Acknowledgments. A Specific Diagnostic Task: Lung Nodule Detection. A Specific Diagnostic Task: Chest CT Protocols. Chest CT Protocols

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1 Personalization of Pediatric Imaging in Terms of Needed Indication-Based Quality Per Dose Acknowledgments Duke University Medical Center Ehsan Samei, PhD Donald Frush, MD Xiang Li PhD DABR Cleveland Clinic Formerly, Duke University Medical Center 2 A Specific Diagnostic Task: Lung Nodule Detection Children with (extra-thoracic) solid tumors are at risk for pulmonary metastatic disease, manifested as lung nodules. Small size (3-5 mm) low contrast ( HU) A Specific Diagnostic Task: Lung Nodule Detection Presence of a single nodule affects treatment plan and prognosis Chest CT to screen for lung nodules at Many CT scans! > initial evaluation > throughout treatment > during routine follow-up Curable cancers long life expectancy Small size (3-5 mm) low contrast ( HU) Easily missed under high-noise conditions require low dose require high dose 3 4 Mean Age (year) Chest CT s GE LightSpeed VCT scanner kvp Scan FOV Slice Thickness Collimation Pitch Noise Max Index ma pink Ped Body red Ped Body purple.4 00 Small Body yellow Small Body white Small Body blue Medium Body orange Medium Body green.3 20 Medium Body black Large Body Mean Age (year) Chest CT s GE LightSpeed VCT scanner kvp Scan FOV Slice Thickness Collimation Pitch Noise Max Index ma pink Ped Body red Ped Body purple.4 00 Small Body yellow Small Body white Small Body blue Medium Body orange Medium Body green.3 20 Medium Body black Large Body intended for general diagnostic purposes, but not tailored to a specific task 6

2 Task s consistent diagnostic accuracy? Step 2 How to optimize for a specific task? Step How can we obtain this relationship quicker? Monte Carlo study CTDI vol or SSDE Study Study 2 Study 3 E / DLP exp( d ) k chest k 9 Li et al., Med Phys, 38(), (20) Li et al., Radiology, 259, (20) 0 lung nodule detection: () nodule contrast (2) nodule size (3) noise in the lung How can we obtain this relationship quicker? Data from CT manufacturers? AAPM TG 233: (diameter,scan parameters) f (noise index) Li X et al., Med Phys. 38(5): (20). Solomon JB et al., AJR Am J Roentgenol. 200(3): (203). Image Quality = f (Diameter, Scan Parameters) Wilson et al., Medical physics 40 (3): 03908,

3 diagnostic accuracy: area under ROC curve (AUC) image quality: CDNR display Contrast Displayed Diameter Noise ROC observer study real images + simulated nodules + simulated noise noise = 0 HU noise = 4 HU noise = 20 HU b y a cexp( d log x) Li et al. Br J Radiol. 82(977):40- (2009) Li et al. Med Phys 38(5), (20) Li et al. Med Phys 38(5), (20) How can we obtain this relationship quicker? model observers Study Study 2 Study 3 Yu et al., Med. Phys doi:0.002/mp.2380 Barrett et al. Physics in medicine and biology 60.2 (205): R. Solomon et al., Proc. SPIE. Vol AUC=0.89 AUC=

4 average AUC=0.83 Step no iodinated contrast used low incidence of calcification Nodules low-density soft tissue For the purpose of detecting lung nodules, choice of kvp is unimportant Soft-tissue contrast is superior at a lower kvp How about using 80 kvp for all pediatric patients? require higher ma limitations of low kvp exceed system limit increase rotation time decrease pitch more beam-hardening artifact 80 kvp tube voltage (kvp) category weight (kg) Singh et al. Yu et al. our choice pink red purple yellow white blue /20 00 orange / green black prolong scan time more motion artifact Cody et al., AJR, Singh et al. Radiology 2009;252(): Yu et al. RadioGraphics 20; 3:

5 Optimize Slice Thickness Optimize Slice Thickness Mean Slice Age Thickness (year) Small Size (3-5 mm) pink red 0.7 purple.4 yellow white 4. 5 blue orange green.3 5 black t 25 5-mm 4-mm partial volume averaging 26 Optimize Slice Thickness current Mean Slice Age Thickness (year) pink red 0.7 purple.4 yellow white 4. 5 blue orange green.3 5 black optimized Slice Thickness 2.5 Mean Age (year) kvp Scan FOV (bowtie filter) Slice Collimation Thickness Pitch pink Ped Body (s) red Ped Body (s) purple.4 00 Small Body (s) yellow Medium Body (m) white Medium Body (m) blue Medium Body (m) orange Medium Body (m) green.3 20 Medium Body (m) black Medium Body (m) Maximize dose efficiency Achieve desired spatial resolution Respect system limit and scanning speed requirement Step 2 Step 3 29 Samei et al., J. Med. Imag. (207)

6 Breathing Artifact 0.9 msv 4-month old AUC=0.83 Not factored into image quality metric: CDNR display Contrast Displayed Diameter Noise 2 msv Slightly blurred blood vessels Higher lung density (less air in lung due to shallow breathing) 3 32 Conclusions A framework for formulating size-specific pediatric protocols for a given diagnostic task Diagnostic Accuracy = f (Radiation Dose) To achieve the same diagnostic accuracy, more dose is needed to scan a larger/older patient Optimize individual scan parameters Achieve consistent diagnostic accuracy across pediatric sizes 33 Thank you!