Reduced Kilovoltage in Computed Tomography–Guided Intervention in a Community Hospital: Effect on the Radiation Dose

Application of Adaptive Statistical Iterative Reconstruction-V With Combination of 80 kV for Reducing Radiation Dose and Improving Image Quality in Renal Computed Tomography Angiography for Slim Patients

OBJECTIVES

To explore the application of adaptive statistical iterative reconstruction-V (ASIR-V) with combination of 80 kV for reducing radiation dose and improving image quality in renal computed tomography angiography (CTA) for slim patients compared with traditional filtered back projection (FBP) reconstruction using 120 kV.

METHODS

Eighty patients for renal CTA were prospectively enrolled and randomly divided into group A and group B. Group A used 120 kV and 600 mgI/kg contrast agent and FBP reconstruction, while group B used 80 kV and 350 mgI/kg contrast agent and both FBP and ASIR-V reconstruction from 10%ASIR-V to 100%ASIR-V with 10%ASIR-V interval. The CT values and SD values of the right renal artery and left renal artery were measured to calculate the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). The image quality was subjectively scored by two experienced radiologists blindly using a five-point criterion. The contrast agent, volumetric CT dose index (CTDI_vol), and dose length product in both groups were recorded and the effective radiation dose was calculated.

RESULTS

There were no significant difference in patient characteristics between two groups (p > 0.05). The CTDI_vol, dose length product and effective radiation dose in group B were 59.0%, 65.0%, and 65.1% lower than those in group A, respectively (all p < 0.05), and the contrast agent in group B was 42.2% lower than that in group A (p < 0.05). In group B, with the increase of ASIR-V percentage, CT values showed no significant difference, SD values decreased gradually, SNR values and CNR values increased gradually. The CT values showed no statistically significant difference (p > 0.05) between two groups with different reconstructions. The SD values with 40%ASIR-V to 100%ASIR-V reconstruction in group B was significantly lower(p < 0.5), while the SNR values with 50% ASIR-V to 100% ASIR-V reconstruction and CNR values with 70%ASIR-V to 100%ASIR-V were significantly higher than those of group A with FBP reconstruction (p < 0.5). Two radiologists had excellent consistency in subjective scores of image quality for renal CTA (kappa >0.75, p < 0.05). The subjective scores with 60% ASIR-V to 90% ASIR-V in group B were significantly higher than those of FBP in group A (p < 0.5), of which 70%ASIR-V reconstruction obtained the highest subjective score for renal CTA.

CONCLUSION

ASIR-V with combination of 80 kV can significantly reduce effective radiation dose (about 65.1%) and contrast agent (about 42.2%) and improve image quality in renal CTA for slim patients compared with traditional FBP reconstruction using 120 kV, and the 70% ASIR-V was the best reconstruction algorithm in 80 kV renal CTA.

ADVANCES IN KNOWLEDGE

Using 80 kV with combination of ASIR-V can significantly reduce radiation dose and contrast agent dose as well as improve image quality in renal CTA for thin patients when compared with FBP using 120 kV.

Ultralow dose computed tomography protocol for hook-wire localization of solitary pulmonary nodules prior to video-assisted thoracoscopic surgery

BACKGROUND

This study prospectively investigated the efficacy and radiation dose of ultralow dose computed tomography (CT)-guided hook-wire localization (HWL) at 100 kV with tin filtration (100Sn kV) for small solitary pulmonary nodules.

METHODS

All HWL procedures were performed on a third generation dual-source CT system. Eighty-eight consecutive patients undergoing CT-guided HWL were randomly assigned to standard dose CT (Group A: n = 44; reference 110 kV and 50 mA) or ultralow dose CT (Group B: n =44; ¹⁰⁰ Sn kV and 96 mA) protocols. The technical success rate, complications, subjective image quality, and radiation dose were compared between the groups.

RESULTS

The mean volume CT dose index and total dose-length product were significantly lower in Group B compared to Group A (0.32 mGy vs. 3.2 ± 1.1 mGy and 12.1 ± 0.97 mGy-cm vs. 120 ± 40.6 mGy-cm; P < 0.001). The effective dose in Group B was significantly lower than in Group A (0.17 ± 0.01 mSv vs. 1.68 ± 0.57 mSv, -89.8%; P < 0.001). The technical success rates were 100% for both groups. There were no significant differences in complication rates between the protocols (P > 0.05). The image quality of ultralow dose CT met the requirements for HWL procedure.

CONCLUSION

Ultralow dose CT-guided HWL of solitary pulmonary nodules performed at ¹⁰⁰ Sn kVp spectral shaping significantly reduced the radiation dose compared to standard dose CT, with high technical success and acceptable patient safety.

Practical dose reduction tips for abdominal interventional procedures using CT-guidance

Reducing the radiation dose should be an endeavor not only for diagnostic CT exams but also for interventional procedures using CT-guidance. Given that interventional procedures vary in scope and complexity, there is greater variability in radiation doses delivered during CT procedures. The goal in an interventional procedure is simply to advance the interventional instruments into the target lesions, and as such diagnostic level doses are not required and only narrow scan range scans need to be acquired. Adherence to the principles outlined in this article will allow such procedures to be performed with reduced radiation doses.

Cone-Beam CT with Fluoroscopic Overlay Versus Conventional CT Guidance for Percutaneous Abdominopelvic Abscess Drain Placement

PURPOSE

To compare technical success and procedure time for percutaneous abscess drain placement with fluoroscopic cone-beam computed tomography (CT) and two-axis needle guidance versus conventional CT guidance.

MATERIALS AND METHODS

A total of 85 consecutive patients undergoing abdominopelvic abscess drain placement guided by fluoroscopic cone-beam CT or conventional CT were retrospectively reviewed over a 2-year period. Forty-three patients underwent drain placement with cone-beam CT using XperGuide navigation and 42 underwent placement with conventional 64-slice CT. Patient characteristics, median abscess size (6.8 cm vs 7.8 cm; P = .14), and depth to abscess (7.2 cm vs 7.7 cm; P = .88) were similar between groups.

RESULTS

Technical success rates were 98% (42 of 43) in the cone-beam CT group and 100% (42 of 42) in the conventional CT group (P = .32), with a 10-F pigtail drainage catheter inserted in the majority of cases. There were no complications in either group. There was no significant difference in effective dose between groups (9.6 mSv vs 10.7 mSv; P = .30). Procedure times were significantly shorter in the cone-beam CT group (43 min vs 62 min; P = .02). In addition, during the study period, there was a gradual improvement in procedure time in the cone-beam CT group (50% reduction), whereas procedure time did not change for the conventional CT group.

CONCLUSIONS

Cone-beam CT guidance appears to be equivalent to conventional CT guidance for drain placement into medium-sized abdominopelvic collections, yielding similar technical success rates and radiation doses, with the additional benefit of reduced procedure times.

CT of the Abdomen with Reduced Tube Voltage in Adults: A Practical Approach

Recent innovations in computed tomographic (CT) hardware and software have allowed implementation of low tube voltage imaging into everyday CT scanning protocols in adults. CT at a low tube voltage setting has many benefits, including (a) radiation dose reduction, which is crucial in young patients and those with chronic medical conditions undergoing serial CT examinations for disease management; and (b) higher contrast enhancement. For the latter, increased attenuation of iodinated contrast material improves the evaluation of hypervascular lesions, vascular structures, intestinal mucosa in patients with bowel disease, and CT urographic images. Additionally, the higher contrast enhancement may provide diagnostic images in patients with renal dysfunction receiving a reduced contrast material load and in patients with suboptimal peripheral intravenous access who require a lower contrast material injection rate. One limitation is that noisier images affect image quality at a low tube voltage setting. The development of denoising algorithms such as iterative reconstruction has made it possible to perform CT at a low tube voltage setting without compromising diagnostic confidence. Other potential pitfalls of low tube voltage CT include (a) photon starvation artifact in larger patients, (b) accentuation of streak artifacts, and (c) alteration of the CT attenuation value, which may affect evaluation of lesions on the basis of conventional enhancement thresholds. CT of the abdomen with a low tube voltage setting is an excellent radiation reduction technique when properly applied to imaging of select patients in the appropriate clinical setting.

Impact of Dose-Modified Protocols on Radiation Doses in Patients Undergoing CT Examinations following Image-Guided Catheter Placement

PURPOSE

To investigate the impact of dose-modified (DM) scan protocols on decreasing radiation exposure from computed tomography (CT) scans obtained following image-guided catheter procedures.

MATERIALS AND METHODS

In this retrospective analysis, between December 2012 and June 2014, 192 patients (mean age, 60.7 y; 102 men) who underwent abdomen/pelvis CT examinations for catheter placement follow-up were included. The standard-dose (SD) baseline CT parameters included tube potential of 120 kVp, tube current of 75-550 mA, and noise index (NI) of 18-22. Weight-based scan parameters applied for follow-up CT were based on two reconstruction algorithms: filtered back projection (FBP; 120 kVp, 75-350 mA, NI = 30) and iterative reconstruction technique (IRT; 100/120 kVp, 75-250/350 mA, NI = 35). Two readers reviewed image quality (IQ) of follow-up and baseline CT examinations for 22 randomly sampled patients. Radiation doses were retrieved by dose monitoring software.

RESULTS

Compared with baseline, DM follow-up CT protocols enabled substantial (62.4%) dose reductions (mean CT dose indexes: 4.1 mGy at follow-up, 10.9 mGy at baseline; P < .0001). Doses were significantly lower for IRT follow-up CT examinations compared with FBP (mean CT dose indexes: IRT, 3.6 mGy; FBP, 4.6 mGy; P < .05). In 47 patients with more than one follow-up CT examination (mean, 3.1 examinations per patient; range, 2-6), the observed cumulative radiation dose (CRD) was 42.1% lower than the expected CRD (observed, 1,437.9 mGy·cm; expected, 2,483.6 mGy·cm; P < .0001). Subjective IQ scores were acceptable for follow-up CT examinations (follow-up, 3.6; baseline, 4; P < .05).

CONCLUSIONS

DM CT examinations enable substantial dose reduction (62.4%) for each follow-up examination compared with SD baseline scans, without any IQ concerns. Use of IRT decreases dose by an additional 22%. The CRD is lowered by 42% in patients undergoing multiple DM follow-up CT examinations.