine dose.

METHODS

From July 2011 to June 2013, 50 patients with chronic liver disease who underwent baseline and follow-up 128-slice multidetector computed tomography(MDCT) using contrast media with 350 mg I/mL (group A) and 400 mg I/mL (group B) iodine concentrations were included in this prospective study. The patients were randomly allocated to one of two protocols: 350 mg I/mL initially and then 400 mg I/mL; and 400 mg I/mL initially and then 350 mg I/mL. The bolus tracking technique was used to initiate the arterial phase scan. The computed tomography values of hepatic parenchyma, abdominal aorta and portal vein were measured. The degrees of hepatic and vascular enhancement were rated on a 4-point scale for qualitative assessment. The paired Student t test was used to compare outcome variables.

RESULTS

The mean hepatic enhancement was significantly higher in group B than in group A during the portal (p = 0.025) and equilibrium phases (p = 0.021). In all phases, group B had significantly higher mean liver-to-aorta contrast (p < 0.05) and mean visual scores for hepatic and vascular enhancement (p < 0.001).

CONCLUSIONS

This study showed that a higher iodine concentration (400 mg I/mL) in contrast media was more effective at improving hepatic enhancement in portal and equilibrium phase images and overall image quality using 128-slice MDCT in chronic liver disease patients.

Automatic spectral imaging protocol selection and iterative reconstruction in abdominal CT with reduced contrast agent dose: initial experience

OBJECTIVE

To evaluate the feasibility, image quality, and radiation dose of automatic spectral imaging protocol selection (ASIS) and adaptive statistical iterative reconstruction (ASIR) with reduced contrast agent dose in abdominal multiphase CT.

METHODS

One hundred and sixty patients were randomly divided into two scan protocols (n = 80 each; protocol A, 120 kVp/450 mgI/kg, filtered back projection algorithm (FBP); protocol B, spectral CT imaging with ASIS and 40 to 70 keV monochromatic images generated per 300 mgI/kg, ASIR algorithm. Quantitative parameters (image noise and contrast-to-noise ratios [CNRs]) and qualitative visual parameters (image noise, small structures, organ enhancement, and overall image quality) were compared.

RESULTS

Monochromatic images at 50 keV and 60 keV provided similar or lower image noise, but higher contrast and overall image quality as compared with 120-kVp images. Despite the higher image noise, 40-keV images showed similar overall image quality compared to 120-kVp images. Radiation dose did not differ between the two protocols, while contrast agent dose in protocol B was reduced by 33 %.

CONCLUSION

Application of ASIR and ASIS to monochromatic imaging from 40 to 60 keV allowed contrast agent dose reduction with adequate image quality and without increasing radiation dose compared to 120 kVp with FBP.

KEY POINTS

• Automatic spectral imaging protocol selection provides appropriate scan protocols. • Abdominal CT is feasible using spectral imaging and 300 mgI/kg contrast agent. • 50-keV monochromatic images with 50 % ASIR provide optimal image quality.

The prevalence and significance of thoracic findings in patients undergoing extended coverage computed tomography for assessment of abdominal aortic aneurysms

OBJECTIVE

Many major vascular centres, including ours, incorporate coverage of the thoracic aorta in CT scans evaluating abdominal aortic aneurysms (AAAs) (extended coverage contrast-enhanced CT (EC-CECT) scan]. We sought to determine the prevalence of thoracic pathology in a large consecutive series of patients with AAA undergoing EC-CECT.

METHODS

All patients who underwent EC-CECT for AAA between April 2013 and 2014 were identified from our radiology information system. Reports were retrospectively reviewed and for each study, sex, age and reported thoracic aortic and other non-vascular findings were extracted. Findings were initially categorized into "major" or "minor" depending on if they were mentioned in the report impression/conclusion. Any major thoracic pathology was termed "significant" if there was a new diagnosis/patient intervention/investigation and a change in patient management.

RESULTS

Of the 150 scans included in the study, 97 (65%) had at least one thoracic finding. These findings included 24 scans (16%) with major findings and 73 scans (48%) with minor findings. In 13 scans (9%), the findings were significant and resulted in a delay (n = 11) or cancellation (n = 2) of AAA repair.

CONCLUSION

Pre-procedural EC-CECT helps to identify significant intrathoracic findings in patients with AAA, which can have a major impact on AAA repair. This study supports the routine use of pre-procedural EC-CECT in planning AAA repair.

ADVANCES IN KNOWLEDGE

This study describes the prevalence of significant thoracic pathology, which can impact on AAA repair. This information could potentially change the pre-procedure imaging protocol for patients with AAA.

Liver detection algorithm: its efficacy for CT noise reduction in the liver

OBJECTIVES

This study was performed to evaluate the efficacy of a novel computed tomography (CT) liver detection algorithm (LDA), which allows for targeted increase of radiation dose to the upper abdomen, on image quality of the liver.

METHODS

We retrospectively evaluated the LDA by comparing 40 consecutive patients who had portal venous CT abdomen performed without use of the algorithm, to 40 patients in whom the algorithm was used. Image quality was assessed objectively by comparing the standard deviation (SD) of attenuation values in Hounsfield units (HU) of the abdominal organs. Qualitative analysis was performed by two blinded radiologists who independently graded the image quality of abdominal organs

RESULTS

There was significant noise reduction in the liver (P < 0.001) and spleen (P < 0.001) in the LDA group compared to the conventional group. There was also a significant improvement in image quality of the liver (P < 0.001), kidney (P < 0.001), spleen (P < 0.001), pancreas (P < 0.001), and psoas (P = 0.005) in the LDA group compared to the conventional group. Overall dose between the two groups was similar.

CONCLUSIONS

This liver detection algorithm improves the subjective image quality of upper abdominal organs, in particular the liver, without increasing overall radiation dose.

A new method with variable injection parameters in contrast-enhanced CT: a phantom study for evaluating an aortic peak enhancement

Contrast-enhanced CT employs a standard uniphasic single-injection method (SIM), wherein administration is based on two parameters: the iodine administration rate (mgI/s) and the injection duration (s). However, as the SIM uses a fixed iodine administration rate, only a uniform contrast enhancement can be achieved with this method. The iodine administration rate can be increased only by increasing the iodine dose or shortening the injection duration, and no arbitrary adjustments can be made to the peak enhancement characteristics of the time-enhancement curves (TECs) at the fixed injection parameters used in the SIM. To address this problem, we developed a variable injection method (VIM) with a new parameter, the variation factor (VF), to adjust the TECs. A phantom study with the VIM indicated that arbitrary adjustments to the iodine administration rate could be made without changing the injection duration or increasing the iodine load. In our study, VFs of 0.3 and 0.5, which showed earlier achievement of peak enhancements, showed better temporal separation between arterial vasculature and parenchyma or the venous vasculature than that obtained with the SIM. The higher peak enhancement provided by the VF of 0.3 was also considered to improve the contrast in qualitative diagnostic examinations. A VF of 0.5 increased the duration of the enhancement and was considered to produce stable enhancement of contrast in vascular investigations. The VF is now an essential parameter, and the VIM is useful as a reasonable contrast method that may contribute to both improved visualization and improvement in the accuracy of morphologic diagnosis.

Computed tomography: revolutionizing the practice of medicine for 40 years

Computed tomography (CT) has had a profound effect on the practice of medicine. Both the spectrum of clinical applications and the role that CT has played in enhancing the depth of our understanding of disease have been profound. Although almost 90 000 articles on CT have been published in peer-reviewed journals over the past 40 years, fewer than 5% of these have been published in Radiology. Nevertheless, these almost 4000 articles have provided a basis for many important medical advances. By enabling a deepened understanding of anatomy, physiology, and pathology, CT has facilitated key advances in the detection and management of disease. This article celebrates this breadth of scientific discovery and development by examining the impact that CT has had on the diagnosis, characterization, and management of a sampling of major health challenges, including stroke, vascular diseases, cancer, trauma, acute abdominal pain, and diffuse lung diseases, as related to key technical advances in CT and manifested in Radiology.

Attenuation-based automatic kilovoltage selection and sinogram-affirmed iterative reconstruction: effects on radiation exposure and image quality of portal-phase liver CT

Objective

To compare the radiation dose and image quality between standard-dose CT and a low-dose CT obtained with the combined use of an attenuation-based automatic kilovoltage (kV) selection tool (CARE kV) and sinogram-affirmed iterative reconstruction (SAFIRE) for contrast-enhanced CT examination of the liver.

Materials and Methods

We retrospectively reviewed 67 patients with chronic liver disease in whom both, standard-dose CT with 64-slice multidetector-row CT (MDCT) (protocol A), and low-dose CT with 128-slice MDCT using CARE kV and SAFIRE (protocol B) were performed. Images from protocol B during the portal phase were reconstructed using either filtered back projection or SAFIRE with 5 different iterative reconstruction (IR) strengths. We performed qualitative and quantitative analyses to select the appropriate IR strength. Reconstructed images were then qualitatively and quantitatively compared with protocol A images.

Results

Qualitative and quantitative analysis of protocol B demonstrated that SAFIRE level 2 (S2) was most appropriate in our study. Qualitative and quantitative analysis comparing S2 images from protocol B with images from protocol A, showed overall good diagnostic confidence of S2 images despite a significant radiation dose reduction (47% dose reduction, p < 0.001).

Conclusion

Combined use of CARE kV and SAFIRE allowed significant reduction in radiation exposure while maintaining image quality in contrast-enhanced liver CT.

Hybrid iterative reconstruction technique for liver CT scans for image noise reduction and image quality improvement: evaluation of the optimal iterative reconstruction strengths

PURPOSE

This study sought to investigate the effect of the hybrid iterative reconstruction (IR) algorithm (iDose, Philips Healthcare) on the improvement of image quality of computed tomography (CT) scans of the liver and determine the appropriate level of IR strength for clinical use.

MATERIALS AND METHODS

A total of 75 patients (41 men and 34 women; mean age, 59.5 years) with a primary abdominal malignancy who underwent two-phase liver CT scans for the work-up of their liver metastases, were included in this study. The CT images during the portal phase were reconstructed using either filtered back projection (FBP) or the hybrid IR algorithm with six different levels of IR strengths. The signal-to-noise ratio of the liver (SNR(liver)) and the contrast-to-noise ratio of the portal vein to muscle (CNR(pv to m)) were measured. For qualitative analysis, image noise, visibility of small intrahepatic vascular structures, beam-hardening artefact, lesion conspicuity, and overall image quality were graded by two radiologists.

RESULTS

Quantitative analysis demonstrated that image noise was significantly reduced along with the increasing level of iDose and that the values of SNR(liver) and CNR(pv to m) were significantly better with iDose than those of FBP images. Qualitative assessment also showed significantly better results with iDose compared with FBP (p < 0.05) and the parameters for subjective image quality were highest with iDose level 4.

CONCLUSIONS

The hybrid IR technique is able to reduce image noise and to provide better image quality than FBP, and an intermediate strength of iDose (level 4) provided the highest quality images.

Use of high-concentration contrast media in multiple-detector-row CT: principles and rationale

Contrast-medium-enhanced multiple-detector-row CT (MDCT) is a powerful technique for vascular and hepatic imaging. With increasingly faster acquisition speeds, which have become possible with latest 8- and 16-channel scanner systems, contrast medium delivery is becoming increasingly difficult. This article reviews the pharmacokinetic and physiologic principles of vascular and hepatic enhancement following the intravenous injection of iodinated contrast medium. The effects of user-selectable injection parameters, such as the injection rate, the injection duration, and the contrast medium concentration on arterial and parenchymal enhancement are elucidated. Equipped with this knowledge, rational injection strategies for CT angiographic protocols for scanners with different acquisition speeds are derived. Furthermore, injection and timing protocols, optimized for hepatic MDCT during the early arterial, late arterial, and parenchymal phases, are developed.

MDCT of renal and mesenteric vessels

Computed tomography angiography (CTA) with multiple detector-row CT (MDCT) has evolved into an established technique for non-invasive imaging of renal and mesenteric vessels. With adequate selection of acquisition parameters (thin collimation) high spatial-resolution volumetric data sets for subsequent 2D and 3D reformation can be acquired. Contrast medium (CM) injection parameters need to be adjusted to the acquisition speed of the scanners. Whereas fast acquisitions allow a reduction of total CM volume in the setting of CTA, this is not the case when CTA is combined with a second-phase abdominal MDCT acquisition for parenchymal (e.g., hepatic) imaging. Renal CTA is an accurate and reliable test for visualizing vascular anatomy and renal artery stenosis, and therefore a viable alternative to MRA in the assessment of patients with renovascular hypertension and in potential living related renal donors. CTA, combined with abdominal/parenchymal MDCT is a first-line diagnostic test in patients with suspected abdominal vascular emergencies, such as acute mesenteric ischemia, and an excellent tool to assess a wide variety of vascular abnormalities of the abdominal viscera.

Evaluation of a method for improving the detection of hepatocellular carcinoma

OBJECTIVE

To improve the detection of liver lesions in patients with hepatocellular carcinoma (HCC) via an iodine contrast enhancement tool.

METHODS

Thirty-two patients with clinically proven HCCs underwent imaging with a three-phase protocol on a 256-slice MDCT. The contrast enhancement in the reconstructed slices was improved via a post-processing tool. Mean image noise was measured in four different regions: liver lesion, healthy liver, subcutaneous fat and bone. For each image set the image noise and contrast-to-noise ratio (CNR) were assessed. For subjective image assessment, four experienced radiologists evaluated the diagnostic quality.

RESULTS

While employing the post-processing algorithm, CNR between the liver lesion and healthy liver tissue improves significantly by a factor of 1.78 (CNRwithout vC = 2.30 ± 1.92/CNRwith vC = 4.11 ± 3.05) (P* = 0.01). All results could be achieved without a strengthening of artefacts; mean HU values of subcutaneous fat and bone did not significantly change. Subjective image analysis illustrated a significant improvement when employing post-processing for clinically relevant criteria such as diagnostic confidence.

CONCLUSION

With post-processing we see a significantly improved detection of arterial uptake in hepatic lesions compared with non-processed data. The improvement in CNR was confirmed by subjective image assessment for small lesions and for lesions with limited uptake.

KEY POINTS

• Enhancement with iodine-based contrast agents is an essential part of CT. • A new post-processing tool significantly improves the diagnostics of hepatocellular carcinoma. • It also improves detection of small lesions with limited iodine uptake.

Feasibility of low-radiation-dose CT for abdominal examinations with hybrid iterative reconstruction algorithm: low-contrast phantom study

Our purpose in this study was to evaluate the image quality of low-radiation-dose CT using hybrid iterative reconstruction (HIR), and to compare the results with those of filtered back projection (FBP) at routine doses. We measured the mean values and standard deviation of the CT numbers within and outside a 15-mm low-contrast object cylinder at 1.0% contrast level. The noise reduction levels of the HIR were 1 (weak) to 7 (strong). Visual inspection of the low-contrast detectability was done by six radiologic technologists. The low-contrast detectability of the cylinder at the 1.0% contrast level with HIR at all mAs levels was equal to that obtained with FBP, and thus the use of HIR did not result in any improvement of low-contrast detectability.

Optimization of the dynamic, Gd-EOB-DTPA-enhanced MRI of the liver: the effect of the injection rate

BACKGROUND

Tissue-specific gadolinium-based contrast agents such as Gd-BOPTA, Gd-EOB-DTPA are increasingly used for liver imaging. Despite the added value of the hepatobiliary phase a proper arterial phase is still critical, especially in patients with chronic liver diseases. So far, there are limited data in the literature about the effect of the injection speed of Gd-EOB-DTPA in liver and vessel enhancement.

PURPOSE

To evaluate the effect of injection rate on the enhancement of liver parenchyma and vasculature in Gd-EOB-DTPA-enhanced liver MRI.

MATERIAL AND METHODS

Eighty patients who underwent Gd-EOB-DTPA-enhanced liver MRI (1.5T multi-channel MR-system) were retrospectively evaluated. We used a Care Bolus technique with an injection rate of 2 mL/s in group 1 (n = 40) and a Care Bolus technique with an injection rate of 1 mL/s in group 2 (n = 40) to determine the start of the arterial-dominant phase. Signal intensities were measured in vascular structures and liver parenchyma. Signal-to-noise-ratio (SNR), SNR increase (SNRi), and percentage enhancement (PE) were calculated and compared by a students t-test.

RESULTS

The SNR, SNRi, and PE of the aorta in the arterial phase were significantly higher in group 2 in comparison to group 1 (P = 0.007, P = 0.0043, and P < 0.001, respectively). There were no significant differences concerning the SNR, SNRi, or PE of the portal vein and the normal liver parenchyma between both groups at all time points.

CONCLUSION

The study shows that a lower injection rate of 1 mL/s enables a higher enhancement in the aorta in the arterial phase compared with Gd-EOB-DTPA-enhanced MRI with the more commonly used injection rate of 2 mL/s.

Feasibility of a fixed scan delay technique using a previous bolus tracking technique data for dynamic hepatic CT

OBJECTIVE

To compare the quality of contrast enhancement and hepatic CT images acquired using bolus tracking technique at two different time points and those acquired with fixed scan delay technique using a previous bolus tracking data.

MATERIALS AND METHODS

Fifty patients who underwent 3 different hepatic CT exams (25-s fixed injection of 600 mg iodine (I)/kg or 100mL of 370 mg I/mL nonionic contrast medium) were enrolled. The first and second exams were performed with a bolus tracking technique. The third exam was performed with a fixed scan delay technique using the first exam data. Differences in attenuation values in the abdominal organs were examined and evaluated visually on hepatic arterial phase images.

RESULTS

There was no significant difference in the mean 50-HU threshold times between the first and second bolus tracking exams with intra-patient differences between them (1.3±0.9 s). No significant intra-patient differences were noted in organ attenuation and visual evaluation on hepatic arterial phase images between the 3 exams.

CONCLUSION

The fixed scan delay technique using a previous bolus tracking data is feasible for hepatic CT exams to follow up hepatocellular carcinoma.

Effect of low tube voltage on image quality, radiation dose, and low-contrast detectability at abdominal multidetector CT: phantom study

PURPOSE

To investigate the effect of low tube voltage (80 kV) on image quality, radiation dose, and low-contrast detectability (LCD) at abdominal computed tomography (CT).

MATERIALS AND METHODS

A phantom containing low-contrast objects was scanned with a CT scanner at 80 and 120 kV, with tube current-time product settings at 150-650 mAs. The differences between image noise, contrast-to-noise ratio (CNR), and scores of LCD obtained with 80 kV at 150-650 mAs and those obtained with 120 kV at 300 mAs were compared respectively.

RESULTS

The image noise substantially increased with low tube voltage. However, with identical dose, use of 80 kV resulted in higher CNR compared with CNR at 120 kV. There were no statistically significant difference in CNR and scores of LCD between 120 kV at 300 mAs and 80 kV at 550-650 mAs (P > 0.05). The relative dose delivered at 80 kV ranged from 58% at 550 mAs to 68% at 650 mAs.

CONCLUSION

With a reduction of the tube voltage from 120 kV to 80 kV at abdominal CT, the radiation dose can be reduced by 32% to 42% without degradation of CNR and LCD.

Optimal setting of automatic exposure control based on image noise and contrast on iodine-enhanced CT

RATIONALE AND OBJECTIVES

The aim of this study was to investigate variations in image noise and contrast using automatic exposure control (AEC) and different tube voltages on nonenhanced and iodine-enhanced hepatic computed tomography.

MATERIALS AND METHODS

Nonenhanced and iodine-enhanced simulated liver phantoms and AEC were used. Tube current was automatically adjusted with the noise index. Two types of assessments were performed: at a fixed noise index of 10 Hounsfield units and at different noise indexes, keeping the same contrast-to-noise ratio at different tube voltages (100, 120, and 130 kV). Image noise was measured, and contrast between the computed tomographic number of the simulated liver and nodule was computed.

RESULTS

At a fixed noise index, image noise on iodine-enhanced images was 10% to 13% higher than on nonenhanced images at the same tube voltage. At 130 and 100 kV, contrast was 33.86 and 46.90 Hounsfield units, respectively, and image noise was almost the same. Contrast-to-noise ratios at 100, 120, and 130 kV were 3.31, 3.22, and 3.37, respectively, and volume computed tomographic dose index fell from 22.94 to 12.49 mGy with decreasing tube voltage.

CONCLUSIONS

With AEC, image noise on iodine-enhanced images was higher than on nonenhanced images despite identical noise index settings. As tube voltage decreased, contrast on iodine-enhanced images increased. Considering noise index and contrast variations at different tube voltages, the optimal use of AEC on iodine-enhanced computed tomography facilitates a reduction in x-ray tube output while maintaining contrast-to-noise ratio.

Automatic exposure control at MDCT based on the contrast-to-noise ratio: theoretical background and phantom study

PURPOSE

To develop a new automatic exposure control (AEC) technique based on the contrast-to-noise ratio (CNR) and provide constant lesion detectability.

METHODS

Lesion detectability is affected by factors such as image noise, lesion contrast, and lesion size. We performed ROC analysis to assess the relationship between the optimum CNR and the lesion diameter at various levels of lesion contrast. We then developed a CNR-based AEC algorithm based on lesion detectability. Using CNR- based AEC algorithm, we performed visual evaluation of low-contrast detectability by 5 radiologists on a low-contrast module of the Catphan phantom, a contrast-difference level of 1.0% (difference in the CT number = 10 HU), and objects 3.0-9.0 mm in diameter.

RESULTS

On step-and-shoot scans the mean detection fraction with CNR-based AEC remained almost constant from 88 to 99 % regardless of the lesion size. We observed the same trend on helical scans, the mean detection fraction with CNR-based AEC exhibited a high score from 91 to 100%. Although CNR-based AEC maintains higher CNR for smaller size or lower contrast lesion, radiation dose on 3 mm lesion resulted in about 13 times larger than that of 9 mm lesion size. CTDI(vol) for the CNR-based AEC technique changed dramatically with the SD(Z) from 7.5 to 100.0 mGy for step-and-shoot scans and from 9.1 to 121.5 mGy for helical scans.

CONCLUSIONS

From the viewpoint of ROC analysis-based CNR for lesion detection, CNR-based AEC potentially provide image quality advantages for clinical implementation.

Multiphase contrast-enhanced CT with highly concentrated contrast agent can be used for PET attenuation correction in integrated PET/CT imaging

PURPOSE

State-of-the-art positron emission tomography/computed tomography (PET/CT) systems incorporate multislice CT technology, thus facilitating the acquisition of multiphase, contrast-enhanced CT data as part of integrated PET/CT imaging protocols. We assess the influence of a highly concentrated iodinated contrast medium (CM) on quantification and image quality following CT-based attenuation correction (CT-AC) in PET/CT.

METHODS

Twenty-eight patients with suspected malignant liver lesions were enrolled prospectively. PET/CT was performed 60 min after injection of 400 MBq of (18)F-fluorodeoxyglucose (FDG) and following the biphasic administration of an intravenous CM (400 mg iodine/ml, Iomeron 400). PET images were reconstructed with CT-AC using any of four acquired CT image sets: non-enhanced, pre-contrast (n-PET), arterial phase (art-PET), portal venous phase (pv-PET) and late phase (late-PET). Normal tissue activity and liver lesions were assessed visually and quantitatively on each PET/CT image set.

RESULTS

Visual assessment of PET following CT-AC revealed no noticeable difference in image appearance or quality when using any of the four CT data sets for CT-AC. A total of 44 PET-positive liver lesions was identified in 21 of 28 patients. There were no false-negative or false-positive lesions on PET. Mean standardized uptake values (SUV) in 36 evaluable lesions were: 5.5 (n-PET), 5.8 (art-PET), 5.8 (pv-PET) and 5.8 (late-PET), with the highest mean increase in mean SUV of 6%. Mean SUV changes in liver background increased by up to 10% from n-PET to pv-PET.

CONCLUSION

Multiphase CT data acquired with the use of highly concentrated CM can be used for qualitative assessment of liver lesions in torso FDG PET/CT. The influence on quantification of FDG uptake is small and negligible for most clinical applications.

Optimization of exposure parameters for cone beam computed tomography sialography

OBJECTIVES

The assessment of image quality is a crucial step in the development of a new imaging protocol. Having proposed and reported on a preliminary protocol for sialography using cone beam CT (CBCT), the purpose of this study was to further optimize this protocol by maximizing the image signal difference-to-noise ratio (SDNR) and to relate these new data to previously published dosimetric data for CBCT sialography.

METHODS

An imaging phantom was constructed using samples with different concentrations of iodine and a water-immersed mandible. The CB MercuRay (Hitachi Medical Systems, Tokyo, Japan) was used to image the phantom using different peak kilovoltage (kVp) and milliamperage (mA) settings. SDNR was then calculated using the raw images based on mean pixel values (MPV) measured in selected regions of interest (ROI). Finally, a figure of merit (FOM) was calculated to examine the trade-off between image SDNR and effective radiation dose.

RESULTS

The SDNR demonstrated an expected increase as the kVp increased from 60 to 120. Also, images made with the higher mA setting (15) had greater SDNR. The iodine concentration also influenced the image quality such that SDNR increased with increased amounts of iodine. The calculated FOM was greatest for the technique using 80 kVp, with equivalent results for 10 mA and 15 mA.

CONCLUSION

An optimized protocol for CBCT sialography using CB MercuRay entails a 6 inch field of view with 80 kVp and 10 mA.

Effect of varying contrast material iodine concentration and injection technique on the conspicuity of hepatocellular carcinoma during 64-section MDCT of patients with cirrhosis

OBJECTIVES

The aim of this study was to compare the intraindividual effects of contrast material with two different iodine concentrations on the conspicuity of hepatocellular carcinoma (HCC) and vascular and hepatic contrast enhancement during multiphasic, 64-section multidetector row CT (MDCT) in patients with cirrhosis using two contrast medium injection techniques.

METHODS

Patients were randomly assigned to one of two groups with an equal iodine dose but different contrast material injection techniques: scheme A, fixed injection duration (25 s), and scheme B, fixed injection flow rate (4 ml s(-1)). For each group, patients were randomised to receive both moderate-concentration contrast medium (MCCM) and high-concentration contrast medium (HCCM) during two CT examinations within 3 months. Enhancement of the aorta, liver and portal vein and the tumour-to-liver contrast-to-noise ratio (CNR) were compared between MCCM and HCCM.

RESULTS

30 patients (mean age 59 years; range 45-80 years; 16 patients in scheme A and 14 in scheme B) with a total of 31 confirmed HCC nodules were prospectively enrolled. For scheme B, the mean contrast enhancement of the aorta and tumour-to-liver CNR were significantly higher with HCCM than with MCCM during the hepatic arterial phase (+350.5 HU vs +301.1 HU, p = 0.001, and +7.5 HU vs +5.5 HU, p = 0.004). For both groups, there was no significant difference between MCCM and HCCM for all other comparisons.

CONCLUSION

For a constant injection flow rate, HCCM significantly improves the conspicuity of HCC lesions and aortic enhancement during the hepatic arterial phase on 64-section MDCT in patients with cirrhosis.

The optimal contrast media policy in CT of the liver. Part I: Technical notes

Latest developments of multidetector computed tomography (MDCT), which is today considered a real volumetric technique, have revolutionized abdominal imaging. Technological improvements such as higher spatial resolution, larger volume coverage and higher temporal resolution, have reduced scan times allowing CT studies of the abdomen within a single breath-hold. Furthermore, the increased number of slices, the submillimetric collimation, and the use of multiple dynamic post-contrast phases per single examination, may all contribute to increase the radiation exposure of single patients. The aim of this review is to discuss different parameters affecting contrast media enhancement, as vascular enhancement, parenchymal enhancement and timing, in order to minimize the amount of contrast medium injected and the radiation exposure.

[Radiation reduction and image quality improvement with iterative reconstruction at multidetector-row computed tomography]

The purpose of our study was to investigate the relationship between image quality and radiation dose for the filtered backprojection (FBP) with smooth kernel and the iterative reconstruction (iDose) based on image noise, image resolution, CT number, and low-contrast detectability. We used the Catphan phantom and scanned at 65, 45, 32, and 20 mAs on a 64-detector CT. Image reconstruction algorithm and kernel were employed FBP with standard (C type) and FBP with smooth (A type) kernel as images obtained at 20-65 mAs. Regarding to 20-45 mAs, we additionally reconstructed it using the iDose. After scanning, we measured image noise, full width at half maximum (FWHM), and CT number and assessed low-contrast detectability. Image noise acquired at iDose was 10.9, 11.1, and 11.2 HU corresponding to 45, 32, and 20 mAs, respectively. Compared to FBP with standard kernel, FBP with smooth kernel increased the image noise range from 6.7 HU at 65 mAs to 12.3 HU at 20 mAs with decreasing tube current-time product. Unlike iDose and FBP with standard kernel, there was a statistically significant difference between FBP with standard and smooth kernel with respect to image resolution (P=0.002). Reconstruction algorithm of the iDose resulted in the same or better image quality improvements despite a reduction in the radiation dose compared to the FBP with standard or with smooth kernel. From our findings, iDose facilitates the reduction in radiation dose while maintaining image quality.

Aortic and hepatic enhancement at multidetector CT: evaluation of optimal iodine dose determined by lean body weight

PURPOSE

To determine the optimal iodine dose for aortic and hepatic enhancement at MDCT by comparing lean body weight (LBW) with total body weight (TBW).

MATERIALS AND METHODS

This study was approved by our institutional review committee. One hundred and thirty-six patients were randomized into four groups: 550, 650, 750 mg iodine/(kg of LBW) and 600 mgI/(kg of TBW). The aortic and hepatic contrast enhancements (Δ HUs) during the portal venous-phase and variances of ΔHUs were compared.

RESULTS

Mean ΔHUs for 550, 650, 750 mgI/kg LBW and 600 mgI/kg TBW were: 95.1, 109.9, 122.4, and 131.2HU, respectively, for the aorta. For the liver, 43.1, 55.4, 60.8, and 63.5 HU. Mean Δ HUs increased with iodine dose per kg LBW (p<0.01), but no significant difference between 750 mgI/kg LBW and 600 mgI/kg TBW groups. Hepatic enhancement increased by ≥50 HU in 94% of patients with 750 mg/kg LBW. Variance of hepatic enhancement was marginally greater in the 600 mgI/kg TBW than in the 550 and 750 mgI/kg LBW.

CONCLUSION

Hepatic enhancement variation was reduced with iodine doses based on LBW. Iodine dose of 750 mg iodine/kg LBW was appropriate to achieve hepatic enhancement≥50 HU in 94% of patients.

An optimal contrast dose indicator for the determination of hepatic enhancement in abdominal multidetector computed tomography: comparison of patient attenuation indicator with total body weight and body mass index

PURPOSE

To evaluate a patient attenuation indicator (PAI) as compared with traditional patient-related factors of total body weight and body mass index (BMI) as a predictor of hepatic enhancement in contrast-enhanced abdominal multidetector computed tomography (MDCT).

MATERIALS AND METHODS

Institutional review board approval was obtained, and the study was Health Insurance Portability and Accountability Act compliant. A total of 77 patients (mean age, 53 years; male-female ratio, 32:45) underwent routine contrast-enhanced abdominal CT on a 16-slice multidetector CT (LightSpeed 16; GE Medical Systems, Milwaukee, Wis). Contrast enhancement was achieved by administering a 120-mL iodine contrast medium (350-mg iodine per milliliter) at an injection rate of 3 mL/s followed by an injection of 40-mL saline at 3 mL/s. Computed tomographic attenuation values (Hounsfield units [HU]) of liver parenchyma, main portal vein, and abdominal aorta were measured in each patient. Statistical analysis was performed with linear regression to determine the correlation of PAI, total body weight, and BMI with abdominal organ enhancement.

RESULTS

The mean of PAI, total body weight, and BMI were 28.0 (range, 22.1-34.2), 79.0 kg (range, 49.6-112.2 kg), and 27.5 kg/m (range, 16.8-43 kg/m), respectively. Mean hepatic enhancement was 128.2 HU (range, 73.6-175 HU), mean main portal vein enhancement was 214.2 HU (range, 118-327 HU), and mean abdominal aorta enhancement was 208.9 HU (range, 116-395 HU). Patient attenuation indicator, total body weight, and BMI showed a negative correlation with liver enhancement (r = -0.55, r = -0.4, and r = -0.3, respectively). Patient attenuation indicator exhibited a significantly higher correlation with hepatic enhancement than total body weight and BMI (P < 0.01, respectively).

CONCLUSIONS

Patient attenuation indicator exhibits a moderately inverse correlation with liver enhancement that is greater than those of total body weight and BMI. Patient attenuation indicator may be reliable in predicting the hepatic enhancement degree for a given dose of contrast material and has a potential use in customizing individual patient contrast medium dose during contrast-enhanced abdominal CT.

Evaluation of hypervascular hepatocellular carcinoma in cirrhotic liver: comparison of different concentrations of contrast material with multi-detector row helical CT--a prospective randomized study

PURPOSE

To evaluate two different iodine concentrations of contrast material for detecting hypervascular hepatocellular carcinomas (HCCs) in cirrhotic liver by multi-detector row helical CT (MDCT) when a fixed contrast material volume and injection rate is used.

MATERIALS AND METHODS

Institutional Review Board approval was obtained, and informed consent was obtained from all patients. In this prospective study, 105 patients were randomly assigned a group A (an iodine concentration of 300 mg I/mL), and a group B (an iodine concentration of 370 mg I/mL). In both groups the volume of contrast material was 100 mL and the injection rate was 4 mL/s. Fifty-two patients had 122 hypervascular HCCs. The diagnosis of HCCs was established histopathologically (n=24) and by imaging findings (n=98). Three readers independently analyzed four image sets: an arterial phase (AP), a portal phase (PP), an equilibrium phase (EP), and combined all three phase images set. Sensitivity, specificity, and diagnostic accuracy were calculated by receiver operating characteristic (ROC) analysis.

RESULTS

The mean sensitivity for detecting hypervascular HCCs of the AP set, EP set, and combination set in group B (0.94, 0.81, and 0.93) was significantly higher than in group A (0.84, 0.69, and 0.80). Area under the ROC curve of the AP set and the combination set in group B (0.974 and 0.981) was significantly higher than in group A (0.939 and 0.958).

CONCLUSION

At the same contrast material volume and injection rate, higher iodine concentration of contrast material was effective for detecting hypervascular HCCs by MDCT.