Influence of Different Arm Positions in the Localizer Radiograph(s) on Patient Dose during Exposure-Controlled CT Examinations of the Neck to Pelvis

Effect of arm position on image quality and radiation dose during thorax and abdomen computed tomography scans

INTRODUCTION

During Computed Tomography (CT) scans of the Thorax-Abdomen-Pelvis (TAP) the patient's arms should be positioned above the head to obtain optimal image quality and expose the patient to the lowest possible radiation dose. This may be impossible with patients with shoulder problems leading to arms being positioned in other ways. This study aimed to investigate differences in objective image quality and estimated effective dose (E), when positioning the arms below shoulder level in CT-TAP.

METHODS

An anthropomorphic phantom with cadaver arms was used. Four arm positions were tested: Along the torso (A), on the pelvis (B), on a pillow on the pelvis (C), and one arm on pillow on the pelvis and the other arm on the pelvis (D). A Siemens SOMATOM Definition Flash CT-scanner with CareDose 4D was used. The dose length product was read to estimate E. Image quality was assessed objectively by measuring noise within the region of interest in the liver and urinary bladder.

RESULTS

Significant differences in E between all arm positions were seen (p = 0.005). The lowest E was obtained in position C, reducing E by 8.42%. Position A provided the best image quality but the highest E.

CONCLUSION

This study showed no unequivocal optimal positioning of arms in CT-TAP. Position A provided the best object image quality, while position C yielded the lowest E. These results may impact the planning of diagnostic CT where positioning of arms may influence optimal image quality and radiation dose.

IMPLICATION FOR PRACTICE

This study illustrates tendencies for objective image quality and E when arms are positioned below shoulder level. Further research is needed to assess the clinical relevance with the diagnostic potential.

Advanced intraoperative imaging guidance for inside-out central venous recanalization using a novel catheter access system

BACKGROUND

The novel Surfacer Inside-Out recanalization technique facilitates right-sided central venous access in occluded vessels but carries a risk of arterial and pleural injuries. This article demonstrates how an advanced intraoperative imaging protocol can help to avoid these potential complications.

METHODS

This retrospective review included patients undergoing the Surfacer Inside-Out central venous recanalization procedure between December 2017 and October 2021. The study sample comprised patients included in the SAVE-US trial at our site as well as patients treated after US Food and Drug Administration approval of the device. All procedures were performed using intraoperative cone-beam computed tomography (CBCT) angiography to map out the trajectory of the device through the mediastinum and supraclavicular space with fusion imaging for guidance. Procedures were aborted if CBCT findings predicted injury to arterial or respiratory structures. The intraoperative coronal and sagittal orientation of the device was compared to preoperatively predicted trajectory.

RESULTS

A total of 17 procedures were performed in 16 patients with end-stage renal disease and a mean age of 61 ± 11 years. Most patients presented a type 3 central venous occlusion (9/15). Successful recanalization was achieved in 14 of the 17 cases (82.4%) with no intraoperative complications. The procedure had to be aborted in 3 of the 17 cases based on intraoperative CBCT findings, which projected the device to perforate the right pleural space in one patient, the trachea and right subclavian artery in another, and the innominate artery in the third patient. The total radiation dose per procedure was 753 ± 346 mGy and the mean procedural time was 101.6 ± 29.7 minutes. A median of 2 (range, 1-5) intraoperative CBCT scans were performed per patient and accounted for 70% of the total radiation dose. Statistical analysis showed intraoperative CBCT findings to differ significantly from preoperative predicted values.

CONCLUSIONS

The nonsteerable and penetrating nature of the Surfacer device may lead to serious complications when performed under fluoroscopic guidance alone. Intraoperative CBCT with fusion overlay enhances the safety and effective use of this device and inside out crossing technique.

Radiation Dose Management in Pediatric Brain CT According to Age and Weight as Continuous Variables

The diagnostic reference levels (DRLs) for pediatric brain computed tomography (CT) are provided for groups divided according to age. We investigated the relationships of radiation dose indices (volume CT dose index and dose length product) with age and weight, as continuous variables, in pediatric brain CT. In a retrospective analysis, 980 pediatric brain CT examinations were analyzed. Curve fitting was performed for plots of the CT dose indices versus age and weight, and equations to estimate age- and weight-dependent standard dose indices were derived. Standard dose indices were estimated using the equations, and the errors were calculated. The results showed a biphasic increase in dose indices with increasing age and weight, characterized by a rapid initial and subsequent slow increase. Logarithmic, power, and bilinear functions were well fitted to the plots, allowing estimation of standard dose indices at an arbitrary age or weight. Error analysis suggested that weight was mildly better than age and that the best results were obtained with the bilinear function. Curve fitting of the relationship between CT dose indices and age or weight facilitates the determination of standard dose indices in pediatric brain CT at each facility and is expected to aid the establishment and application of the DRLs.