Hao Dang Tackles Truncation Using Multi-Resolution CT Reconstruction

January 4, 2017

A recent paper published in Physics in Medicine and Biology by Hao Dang and coauthors in the I-STAR Lab reports a multi-resolution CT image reconstruction method that efficiently overcomes truncation effects, which are a particularly important problem in cone-beam CT (which often has limited field of view) and can confound iterative model-based image reconstruction (MBIR) methods.

Data truncation in CBCT results in artifacts that reduce image uniformity and challenge reliable diagnosis. For a recently developed prototype CBCT head scanner, truncation of the head and/or head holder can hinder the detection of intracranial hemorrhage (ICH).

The multi-resolution method is based on a similar approach shown by Qian Cao and coauthors for orthopaedic imaging, which allows simultaneous high-resolution reconstruction of bone regions and lower-resolution (lower-noise) reconstruction of surrounding soft tissue. In Hao Dang’s paper, a similar concept is used to overcome truncation artifacts by performing a high-resolution reconstruction of the interior with a lower-resolution reconstruction outside the RFOV.

The algorithm was tested in experiments involving CBCT of the head with truncation due to a carbon-fiber head support. Conventional (single-resolution) MBIR,  showed severe artifacts and poor convergence properties, and the proposed method with a multi-resolution extension of the RFOV minimized truncation artifacts. Compared to brute-force reconstruction of the larger RFOV, the multi-resolution approach reduced computation time by as much as 95% (for an image volume up to 10003 voxels).

The findings provide a promising method for minimizing truncation artifacts in CBCT and may be useful for MBIR methods in general, which can be confounded by truncation effects.

Read the full paper in Phys Med Biol here.

Ja Reaungamornrat Earns PhD in Computer Science

January 3, 2017

Sureerat (Ja) Reaungamornrat successfully defended her PhD dissertation, entitled “Deformable Image Registration for Surgical Guidance Using Intraoperative Cone-Beam CT” in December 2016. Her work addresses new methods for deformable image registration in image-guided interventions, including: (1) a hybrid model for resolving large deformations of the tongue in multi-modality image-guided transoral robotic surgery; (2) a free-form registration method with rigid-body constraints on bones moving within an otherwise deformable soft-tissue context; and (3) a modality-insensitive neighborhood descriptor (MIND) method for registering preoperative MRI to intraoperative CT or cone-beam CT. Ja was supervised in both her Master’s and Doctoral work by Dr. Jeff Siewerdsen (Biomedical Engineering), and her PhD thesis examiners included Dr. Jerry Prince (Electrical and Computer Engineering), Dr. Russ Taylor (Computer Science), and Dr. A. Jay Khanna (Orthopaedic Surgery). Congratulations, Ja!

Jennifer Xu Earns PhD in Biomedical Engineering

November 29, 2016

Jennifer Xu earned her Ph.D. in Biomedical Engineering from Johns Hopkins University. She successfully defended her thesis entitled “Image Quality, Modeling, and Design for High-Performance Cone-Beam CT of the Head” in Hurd Hall Auditorium on November 17, 2016.

Her dissertation shows that diagnosis and treatment of neurological and otolaryngological disease rely on accurate visualization of subtle anatomical structures in the head. Her work involved development of high-quality imaging of the head at the point of care to improve timeliness of patient monitoring and reduce risk associated with patient transport to and from the radiology suite. X-ray cone-beam computed tomography (CBCT) presents a promising technology for point-of-care head imaging with relatively low cost, mechanical simplicity, and high spatial resolution; however, CBCT systems are conventionally challenged in imaging of low-contrast structures (e.g., intracranial hemorrhage). Jennifer Xu’s PhD thesis detailed the design and development of CBCT imaging capability suitable to low-contrast lesion visualization. Her work encompasses physics-based modeling of image quality, system design and optimization, technical assessment of the resulting CBCT prototype CBCT, and translation to first clinical studies in the NCCU.

2016 Best New Radiology Device! Extremity Cone-Beam CT

October 26, 2016

The winner of the 2016 Best New Radiology Device from Aunt Minnie this year began as an industry collaboration betewen Johns Hopkins University  and Carestream Health that eventually evolved into a commercial product. The system also won the 2016 Frost & Sullivan Award for New Product Innovation.

OnSight 3D is designed to bring advanced 3D imaging to orthopaedic surgeons, musculoskeletal radioloigsts, and rheumatologists. The system allows high-resolution imaging of the extremities, including weight-bearing lower extremities. It also features image processing algorithms for fast 3D image reconstruction, rendering, metal artifact reduction, and image analysis.

Tharindu DeSilva reports clinical utility of LevelCheck.

The “LevelCheck” algorithm for automatic radiographic labeling of the spine during surgery was evaluated by Tharindu De Silva and colleagues in a recent paper published in Spine. The clinical utility was assessed, and scenarios in which LevelCheck was most likely to be the beneficial were assessed in a retrospective study of 398 cases.

The results showed that LevelCheck was helpful in 42.2% of the cases (168/398), to improved confidence in 30.6% of the cases (122/398), and in no case diminished performance (0/398), supporting its potential as an independent check and assistant to decision support in spine surgery.

The scenarios for which LevelCheck was most likely to be beneficial included: cases with a lack of conspicuous anatomical landmarks; level counting across long spine segments; vertebrae obscured by other anatomy (e.g., shoulders); poor radiographic image quality; and anatomical variations/abnormalities.

The method demonstrated 100% geometric accuracy (i.e., correctly overlaid spine labels within the correct vertebral level in all cases) and did not introduce ambiguity in image interpretation.  The study shows LevelCheck to be a potentially useful means of decision support in spine surgery target localization and motivates translation to prospective clinical studies.

Read the full paper in Spine.