Imaging Pearls ❯ Radiation Dose ❯ Dose Reduction Techniques
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- Dose Reduction Protocols
- Lower kVp selection (140 vs 120 vs 100 vs 80)
- Use of Iterative reconstruction protocols
- Dual energy CT scanning
- Elimination of unnecessary phases like non-contrast CT scans in many applications
- Limit volume of area scanned (scan only what is needed) - The Role of the Referring Physician in Dose Reduction
- Proper exam selection
- Provide the clinical history and the questions that need to be answered
- Provide information if available to prior studies at outside institutions
- Consult with Radiology routinely - Radiation Dose and the CT Scanner Used
- Dose is often dependent on the scanner used
- Vendor specific (Siemens, GE Healthcare, Phillips, Toshiba)
- Type of scanner available from the vendor (16, 32, 64, 128, 256, 320, Dual Source) - Radiation Dose and the Clinical Application
- What is the clinical application and what information do I need to provide?
- Is it an adult or pediatric patient?
- What is the patient size and body habitus?
- What is the best scan protocol for the clinical problem to be evaluated (single vs dual phase vs triple phase examinations) - Tips to Reduce Dose
- Scan only the volume in question (i.e. limit scan volume in PE study as opposed to lung metastases evaluation)
- What is the clinical question to be answered? (i.e. is this a new study or a follow up of a prior study-as in follow up of a lung nodule)
- Contrast (IV Contrast) enhanced images may make it easier to reduce dose. - SAFIRE
- Sinogram Affirmed Iterative Reconstruction
- Iterative reconstruction that is specific to the Siemens scanner - SAFIRE
- Creates 5 different images with varying noise levels and you select the best one (1 has most noise and 5 has least noise)
- Allows for dose reduction by improving image quality by decreasing noise
- Better than previous techniques in imaging and better than FBP or IRIS
- Dose reduction in the 60% range (FDA Approved) - Radiation Dose Optimization
- Localizer radiographs (topogram)
- Tube current
- Tube voltage
- Pitch
- Scan length
- Image processing - Image Reconstruction: FBP vs IR
- FBP is classic reconstruction technique for CT (filtered back projection)
- Statistical iterative reconstruction technique (IR) works by focusing on image noise and attempting to decrease it
- New IR techniques include MBIR and SAFIRE
- Bottom line: may decrease dose 60-90% while maintaining image quality