Dataset Information

Three-dimensional printing of MRI-visible phantoms and MR image-guided therapy simulation.

ABSTRACT: To demonstrate the use of anatomic MRI-visible three-dimensional (3D)-printed phantoms and to assess process accuracy and material MR signal properties.A cervical spine model was generated from computed tomography (CT) data and 3D-printed using an MR signal-generating material. Printed phantom accuracy and signal characteristics were assessed using 120 kVp CT and 3 Tesla (T) MR imaging. The MR relaxation rates and diffusion coefficient of the fabricated phantom were measured and 1 H spectra were acquired to provide insight into the nature of the proton signal. Finally, T2 -weighted imaging was performed during cryoablation of the model.The printed model produced a CT signal of 102?±?8 Hounsfield unit, and an MR signal roughly 1/3rd that of saline in short echo time/short repetition time GRE MRI (456?±?36 versus 1526?±?121 arbitrary signal units). Compared with the model designed from the in vivo CT scan, the printed model differed by 0.13?±?0.11?mm in CT, and 0.62?±?0.28?mm in MR. The printed material had T2 ?32 ms, T2*?7 ms, T1 ?193 ms, and a very small diffusion coefficient less than olive oil. MRI monitoring of the cryoablation demonstrated iceball formation similar to an in vivo procedure.Current 3D printing technology can be used to print anatomically accurate phantoms that can be imaged by both CT and MRI. Such models can be used to simulate MRI-guided interventions such as cryosurgeries. Future development of the proposed technique can potentially lead to printed models that depict different tissues and anatomical structures with different MR signal characteristics. Magn Reson Med 77:613-622, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

SUBMITTER: Mitsouras D

PROVIDER: S-EPMC5108690 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Three-dimensional printing of MRI-visible phantoms and MR image-guided therapy simulation.

Mitsouras Dimitris D Lee Thomas C TC Liacouras Peter P Ionita Ciprian N CN Pietilla Todd T Maier Stephan E SE Mulkern Robert V RV

Magnetic resonance in medicine 20160211 2

<h4>Purpose</h4>To demonstrate the use of anatomic MRI-visible three-dimensional (3D)-printed phantoms and to assess process accuracy and material MR signal properties.<h4>Methods</h4>A cervical spine model was generated from computed tomography (CT) data and 3D-printed using an MR signal-generating material. Printed phantom accuracy and signal characteristics were assessed using 120 kVp CT and 3 Tesla (T) MR imaging. The MR relaxation rates and diffusion coefficient of the fabricated phantom we ...[more]

PMID: 26864335

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Project description:Background3D printers have gained prominence in rapid prototyping and viable in creating dimensionally accurate objects that are both safe within a Magnetic Resonance Imaging (MRI) environment and visible in MRI scans. A challenge when making MRI-visible objects using 3D printing is that hard plastics are invisible in standard MRI scans, while fluids are not. So typically, a hollow object will be printed and filled with a liquid that will be visible in MRI scans. This poses an engineering challenge however since objects created using traditional Fused Deposition Modeling (FDM) 3D-printing techniques are prone to leakage. Digital Light Processing (DLP) is a relatively modern and affordable 3D-printing technique using UV-hardened resin, capable of creating objects that are inherently liquid-tight. When printing hollow parts using DLP printers, one typically requires adding drainage holes for uncured liquid resin to escape during the printing process. If this is not done liquid resin will remain inside the object, which in our application is the desired outcome.PurposeWe devised a method to produce an inherently MRI-visible accessory using DLP technology with low dimensional tolerance to facilitate MRI-guided breast biopsies.MethodsBy hollowing out the object without adding drainage holes and tuning printing parameters such as z-lift distance to retain as much uncured liquid resin inside as possible through surface tension, objects that are inherently visible in MRI scans can be created without further post-processing treatment.ResultsObjects created through our method are simple and inexpensive to recreate, have minimal manufacturing steps, and are shown to be dimensionally exact and inherently MRI visible to be directly used in various applications without further treatment.ConclusionOur proposed method of manufacturing objects that are inherently both MRI safe, and MRI visible. The proposed process is simple and does not require additional materials and tools beyond a DLP 3D-printer. With only an inexpensive DLP 3D-printer kit and basic cleaning and sanitation materials found in the hospital, we have demonstrated the viability of our process by successfully creating an object containing fine structures with low spatial tolerances used for MRI-guided breast biopsies.

Project description:Background Magnetic resonance imaging (MRI) is currently used for online target monitoring and plan adaptation in modern image-guided radiotherapy. However, storing a large amount of data accumulated during patient treatment becomes an issue. In this study, the feasibility to compress MRI images accumulated in MR-guided radiotherapy using video encoders was investigated. Methods Two sorting algorithms were employed to reorder the slices in multiple MRI sets for the input sequence of video encoder. Three cropping algorithms were used to auto-segment regions of interest for separate data storage. Four video encoders, motion-JPEG (M-JPEG), MPEG-4 (MP4), Advanced Video Coding (AVC or H.264) and High Efficiency Video Coding (HEVC or H.265) were investigated. The compression performance of video encoders was evaluated by compression ratio and time, while the restoration accuracy of video encoders was evaluated by mean square error (MSE), peak signal-to-noise ratio (PSNR), and video quality matrix (VQM). The performances of all combinations of video encoders, sorting methods, and cropping algorithms were investigated and their effects were statistically analyzed. Results The compression ratios of MP4, H.264 and H.265 with both sorting methods were improved by 26% and 5%, 42% and 27%, 72% and 43%, respectively, comparing to those of M-JPEG. The slice-prioritized sorting method showed a higher compression ratio than that of the location-prioritized sorting method for MP4 (P=0.00000), H.264 (P=0.00012) and H.265 (P=0.00000), respectively. The compression ratios of H.265 were improved significantly with the applications of morphology algorithm (P=0.01890 and P=0.00530), flood-fill algorithm (P=0.00510 and P=0.00020) and level-set algorithm (P=0.02800 and P=0.00830) for both sorting methods. Among the four video encoders, H.265 showed the best compression ratio and restoration accuracy. Conclusions The compression ratio and restoration accuracy of video encoders using inter-frame coding (MP4, H.264 and H.265) were higher than that of video encoders using intra-frame coding (M-JPEG). It is feasible to implement video encoders using inter-frame coding for high-performance MRI data storage in MR-guided radiotherapy.

Project description:BackgroundClosure of a percutaneous paravalvular leak (PVL) is a technically challenging procedure because of the specific anatomy postoperatively and the complex catheter techniques required. Transesophageal echocardiography (TEE) and three-dimensional (3D) printing might be helpful in identifying complex anatomical structures and the procedural design.ObjectivesThe purpose of this study was to review our experiences with transcatheter closure of PVL guided by TEE and 3D (TEE&3D) printing.MethodsA total of 166 patients with PVL after surgical valve replacement underwent transcatheter closure, from January 2015 through December 2020. Among these patients, 68 had preoperative guidance from TEE&3D printing. We reviewed the catheter techniques, perioperative characteristics, and prognosis. The median follow-up period was 36 (3-70) months.ResultsAcute procedural success was achieved in 154/166 (92.8%) patients; of these, 64/68 (94.1%) had TEE&3D guidance and 90/98 (91.8%) had transthoracic echocardiography (TTE) guidance. No hospital deaths occurred. All patients having percutaneous procedures were given local anesthesia, while 13 patients having transapical procedures were given general anesthesia. Multiple approaches were used, including transfemoral, transapical, and transseptal via the arteriovenous loop. We also deployed multiple devices, including the Amplatzer Vascular Plug II (AVP II), the Amplatzer duct occluder II, the patent ductus arteriosus (PDA) occluder, and the Amplatzer muscular ventricular septal defect occluder. Those cases guided by TEE&3D printing had shorter procedural times compared with those guided by TTE [(61.2 ± 23.4) vs. (105.7 ± 53.9) min, p < 0.05]. The fluoroscopic time was also shorter for operations guided by TEE&3D printing compared with those guided by TTE alone [(18.5 ± 11.4) vs. (27.3 ± 5.6) min, p < 0.05]. The complications included recurrent hemolysis, residual regurgitation, acute renal insufficiency, and anemia. There was no significant difference in the incidence of complications between the 2 groups.ConclusionTransesophageal echocardiography and 3D printing show advantages compared with standalone TTE in guiding the transcatheter closure of PVL with shorter procedural and fluoroscopic times. This minimally invasive treatment could provide reliable outcomes in selected patients.Clinical trial registration[www.ClinicalTrials.gov], identifier [NCT02917980].

Dataset Information

Three-dimensional printing of MRI-visible phantoms and MR image-guided therapy simulation.

Publications

Three-dimensional printing of MRI-visible phantoms and MR image-guided therapy simulation.

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