Strategies for Efficient Chest ct interpretation

Transcription

1 10th Annual International Symposium on Multidetector-Row CT Stanford Radiology, Las Vegas, May 13-16, 2008 Strategies for Efficient Chest ct interpretation Justus E. Roos Stanford University 1 History - single slice ct --> multislice CT data explosion transverse images insufficient 2 Strategies chest ct interpretation - What changed with MDCT? - tools that can improve our efficiency - Future tools on our wish list 3

2 workhorse Routine Chest 64 MDCT protocol image reconstruction - 1 mm / 1 mm axial (B45 kernel) - 5 mm / 5 mm axial (B31 Kernel) --> transverse images ( ) Visualization tools on current pacs - stack view / cine paging - simple measurements tools - multi-window display ~ single slice ct --> Isotropic voxel dimensions --> choose thicker slices --> use alternatives to transverse images 4 alternatives --> Reconstruct thicker slices (5mm) + less slices ( ) - detection rate 1.25 mm # nodules Collimation 5 mm missed 2-5 mm % 6-10 mm % mm 9 9 0% 5 mm 1.25 mm 5 * mean of 2 readers alternatives --> Isotropic voxel dimensions - sag. dimension of thorax < cc dimension - coronal Mpr less images - 5mm axial <> 5mm coronal --> primary coronal image interpretation is less sensitive and more time consuming as transverse images -cause: familiarity / rapid cine viewing Panbronchioltis; image Courtesy N.Mueller, VGH 6

3 Strategies chest ct interpretation - What changed with MDCT? - tools that can improve our efficiency - Future tools on our wish list 7 workhorse Routine Chest 64 MDCT protocol image reconstruction - 1 mm / 1 mm axial (B45 kernel) - 5 mm / 5 mm axial (B31 Kernel) - 2 mm / 2 mm sagittal mpr - 2 mm / 2 mm coronal mpr --> transverse images ( ) --> cor / sag MPR images ( ) Cor. MPR Sag. MPR 8 workhorse Routine Chest 64 MDCT protocol image reconstruction - 1 mm / 1 mm axial (B45 kernel) - 5 mm / 5 mm axial (B31 Kernel) - 2 mm / 2 mm sagittal mpr - 2 mm / 2 mm coronal mpr - 7 mm / 3.5 mm thin-slab MIP --> transverse images ( ) --> cor / sag MPR images ( ) --> thin slab MIP images ( ) 9

4 Strategies chest ct interpretation Thick Thin Thin Slab MIP or VR - error rate 40-55% / speed 1.5 to 5x - Not for measurements * Diederich et al. European Radiology (2001) vol. 11 (8) pp * Gruden et al. (2002) vol. 179 (1) pp * Ko. Journal of thoracic imaging (2005) vol. 20 (3) pp * Jankowski et al. (2007) Radiology vol. 17 (12) pp * Napel S et al. (1993) JCAT Vol yo female - High grade sarcoma of left thigh yo female - High grade sarcoma of left thigh Thin Slab MIP 12

5 - 49 yo female - High grade sarcoma of left thigh Thin Slab VR 13 Peloschek et al. Radiology (2007) vol. 243 (2) pp workhorse Routine Chest 64 MDCT protocol image reconstruction - 1 mm / 1 mm axial (B45 kernel) - 5 mm / 5 mm axial (B31 Kernel) - 2 mm / 2 mm sagittal mpr - 2 mm / 2 mm coronal mpr - 7 mm / 3.5 mm thin-slab MIP --> transverse images --> cor / sag MPR images --> thin slab MIP images ( ) ( ) ( ) ( ) - prescribed in scan protocol - reconstructed automatically on scanner - no additional costs - image viewing on good old pacs 14 High Resolution Scans (HRCT) --> all >16 MDCT = requirement of HRCT: dis-continuous HRCT <> Volumetric HRCT + High Spatial Resolution + Pattern analysis of dld + Low dose CTDIw CTDIvol [mgy] 2x0.5mm increment 10mm Traditional HRCT x 0.75mm Pitch 1.5 Volumetric HRCT 16 MDCT 15

6 High Resolution Scans (HRCT) --> all >16 MDCT = requirement of HRCT: discontinuous HRCT <> Volumetric HRCT Image quality Traditional HRCT Volumetric HRCT 16 MDCT 16 High Resolution Scans (HRCT) --> all >16 MDCT = requirement of HRCT: discontinuous HRCT <> Volumetric HRCT Image quality traditional HRCT Volumetric HRCT 64 MDCT 17 High Resolution Scans (HRCT) --> all >16 MDCT = requirement of HRCT: discontinuous HRCT <> Volumetric HRCT + High Spatial Resolution + Pattern analysis of dld + Low dose = Bronchiectasis = bronchial tree segm. = F/U = disease quantification =... --> volumetric HRCT is not necessary for detection and characterization of diffuse lung disease with a couple exceptions 18

7 Strategies chest ct interpretation - What changed with MDCT? - tools that can improve our efficiency - Future tools on our wish list 19 3 Wishes 1) Volumetric measurements tools 2) chest ct registration tools 3) computer aided detection 20 Wish #1-5mm Nodule - Pixel Size 0.7mm (FOV 35CM, 512 X 512 MATRIX) - one pixel off --> 14% diameter - --> 48% volume - Error Vol: 70 mm 3 Gietema et al. radiology (2007) vol. 245 (3) pp Volumetric measurements --> 4-7 x Better 21

8 Wish #2 Relationships Over Time matching of nodules detected in two scans Where was it? Today 6 months ago Mean error: 1.2 ±.9 mm; worst case 4.3 mm Sun, et. al, Medical Physics 2007; 34(2): Wish #3 Computer Aided Detection (CAD) % Detection rate Wishes S C A P 1) Volumetric measurements tools 2) chest ct registration tools 3) computer aided detection...at least in thin client solutions running on computers next to each pacs workstation... 24

9 Strategies for efficient chest ct interpretation (summary) transverse images remain the workhorse use MPR and Thin slab Mips keep the option to use non continuous hrct ask for integration of next generation post processing and visualization tools into pacs or at least as a thin client solution next to your workstation 25 10th Annual International Symposium on Multidetector-Row CT Stanford Radiology, Las Vegas, May 13-16, 2008 Thank you... Justus E. Roos Stanford University 26