Using DRLs for CT optimization: Sources and management of dose - PDF document

11/21/19 Using DRLs for CT optimization: Sources and management of dose variability Ehsan Samei (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 1

11/21/19 Overarching premise Medicine: Discerning and intervening in the health state of the patient with sufficient accuracy, precision, and safety for definitive clinical outcome Healthcare is about the patient, not the particularities of the techniques – techniques and quantities are valued to the extent they are relevant to the patient (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 2

11/21/19 Reality check 1: Clinical practice Heterogeneous and Complex: • Varying technologies • Varying technical parameters • Varying patients • Varying human operators • Competing interests Variability in the quality of care Variability across practice 4.0 Abdomen-Pelvis CT 3.5 Total DLP of study (Gy*cm) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Exam Date (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 3

11/21/19 Noise versus patient size: Phantom Siemens Flash GE HD750 35 50 45 30 40 25 35 noise (HU) 30 20 25 15 20 10 15 10 5 5 0 0 20 25 30 35 40 45 20 25 30 35 40 45 patient diameter (cm) patient diameter (cm) Ria et al, AAPM 2018 Noise versus patient size: Patients Siemens Flash GE HD750 35 50 45 30 40 25 35 noise (HU) 30 20 25 15 20 10 15 10 5 5 0 0 20 25 30 35 40 45 20 25 30 35 40 45 patient diameter (cm) patient diameter (cm) (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 4

11/21/19 Reality check 2: There is a cost! • Most people will experience at least one diagnostic error in their lifetime – 10% of patient deaths – 6-17% hospital adverse events – Leading type of paid medical malpractice – Claims twice as likely to result in death – Highest proportion of total payments. Improving Diagnosis in Healthcare, NAM 2015 Drive towards high-quality, consistent, patient-centric, evidence-based, precise, and safe healthcare (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 5

11/21/19 Patient-oriented Drive towards high-quality, consistent, patient-centric, optimization of evidence-based, precise, quality and safety and safe healthcare Quality and safety optimization A process to enable and ensure high-quality (accurate), consistent (precise), patient-centric, and safe, use of imaging in medicine (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 6

11/21/19 Optimization Quality indices (d’, A z , …) framework Different patients e m and indications i g e r t i f e n e B Optimization regime Safety indices (organ dose, e m eff. dose, …) i g e r k s Scan factors i R (mAs, kVp, pitch, recon, kernel, …) Optimization taxonomy Independent variables (imaging parameters) Dependent variables Benefit Risk Physical Quality indices Output indices (eg, MTF) (eg, CTDI) Clinical Performance indices Safety indices (eg, d’, AUC) (eg, ED, RI) (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 7

11/21/19 Quality vs dose: the right balance? Image ? Quality Radiation Dose Metrology matters! Metrology matters! Image Image Quality Quality Diagnosis Diagnosis ? ? Preference Preference ? ? Radiation Dose Radiation Dose (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 8

11/21/19 What are the right metrics? 1. Relevant: As much as possible, patient-/indication-centric (not modality or machine) 2. Robust: To ensure reliability and applicability (quantitative not subjective) 3. Smart: Maintained balance between robustness and relevance 4. Relatability: Surrogates relatable to clinical task/safety 5. Practical: Economic to measure Variability from systematic (age, size) and operational effects Image Quality Radiation Dose (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 9

11/21/19 DRL as variability management Image Quality Range w/ DRL Image Quality Range DRL w/o DRL Radiation Dose Reference range as variability management Image Quality Range w/ RR Image Quality Range RR w/o DRL Radiation Dose (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 10

11/21/19 Precision by inference Technology assessment Precision by prescription Precision by outcome Prospective use definition Retrospective quality audit Precision by inference Technology assessment Apply constraints to machine performance in concordance with self, peer, or mandates (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 11

11/21/19 Characterizing relevant intrinsic performance of CT system, TG233 • Mercury Phantom 4.0 • Size matching population cohorts 85 mm 90 mm 60 mm 60 mm 85 mm m m 2 1 m 1 m 7 7 m 1 m 0 2 2 m m 0 9 m 2 m 5 5 3 Automated Characterization • HU, Contrast, Noise, CNR, MTF, NPS • TCM-dependency • Detectability index • Detectability indices for reference tasks – 1, 5, 10 mm, 10 and 100 HU, designer, rect, Gaussian 2 ( u , v ) 2 " $ MTF 2 ( u , v ) W Task E 2 ( u , v ) dudv ∫∫ 2 # % ( d NPWE ' ) = 2 ( u , v ) 2 ( u , v ) N i dudv MTF 2 ( u , v ) W Task NPS ( u , v ) E 4 ( u , v ) + MTF 2 ( u , v ) W Task ∫∫ (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 12

11/21/19 Automated Characterization Detectability Indices Across Systems Intersystem Variability 8.0% QC Detectability - ACR Phantom Intrasystem Variability SIEMENS - Force - DMPCT3 0.1% 12 SIEME NS - Force - DMPCT 3 SIEMENS - Flash - ERCT1 1.0% SIEME NS - Flash - ERCT1 SIEMENS - Flash - DMPCT3 3.5% SIEME NS - Flash - DMPCT3 11 SIEMENS - Flash - CCCT5 1.9% SIEME NS - Flash - CCCT5 SIEMENS - Flash - CCCT4 4.2% SIEME NS - Flash - CCCT4 SIEMENS - Flash - C3 2.1% 10 SIEME NS - Flash - C3 Detectability SIEMENS - Flash - C1 2.4% SIEME NS - Flash - C1 GE - LSXtra - J1 GE - LSXtra - J1 2.4% 9 GE - LSVCT - ERCT2 GE - LSVCT - ERCT2 3.1% GE - LSVCT - CCCT3 GE - LSVCT - CCCT3 2.0% GE - LSVCT - CaryCT 8 GE - LSVCT - CaryCT 1.7% GE - LS16 - SP GE - LS16 - SP 2.1% GE - DIQ - PETCT1 GE - DIQ - PETCT1 3.2% 7 GE - DCT75 0 HD - DMPCT 2 GE - DCT75 0 HD - DMPCT 1 GE - DCT750 HD - DMPCT2 2.8% GE - DCT75 0 HD - CCCT2 GE - DCT750 HD - DMPCT1 1.4% 6 GE - DCT75 0 HD - CCCT1 GE - DCT750 HD - CCCT2 1.8% 05/15/2013 02/23/2014 05/15/2014 07/24/2014 10/18/2014 01/08/2015 03/26/2015 06/10/2015 08/27/2015 11/24/2015 02/11/2016 04/14/2016 07/19/2016 09/20/2016 GE - DCT75 0 HD - B5 GE - DCT750 HD - CCCT1 2.2% GE - D690 - PETCT2 GE - DCT750 HD - B5 3.0% GE - BrightSpeed - DMP67 0 GE - D690 - PETCT2 3.0% GE - BrightSpeed - D670 Date GE - BrightSpeed - DMP670 2.4% GE - BrightSpeed - D670 3.8% Intra-system variability: 1-4% Inter-system variability: 8% (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 13

11/21/19 Apply constraints to protocol definitions in concordance with self, peer, or mandates Precision by prescription Prospective use definition Detectability Indices Across the US ACR-RSNA-Duke Collaborative project Zhang et al, RSNA, 2018 (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 14

11/21/19 Matching protocols across imaging systems GE ? Siemens Siemens Siemens Sharpness (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 15

11/21/19 GE to Siemens “best match” STD ASiR 40% i40 SAFIRE 3 GE to Siemens “best match” BONE PLUS ASiR 0% b70 SAFIRE 0 (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 16

11/21/19 Matching Image Quality Across CTs Log of dose needed for a target noise of 10 Average resolution (f 50 ) Average noise texture (f avg ) Winslow et al, Med Phys 2018 Protocol Matcher TM (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 17

11/21/19 (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 18

11/21/19 Quality vs dose: the right balance? Image Quality Radiation Dose Iso-dose? Image Quality Inconsistency in image quality Radiation Dose (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 19

11/21/19 Iso-quality? Image Quality Wide variation in dose Radiation Dose Iso-balance Image Quality Smart balance between quality and dose Radiation Dose (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 20

11/21/19 Optimization of dose for size for-your-child.blogspot.com http://www.pedrad.org Age Iso-balance in practice ALARA? � Samei et al, JMI, 2017 Samei et al, RPD, 2018 (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 21

11/21/19 Duke Pediatric Protocols … Li, et al, RSNA 2010 1.0 Radiation risk index 0.8 0.6 Risk 0.4 0.2 0.0 0 10 20 Dose (c) Ehsan Samei, 2019. Use for non- personal purposes by prior permission only. 22