GE Healthcare BrightSpeed Elite CT with ASiR: Comparing Dose & Image Quality Rule Out Pulmonary Embolism on Initial & Follow-Up Exam Michael Swack, MD Diagnostic Radiologist Irvington Radiologists, PC Community Hospital East, Indianapolis, IN 1
Patient History: A 48-year-old male patient has a history of presenting to the emergency department (ED) with symptoms including shortness of breath, severe right-sided chest pain, history of a pulmonary embolism (PE) and deep vein thrombosis (DVT). Patient had a CT scan in May 2011 on a BrightSpeed Elite. He subsequently returned to the ED with the same symptoms for rule out PE back in June of 2011. Based on this patients previous history, we felt it was appropriate to perform another CT scan. Radiation dose was a concern since his last CT exam was only 21 days prior. This scan was performed on the same BrightSpeed Elite but with newly-installed ASiR (Adaptive Statistical Iterative Reconstruction) low dose technology. Staff was able to pull archived images from our PACs system in order to compare the radiation dose levels from initial findings in November 2010 to the patient s most recent scan. CT Exam from May 2011 Scan type conducted: Chest with contrast for PE Scanner type: BrightSpeed Elite Scan protocol: Slice thickness: 1.25 x 0.625 Pitch: 1.375:1 Table speed or travel distance of scan: 27.5mm/rot- 29cm Rotation time: 0.5sec Total Acquisition 5.78 sec ma = 433 mas = 216.6 kv= 120 Recon kernel: Standard Noise Index 21.45 ASiR = 0 Dose Report - DLP = 20.69 mgy - CTDIvol = 659.41 - Phantom type = Body 32 - Total dose = 11.20 msv 2
CT Exam from June 2011 Scan type conducted: Chest with contrast for PE Scanner type: BrightSpeed Elite with ASiR Scan protocol: Slice thickness: 1.25 x 0.625 Pitch: 1.375:1 Table speed or travel distance of scan: 27.5mm/rot- 35cm Rotation time: 0.5sec Total Acquisition 6.92 sec ma = 380 mas = 190 kv= 120 Recon kernel: Chest Noise Index 28.22 ASiR = 40% Dose Report - DLP = 14.30 mgy - CTDIvol = 544.29 - Phantom type = Body 32 - Total dose = 9.25 msv Clinical Findings: There remains a significant amount of pulmonary emboli throughout both pulmonary arteries with a saddle type embolus extending toward the distal main pulmonary artery. This portion of the thrombus within the distal main appears to have undergone slight lysis. There is no clear evidence of progression of the emboli. Patient dose on this exam was 18% less than the previous CT exam. 3
Advantages of BrightSpeed Elite with ASiR in this exam: The patient was scanned on the same Bright Speed Elite pre and post ASiR. The CT imaging staff set the ASiR at 40% and subsequently increased the noise index 24% from 21.45 to 28.09. We had the opportunity to compare the dose as well as the image quality from the patient s previous scan. The radiologist reading the exam noted the image quality of the BrightSpeed Elite is comparable to images seen on the LightSpeed VCT XTe. Community Hospital East also has a LightSpeed VCT XTe with ASiR used for diagnostic imaging. Initial scan parameters: Dose DLP 20.69 CTDIvol 659.41 Coverage 289 mm Estimated effective* 11.2 msv Follow-up scan parameters: Dose DLP 14.30 CTDIvol 544.29 Coverage 350 mm Estimated effective* 9.2 msv Please note there is 17% less coverage in initial scan vs. the follow up scan *Obtained by EUR-16262 EN chest factor of 0.017 x DLP using a 32 cm phantom. 4
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