Radiation exposure, organ and effective dose of CT-guided liver biopsy as a function of lesion depth and size

Computed tomography (CT)-guided percutaneous biopsies play an important role in the diagnostic workup of liver lesions. Because radiation dose accumulates rapidly due to repeated image acquisition in a relatively small scan area, analysing radiation exposure is critical for improving radiation protection of CT-guided interventions. The aim of this study was to assess the radiation dose of CT-guided liver biopsies and the influence of lesion parameters, and to establish a local diagnostic reference level (DRL). In this observational retrospective cohort study, dose data of 60 CT-guided liver biopsies between September 2016 and July 2017 were analysed. Radiation exposure was reported for volume-weighted CT dose index (CTDI_vol), size-specific dose estimate (SSDE), dose-length product (DLP) and effective dose (ED). Radiation dose of CT-guided liver biopsy was (median (interquartile range)): CTDI_vol9.91 mGy (8.33-11.45 mGy), SSDE 10.42 mGy (9.39-11.70 mGy), DLP 542 mGy cm (410-733 mGy cm), ED 8.52 mSv (7.17-13.25 mSv). Radiation exposure was significantly higher in biopsies of deep liver lesions compared to superficial lesions (DLP 679 ± 285 mGy cm vs. 497 ± 167 mGy cm,p= 0.0046). No significant dose differences were observed for differences in lesion or needle size. With helical CT spirals additional to the biopsy-guiding axial CT scans, radiation exposure was significantly increased: 797 ± 287 mGy cm vs. 495 ± 162 mGy cm,p< 0.0001. The local DRL is CTDI_vol9.91 mGy, DLP 542 mGy cm. Radiation dose is significantly increased in biopsies of deeper liver lesions compared with superficial lesions. Interventions with additional biopsy-guiding CT spirals lead to higher radiation doses. This study provides a detailed analysis of local radiation doses for CT-guided liver biopsies and provides a benchmark for optimising radiation protection in interventional radiology.

Comparison of acquisition and iterative reconstruction parameters in abdominal computed tomography-guided procedures: a phantom study

BACKGROUND

Many computed tomography (CT) navigation systems have been developed to help radiologists improve the accuracy and safety of the procedure. We evaluated the accuracy of one CT computer-assisted guided procedure with different reduction dose protocols.

METHODS

A total of 128 punctures were randomly made by two operators on two different anthropomorphic phantoms. The tube voltage was fixed to 100 kVp. Tube currents (mAs) were defined to obtain 4 dose levels: 180 mAs (D1.00), 90 mAs (D0.50), 45 mAs (D0.25) and 15 mAs (D0.10) with respective volume CT dose index (CTDIvol) of 7.02, 3.52, 1.75 and 0.59 mGy. The raw data were reconstructed using level 2 of advanced model-based iterative reconstruction (ADMIRE) (A2) for D1.00, A3 for D0.50, A4 for D0.25 and A5 for D0.10. Two 12-mm targets per phantom were selected. The mean Euclidean distance (EuD) between the tip of the needle and the isocenter of the target was measured for each puncture. The different measures were compared by paired Student's t-tests.

RESULTS

The mean EuD was 7.0±3.1 mm for the 128 punctures performed. Regardless of which phantom was considered, no significant difference in accuracy occurred between the 4 dose levels, which were 7.1±3.5 mm for D1.00; 7.1±3.1 mm for D0.50; 7.2±3.0 mm for D0.25 and 6.6±2.6 mm for D0.10.

CONCLUSIONS

Abdominal CT-guided procedures, using computer-assisted navigation and iterative reconstruction algorithms, allow precise punctures on anthropomorphic phantoms with a dose reduction of -92% compared to a standard protocol.

[Alternatives of histological material collection - When and how is histological confirmation by ultrasound (US), computer tomography (CT) or endosonography (EUS) useful?]

Histological classifications of tumorous lesions together with adequate staging are necessary for stage-appropriate and personalized therapies. The indications, technical possibilities, and limitations as well as potential complications of image-guided needle biopsy by ultrasound, computed tomography, and endosonography are described. Which procedure for which organ and which lesion?

Validation of a method for estimating peak skin dose from CT-guided procedures

A method for estimating peak skin dose (PSD) from CTDI_vol has been published but not validated. The objective of this study was to validate this method during CT‐guided ablation procedures. Radiochromic film was calibrated and used to measure PSD. Sixty‐eight patients were enrolled in this study, and measured PSD were collected for 46 procedures. CTDI_vol stratified by axial and helical scanning was used to calculate an estimate of PSD using the method [1.2 × CTDI_vol(helical) + 0.6 × CTDI_vol(axial)], and both calculated PSD and total CTDI_vol were compared to measured PSD using paired t‐tests on the log‐transformed data and Bland‐Altman analysis. Calculated PSD were significantly different from measured PSD (P < 0.0001, bias, 18.3%, 95% limits of agreement, −63.0% to 26.4%). Measured PSD were not significantly different from total CTDI_vol (P = 0.27, bias, 3.97%, 95% limits of agreement, −51.6% to 43.7%). Considering that CTDI_vol is reported on the console of all CT scanners, is not stratified by axial and helical scanning modes, and is immediately available to the operator during CT‐guided interventional procedures, it may be reasonable to use the scanner‐reported CTDI_vol as an indicator of PSD during CT‐guided procedures. However, further validation is required for other models of CT scanner.

First experiences of a low-dose protocol for CT-guided musculoskeletal biopsies combining different radiation dose reduction techniques

Background

The use of computed tomography (CT) for image guidance during biopsies is a powerful approach. The method is, however, often associated with a significant level of radiation exposure to the patient and operator.

Purpose

To investigate if a low-dose protocol for CT-guided musculoskeletal (MSK) biopsies, including a combination of different radiation dose (RD) techniques, is feasible in a clinical setting.

Material and Methods

Fifty-seven patients underwent CT-guided fine-needle aspiration cytology (FNAC) utilizing the low-dose protocol (group A). A similar number of patients underwent CT-guided FNAC using the reference protocol (group B). Between-group comparisons comprised radiation dose, success rate, image quality parameters, and workflow.

Results

In group A, the mean total dose-length product (DLP) was 41.2 ± 2.9 mGy*cm, which was statistically significantly lower than of group B (257.4 ± 22.0 mGy*cm), corresponding to a mean dose reduction of 84% ( P<0.001). The mean CTDIvol for the control scans were 1.88 ± 0.09 mGy and 13.16 ± 0.40 mGy for groups A and B, respectively ( P < 0.001). The success rate in group A was 91.2% and 87.9% in group B ( P = 0.56). No negative effect on image-quality parameters, time of FNAC, and number of control scans were found.

Conclusion

We successfully developed a low-dose protocol for CT-guided MSK biopsies that maintains diagnostic accuracy and image quality at a fraction of the RD compared to the reference biopsy protocol at our clinic.

CT-guided biopsy of breast lesions: When should it be considered?

Mammography, ultrasound, and magnetic resonance imaging (MRI) are the most commonly used modalities for interventional radiology procedures involving the breast. Computed tomography (CT) is rarely used for breast imaging yet it is able to detect breast lesions and can often provide safe and effective access to breast lesions. The aim of this study was to demonstrate situations in which CT should be considered as an alternative guidance method for the biopsy of breast lesions that are not accessible with conventional imaging modalities.

Reinforcing the Importance and Feasibility of Implementing a Low-dose Protocol for CT-guided Biopsies

RATIONALE AND OBJECTIVES

This study sought to more definitely illustrate the impact and feasibility of implementing a low-dose protocol for computed tomography (CT)-guided biopsies using size-specific dose estimates and multivariate analyses.

MATERIALS AND METHODS

Fifty consecutive CT-guided lung and extrapulmonary biopsies were reviewed before and after implementation of a low-dose protocol (200 patients total, mean age 61 ± 15 years, 128 women). Analyses of variance with Bonferroni correction were used to compare standard and low-dose protocols in terms of patient demographics, physician experience, target lesion size, total dose-length product, total acquisitions, size-specific dose estimate, signal-to-noise ratio, contrast-to-noise ratio, and lesion conspicuity ratings. All procedures were performed on the same 16-slice CT scanner.

RESULTS

Voluntary protocol adherence was 100% (lung) and 89% (extrapulmonary). The low-dose protocol achieved significantly lower total average dose-length product [(lung) 735.6 ± 599.4 mGy × cm to 252.1 ± 101.9 mGy × cm, P < .001; (extrapulmonary) 724.7 ± 545.0 mGy × cm to 392.9 ± 239.5 mGy × cm, P < .001] and size-specific dose estimate [(lung) 5.2 ± 0.8 mGy × cm to 4.3 ± 1.5 mGy, P < .001; (extrapulmonary) 10.1 ± 6.7 mGy to 6.5 ± 2.7 mGy, P < .001]. Only the change in protocol was independently associated with lower size-specific dose estimates when controlling for the other variables (P < .0001). This was achieved with no significant differences in signal-to-noise ratio, contrast-to-noise ratio, or lesion conspicuity.

CONCLUSIONS

Implementation of a low-dose protocol for CT-guided biopsies resulted in 21% and 36% of size-specific dose estimate reduction for lung and extrapulmonary biopsies, respectively, with excellent adherence. Interventional and body radiologists should implement low dose CT-guidance protocols aiming to improve 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.