Comparison of dose length product and image quality of a biphasic whole-body polytrauma CT protocol with and without the automatic tube voltage selection

BACKGROUND AND AIMS

A significant source of man-made radiation is now linked to medical devices especially X-ray imaging based ones like CT scans which expose the body to cumulative ionizing radiation and thus attendant cancer risks. The aim of this study was to determine whether using a combination of Automatic Tube Current Modulation (ATCM) and Automatic Tube Voltage Selection (ATVS) during two-phase whole-body CT (2PWBCT) examinations would reduce the radiation dose while preserving the image quality.

PATIENTS AND METHODS

This was a prospective, observational, single-centre study of 127 adult patients who had undergone the 2PWBCT polytraumatic protocol. All were examined on a Somatom Drive scanner (Siemens). The patients were divided into two groups: ATCM only (42 patients) and ATCM +ATVS (85 patients). Patients' arm positions during examination and the examination dose length product (DLP) values were recorded, as well the standard deviations (SD) of the density in reference areas on CT scans for the image quality assessment. The DLP values and image quality in the groups were compared using ANOVA.

RESULTS

Mean Total DLP (in mGy*cm): ATCM only: 3337 +/-797, ATCM+ATVS: 3402 +/-830; P=0.674. No effect of arm position (P=0.586). Mean density SD values in reference areas (in HU) in ATCM only: 49 +/-45, 15 +/-6, 9 +/-2, 12 +/-4, 10 +/-3, in ATCM+ATVS: 48 +/-45, 17 +/-6, 11 +/-3, 15 +/-6, 12 +/-4. SD values was higher in ATCM+ATVS group (P<0.001).

CONCLUSION

Combination of ATVS and ATCM in polytraumatic 2PWBCT leads to no significant radiation load reduction compared with ATCM only but does lead to a slight degradation of image quality. The radiation load is significantly reduced if the patient has their arms behind the head when scanning, regardless of the activation of ATVS.

A systematic review of conversion factors between kerma-area product and effective/organ dose for cardiac interventional fluoroscopy procedures performed in adult and paediatric patients

The aim of this systematic review is to undertake a critical appraisal of the evidence in the published literature concerning the conversion factors between kerma-area product (P KA) and effective/organ dose (DCED_PKA, DCHT_PKA) for cardiac interventional fluoroscopy procedures performed in adults and paediatric patients and to propose reference conversion factors to help standardize dose calculations. A search strategy utilizing MeSH headings in three databases identified 59 (adult) and 37 (paediatric) papers deemed eligible for the review. Exclusion criteria were adopted to select data only from publications which established DCED_PKA in patients using the ICRP 103 tissue weighting factors. A time restriction from January 2007 was introduced in the search to capture the evolving trends of utilization of fluoroscopy-guided intervention technologies only in recent years. The suggested DCED_PKA and DCHT_PKA were synthesized by calculating the weighted averages of the values reported by the authors with weights corresponding to the study sample size. Eighteen studies for both adult (9) and paediatric (9) patients matching the search terms fulfilled the inclusion criteria. The suggested value for DCED_PKA in adult patients amounts to 0.24 mSv Gy−1cm−2. The suggested values for DCHT_PKA ranged from a minimum of 0.15 mSv Gy−1cm−2 for the female breast to a maximum of 0.97 mSv Gy−1cm−2 for the lungs. The suggested values for DCED_PKA in paediatric patients ranged from 3.45 mSv Gy−1cm−2 for the new-born to 0.49 mSv Gy−1cm−2 in the 15 years age class. The suggested values for DCHT_PKA ranged from a minimum of 0.33 mSv Gy−1cm−2 for bone marrow in the 15 years age class to a maximum of 11.49 mSv Gy−1cm−2 for the heart in the new-born. To conclude, values of DCED_PKA/DCHT_PKA were provided for calculating effective/organ doses in cardiac interventional procedures. They can be useful for standardizing dose calculations, hence for comparison of the radiation detriment from different imaging procedures and in the framework of epidemiologic studies.

P6472Novel cardiac imaging prognostic markers of clinical outcome in patients with bicuspid aortic valve and chronic aortic regurgitation

Background

Patients with chronic aortic regurgitation (AR) can have a substantial myocardial damage despite being asymptomatic. Early surgical strategy might be beneficial. Bicuspid aortic valve (BAV) is a congenital heart disease present in almost 30% of these patients.

Purpose

Identify novel imaging predictors of early disease progression.

Methods

Prospective three-centre study of patients with chronic AR of at least moderate to severe (3+) grade and BAV morphology. Patients without currently recognised indication for surgical treatment were enrolled. Baseline examination included echocardiography (ECHO) with 3-dimensional (3D) vena contracta area and magnetic resonance (MR) with regurgitant fraction measured from flow sequence. All imaging studies were analysed in CoreLab. The primary endpoint was defined as a combination of cardiovascular death, surgical treatment or hospitalization for heart failure.

Results

A total of 83 patients with BAV and at least 3+ AR were enrolled during 2015–2018. Median follow-up was 759±455 days, primary composite endpoint occurred in 13 patients who met criteria for surgical treatment, no patient died or was hospitalized for heart failure. Baseline parameters were compared between two groups: patients with and without endpoint. Clinical and laboratory data did not differ between the two groups. Left ventricular (LV) ejection fraction was normal in all patients. LV diameters and volumes were significantly larger in patients with primary endpoint. This was most pronounced in MR measured indexed volumes in end-diastole and end-systole, P=0.003 and P=0.003. Non-invasive markers of diffuse myocardial fibrosis (native T1 relaxation time and global longitudinal strain, P=0.614 and P=0.137 respectively) were not different. Novel markers of AR severity were significantly increased in surgically treated patients: 3D vena contracta 0.26±0.10 cm2 versus 0.38±0.11 cm2 (P<0.001), MR regurgitant fraction 33.9±15.4 versus 50.2±12.2% (P=0.001). Both 3D vena contracta with cutoff value ≥0.4 cm2 (sensitivity=85%, specificity=84%, area under the curve=0.85) and MR regurgitant fraction with cutoff value ≥34% (sensitivity=94%, specificity=58%, area under the curve=0.76) showed high accuracy to identify patients who require early surgical intervention. Adding 3D vena contracta and MR regurgitant fraction to indexed LV end-systolic volumetric parameters significantly increases the predictive value for early disease progression with p=0.001 and p=0.006 (Likelihood-ratio test).

3D vena contracta predictive value

Conclusions

Novel imaging parameters of AR severity such as 3D vena contracta and MR derived regurgitant fraction predict early disease progression in patients with BAV and at least 3+ chronic AR. These values significantly increase the predictive value of traditional parameters based on LV size measures.

Selective coronary angiography, percutaneous coronary intervention and asymptomatic peri-procedural myocardial injury

BACKGROUND

While there have been a number of studies reporting the incidence and implications of elevated troponin levels after percutaneous coronary intervention (PCI), the body of information about the incidence, associations, and implications of elevated troponin levels following coronary angiography (CAG) is limited.

MATERIALS AND METHODS

A total of 220 consecutive patients with stable coronary artery disease or intermediate or low-risk acute coronary syndrome without persistent ST-segment elevation (NSTE-ACS) were included in our study. High-sensitivity cardiac troponin I (hs-cTnI) levels were measured before and after coronary angiography (CAG) in patients with or without PCI and correlated with a number of clinical variables.

RESULTS

Hs-cTnI elevations above the 99^th percentile upper reference limit (URL), or above 20% of the initially positive, yet already declining values, were found in 60 (37.2%) patients after CAG and in 45 (76.2%) patients undergoing PCI. Significant correlations of hs-cTnI elevation were found with the following variables: volume of contrast, fluoroscopy time, dose-area product, amount of contrast agent injected directly into the coronary arteries, total time of balloon dilation and the number and total length of implanted stents (P<0.001 for all).

CONCLUSION

While an asymptomatic elevation of hs-cTnI is a common finding after PCI, it does occur, quite surprisingly, also after CAG. Despite contradictory views regarding the clinical relevance of asymptomatic post-procedural elevated hs-cTnI levels, it is generally believed that a mild elevation is not associated with an increased risk. Still, it may pose a diagnostic quandary following a successful interventional procedure and even more so after an uncomplicated CAG.

TRIAL REGISTRATION

Clinicaltrials.gov - NCT02960321.

Patient skin dosimetry in interventional cardiology in the Czech Republic

In this study, skin dosimetry of patients undergoing interventional cardiology procedures is presented. Three hospitals were included. Two methods were used for skin dosimetry--radiochromic dosimetry films and reconstruction of skin dose distribution based on examination protocol. Maximum skin doses (MSD) obtained from both methods were compared for 175 patients. For patients for whom the film MSD was >1 Gy, the reconstruction MSD differed from the film MSD in the range of ± 50 % for 83 % of patients. For remaining patients, the difference was higher and it was caused by longer fluoroscopy time. For 59 patients for whom the cumulative dose was known, the cumulative dose was compared with the film MSD. Skin dosimetry with radiochromic films is more accurate than the reconstruction method, but films do not include X-ray fields from lateral projections whilest reconstructions do.