OBJECTIVES/SPECIFIC AIMS: Computed tomography (CT) enables3-dimensional (3D) visualization of cortical bone structures with high spatialresolution, and thus has been the gold-standard method for evaluation anddiagnosis of craniofacial skeletal pathologies. However, ionizing radiation and,in particular, repeated scanning for presurgery and postsurgery assessments, isof concern when applied to infants and young children. Recent advances insolid-state MRI allow the capture of the short-T2 signals in cortical bone whilesuppressing the signal from soft-tissue protons having T2 relaxation time1–2 orders of magnitude longer (50–100 ms). One approach,a dual-radiofrequency (RF) pulse and ultrashort echo time (UTE) imaging basedmethod, exploits different sensitivities of bone and soft tissue to different RFpulse widths and TEs. This study aims to demonstrate the feasibility ofproducing 3D renderings of the human skull and visualization of cranial suturesusing the bone-selective MRI technique in comparison to CT.METHODS/STUDY POPULATION: Imaging technique: Two RF pulses differingin duration and amplitude are alternately applied in successive repetition time(TR) along the pulse train. Within each TR, 2 echoes are acquired. Acquisitionof the first echo starts at the ramp-up of the encoding gradient (TE1), allowingfor capture of signals with very short lifetimes (bone), while that of thesecond starts after a longer delay (TE2). In total, 4 echoes are obtained:ECHO11 (RF1TE1), ECHO12 (RF1TE2), ECHO21 (RF2TE1), and ECHO22 (RF2TE2). Duringreconstruction, ECHO11 is combined with ECHO21 and ECHO12 is combined withECHO22, resulting in 2 images. The subtraction of these 2 images yields anenhanced bone contrast. Data acquisition/processing: The pulsesequence described above was applied for MR imaging of a human cadaveric skulland 2 adult human subjects in vivo, at 3T field strength (Siemens Prisma,Erlangen, Germany). Imaging parameters:TR/TE1/TE2=7/0.06/2.46ms, RF1/RF2 durations=40/520 μs,flip angle=12°, matrix size=2563, field ofview=2803 mm3, voxel size=1.1 mm isotropic,number of radial spokes=25,000, and scan time=6 minutes.Segmentation of bone voxels was performed using ITK-SNAP in a semi-automaticfashion, leading to 3D renderings of the skull. For comparison, a CT scan wasalso performed in the human cadaveric skull with 1 mm isotropic resolution.Validation: The biometric accuracy was assessed by measuring eight anatomicdistances: (1) Maximum craniocaudal aperture of the right orbit. (2) Maximumcraniocaudal aperture of the left orbit. (3) Maximum height of the mandible fromchin point in the midline. (4) Maximum cranial length (5) Maximum cranial width.(6) Maximum height of piriform aperture. (7) Distance between lateral mostaspect of mandibular condyles. (8) Distance between lateral most aspect ofposterior hard palate in both CT- and MRI-based 3D renderings of the humancadaveric skull using Mimics software (Materialise®,Ghent, Belgium). These distances were compared with those directly measured onthe cadaveric skull. RESULTS/ANTICIPATED RESULTS: Compares CT withthe proposed MRI method on cadaveric human skull images, along withcorresponding 3D renderings. Compared with CT, the 3D rendered images maintainmost features over the entire head (e.g., zygomatic arch), except for appearanceof some artifacts in the mandibular region. In vivo head images in 2 adultsubjects: axial magnitude images and 3D rendering. In the axial images, bonevoxels as well as the inner table of the cranium are clearly visualized, andcranial and spinal bone structures are well depicted in the 3D renderings. Somevoxels were erroneously included or excluded in the renderings. The meandifference in measurements of the 8 anatomic distances was 6, 4, and 2 mm whencomparing MRI Versus CT, MRI Versus in situ, and CT Versus in situ,respectively. DISCUSSION/SIGNIFICANCE OF IMPACT: Bone protonmagnetization exhibits a substantial level of signal decay during the relativelylong duration of RF2 due to its very short T2 relaxation time. In contrast,soft-tissue retains nearly the same level of signal intensities over all echoes.Thus, subtraction of ECHO22 from ECHO11, when compared with the differencebetween ECHO11 and ECHO12, enhances bone contrast from soft tissue. Theproposed, dual-RF dual-echo 3D UTE imaging technique produces isotropichigh-resolution bone-specified images in the whole head within a clinicallyfeasible imaging time (6 min), leading to clear visualization of craniofacialskeletal structures. These are key components necessary for translation to theclinical setting. Optimization of postprocessing for more realistic 3Drenderings and thus accurate anatomic measurements is currently beingimplemented. The proposed method’s potential as a nonradiativealternative to CT will then be thoroughly evaluated in pediatric patients.