8th Baltic Congress of Radiology

Radioprotection and management

oral abstract

It has been a holy grail of CT manufacturers to achieve x-ray dose neutrality of Dual Energy exams (DECT) compared to Single Energy CT exams (SECT). The goal has been to get more information with the same price of x-ray dose. Various research studies for dose comparison of single -energy CT (SECT) and dual-energy CT (DECT) have been investigated and have shown no significant difference in dose. However, in some cases, DECT can require higher radiation doses. The purpose of the study was to retrospectively assess the utilization of three of Pärnu Hospital’s most widely used Dual Energy scanning protocols, one for thromboembolism of pulmonary artery and the other two protocols for oncology staging (region form chest to pelvis and abdomen to pelvis) at Pärnu Hospital.

Comparison was done on optimized protocols which were clinically validated by radiologist and medical physicist. Default protocols provided by CT manufacturers were not used in the comparison as this would yield unrealistic results. Two different approaches were used to compare the protocols of SECT and DECT. First approach was to compare the same patients projected dose of not scanned SECT protocol to the scanned DECT exams dose. This required some of the data to be collected manually between January and March 2022 as the not scanned data is not collected automatically by dose tracking software. Most of the data was collected using dose tracking system DoseWatch from GE Healthcare. The other approach was to compare two different distributions of the doses where the clinical question and the target region is the same but where one group of patients was scanned with SECT and the other with DECT protocol.

For pulmonary embolism DECT protocol had approximately 27% higher dose than previously used SECT protocol. Using reasonably higher dose was justified with better clinical outcome as DECT exam would give iodine perfusion map to show under perfused areas caused by small emboly. When comparing DECT protocol dose to DRL values dose was still much lower than DRL values. Comparison of cancer staging DECT and SECT protocols dose was not significantly different between the two however virtual native reconstruction was possible from DECT scan which yielded possibility to lower the dose of DECT scan to about half of the dose of SECT protocol.

This study revealed that Dual Energy protocol for thromboembolism of pulmonary artery imaging produce needed somewhat higher radiation doses in comparison with SECT. As the study was carried out retrospectively and without testing if DECT protocol dose could be lowered even further it cannot be concluded that it is not possible to scan DECT exam with even lower dose or even dose neutral comparing to SECT protocol. Both DECT and SECT protocols were optimized bearing in mind that the final image must be give high assurance on the description given by radiologists but use as low dose as reasonably achievable. DECT on the other hand yield more information than conventional CT exam. The protocols for oncology staging (region form chest to pelvis and abdomen to pelvis) revealed that DECT exposes patients to radiation doses similarly or with little difference to those received during conventional single-energy CT. For oncology patients it is good practice to use Dual Energy technique because in a single examination scan it is possible to reconstruct images with and without contrast agents. Additionally, there is different possibilities in Dual Energy for example measure concentration of chemical substances in the body or, reconstruct virtually monochromatic images to increase contrast of the image making some abnormalities clearer.

It has been a holy grail of CT manufacturers to achieve x-ray dose neutrality of Dual Energy exams (DECT) compared to Single Energy CT exams (SECT). In this study an assessment of the utilization of three of Pärnu Hospital’s most widely used Dual Energy scanning protocols (DECT) is given in comparison with a single-energy CT (SECT) protocols.

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