Safe usage of Mini 'C'-arm in operating room environment: Implications for clinical practice.

BACKGROUND: Mini 'C'-arm machine is an advanced medical imaging device used primarily for intraoperative imaging during surgical, orthopaedic and emergency care procedures. Since the technology is based on ionising radiation, safe usage of Mini 'C'-arm machine is mandatory to protect patients and operating personnel. OBJECTIVE: The main objective is to describe the various components related to patients, operator and equipment to ensure safe usage of Mini 'C'-arm machine. A comprehensive search strategy using the PEO (Population, Exposure, Outcome) framework was conducted using Embase, PubMed, Google Scholar and ResearchGate databases to identify suitable literature. The keywords used for the search included 'Fluoroscopy', 'Ionising Radiation' and 'surgical safety'. KEY FINDINGS: Safe usage of Mini 'C'-arm equipment involves components of operator training, operator safety, patient safety, radiation dose, operating room logistics, handling of images and auditing of Mini 'C'-arm use. CONCLUSION: Mini 'C'-arm provides an invaluable, portable imaging tool in a spectrum of general surgical and orthopaedic interventional procedures. However, safe usage of Mini 'C'-arm machine requires a multifaceted approach including operator responsibility and safety, patient protection, equipment maintenance, radiation dose awareness, documentation and sound reporting mechanisms.

Surgical outcomes of intraoperative O-arm versus C-arm fluoroscopy in occipitocervical fixation: a retrospective analysis.

PURPOSE: This study aims to compare the effect of using O-arm and C-arm fluoroscopy on the surgical outcomes of occipitocervical fixation. METHODS: The study included patients who underwent occipitocervical fixation using O-arm or C-arm between 2005 and 2021. Of 56 patients, 34 underwent O-arm-assisted surgery (O-group) and 22 underwent C-arm-assisted surgery (C-group). We assessed surgical outcomes, including operative time, intraoperative blood loss, perioperative complications, and bone union. RESULTS: Almost half of the patients had rheumatoid arthritis-related disorders in both groups. Sixteen cases (47.1%) in the O-group and 12 cases (54.5%) in the C-group were fixed from occipito (Oc) to C3, 12 cases (38.2%) in the O-group and 7 cases (31.8%) in the C-group from Oc to C4-7, 5 cases (14.7%) in the O-group, and 3 cases (13.6%) in the C-group from Oc to T2 (p = 0.929). There was no significant difference in operative time (p = 0.239) and intraoperative blood loss (p = 0.595) between the two groups. Dysphagia was the most common complication in both groups (O-group vs. C-group, 11.7% vs. 9.1%). Regarding implant-related complications, occipital plate dislodgement was observed in four cases (18.2%) in the C-group (p = 0.02). The bone union rate was 96.3% in the O-group and 93.3% in the C-group (P = 1). CONCLUSIONS: O-arm use is associated with a reduced rate of occipital plate dislodgment and has a similar complication incidence compared with C-arm-assisted surgery and does not prolong operative time despite the time needed for setting and scanning. Accordingly, an O-arm is safe and useful for occipitocervical fixation surgery.

Intraoperative assessment of hindfoot alignment using C-arm fluoroscopy.

BACKGROUND: Hindfoot malalignment can cause various foot and ankle problems. For better surgical performance and correction of hindfoot malalignments, reliable intraoperative determination of hindfoot alignment is essential. However, there is no standard method for the intraoperative assessment of hindfoot alignment. We devised an intraoperative modified Méary posteroanterior (IOPPA) view to assess intraoperative hindfoot alignment. This study aimed to compare this intraoperative method with other radiographic hindfoot alignment measurements. METHODS: Thirty-seven patients (47 feet) with various foot and ankle conditions scheduled to undergo surgery were prospectively recruited. Before surgery, the Saltzman, long axial, and modified Méary views were taken in a controlled and standardized fashion. IOPPA views were obtained under simulated weight bearing conditions using C-arm fluoroscopy in the operating room before surgery. The relationship between the IOPPA view and the three radiographic hindfoot alignments was evaluated using Pearson's correlation. RESULTS: The mean hindfoot alignment angle was varus 3.50° (CI, varus 1.91 to 5.08) on the Saltzman view, varus 2.00° (CI, varus 0.60 to 3.39) on the long axial view, varus 0.13° (CI, valgus 1.41 to varus 1.67) on the modified Méary view, and varus 1.32° (CI, valgus 0.02 to varus 2.65) on IOPPA view. The IOPPA view and the three other hindfoot alignment views were found to be significantly correlated (r = 0.60 for the Saltzman view, r = 0.50 for the long axial view, r = 0.71 for the modified Méary view, P < .05). The intraobserver ICC (Intraclass Correlation Coefficient) value was 0.974 and interobserver ICC (Intraclass Correlation Coefficient) value was 0.988 for the IOPPA view (P < .001). CONCLUSION: There was a statistically significant correlation between the IOPPA view and the other three hindfoot alignment views. We also found that interobserver and intraobserver ICC values were excellent. This study proposes that the IOPPA view can be used as a reliable intraoperative assessment tool for hindfoot alignment. LEVEL OF EVIDENCE: Prospective study.

The combination of intraoperative CT navigation and C-arm fluoroscopy for INFIX and percutaneous TITS screw placement in the treatment of pelvic ring injury: technical note.

BACKGROUND: The subcutaneous screw rod system, commonly known as the internal pelvic fixator (INFIX), is useful in managing unstable pelvic ring fractures. Conventional INFIX and transiliac-transsacral (TITS) screw techniques are performed using C-arm fluoroscopy. There have been problems with medical exposure and screw insertion accuracy with these techniques. This work describes new INFIX and TITS techniques using intraoperative computed tomography (CT) navigation and C-arm fluoroscopy for pelvic ring fracture. METHODS: A typical case is presented in this study. An 86-year-old woman suffered from an unstable pelvic ring fracture due to a fall from a height. INFIX and TITS screw fixation with intraoperative CT navigation were selected to optimize surgical invasiveness and proper implant placement. RESULTS: The patient was placed in a supine position on a Jackson table. An intraoperative CT navigation was imaged, and screws were inserted under the navigation. Postoperative X-rays and CT confirmed that the screw was inserted correctly. This technique was less invasive to the patient and had little radiation exposure to the surgeon. Rehabilitation of walking practice was started early after the surgery, and she was able to walk with the assistance of a walker by the time of transfer. CONCLUSIONS: The technique employed in our case study has the cumulative advantages of safety, accuracy, and reduced radiation exposure, together with the inherent advantages of functional outcomes of previously reported INFIX and TITS screw techniques. Further experience with this approach will refine this technique to overcome its limitations and facilitate its wider use.

A Prospective Comparison of the Effects of Instrument Tracking on Time and Radiation During Minimally Invasive Lumbar Interbody Fusion.

BACKGROUND: Minimally invasive surgical techniques have resulted in improved patient outcomes. One drawback has been the increased reliance on fluoroscopy and subsequent exposure to ionizing radiation. We have previously shown the efficacy of a novel instrument tracking system in cadaveric and preliminary clinical studies for commonplace orthopedic and spine procedures. In the present study, we examined the radiation and operative time using a novel instrument tracking system compared with standard C-arm fluoroscopy for patients undergoing minimally invasive lumbar fusion. METHODS: The radiation emitted, number of radiographs taken, and time required to complete 2 tasks were recorded between the instrument tracking systems and conventional C-arm fluoroscopy. The studied tasks included placement of the initial dilator through Kambin's triangle during percutaneous lumbar interbody fusion and placement of pedicle screws during both percutaneous lumbar interbody fusion and minimally invasive transforaminal lumbar interbody fusion with or without instrument tracking. RESULTS: A total of 23 patients were included in the analysis encompassing 31 total levels. For the task of placing the initial dilator into Kambin's triangle, an average of 4.21 minutes (2.4 vs. 6.6 minutes; P = 0.002), 15 fluoroscopic images (5.4 vs. 20.5; P = 0.002), and 8.14 mGy (3.3 vs. 11.4; P = 0.011) were saved by instrument tracking. For pedicle screw insertion, an average of 5.69 minutes (3.97 vs. 9.67; P < 0.001), 14 radiographs (6.53 vs. 20.62; P < 0.001), and 7.89 mGy (2.98 vs. 10.87 mGy; P < 0.001) were saved per screw insertion. CONCLUSIONS: Instrument tracking, when used for minimally invasive lumbar fusion, leads to significant reductions in radiation and operative time compared with conventional fluoroscopy.

Shielding effect of radiation dose reduction fiber during the use of C-arm fluoroscopy: a phantom study.

This study evaluated the shielding effect of a newly developed dose-reduction fiber (DRF) made from barium sulfate, in terms of radiation doses delivered to patients' radiosensitive organs and operator during C-arm fluoroscopy and its impact on the quality of images. A C-arm fluoroscopy unit was placed beside a whole-body phantom. Radiophotoluminescent glass dosimeters were attached to the back and front of the whole-body phantom at 20 cm intervals. Radiation doses were measured without DRF and with it applied to the back (position 1), front (position 2) or both sides (position 3) of the phantom. To investigate the impact of DRF on the quality of fluoroscopic images, step-wedge and modulation transfer function phantoms were used. The absorbed radiation doses to the back of the phantom significantly decreased by 25.3-88.8% after applying DRF to positions 1 and 3. The absorbed radiation doses to the front of the phantom significantly decreased by 55.3-93.6% after applying DRF to positions 2 and 3. The contrast resolution values for each adjacent step area fell in the range 0.0119-0.0209, 0.0128-0.0271, 0.0135-0.0339 and 0.0152-0.0339 without and with DRF applied to positions 1, 2 and 3, respectively. The investigated DRF effectively reduces absorbed radiation doses to patients and operators without decreasing the quality of C-arm fluoroscopic images. Therefore, routine clinical use of the DRF is recommended during the use of C-arm fluoroscopy.

Fluoroscopic images-based aiming and targeting system with two line lasers for insertion guidance of interlocking screw.

PURPOSE: Minimally invasive surgery is widely used for managing fractures; however, it is difficult to determine the exact screwing position of intramedullary nails inserted into bone. To address this problem, we developed the aiming and targeting system by laser (ATLAS) using two line lasers to mark the position of the surgical tool directly on the skin. METHODS: ATLAS consists of a laser module, controller, personal computer, and display device. The laser module is fixed to the intensifier side of the C-arm. Calibration with dedicated markers is required prior to using the system. After calibration, the laser modules can mark the selected point on a fluoroscopic image acquired with the C-arm as the intersection of the two line lasers on the skin. RESULTS: To verify the effectiveness of ATLAS, marking accuracy was measured. The average control error of the device itself was 0.57 mm. In the experimental setting using C-arm fluoroscopy, the accuracy was within 1.5 mm at 23 of the 25 measurement points and within 3 mm at the remaining two points. CONCLUSION: ATLAS shows the corresponding points in real space with respect to fluoroscopic images using cross-points of lasers. The proposed method is clinically useful to aid the insertion of interlocking screws in minimally invasive surgeries for bone fractures. We believe that ATLAS enables more accurate marking through C-arm fluoroscopy and is more convenient, and it can thus be applied in various orthopedic surgeries.

Surgical Results of Intraoperative C-arm Fluoroscopy Versus O-arm in Transarticular Screw Fixation for Atlantoaxial Instability.

OBJECTIVE: This study compared the surgical results of transarticular screw (TAS) fixation for atlantoaxial instability between C-arm fluoroscopy and O-arm. METHODS: Of 58 patients who underwent TAS fixation for atlantoaxial instability, 35 underwent C-arm-assisted surgery (C-group) and 23 underwent O-arm-assisted surgery (O-group). In total, 78 TASs were placed: 39 in the C-group and 39 in the O-group. Unilateral and bilateral TAS fixation was performed in 38 and 20 patients, respectively. All patients underwent Brook's procedure with TAS. TAS fixation accuracy on postoperative computed tomography, operative time, intraoperative bleeding, perioperative complications, and bone union were evaluated. Screw accuracy was assessed using Neo's classification: grade (G) 0, no perforation; G1, perforation <2 mm; G2, perforation 2-4 mm; G3, perforation >4 mm. RESULTS: TAS fixation accuracy was greater in the O-group than the C-group: G0: 38, 97.4%; G1: 1, 2.6% (O-group) vs G0: 22, 56.4%; G1: 11, 28.2%; G2: 3, 7.7%; G3: 3, 7.7% (C-group) (P < 0.001). Median operative time and median blood loss were similar between both groups. Bone union rate was greater with bilateral than unilateral TAS fixation (P < 0.05). There were no complications regarding screw malposition. Deep wound infection was observed in 1 case in the C-group. CONCLUSIONS: O-arm use improved TAS fixation accuracy. Blood loss was equivalent between the groups. O-arm-assisted TAS fixation did not prolong operative time despite the time required for setting and scanning. The O-arm is safe and useful for TAS fixation in atlantoaxial instability.

Value of CT-guided Core Needle Biopsy in Diagnosing Spinal Lesions: A Comparison Study.

OBJECTIVE: A retrospective study was designed to evaluate the effectiveness of CT-guided core needle biopsy in diagnosing spinal lesions through comparison with C-arm guidance. METHODS: From April 2013 to July 2017, a total of 188 patients, who suffered from spinal lesions or had malignant tumor history with a new spinal fracture, were included in this study. There were 96 men and 92 women, with an average of 57.1 years. A total of 238 core needle biopsies were performed. A total of 140 core needle biopsies were carried out under C-arm guidance in 102 patients (group 1); 98 core needle biopsies were carried out under CT guidance in 86 patients (group 2); 108 core needle biopsies were performed in thoracic vertebrae, 116 were in lumbar vertebrae, and 14 were in sacral vertebrae. Seventy-eight patients accepted surgical treatment after biopsies. For these patients, the histological pathologies of the biopsy and surgery were compared to evaluate the accuracy of the biopsy. For the other 110 patients who did not receive surgical treatment, the treatment response and the clinical course were used to evaluate the accuracy of the biopsy. The success rate, the diagnostic accuracy rate, the true positive/negative rate, and complications of the two groups were calculated and compared. RESULTS: There were no significant differences in sex, age, and lesion sites between the C-arm guidance group (group 1) and the CT guidance group (group 2). There were no complications in the two groups. Pathological diagnoses were established in 232 of 238 biopsies. They revealed that 52 were primary malignant tumors, 12 were benign tumors, 70 were metastatic tumors, 4 were tuberculosis, and 94 were classified as "other." The success rate of group 2 was higher than that of group 1, but it was not statistically significant (95.7% vs 100%; P = 0.098). According to the final diagnosis, the diagnostic accuracy rates were calculated and compared. There was no significant difference between the two groups (95.5% vs 96.9%; P = 0.835). The kappa coefficient was used to analyze the concordance between the histological pathologies of the biopsy and the final diagnosis in the two groups. The kappa values of the two group were 0.909 and 0.939, respectively. The results showed good consistency in both groups, but seemed better for group 2. CONCLUSION: CT-guided core needle biopsy is a relatively safe and effective procedure for diagnosing spinal lesions with a high diagnostic accuracy rate and few complications.

Treatment of recurrent patellar dislocation via knee arthroscopy combined with C-arm fluoroscopy and reconstruction of the medial patellofemoral ligament.

Recurrent patellar dislocations were treated via knee arthroscopy combined with C-arm fluoroscopy, and reconstruction of the medial patellofemoral ligaments. Between October 2013 and March 2017, 52 cases of recurrent patellar dislocation [27 males and 25 females; age, 16-47 years (mean, 21.90 years)] were treated. Arthroscopic exploration was performed and patellofemoral joint cartilage injuries were repaired. It was subsequently determined whether it was necessary to release the lateral patellofemoral support belt. Pre-operative measurements were used to decide whether tibial tubercle osteotomy was required. Medial patellofemoral ligaments were reconstructed using autologous semitendinosus tendons. Smith and Nephew model 3.5 line anchors were used to double-anchor the medial patellofemoral margin. On the femoral side, the medial patellofemoral ligament was fixed using 7-cm, absorbable, interfacial compression screws. All cases were followed for 1-40 months (average, 21 months). The Q angle, tibial tuberosity trochlear groove distance, Insall-Salvati index, patellofemoral angle, lateral patellofemoral angle and lateral shift were evaluated on X-Ray images using the picture archiving and communication system. Subjective International Knee Documentation Committee (IKDC) knee joint functional scores and Lysholm scores were recorded. Post-operative fear was absent, and no patellar re-dislocation or re-fracture was noted during follow-up. At the end of follow-up, the patellofemoral angle (0.22±4.23°), lateral patellofemoral angle (3.44±1.30°), and lateral shift (0.36+0.14°) differed significantly from the pre-operative values (all, P<0.05). Furthermore, IKDC and Lysholm scores (87.84+3.74 and 87.48+3.35, respectively) differed significantly from the pre-operative values (both, P<0.05). These findings suggest that, in the short term, recurrent patellar dislocation treatment via knee arthroscopy combined with C-arm fluoroscopy and reconstruction of the medial patellofemoral ligament was effective.

Computer-assisted surgery: The use of stored intraoperative images for accurate restoration of femoral length and rotational alignment after fracture.

Most femoral fractures are now managed with minimally invasive internal fixation. In the absence of formal exposure of the fracture lines, these procedures make heavy use of C-arm fluoroscopy to allow both fracture reduction and placement of implants, at the expense of measurable radiation exposure to both patient and surgeon. Although this technology has been commercially available for over a decade, it has not yet been widely accepted by the Orthopaedic community.

Inverse visualization concept for RGB-D augmented C-arms.

X-ray is still the essential imaging for many minimally-invasive interventions. Overlaying X-ray images with an optical view of the surgery scene has been demonstrated to be an efficient way to reduce radiation exposure and surgery time. However, clinicians are recommended to place the X-ray source under the patient table while the optical view of the real scene must be captured from the top in order to see the patient, surgical tools, and the surgical site. With the help of a RGB-D (red-green-blue-depth) camera, which can measure depth in addition to color, the 3D model of the real scene is registered to the X-ray image. However, fusing two opposing viewpoints and visualizing them in the context of medical applications has never been attempted. In this paper, we propose first experiences of a novel inverse visualization technique for RGB-D augmented C-arms. A user study consisting of 16 participants demonstrated that our method shows a meaningful visualization with potential in providing clinicians multi-modal fused data in real-time during surgery.

A case report of successful removal of multiples sewing needles in the gastrointestinal tract and pancreas using intraoperative C-arm fluoroscopy.

BACKGROUND: Most ingested foreign bodies pass uneventfully through the digestive tract without any major disturbances. OBJECTIVES: We reports a rare case of successful localization and surgical removal of needles in the gastrointestinal tract using C-arm fluoroscopy intraoperatively. CASE REPORT: A 46year old female, a non-hospitalized psychiatric patient, presented with acute abdominal pain. Imaging showed 16 needles all over the digestive tract. C arm fluoroscopy was used to successfully localize and remove all of the needles intraoperatively. One needle was withdrawn from the pancreas manually without pancreatic resection. DISCUSSION: It is estimated that up to 10-20% cases require endoscopic removal and 1% cases with the presence of obstruction or perforation necessitate surgical interventions [1-4] (Hsieh et al., 2005; Anderson and Dean, 2011; Cheng and Tam, 1999; Ricci et al., 2014). Migration to the pancreas extremely rare [5,6] (Toyonaga et al., 2001; Yasuda et al., 2010). Timely diagnosis can be difficult [7] (Tsui and Mossey, 1997). CT scan is a modality of choice to preoperatively locate the foreign body [8] (Takada et al., 2000). We herein successfully localized and removed 15 needles using C-arm fluoroscopy intraoperatively. It is extremely useful to accurately detect radiopaque foreign bodies. On the basic of findings on CT, treatment of choice such as endoscopic removal or surgical intervention may be attempted. CONCLUSIONS: CT scan is a modality of choice to preoperatively locate the foreign body. Sharp-pointed objects should be removed even if the patient is asymptomatic as the increased mortality and the risk of related complications. Intraoperative C-arm fluoroscopy is a feasible, cost-effective modality with real-time image to accurately detect multiple radiopaque objects especially when they are disseminating throughout the digestive tract.

An augmented reality C-arm for intraoperative assessment of the mechanical axis: a preclinical study.

BACKGROUND: Determination of lower limb alignment is a prerequisite for successful orthopedic surgical treatment. Traditional methods include the electrocautery cord, alignment rod, or axis board which rely solely on C-arm fluoroscopy navigation and are radiation intensive. STUDY OBJECTIVES: To assess a new augmented reality technology in determining lower limb alignment. METHODS: A camera-augmented mobile C-arm (CamC) technology was used to create a panorama image consisting of hip, knee, and ankle X-rays. Twenty-five human cadaver legs were used for validation with random varus or valgus deformations. Five clinicians performed experiments that consisted in achieving acceptable mechanical axis deviation. The applicability of the CamC technology was assessed with direct comparison to ground-truth CT. A t test, Pearson's correlation, and ANOVA were used to determine statistical significance. RESULTS: The value of Pearson's correlation coefficient R was 0.979 which demonstrates a strong positive correlation between the CamC and ground-truth CT data. The analysis of variance produced a p value equal to 0.911 signifying that clinician expertise differences were not significant with regard to the type of system used to assess mechanical axis deviation. CONCLUSION: All described measurements demonstrated valid measurement of lower limb alignment. With minimal effort, clinicians required only 3 X-ray image acquisitions using the augmented reality technology to achieve reliable mechanical axis deviation.

Evaluation of the use of fluoroscopy guided needle biopsies for diagnosing cases of suspected pathological fractures.

AIM: Establishing an early and accurate diagnosis in cases of suspected pathological fractures is crucial to initiate optimal treatment without delay. The use of percutaneous biopsy has become popular over the past few years. However, there is a paucity of information regarding the efficacy and safety of percutaneous biopsy procedures guided by fluoroscopy. METHODS: A total of 137 percutaneous C-arm fluoroscopy-guided core needle biopsy (CNB) procedures were performed in 135 patients with suspected pathological fractures. The sensitivity, specificity, accuracy, and overall prognostic value of these procedures were evaluated. Complications, if any, were documented for all cases. RESULTS: The overall sensitivity, specificity, and accuracy were 82.0%, 100%, and 83.2%, respectively. The positive and negative predictive value was 100% and 28.1%, respectively. There were 23 "false negative" cases in our study, of which 15 were benign lesions and eight were malignant tumors. No "false-positives" were found. Major procedure-related complications occurred in three patients (2.2%). These complications, however, did not alter the prognosis of these patients. CONCLUSION: Percutaneous C-arm fluoroscopy-guided biopsy procedures are both effective and safe for diagnosis of suspected pathological fractures in the appendicular skeleton.

Automatic 3D reconstruction of electrophysiology catheters from two-view monoplane C-arm image sequences.

PURPOSE: Catheter guidance is a vital task for the success of electrophysiology interventions. It is usually provided through fluoroscopic images that are taken intra-operatively. The cardiologists, who are typically equipped with C-arm systems, scan the patient from multiple views rotating the fluoroscope around one of its axes. The resulting sequences allow the cardiologists to build a mental model of the 3D position of the catheters and interest points from the multiple views. METHOD: We describe and compare different 3D catheter reconstruction strategies and ultimately propose a novel and robust method for the automatic reconstruction of 3D catheters in non-synchronized fluoroscopic sequences. This approach does not purely rely on triangulation but incorporates prior knowledge about the catheters. In conjunction with an automatic detection method, we demonstrate the performance of our method compared to ground truth annotations. RESULTS: In our experiments that include 20 biplane datasets, we achieve an average reprojection error of 0.43 mm and an average reconstruction error of 0.67 mm compared to gold standard annotation. CONCLUSIONS: In clinical practice, catheters suffer from complex motion due to the combined effect of heartbeat and respiratory motion. As a result, any 3D reconstruction algorithm via triangulation is imprecise. We have proposed a new method that is fully automatic and highly accurate to reconstruct catheters in three dimensions.

Implanted brachytherapy seed movement reflecting transrectal ultrasound probe-induced prostate deformation.

PURPOSE: Compression of the prostate during transrectal ultrasound-guided permanent prostate brachytherapy is not accounted for during treatment planning. Dosimetry effects are expected to be small but have not been reported. The study aims to characterize the seed movement and prostate deformation due to probe pressure and to estimate the effects on dosimetry. METHODS AND MATERIALS: C-arm fluoroscopy imaging was performed to reconstruct the implanted seed distributions (compressed and relaxed prostate) for 10 patients immediately after implantation. The compressed prostate was delineated on ultrasound and registered to the fluoroscopy-derived seed distribution via manual seed localization. Thin-plate spline mapping, generated with implanted seeds as control points, was used to characterize the deformation field and to infer the prostate contour in the absence of probe compression. Differences in TG-43 dosimetry for the compressed prostate and that on probe removal were calculated. RESULTS: Systematic seed movement patterns were observed on probe removal. Elastic decompression was characterized by expansion in the anterior-posterior direction and contraction in the superior-inferior and lateral directions up to 4 mm. Bilateral shearing in the anterior direction was up to 6 mm, resulting in contraction of the 145 Gy prescription isodose line by 2 mm with potential consequences for the posterior-lateral margin. The average whole prostate D90 increased by 2% of prescription dose (6% max; p < 0.01). CONCLUSIONS: The current investigation presents a novel study on ultrasound probe-induced deformation. Seed movements were characterized, and the associated dosimetry effects were nonnegligible, contrary to common expectation.

Augmented depth perception visualization in 2D/3D image fusion.

2D/3D image fusion applications are widely used in endovascular interventions. Complaints from interventionists about existing state-of-art visualization software are usually related to the strong compromise between 2D and 3D visibility or the lack of depth perception. In this paper, we investigate several concepts enabling improvement of current image fusion visualization found in the operating room. First, a contour enhanced visualization is used to circumvent hidden information in the X-ray image. Second, an occlusion and depth color-coding scheme is considered to improve depth perception. To validate our visualization technique both phantom and clinical data are considered. An evaluation is performed in the form of a questionnaire which included 24 participants: ten clinicians and fourteen non-clinicians. Results indicate that the occlusion correction method provides 100% correctness when determining the true position of an aneurysm in X-ray. Further, when integrating an RGB or RB color-depth encoding in the image fusion both perception and intuitiveness are improved.

Video-guided calibration of an augmented reality mobile C-arm.

PURPOSE: The augmented reality (AR) fluoroscope augments an X-ray image by video and provides the surgeon with a real-time in situ overlay of the anatomy. The overlay alignment is crucial for diagnostic and intra-operative guidance, so precise calibration of the AR fluoroscope is required. The first and most complex step of the calibration procedure is the determination of the X-ray source position. Currently, this is achieved using a biplane phantom with movable metallic rings on its top layer and fixed X-ray opaque markers on its bottom layer. The metallic rings must be moved to positions where at least two pairs of rings and markers are isocentric in the X-ray image. The current "trial and error" calibration process currently requires acquisition of many X-ray images, a task that is both time consuming and radiation intensive. An improved process was developed and tested for C-arm calibration. METHODS: Video guidance was used to drive the calibration procedure to minimize both X-ray exposure and the time involved. For this, a homography between X-ray and video images is estimated. This homography is valid for the plane at which the metallic rings are positioned and is employed to guide the calibration procedure. Eight users having varying calibration experience (i.e., 2 experts, 2 semi-experts, 4 novices) were asked to participate in the evaluation. RESULTS: The video-guided technique reduced the number of intra-operative X-ray calibration images by 89% and decreased the total time required by 59%. CONCLUSION: A video-based C-arm calibration method has been developed that improves the usability of the AR fluoroscope with a friendlier interface, reduced calibration time and clinically acceptable radiation doses.