CT versus MR guidance for radiofrequency ablation in patients with colorectal liver metastases: a 10-year follow-up favors MR guidance.

OBJECTIVES: To compare the results of CT- vs MR-guided radiofrequency ablation (RFA) of liver metastases (LM) from colorectal cancer after 10 years of follow-up in an observational, retrospective, and multicentric study. METHODS: A total of 238 patients with 496 LM were treated with RFA either with CT (CT group) or magnetic resonance (MR group) guidance. Every ablated LM was assessed and followed up with diagnostic MRI. Technical success, technique efficacy, predictive factors, recurrence rates, and overall survival were assessed. RESULTS: The CT group comprised 143 patients and the MR group 77 patients. Eighteen patients underwent ablation with both modalities. Technical success per patient and per lesion was 88% and 93% for CT and 87% and 89.6% for MR, and technique efficacy was 97.1% and 98.6% for CT and 98.7% and 99.3% for MR respectively. Local recurrence following the first ablation (primary patency) occurred in 20.1% (CT) vs 4.6% (MR) (p < 0.001). Residual liver tumor, size of LM, and advanced N and M stage at initial diagnosis were independent predictors for overall survival in both groups. The median overall survival measured from first RFA treatment was 2.6 years. The 1-year, 5-year, and 10-year survival were 85.9%, 25.5%, and 19.1% respectively. CONCLUSIONS: The MR group had significantly better local control compared to the CT group. There was no significant difference in patient survival between the two groups. CLINICAL RELEVANCE STATEMENT: MR-guided radiofrequency ablation of colorectal liver metastases is safe and effective, and offers better local control than CT-guided ablation. KEY POINTS: • Imaging modality for radiofrequency ablation guidance is an independent predictor of local recurrence in colorectal liver metastases. • MR-guided radiofrequency ablation achieved better local control of liver metastases from colorectal cancer than CT-guided. • The number and size of liver metastases are, among others, independent predictors of survival. Radiofrequency ablation with MR guidance improved clinical outcome but does not affect survival.

Robotic systems for percutaneous needle-guided interventions.

Several groups have developed robotic systems for invasive medical procedures. In this article we will focus on selected robotic systems for percutaneous needle-guided interventions using CT or MR imaging. We present six interventional robotic systems designed to work with imaging modalities such as CT, Cone-beam CT and MRI. The details of each system are given along with any phantom, animal, or human trials performed with each particular robot. Although each of these systems has specific features, they are all of great clinical value since they provide very stable needle guidance -- even for angulated approaches, they may allow access to lesions when the width of the CT- or MR- gantry would limit the access for a biopsy needle or other interventional tools such as thermal ablation probes. Then, such a robot may be able to guide the needle into the most promising region of the lesion without the need for a second contrast injection. Thus, more efficacious characterization and treatment, particularly for lesions that are difficult to target, can be anticipated. Although more research and clinical trials are certainly needed, it is, however, our belief that robotic systems will be an important part of future interventions.

Radiofrequency ablation suppresses distant tumour growth in a novel rat model of multifocal hepatocellular carcinoma.

RFA (radiofrequency ablation) is an established therapy for HCC (hepatocellular carcinoma). The multikinase inhibitor sorafenib prolongs survival in advanced HCC. We examined the effects of RFA alone and in combination with sorafenib on a bystanding tumour in a two-tumour rat model of HCC. A total of 80 rats were implanted with two liver tumours and randomized to four treatment groups: vehicle and sham operation (control), sorafenib and sham operation (Sora/Sham), vehicle and RFA (Vh/RFA), and sorafenib and RFA (Sora/RFA) (n=10/group per time point). RFA or sham-operation was performed on the left lobe tumour on day 15. Animals were killed at day 18 and day 30. Non-RFA-targeted right lobe tumours were analysed for angiogenesis, growth factors [HGF (hepatocyte growth factor), EGF (epidermal growth factor) and VEGF (vascular endothelial growth factor)] and infiltrating immune cells (CD3 and CD68). At day 30, the non-RFA-targeted tumours were significantly smaller in all three treatment groups compared with control (Sora/Sham P≤0.0001, Vh/RFA P=0.005 and Sora/RFA P≤0.0001). The smallest tumours were observed in animals treated with a combination of sorafenib and RFA, whereas the size reduction seen in the RFA-only group indicated an RFA-mediated distant suppression of tumour growth. Growth factor measurement revealed transiently decreased EGF levels after RFA (P=0.008), whereas sorafenib treatment decreased HGF levels (P=0.001). MVD (microvessel density) was reduced by sorafenib (P=0.002) despite increased VEGF levels (P≤0.0001). The immune parameters revealed augmented T-cells and IL-10 (interleukin 10) levels in all three treatment groups; sorafenib additionally increased macrophage numbers (P≤0.0001). RFA and sorafenib alone resulted in significant volume reduction of the non-RFA-targeted tumour; this effect was enhanced when both modalities were combined.

Factors affecting screening for hepatocellular carcinoma.

BACKGROUND AND AIM: Hepatocellular carcinoma (HCC) is a frequent cancer. Its prognosis is highly dependent on early diagnosis. Patients at risk for developing HCC should be enrolled in a surveillance programme. Nevertheless, many patients at risk are not regularly screened. We aimed at exploring the characteristics that affect enrolment in a surveillance programme. MATERIAL AND METHODS: The characteristics of the patients included in the prospective Bern HCC cohort between August 2010 and August 2011 were analysed according to their participation in a surveillance programme. RESULTS: Among the 82 patients included in the cohort during this period of time, 48 were in a surveillance program before the diagnosis of HCC. Thirty five percent of cirrhotic patients were not screened. Age, sex, level of education, Child-Pugh status and MELD score were similar between the patients who were screened and those who were not screened. Patients with a private insurance and patients treated by a liver specialist were more frequently enrolled in a surveillance program. Sixty seven percent of the screened patients were eligible for curative treatment whereas only 15% of the non-screened patients were. CONCLUSIONS: In conclusion the surveillance of patients at risk for developing HCC increases their chances to be diagnosed at an early stage to allow curative treatment. More than one third of cirrhotic patients were not regularly screened. Patients with chronic liver disease should be referred to identify those at risk and enrol them in a surveillance program.

A robotic needle-positioning and guidance system for CT-guided puncture: Ex vivo results.

PURPOSE: To test the feasibility of a robotic needle-guidance platform during CT-guided puncture ex vivo. MATERIAL AND METHODS: Thin copper wires inserted into a torso phantom served as targets. The phantom was placed on a carbon plate and the robot-positioning unit (RPU) of the guidance platform (iSYS Medizintechnik GmbH, Kitzbuehel, Austria) was attached. Following CT imaging and automatic registration a double oblique trajectory was planned and the RPU was remotely moved into appropriate position and angulation. A 17G-puncture needle was then manually inserted until the preplanned depth, permanently guided by the RPU. The CT scan was repeated and the distance between the actual needle tip and the target was evaluated. RESULTS: Automatic registration was successful in ten experiments and the median duration of an experiment was 9.6 (6.4-46.0) minutes. The angulation of the needle path in x-y and z-axis was within 15.6° to 32.6°, and -32.8° to 3.2°, respectively and the needle insertion depth was 92.8 ± 14.4 mm. The Euclidean distance between the actual needle tip and the target was 2.3 ± 0.8 (range, 0.9-3.7) mm. CONCLUSION: Automatic registration and accurate needle placement close to small targets was demonstrated. Study settings and torso phantom were very close to the clinical reality.

Source-detector trajectory optimization for CBCT metal artifact reduction based on PICCS reconstruction.

Precise instrument placement plays a critical role in all interventional procedures, especially percutaneous procedures such as needle biopsies, to achieve successful tumor targeting and increased diagnostic accuracy. C-arm cone beam computed tomography (CBCT) has the potential to precisely visualize the anatomy in direct vicinity of the needle and evaluate the adequacy of needle placement during the intervention, allowing for instantaneous adjustment in case of misplacement. However, even with the most advanced C-arm CBCT devices, it can be difficult to identify the exact needle position on CBCT images due to the strong metal artifacts around the needle. In this study, we proposed a framework for customized trajectory design in CBCT imaging based on Prior Image Constrained Compressed Sensing (PICCS) reconstruction with the goal of reducing metal artifacts in needle-based procedures. We proposed to optimize out-of-plane rotations in three-dimensional (3D) space and minimize projection views while reducing metal artifacts at specific volume of interests (VOIs). An anthropomorphic thorax phantom with a needle inserted inside and two tumor models as the imaging targets were used to validate the proposed approach. The performance of the proposed approach was also evaluated for CBCT imaging under kinematic constraints by simulating some collision areas on the geometry of the C-arm. We compared the result of optimized 3D trajectories using the PICCS algorithm and 20 projections with the result of a circular trajectory with sparse view using PICCS and Feldkamp, Davis, and Kress (FDK), both using 20 projections, and the circular FDK method with 313 projections. For imaging targets 1 and 2, the highest values of structural similarity index measure (SSIM) and universal quality index (UQI) between the reconstructed image from the optimized trajectories and the initial CBCT image at the VOI was calculated 0.7521, 0.7308 and 0.7308, 0.7248 respectively. These results significantly outperformed the FDK method (with 20 and 313 projections) and the PICCS method (20 projections) both using the circular trajectory. Our results showed that the proposed optimized trajectories not only significantly reduce metal artifacts but also suggest a dose reduction for needle-based CBCT interventions, considering the small number of projections used. Furthermore, our results showed that the optimized trajectories are compatible with spatially constrained situations and enable CBCT imaging under kinematic constraints when the standard circular trajectory is not feasible.

Silicone phantoms fabricated with multi-material extrusion 3D printing technology mimicking imaging properties of soft tissues in CT.

Recently, 3D printing has been widely used to fabricate medical imaging phantoms. So far, various rigid 3D printable materials have been investigated for their radiological properties and efficiency in imaging phantom fabrication. However, flexible, soft tissue materials are also needed for imaging phantoms for simulating several clinical scenarios where anatomical deformations is important. Recently, various additive manufacturing technologies have been used to produce anatomical models based on extrusion techniques that allow the fabrication of soft tissue materials. To date, there is no systematic study in the literature investigating the radiological properties of silicone rubber materials/fluids for imaging phantoms fabricated directly by extrusion using 3D printing techniques. The aim of this study was to investigate the radiological properties of 3D printed phantoms made of silicone in CT imaging. To achieve this goal, the radiodensity as described as Hounsfield Units (HUs) of several samples composed of three different silicone printing materials were evaluated by changing the infill density to adjust their radiological properties. A comparison of HU values with a Gammex Tissue Characterization Phantom was performed. In addition, a reproducibility analysis was performed by creating several replicas for specific infill densities. A scaled down anatomical model derived from an abdominal CT was also fabricated and the resulting HU values were evaluated. For the three different silicone materials, a spectrum ranging from -639 to +780 HU was obtained on CT at a scan setting of 120 kVp. In addition, using different infill densities, the printed materials were able to achieve a similar radiodensity range as obtained in different tissue-equivalent inserts in the Gammex phantom (238 HU to -673 HU). The reproducibility results showed good agreement between the HU values of the replicas compared to the original samples, confirming the reproducibility of the printed materials. A good agreement was observed between the HU target values in abdominal CT and the HU values of the 3D-printed anatomical phantom in all tissues.

Additively manufactured test phantoms for mimicking soft tissue radiation attenuation in CBCT using Polyjet technology.

OBJECTIVES: To develop and validate a simple approach for building cost-effective imaging phantoms for Cone Beam Computed Tomography (CBCT) using a modified Polyjet additive manufacturing technology where a single material can mimic a range of human soft-tissue radiation attenuation. MATERIALS AND METHODS: Single material test phantoms using a cubic lattice were designed in 3-Matic 15.0 software . Keeping the individual cubic lattice volume constant, eight different percentage ratio (R) of air: material from 0% to 70% with a 10% increment were assigned to each sample. The phantoms were printed in three materials, namely Vero PureWhite, VeroClear and TangoPlus using Polyjet technology. The CT value analysis, non-contact profile measurement and microCT-based volumetric analysis was performed for all the samples. RESULTS: The printed test phantoms produced a grey value spectrum equivalent to the radiation attenuation of human soft tissues in the range of -757 to +286 HU on CT. The results from dimensional comparison analysis of the printed phantoms with the digital test phantoms using non-contact profile measurement showed a mean accuracy of 99.07 % and that of micro-CT volumetric analysis showed mean volumetric accuracy of 84.80-94.91%. The material and printing costs of developing 24 test phantoms was 83.00 Euro. CONCLUSIONS: The study shows that additive manufacturing-guided macrostructure manipulation modifies successfully the radiographic visibility of a material in CBCT imaging with 1 mm3 resolution, helping customization of imaging phantoms.

Realistic 3D printed CT imaging tumor phantoms for validation of image processing algorithms.

Medical imaging phantoms are widely used for validation and verification of imaging systems and algorithms in surgical guidance and radiation oncology procedures. Especially, for the performance evaluation of new algorithms in the field of medical imaging, manufactured phantoms need to replicate specific properties of the human body, e.g., tissue morphology and radiological properties. Additive manufacturing (AM) technology provides an inexpensive opportunity for accurate anatomical replication with customization capabilities. In this study, we proposed a simple and cheap protocol using Fused Deposition Modeling (FDM) technology to manufacture realistic tumor phantoms based on the filament 3D printing technology. Tumor phantoms with both homogenous and heterogeneous radiodensity were fabricated. The radiodensity similarity between the printed tumor models and real tumor data from CT images of lung cancer patients was evaluated. Additionally, it was investigated whether a heterogeneity in the 3D printed tumor phantoms as observed in the tumor patient data had an influence on the validation of image registration algorithms. A radiodensity range between -217 to 226 HUs was achieved for 3D printed phantoms using different filament materials; this range of radiation attenuation is also observed in the human lung tumor tissue. The resulted HU range could serve as a lookup-table for researchers and phantom manufactures to create realistic CT tumor phantoms with the desired range of radiodensities. The 3D printed tumor phantoms also precisely replicated real lung tumor patient data regarding morphology and could also include life-like heterogeneity of the radiodensity inside the tumor models. An influence of the heterogeneity on accuracy and robustness of the image registration algorithms was not found.

A novel pharmacological treatment concept for neuroprotection in severe traumatic brain injury-Two case reports.

Severe traumatic brain injury (sTBI) is a major cause of death and disability worldwide, resulting in a significant individual and socioeconomic burden. Current treatment guidelines do not include any recommendations for neuroprotective or neuoregenerative drugs. Here, we present a combined treatment with Cerebrolysin and Citicoline in two cases. Both drugs are experimentally better than clinically proven in their own effectiveness, but there is almost no clinical data on the combination of the two. Our case study hints at a promising approach that may improve neurological outcome after sTBI. The first patient was a 29 years male motorcyclist suffered polytrauma in a high-speed accident. He had severe bilateral chest trauma and fractures in both thighs and an sTBI. In addition to surgical and standard neurocritical care according to the evidence-based guidelines, he was given neuroprotective therapy with Cerebrolysin (50 ml/day) and Citicoline (3 g/day), by continuous intravenous infusion (IV), for 21 days. The second patient was a 30 years male ski mountaineer who had suffered a fall over 300 m in open terrain. In addition to the sTBI, he had fractures in the cervical spine, ribs, pelvis, and lower extremities, as well as lung contusions and massive soft tissue trauma. After initial treatment in a local hospital, he was transferred to our department and received the same neuroprotective drugs, like all of our patients with sTBI. Considering the severity of the injuries (Injury Severity Score [ISS]: 43/50, Revised Trauma Score [RTS: 5.0304, 2.7794]) and the unfavorable outcome probability (Hukkelhoven Score) of 93.1% and 82.6%, the outcomes of both patients are surprisingly encouraging 1 year after the accident. They achieved a Glasgow Outcome Score of 6 and 5 and grades 2 and 4 on the modified Rankin Scale, respectively. Currently, both are able to take care of themselves in activities of daily life to a large extent. Neuroprotective drugs may improve the regeneration of cell membranes, improve blood brain barrier integrity, and reduce neuroinflammation leading to secondary damage to the injured brain. Our clinical experience and data suggest that the combined administration of Citicoline and Cerebrolysin may contribute to better recovery, without relevant side effects. However, it would be important to validate these results by means of a controlled, prospective study.

CIRSE Standards of Practice on Bronchial Artery Embolisation.

This CIRSE Standards of Practice document is aimed at interventional radiologists and provides best practices for performing bronchial artery embolisation to effectively treat haemoptysis. It has been developed by an expert writing group established by the CIRSE Standards of Practice Committee.

3D printed patient-specific thorax phantom with realistic heterogenous bone radiopacity using filament printer technology.

Current medical imaging phantoms are usually limited by simplified geometry and radiographic skeletal homogeneity, which confines their usage for image quality assessment. In order to fabricate realistic imaging phantoms, replication of the entire tissue morphology and the associated CT numbers, defined as Hounsfield Unit (HU) is required. 3D printing is a promising technology for the production of medical imaging phantoms with accurate anatomical replication. So far, the majority of the imaging phantoms using 3D printing technologies tried to mimic the average HU of soft tissue human organs. One important aspect of the anthropomorphic imaging phantoms is also the replication of realistic radiodensities for bone tissues. In this study, we used filament printing technology to develop a CT-derived 3D printed thorax phantom with realistic bone-equivalent radiodensity using only one single commercially available filament. The generated thorax phantom geometry closely resembles a patient and includes direct manufacturing of bone structures while creating life-like heterogeneity within bone tissues. A HU analysis as well as a physical dimensional comparison were performed in order to evaluate the density and geometry agreement between the proposed phantom and the corresponding CT data. With the achieved density range (-482 to 968 HU) we could successfully mimic the realistic radiodensity of the bone marrow as well as the cortical bone for the ribs, vertebral body and dorsal vertebral column in the thorax skeleton. In addition, considering the large radiodensity range achieved a full thorax imaging phantom mimicking also soft tissues can become feasible. The physical dimensional comparison using both Extrema Analysis and Collision Detection methods confirmed a mean surface overlap of 90% and a mean volumetric overlap of 84,56% between the patient and phantom model. Furthermore, the reproducibility analyses revealed a good geometry and radiodensity duplicability in 24 printed cylinder replicas. Thus, according to our results, the proposed additively manufactured anthropomorphic thorax phantom has the potential to be efficiently used for validation of imaging- and radiation-based procedures in precision medicine.

New insights and antimicrobial stewardship opportunities in viral pneumonia: five lung ultrasound cases.

BACKGROUND: Antimicrobial stewardship is crucial to avoid antimicrobial resistance in microbes and adverse drug effects in patients. In respiratory infections, however, viral pneumonia is difficult to distinguish from bacterial pneumonia, which explains the overuse of antibiotic therapy in this indication. CASES: Five cases of lung consolidation are presented. Lung ultrasound, in conjunction with procalcitonin levels, were used to exclude or corroborate bacterial pneumonia. CONCLUSION: Lung ultrasound is easy to learn and perform and is helpful in guiding diagnosis in unclear cases of pneumonia and may also offer new insights into the spectrum of certain virus diseases. The use of lung ultrasound can raise awareness in clinicians of the need for antimicrobial stewardship and may help to avoid the unnecessary use of antibiotics.

Toward on-the-fly trajectory optimization for C-arm CBCT under strong kinematic constraints.

Cone beam computed tomography (CBCT) has become a vital tool in interventional radiology. Usually, a circular source-detector trajectory is used to acquire a three-dimensional (3D) image. Kinematic constraints due to the patient size or additional medical equipment often cause collisions with the imager while performing a full circular rotation. In a previous study, we developed a framework to design collision-free, patient-specific trajectories for the cases in which circular CBCT is not feasible. Our proposed trajectories included enough information to appropriately reconstruct a particular volume of interest (VOI), but the constraints had to be defined before the intervention. As most collisions are unpredictable, performing an on-the-fly trajectory optimization is desirable. In this study, we propose a search strategy that explores a set of trajectories that cover the whole collision-free area and subsequently performs a search locally in the areas with the highest image quality. Selecting the best trajectories is performed using simulations on a prior diagnostic CT volume which serves as a digital phantom for simulations. In our simulations, the Feature SIMilarity Index (FSIM) is used as the objective function to evaluate the imaging quality provided by different trajectories. We investigated the performance of our methods using three different anatomical targets inside the Alderson-Rando phantom. We used FSIM and Universal Quality Image (UQI) to evaluate the final reconstruction results. Our experiments showed that our proposed trajectories could achieve a comparable image quality in the VOI compared to the standard C-arm circular CBCT. We achieved a relative deviation less than 10% for both FSIM and UQI metrics between the reconstructed images from the optimized trajectories and the standard C-arm CBCT for all three targets. The whole trajectory optimization took approximately three to four minutes.

Use of a latest-generation vascular plug for peripheral vascular embolization with use of a diagnostic catheter: preliminary clinical experience.

PURPOSE: The latest-generation Amplatzer vascular plug (AVP), the AVP 4, is designed for embolization of smaller vessels without a sheath or guiding catheter. This study evaluated the AVP 4 in peripheral vascular embolization. MATERIALS AND METHODS: Embolization with the AVP 4 was attempted in 13 patients (11 men) for trauma (n = 7) and other indications (n = 6). Technical success rate, vascular bed, size of catheter, and number and size of AVP 4 devices were recorded. RESULTS: Embolization with the AVP 4 was successful in 10 of 13 patients (77%). In trauma patients (n = 7), embolization of the splenic artery (n = 4), lumbar artery (n = 2), and superior gluteal artery (n = 1) was performed. In other patients, preoperative embolization of the right portal vein (n = 1), a gastric varix after transjugular intrahepatic portosystemic shunt creation (n = 1), an aneurysm of the internal iliac artery (n = 1), and inferior mesenteric artery (IMA) embolization before aneurysm repair (n = 2) was performed. Sizes of the AVP 4 were 4 mm (n = 6), 6 mm (n = 5), and 8 mm (n = 1). In all patients, 4- and 5-F catheters with a 0.038-inch minimum inner lumen were used. In one patient, IMA embolization was attempted via a femoral approach but was unsuccessful as a result of repeated catheter tip dislocation because of acute angle; coils were used instead. CONCLUSIONS: Peripheral embolization with the AVP 4 was successful in the majority of patients. Future comparative study is necessary to evaluate this device's benefits over other embolization materials such as earlier-generation AVPs or microcoils.

Short Scan Source-detector Trajectories for Target-based CBCT.

We proposed a target-based cone beam computed tomography (CBCT) imaging framework in order to optimize a free three dimensional (3D) source-detector trajectory by incorporating prior 3D image data. We aim to enable CBCT systems to provide topical information about a region of interest (ROI) using a short-scan trajectory with a reduced number of projections. The best projection views are selected by maximizing an objective function fed by the image quality by means of applying different x-ray positions on the digital phantom data. Finally, an optimized trajectory is selected which is applied to a C-arm device able to perform general source-detector positioning. An Alderson-Rando head phantom is used in order to investigate the performance of the proposed framework. Our experiments showed that the optimized trajectory could achieve a comparable image quality in the ROI with respect to the reference C-arm CBCT while using approximately one-quarter of projections. An angular range of 156° was used for the optimized trajectory.

Temperature-induced configuration changes in hydrogel-coated coils and their relevance in embolization procedures.

BACKGROUND: The present study attempted to demonstrate how the configuration of hydrogel-coated coils is influenced by different temperature exposures. Thirty detachable hydrogel-coated coils were evaluated in an in vitro water immersion test under five different temperature ranges (22.6 °C, 37 °C, 40-50 °C, 50-60 °C, and 60-70 °C). The configuration changes were classified (configuration I, configuration II, and configuration III) according to the curling that occurred during 30 min of immersion. Configuration stability of five Hydrogel-coated coils was also evaluated in a two-step temperature immersion test. RESULTS: All hydrogel-coated coils showed some configuration changes during water immersion. However, a logarithmic transformation of the time and temperature data showed a significant (p < 0.05) negative linear correlation between time and temperature for all coil configurations (configuration I: R = 0.97, configuration II: R = 0.98, configuration III: R = 0.97). The time needed to reach configuration III (complete coiling) was 160.4 ± 41.9 s at 37.5 °C (range: 100-205 s), 45.7 ± 22.2 s at 47.5 °C (range: 23-70 s), 20.2 ± 7.2 s at 57.5 °C (range: 14-32 s), and 10.3 ± 2.4 s at 67.5 °C (range: 7-13 s). CONCLUSIONS: Temperatures above 55 °C induced immediate configurational changes in the hydro-coated coils, achieving complete curling within less than 30 s. Temperatures near 36 °C (normal body temperature) require more time to reach optimal coil curling (configuration III). The optimization of HydroCoil preparation can reduce interventional procedural time and improve clinical results.

Frameless Stereotactic Brain Biopsies: Comparison of Minimally Invasive Robot-Guided and Manual Arm-Based Technique.

BACKGROUND: Most brain biopsies are still performed with the aid of a navigation-guided mechanical arm. Due to the manual trajectory alignment without rigid skull contact, frameless aiming devices are prone to considerably lower accuracy. OBJECTIVE: To compare a novel minimally invasive robot-guided biopsy technique with rigid skull fixation to a standard frameless manual arm biopsy procedure. METHODS: Accuracy, procedural duration, diagnostic yield, complication rate, and cosmetic result were retrospectively assessed in 40 consecutive cases of frameless stereotactic biopsies and compared between a minimally invasive robotic technique using the iSYS1 guidance device (iSYS Medizintechnik GmbH) (robot-guided group [ROB], n = 20) and a manual arm-based technique (group MAN, n = 20). RESULTS: Application of the robotic technique resulted in significantly higher accuracy at entry point (group ROB median 1.5 mm [0.4-3.2 mm] vs manual arm-based group (MAN) 2.2 mm [0.2-5.2 mm], P = .019) and at target point (group ROB 1.5 mm [0.4-2.8 mm] vs group MAN 2.8 mm [1.4-4.9 mm], P = .001), without increasing incision to suture time (group ROB 30.0 min [20-45 min vs group MAN 32.5 min [range 20-60 min], P = .09) and significantly shorter skin incision length (group ROB 16.3 mm [12.7-23.4 mm] vs group MAN 24.2 mm [18.0-37.0 mm], P = .008). CONCLUSION: According to our data, the proposed technique of minimally invasive robot-guided brain biopsies can improve accuracy without increasing operating time while being equally safe and effective compared to a standard frameless arm-based manual biopsy technique.

Additively Manufactured Patient-Specific Anthropomorphic Thorax Phantom With Realistic Radiation Attenuation Properties.

Conventional medical imaging phantoms are limited by simplified geometry and radiographic skeletal homogeneity, which confines their usability for image quality assessment and radiation dosimetry. These challenges can be addressed by additive manufacturing technology, colloquially called 3D printing, which provides accurate anatomical replication and flexibility in material manipulation. In this study, we used Computed Tomography (CT)-based modified PolyJetTM 3D printing technology to print a hollow thorax phantom simulating skeletal morphology of the patient. To achieve realistic heterogenous skeletal radiation attenuation, we developed a novel radiopaque amalgamate constituting of epoxy, polypropylene and bone meal powder in twelve different ratios. We performed CT analysis for quantification of material radiodensity (in Hounsfield Units, HU) and for identification of specific compositions corresponding to the various skeletal structures in the thorax. We filled the skeletal structures with their respective radiopaque amalgamates. The phantom and isolated 3D printed rib specimens were rescanned by CT for reproducibility tests regarding verification of radiodensity and geometry. Our results showed that structural densities in the range of 42-705HU could be achieved. The radiodensity of the reconstructed phantom was comparable to the three skeletal structures investigated in a real patient thorax CT: ribs, ventral vertebral body and dorsal vertebral body. Reproducibility tests based on physical dimensional comparison between the patient and phantom CT-based segmentation displayed 97% of overlap in the range of 0.00-4.57 mm embracing the anatomical accuracy. Thus, the additively manufactured anthropomorphic thorax phantom opens new vistas for imaging- and radiation-based patient care in precision medicine.