Andreas Giannopoulos

Medical 3D Printing for the Radiologist

While use of advanced visualization in radiology is instrumental in diagnosis and communication with referring clinicians, there is an unmet need to render Digital Imaging and Communications in Medicine (DICOM) images as three-dimensional (3D) printed models capable of providing both tactile feedback and tangible depth information about anatomic and pathologic states. Three-dimensional printed models, already entrenched in the nonmedical sciences, are rapidly being embraced in medicine as well as in the lay community. Incorporating 3D printing from images generated and interpreted by radiologists presents particular challenges, including training, materials and equipment, and guidelines. The overall costs of a 3D printing laboratory must be balanced by the clinical benefits. It is expected that the number of 3D-printed models generated from DICOM images for planning interventions and fabricating implants will grow exponentially. Radiologists should at a minimum be familiar with 3D printing as it relates to their field, including types of 3D printing technologies and materials used to create 3D-printed anatomic models, published applications of models to date, and clinical benefits in radiology. Online supplemental material is available for this article.

Docetaxel and cisplatin combination chemotherapy in advanced carcinoma of the urothelium: A multicenter phase II study of the Hellenic Cooperative Oncology Group

PURPOSE Both docetaxel and cisplatin have moderate activity in patients with advanced urothelial cancer. We performed a multicenter phase II study in order to assess the efficacy and toxicity of the combination of these two agents in patients with advanced carcinoma of the urothelium. PATIENTS AND METHODS Sixty-six patients not amenable to curative surgery or irradiation were enrolled onto this cooperative group study and treated on an outpatient basis with docetaxel 75 mg/m2 followed by cisplatin 75 mg/m2, both administered intravenously. Granulocyte-colony stimulating factor was administered subcutaneously at a dose of 5 micrograms/kg daily from day 5 until resolution of neutropenia. The chemotherapy was administered every three weeks for a maximum of six courses in patients without evidence of progressive disease. RESULTS Thirty-four of sixty-six patients (52%, 95% confidence interval 40%-64%) demonstrated objective responses, with eight achieving clinical complete responses and twenty-six partial responses. A multivariate logistic regression analysis indicated that the patients most likely to respond were those without lung metastasis and without weight loss before treatment. The median duration of response was 6.1 months and the median times to progression and survival for all patients were 5 and 8 months, respectively. Absence of anemia, of liver metastases and of weight loss correlated with longer survival. Grade > or = 3 toxicities included granulocytopenia in 33% of patients, anemia in 14%, diarrhea in 13% and emesis in 7% of patients. CONCLUSION The combination of docetaxel and cisplatin appeared relatively well tolerated and moderately active in patients with advanced urothelial cancer. The patients most likely to benefit were those without weight loss and without lung or liver metastases.

Vulnerable plaque imaging: updates on new pathobiological mechanisms.

Early identification of vulnerable, rupture-prone atherosclerotic plaques with the optimal goal of cardiovascular event prevention is a field of vigorous research. Despite the advances in imaging modalities and the in vivo identification of many characteristics of vulnerability, few of these plaques actually rupture and even fewer lead to clinical events, questioning the predictive value of the above techniques in clinical practice. Factors causing the higher local vulnerability of the culprit plaque within a prothrombotic environment of widespread inflammation are generally unknown. Newly recognized local features, including microcalcifications and biomechanical factors, seem to contribute. In this review article, we target on new mechanisms, implicated in vulnerable plaque formation and rupture, analysing their potential clinical value.

Further experience with catheter closure of patent ductus arteriosus using the new Amplatzer duct occluder in children.

The aim of the present study was to report our additional experience with transcatheter closure of the patent ductus arteriosus in 65 consecutive patients using the new Amplatzer duct occluder. The median patient age was 3.6 years (range 0.2to 12), and the median weight was 10.5 kg (range 4 to 38). The device was a modified Amplatzer duct occluder made of fabric-free fine Nitinol wire net in to 2 very low profile disks with an articulated connecting waist. It is delivered through a 4Fr to 5Fr delivery sheath. The device was permanently implanted in 62 of 65 patients. The mean patent ductus arteriosus diameter (at the pulmonary end) was 3.6 +/- 1.3 mm (range 0.5 to 5.5). The mean device diameter (waist diameter) was 4.2 +/- 1.5 mm (range 3 to 6). Complete echocardiographic closure of the PDA at 1 month follow-up was observed in 61 (98%) of 62 patients. Immediately after the procedure, mild left pulmonary stenosis (peak pressure gradient of 8, 10, and 12 mm Hg) in 3 of 63 patients. Device embolization in 1 patient was the main complication of the procedure. No other complications were observed. In conclusion, catheter closure using the Amplatzer duct occluder II is an effective and safe therapy for most patients with patent ductus arteriosus. Additional studies are required to document its efficacy, safety, and long-term results in a larger patient population.

Cardiothoracic Applications of 3-dimensional Printing.

Medical 3-dimensional (3D) printing is emerging as a clinically relevant imaging tool in directing preoperative and intraoperative planning in many surgical specialties and will therefore likely lead to interdisciplinary collaboration between engineers, radiologists, and surgeons. Data from standard imaging modalities such as computed tomography, magnetic resonance imaging, echocardiography, and rotational angiography can be used to fabricate life-sized models of human anatomy and pathology, as well as patient-specific implants and surgical guides. Cardiovascular 3D-printed models can improve diagnosis and allow for advanced preoperative planning. The majority of applications reported involve congenital heart diseases and valvular and great vessels pathologies. Printed models are suitable for planning both surgical and minimally invasive procedures. Added value has been reported toward improving outcomes, minimizing perioperative risk, and developing new procedures such as transcatheter mitral valve replacements. Similarly, thoracic surgeons are using 3D printing to assess invasion of vital structures by tumors and to assist in diagnosis and treatment of upper and lower airway diseases. Anatomic models enable surgeons to assimilate information more quickly than image review, choose the optimal surgical approach, and achieve surgery in a shorter time. Patient-specific 3D-printed implants are beginning to appear and may have significant impact on cosmetic and life-saving procedures in the future. In summary, cardiothoracic 3D printing is rapidly evolving and may be a potential game-changer for surgeons. The imager who is equipped with the tools to apply this new imaging science to cardiothoracic care is thus ideally positioned to innovate in this new emerging imaging modality.

Initial and Six-Year Results of Stent Implantation for Aortic Coarctation in Children

Although stenting has been used as a treatment option for aortic coarctation (CoA) at increasingly younger ages, limited information is available on the long-term follow-up of stent implantation for CoA in pediatric patients. A total of 74 patients with CoA (mean age 8 ± 3 years) underwent stent implantation; 42 were treated for isolated native CoA and 32 for recurrent CoA. A total of 87 stents were implanted (bare metal stents in 71 patients and covered stents in 3 patients). Redilation of a previously implanted stent was performed in 32 patients. Immediately after stenting, the peak systolic pressure gradient decreased from 68 ± 16 mm Hg to 8 ± 5 mm Hg (p <0.05), and the CoA diameter increased from 5 ± 3 mm to 16 ± 3 mm (p <0.05). The most important procedural complication was aneurysm formation in 1 patient that was successfully treated with implantation of a covered stent. No early or late deaths occurred and no evidence was found of late aneurysm formation during a follow-up period of 6 years. Late stent fracture was observed in 3 patients. At the end of follow-up, no cases of recoarctation were identified on multislice computed tomography or magnetic resonance imaging, and 67 (85%) of the 74 patients were normotensive, receiving no medications. In conclusion, stent implantation is an effective and safe treatment alternative to conventional surgical management for the treatment of CoA in selected pediatric patients.

3D printed ventricular septal defect patch: a primer for the 2015 Radiological Society of North America (RSNA) hands-on course in 3D printing

Hand-held three dimensional models of the human anatomy and pathology, tailored-made protheses, and custom-designed implants can be derived from imaging modalities, most commonly Computed Tomography (CT). However, standard DICOM format images cannot be 3D printed; instead, additional image post-processing is required to transform the anatomy of interest into Standard Tessellation Language (STL) format is needed. This conversion, and the subsequent 3D printing of the STL file, requires a series of steps. Initial post-processing involves the segmentation-demarcation of the desired for 3D printing parts and creating of an initial STL file. Then, Computer Aided Design (CAD) software is used, particularly for wrapping, smoothing and trimming. Devices and implants that can also be 3D printed, can be designed using this software environment. The purpose of this article is to provide a tutorial on 3D Printing with the test case of complex congenital heart disease (CHD). While the infant was born with double outlet right ventricle (DORV), this hands-on guide to be featured at the 2015 annual meeting of the Radiological Society of North America Hands-on Course in 3D Printing focused on the additional finding of a ventricular septal defect (VSD). The process of segmenting the heart chambers and the great vessels will be followed by optimization of the model using CAD software. A virtual patch that accurately matches the patient’s VSD will be designed and both models will be prepared for 3D printing.

Association of global and local low endothelial shear stress with high-risk plaque using intracoronary 3D optical coherence tomography: Introduction of ‘shear stress score’

Aims The association of low endothelial shear stress (ESS) with high-risk plaque (HRP) has not been thoroughly investigated in humans. We investigated the local ESS and lumen remodelling patterns in HRPs using optical coherence tomography (OCT), developed the shear stress score, and explored its association with the prevalence of HRPs and clinical outcomes. Methods and results A total of 35 coronary arteries from 30 patients with stable angina or acute coronary syndrome (ACS) were reconstructed with three dimensional (3D) OCT. ESS was calculated using computational fluid dynamics and classified into low, moderate, and high in 3-mm-long subsegments. In each subsegment, (i) fibroatheromas (FAs) were classified into HRPs and non-HRPs based on fibrous cap (FC) thickness and lipid pool size, and (ii) lumen remodelling was classified into constrictive, compensatory, and expansive. In each artery the shear stress score was calculated as metric of the extent and severity of low ESS. FAs in low ESS subsegments had thinner FC compared with high ESS (89 ± 84 vs.138 ± 83 µm, P < 0.05). Low ESS subsegments predominantly co-localized with HRPs vs. non-HRPs (29 vs. 9%, P < 0.05) and high ESS subsegments predominantly with non-HRPs (9 vs. 24%, P < 0.05). Compensatory and expansive lumen remodelling were the predominant responses within subsegments with low ESS and HRPs. In non-stenotic FAs, low ESS was associated with HRPs vs. non-HRPs (29 vs. 3%, P < 0.05). Arteries with increased shear stress score had increased frequency of HRPs and were associated with ACS vs. stable angina. Conclusion Local low ESS and expansive lumen remodelling are associated with HRP. Arteries with increased shear stress score have increased frequency of HRPs and propensity to present with ACS.

IVUSAngio Tool

There is an ongoing research and clinical interest in the development of reliable and easily accessible software for the 3D reconstruction of coronary arteries. In this work, we present the architecture and validation of IVUSAngio Tool, an application which performs fast and accurate 3D reconstruction of the coronary arteries by using intravascular ultrasound (IVUS) and biplane angiography data. The 3D reconstruction is based on the fusion of the detected arterial boundaries in IVUS images with the 3D IVUS catheter path derived from the biplane angiography. The IVUSAngio Tool suite integrates all the intermediate processing and computational steps and provides a user-friendly interface. It also offers additional functionality, such as automatic selection of the end-diastolic IVUS images, semi-automatic and automatic IVUS segmentation, vascular morphometric measurements, graphical visualization of the 3D model and export in a format compatible with other computer-aided design applications. Our software was applied and validated in 31 human coronary arteries yielding quite promising results. Collectively, the use of IVUSAngio Tool significantly reduces the total processing time for 3D coronary reconstruction. IVUSAngio Tool is distributed as free software, publicly available to download and use.

Medical 3D printing: methods to standardize terminology and report trends

BackgroundMedical 3D printing is expanding exponentially, with tremendous potential yet to be realized in nearly all facets of medicine. Unfortunately, multiple informal subdomain-specific isolated terminological ‘silos’ where disparate terminology is used for similar concepts are also arising as rapidly. It is imperative to formalize the foundational terminology at this early stage to facilitate future knowledge integration, collaborative research, and appropriate reimbursement. The purpose of this work is to develop objective, literature-based consensus-building methodology for the medical 3D printing domain to support expert consensus.ResultsWe first quantitatively survey the temporal, conceptual, and geographic diversity of all existing published applications within medical 3D printing literature and establish the existence of self-isolating research clusters. We then demonstrate an automated objective methodology to aid in establishing a terminological consensus for the field based on objective analysis of the existing literature. The resultant analysis provides a rich overview of the 3D printing literature, including publication statistics and trends globally, chronologically, technologically, and within each major medical discipline. The proposed methodology is used to objectively establish the dominance of the term “3D printing” to represent a collection of technologies that produce physical models in the medical setting. We demonstrate that specific domains do not use this term in line with objective consensus and call for its universal adoption.ConclusionOur methodology can be applied to the entirety of medical 3D printing literature to obtain a complete, validated, and objective set of recommended and synonymous definitions to aid expert bodies in building ontological consensus.