Live Fluoroscopy Research Articles

Use of three-dimensional computed tomography overlay for real-time cryoballoon ablation in atrial fibrillation reduces radiation dose and contrast dye.

AimsCryoballoon pulmonary vein (PV) isolation in patients with atrial fibrillation has proven to be effective in short-term and long-term follow-up. To visualise the PV anatomy, pre-ablation contrast pulmonary venography is commonly performed. Three-dimensional (3D) computed tomography (CT) overlay is a new technique creating a live 3D image of the left atrium by integrating a previously obtained CT scan during fluoroscopy. To evaluate the benefits of 3D CT overlay during cryoballoon ablation, we studied the use of 3D CT overlay versus contrast pulmonary venography in a randomised fashion in patients with paroxysmal atrial fibrillation undergoing cryoballoon PV isolation.Methods and resultsBetween October 2012 and June 2013, 30 patients accepted for PV isolation were randomised to cryoballoon PV isolation using either 3D CT overlay or contrast pulmonary venography. All patients underwent a pre-procedural cardiac CT for evaluation of the anatomy of the left atrium (LA) and the PVs. In the 3D CT overlay group, a 3D reconstruction of the LA and PVs was made. An overlay of the CT reconstruction was then projected over live fluoroscopy. Patients in the contrast pulmonary venography group received significantly more contrast agent (77.1 ± 21.2 cc vs 40.1 ± 17.6 cc, p < 0.001) and radiation (43.0 ± 21.9 Gy.cm2 vs 28.41 ± 11.7 Gy.cm2, p = 0.04) than subjects in the 3D CT overlay group. There was no difference in total procedure time, fluoroscopy time and the amount of cryoapplications between the two groups.ConclusionThe use of 3D CT overlay decreases radiation and contrast dye exposure and can assist in guiding cryoballoon-based PV isolation.

Three-dimensional rotational angiography of the left atrium and the oesophagus: the short-term mobility of the oesophagus and the stability of the fused three-dimensional model of the left atrium and the oesophagus during catheter ablation for atrial fibrillation.

The objective of this study was to evaluate the mobility of the oesophagus and the stability of the three-dimensional (3D) model of the oesophagus using 3D rotational angiography (3DRA) of the left atrium (LA) and the oesophagus, fused with live fluoroscopy during catheter ablation for atrial fibrillation. From March 2015 to September 2015, 3DRA of the LA and the oesophagus was performed in 33 patients before catheter ablation for atrial fibrillation. Control contrast oesophagography was performed every 30 min. The positions of the oesophagograms and the 3D model of the LA and the oesophagus were repeatedly measured and compared with the spine. The average shift of the oesophagus ranged from 2.7 ± 2.2 to 5.0 ± 3.5 mm. The average real-time oesophageal shift ranged from 2.7 ± 2.2 to 3.8 ± 3.4 mm. No significant shift was detected until the 90th minute of the procedure. The average shift of the 3D model of the LA and the oesophagus ranged from 1.4 ± 1.8 to 3.3 ± 3.0 mm (right-left direction) and from 0.9 ± 1.2 to 2.2 ± 1.3 mm (craniocaudal direction). During the 2 h procedure, there were no significant shifts of the model. During catheter ablation for atrial fibrillation, there is no significant change in the position of the oesophagus until the 90th minute of the procedure and no significant shift in the 3D model of the LA and the oesophagus. The 3D model of the oesophagus reliably depicts the position of the oesophagus during the entire procedure.

Lumbar Epidural Steroid Injections.

Lumbar radiculopathy is a common diagnosis for patients who present with low-back pain and leg pain, typically along a particular dermatome. This pain is commonly associated with a lumbar disc herniation. The prognosis is usually favorable, and the symptoms can resolve spontaneously over time. In patients in whom leg and back symptoms are severe, lumbar epidural (cortico)steroid injections are good options for the short to medium-term management of pain. Currently, lumbar epidural steroid injections are performed with radiographic guidance systems and fluoroscopy. This method is preferred because of the increased accuracy in needle placement and the reduced risk of injury to nerves and vascular structures. The procedure is performed with the following steps: (1) Following appropriate patient selection through clinical evaluation and assessment of imaging studies such as computed tomography or magnetic resonance imaging, the patient is prepared and draped after providing written informed consent. (2) The level of neural compression to be injected is identified with intermittent fluoroscopy and the use of a radiopaque marker. (3) The skin and subcutaneous tissues are anesthetized. (4) A spinal needle (Quincke or Tuohy type) is inserted after tissues are fully anesthetized. The needle is slowly advanced with the use of intermittent fluoroscopy until the target is reached. In the case of an interlaminar approach, this would be associated with a loss of syringe resistance and piercing of the ligamentum flavum. In the case of a transforaminal approach, this would be associated with the 6 o'clock position of the pedicle on the side in question. (5) Contrast material is then injected with the use of live fluoroscopy to confirm appropriate placement and exclude intravascular and intrathecal injection. (6) When adequate placement is confirmed, a solution of steroid and anesthetic is administered. The needle is then removed. Most outcome reports after lumbar epidural steroid injections are favorable for radicular symptoms. Associated back pain may typically improve as well. Common complications include injection site pain or soreness, infections, allergy, and inadvertent dural puncture with spinal headache.

Maximizing Lumen Gain With Directional Atherectomy

Purpose: To describe the use of a low-pressure balloon inflation (LPBI) technique to delineate intraluminal plaque and guide directional atherectomy in order to maximize lumen gain and achieve procedure success. Technique: The technique is illustrated in a 77-year-old man with claudication who underwent superficial femoral artery revascularization using a HawkOne directional atherectomy catheter. A standard angioplasty balloon was inflated to 1 to 2 atm during live fluoroscopy to create a 3-dimensional “lumenogram” of the target lesion. Directional atherectomy was performed only where plaque impinged on the balloon at a specific fluoroscopic orientation. The results of the LPBI technique were corroborated with multimodality diagnostic imaging, including digital subtraction angiography, intravascular ultrasound, and intra-arterial pressure measurements. Conclusion: With the LPBI technique, directional atherectomy can routinely achieve <10% residual stenosis, as illustrated in this case, thereby broadly supporting a no-stent approach to lower extremity endovascular revascularization.

(461) Inadvertent filum terminale needle placement during caudal epidural steroid injection: a case report

Caudal epidural steroid injections (ESI) are a commonly utilized and efficacious means in which to treat radicular leg symptoms arising from the lumbo-sacral spine. Touhe needles are placed via fluoroscopic guidance with utilization of live fluoroscopy to ensure epidural administration. This is a case report of direct needle and catheter placements into and through the filum terminale during a caudal approach to the epidural space. The patient, a 69-year-old woman who suffered from chronic low back and leg pain from lumbosacral radiculopathy, failed back surgery syndrome and lumbar facet arthropathy presented to the outpatient pain clinic for repeat caudal ESI. Her initial caudal ESI, 2 years prior, resulted in pain relief for 2 months. Due to her previous robust response to the caudal ESI the patient was scheduled for a repeat injection. Under AP and lateral fluoroscopic guidance a Coude needle was introduced into the caudal epidural space without advancement beyond S4. An epimed catheter was inserted and tracked to the L4 level. The needle and catheter placement were confirmed via intrathecal contrast spread to be in the filum terminale with flow cephalad into the thecal space, which resulted in the abortion of the procedure. This case illustrates a rare incidence of catheter placement directly into the filum terminale during a routine caudal ESI. Despite a relatively safe and routine intervention, care must be taken to ensure proper placement of needle, catheter and injectate. While contrast is injected to ensure appropriate epidural spread, we present, to the best of our knowledge, the first occasion of a needle being inserted directly into the filum terminale during a caudal ESI.

Inadvertent Intradiscal Injection with TFESI Utilizing Kambin's Retrodiscal Approach in the Treatment of Acute Lumbar Radiculopathy.

There is very strong evidence for the efficacy of transforaminal epidural steroid injection (TFESI) in relieving lumbar radicular pain due to a herniated disk. However, case studies have documented paralysis as a potential complication from this approach as the artery of Adamkiewicz may traverse within the subpedicular "safe triangle." Kambin's retrodiscal approach has been postulated as a safe means to the transforaminal approach to avoid the artery of Adamkiewicz. A 51-year-old woman presented with right-sided lumbar radicular pain at the L3-L4 and L4-L5 level secondary to a herniated disk. As conservative therapies failed to improve her radicular back pain, the patient opted to proceed with an epidural steroid injection. She subsequently underwent a right L3-L4 and L4-L5 transforaminal epidural steroid injection via Kambin's retrodiscal approach. Although anteroposterior and lateral views revealed optimal needle placement, live and postcontrast fluoroscopy revealed an unavoidable and inadvertent intradiscal spread. Kambin's approach is at the level of the intervertebral disk and may increase the incidence of intradiscal needle entry and injection.

Feasibility of Three-Dimensional MR Angiography Image Fusion Guidance for Endovascular Abdominal Aortic Aneurysm Repair

Magnetic resonance (MR) angiography image fusion (IF) with live fluoroscopy guidance was used while performing endovascular repair of abdominal aortic aneurysm (EVAR) in five patients with a history of chronic renal disease or severe contrast allergy. Intraprocedural technical success was 100%. Median procedure time was 120 minutes (range, 60–180 min), fluoroscopy time was 40 minutes (range, 17–65 min), dose-area product was 245,867 mGy × cm2 (range, 68,435–690,053 mGy × cm2), and iodinated contrast volume injected was 15 mL (range, 0–40 mL). Technical success was achieved in four of five patients (80%); one case was complicated by a type 1 endoleak on follow-up MR angiography, which was successfully treated. EVAR with MR angiography IF guidance was technically feasible and safe in five patients and reduced or eliminated the use of iodinated contrast media.

Detection of Intravascular Injection During Lumbar Medial Branch Blocks: A Comparison of Aspiration, Live Fluoroscopy, and Digital Subtraction Technology.

Medial branch blocks may have unrecognized vascular uptake potentially resulting in false- negative results. To determine the rate of unintended vascular injection of contrast medium during medial branch blocks (MBB) with digital subtraction (DS) technology in the context of negative vascular uptake as determined by live fluoroscopy. Prospective Study in an academic medical center. 344 consecutive MBBs in 80 subjects. The presence of vascular flow as determined by live fluoroscopy and DS technology. Unintended vascular injection of contrast medium was determined on 344 consecutive MBBs in 84 subjects, first using live fluoroscopy followed by DS. If live fluoroscopy initially detected vascular uptake, the needle was repositioned until no vascular flow was detected. Once no vascular uptake was confirmed by live fluoroscopy, a contrast medium was then injected while being visualized with DS to again assess the presence or absence of vascular flow undetected by live fluoroscopy. Live fluoroscopy revealed inadvertent vascular uptake in 38 of the 344 blocks [11% (95% CI 8.0-15%)]. DS uncovered an additional 27 of the 344 blocks [7.8% (95% CI 5.3-11.4%)] with evidence of vascular uptake that were not detected with conventional live fluoroscopy. DS enhances the ability to detect inadvertent vascular flow during medial branch blocks. This study demonstrates that standard live fluoroscopy can miss a small percentage of cases with unintentional vascular uptake during MBB when compared with DS and may contribute to occasional false-negative responses.

Minimizing Radiation Exposure During ERCP by Avoiding Live or Continuous Fluoroscopy.

The aim of this study was to assess the cumulative radiation exposure incurred by patients when using single-frame fluoroscopy. Single-frame fluoroscopy is a technique that can be used instead of pulsed fluoroscopy or continuous live fluoroscopy to minimize radiation exposure during endoscopic retrograde cholangiopancreatography (ERCP). We retrospectively reviewed ERCPs performed at our academic medical center. We recorded fluoroscopy time (FT, minutes), total radiation dose (mGy), dose area product (DAP, Gy cm²), and effective dose (ED, mSv). ERCP degree of difficulty was graded based on procedure complexity level. There were 400 ERCP procedures performed on 210 patients, 32 ERCPs were unsuccessful. The mean FT for all procedures was 1.57 minutes (median, 1.2 min); the mean FT for complexity score 1 procedures (0.78 min) was significantly shorter than for all other procedures (P<0.0001). The mean total radiation dose delivered for all procedures was 23.02 mGy (median, 14.95 mGy). The total radiation dose for complexity score 1 procedures (13.15 mGy) was significantly lower than for all other complexity scores (P<0.0001). The mean total DAP was 3.62 Gy cm² and the mean ED was 0.94 mSv. Procedure complexity score 1 DAP (2.1 Gy cm²) and ED (0.55 mSv) were significantly lower than for all other procedures (P<0.0001 for both). There was no statistically significant difference in these parameters when comparing successful and unsuccessful procedures. Successful ERCP can be performed using single-frame fluoroscopy only. Our results demonstrate lower radiation exposure using this technique than what is reported in the literature.

EVAR Guided by 3D Image Fusion and CO2 DSA

Purpose: To present a new combination of imaging techniques that helps reduce the use of iodinated contrast during endovascular aneurysm repair (EVAR) procedures in patients with renal insufficiency. Technique: Relevant anatomical structures are marked in the preprocedure computed tomography (CT) angiogram. A 3D-3D image fusion between the preprocedure CT and an intraprocedure cone-beam CT is performed in order to overlay anatomical information on live fluoroscopy. Verification of the correct overlay matching (or adjustment if necessary) is based on carbon dioxide (CO2) digital subtraction angiograms (DSA) instead of iodine DSA. The stent-graft is placed and deployed based on the overlaid information. Correct device placement is finally verified with conventional contrast angiography. Conclusion: The combination of 3D image fusion of a preoperative CT with live fluoroscopy and CO2 DSA verification is feasible and sufficient for guidance of abdominal EVAR. This method minimizes the use of iodinated contrast media, protecting residual function in the setting of preexisting renal insufficiency.

Value of C-Arm Cone Beam Computed Tomography Image Fusion in Maximizing the Versatility of Endovascular Robotics

To report our initial experience and highlight the value of using intraoperative C-arm cone beam computed tomography (CT; DynaCT(®)) image fusion guidance along with steerable robotic endovascular catheter navigation to optimize vessel cannulation. Between May 2013 and January 2015, all patients who underwent endovascular procedures using DynaCT image fusion technique along with Hansen Magellan vascular robotic catheter were included in this study. As a part of preoperative planning, relevant vessel landmarks were electronically marked in contrast-enhanced multi-slice computed tomography images and stored. At the beginning of procedure, an intraoperative noncontrast C-arm cone beam CT (syngo DynaCT(®), Siemens Medical Solutions USA Inc.) was acquired in the hybrid suite. Preoperative images were then coregistered to intraoperative DynaCT images using aortic wall calcifications and bone landmarks. Stored landmarks were then overlaid on 2-dimensional (2D) live fluoroscopic images as virtual markers that are updated in real-time with C-arm, table movements and image zoom. Vascular access and robotic catheter (Magellan(®), Hansen Medical) was setup per standard. Vessel cannulation was performed based on electronic virtual markers on live fluoroscopy using robotic catheter. The impact of 3-dimensional (3D) image fusion guidance on robotic vessel cannulation was evaluated retrospectively, by assessing quantitative parameters like number of angiograms acquired before vessel cannulation and qualitative parameters like accuracy of vessel ostium and centerline markers. All 17 vessels were cannulated successfully in 14 patients' attempted using robotic catheter and image fusion guidance. Median vessel diameter at origin was 5.4 mm (range, 2.3-13 mm), whereas 12 of 17 (70.6%) vessels had either calcified and/or stenosed origin from parent vessel. Nine of 17 vessels (52.9 %) were cannulated without any contrast injection. Median number of angiograms required before cannulation was 0 (range, 0-2). On qualitative assessment, 14 of 15 vessels (93.3%) had grade = 1 accuracy (guidewire inside virtual ostial marker). Fourteen of 14 vessels had grade = 1 accuracy (virtual centerlines that matched with the actual vessel trajectory during cannulation). In this small series, the experience of using DynaCT image fusion guidance together with a steerable endovascular robotic catheter indicates that such image fusion strategies can enhance intraoperative 2D fluoroscopy by bringing preoperative 3D information about vascular stenosis and/or calcification, angulation, and take off from main vessel thereby facilitating ultimate vessel cannulation.

Simultaneous Bilateral Anterior Approach Total Hip Arthroplasty.

Simultaneous bilateral total hip arthroplasty (THA) has been performed successfully, with good outcomes and low complication rates reported. Most published studies on the topic used anterolateral or posterior surgical approaches. The anterior approach is performed under live fluoroscopy with the patient supine, obviating the need for patient repositioning during bilateral surgery. The authors report their experience with simultaneous bilateral anterior approach total hip arthroplasty. The authors retrospectively reviewed data for 75 patients (150 hips). Mean follow-up was 26 months (range, 5-60 months). Mean patient age was 59 years and the majority were American Society of Anesthesiology class 2 (range, 1-3). Mean total surgical time was 144 minutes (72 minutes per hip). Mean blood loss was 565 mL. Mean hospital length of stay was 2.75 days (range, 1-4 days). Ninety-six percent of patients were able to ambulate on postoperative day 1. Sixty-eight percent of patients were discharged to home. Mean Harris Hip Score improved from 50 to 97. All patients noted a return to preoperative level of activity or higher. Complications included 1 atraumatic minimally displaced trochanteric fracture occurring 2 weeks postoperatively, 1 pulmonary embolism on postoperative day 3 treated without sequelae, 1 episode of postoperative atrial fibrillation, and 4 minor local wound complications. No readmission, infection, nerve palsy, dislocation, reoperation, or death occurred. Anterior approach THA has the advantage of a single supine position for bilateral simultaneous surgery and the current study supports its use in appropriate patients.

Parametric ultrasound and fluoroscopy image fusion for guidance of left ventricle lead placement in cardiac resynchronization therapy.

Recent studies show that the response rate to cardiac resynchronization therapy (CRT) could be improved if the left ventricle (LV) is paced at the site of the latest mechanical activation, but away from the myocardial scar. A prototype system for CRT lead placement guidance that combines LV functional information from ultrasound with live x-ray fluoroscopy was developed. Two mean anatomical models, each containing LV epi-, LV endo- and right ventricle endocardial surfaces, were computed from a database of 33 heart failure patients as a substitute for a patient-specific model. The sphericity index was used to divide the observed population into two groups. The distance between the mean and the patient-specific models was determined using a signed distance field metric (reported in mm). The average error values for LV epicardium were [Formula: see text] and for LV endocardium were [Formula: see text]. The validity of using average LV models for a CRT procedure was tested by simulating coronary vein selection in a group of 15 CRT candidates. The probability of selecting the same coronary branch, when basing the selection on the average model compared to a patient-specific model, was estimated to be [Formula: see text]. This was found to be clinically acceptable.

Urgent endovascular repair for ruptured aortic aneurysm using computed tomography image fusion

Abdominal aortic aneurysm rupture remains a cardiovascular catastrophe with strikingly high morbidity and mortality rates. Endovascular aneurysm repair management has recently emerged as a valuable treatment modality for ruptured abdominal aortic aneurysm, but better outcomes have to be reached. Image fusion may potentially improve perioperative outcomes in selected patients, guiding navigation and device implantation and limiting contrast dosage during interventions. We report an 83-year-old man presenting with an 80-mm infrarenal aortic aneurysm rupture suitable for endovascular aneurysm repair. Endovascular navigation and stent graft deployment were achieved using computed tomography image fusion for the first reported case in English.

A robust and inexpensive phantom for fluoroscopically guided lumbar puncture training.

This report describes the creation process for an inexpensive, durable, lumbar spine phantom for use in fluoroscopically guided lumbar puncture (LP) training. The LP phantom prototype was made from a polyvinyl chloride lumbar spine model embedded in a translucent rectangular block of commercially available thermoplastic polymer gel. Radiology residents with limited previous experience performing LP used the phantom for 20 simulated procedures to gain confidence before starting patient procedures. The residents completed surveys detailing their experiences with the phantom. Quantitative evaluation of the phantom using fluoroscopy and computed tomography suggested good physical agreement with human anatomy. Six board-certified radiologists viewed the phantom under live fluoroscopy and indicated that the phantom represented human anatomy with sufficient accuracy. Furthermore, surveys from resident trainees indicated that the thermoplastic tissue substitute simulated the texture and resistance of human soft tissue reasonably well for the purposes of clinical training. The total material cost of the LP phantom prototype was approximately US $148.00. This novel spine phantom can be produced with relatively low cost when compared with similar commercially available products. The phantom offers reasonable visual and tactile agreement to human anatomy and may be useful for improving the confidence of physician trainees. The LP phantom is durable and can easily be repaired by reheating the polymer tissue substitute.

Image Registration of Cone-Beam Computer Tomography and Preprocedural Computer Tomography Aids in Localization of Adrenal Veins and Decreasing Radiation Dose in Adrenal Vein Sampling.

We assessed whether image registration of cone-beam computed tomography (CT) (CBCT) and contrast-enhanced CT (CE-CT) images indicating the locations of the adrenal veins can aid in increasing the success rate of first-attempts adrenal vein sampling (AVS) and therefore decreasing patient radiation dose. CBCT scans were acquired in the interventional suite (Philips Allura Xper FD20) and rigidly registered to the vertebra in previously acquired CE-CT. Adrenal vein locations were marked on the CT image and superimposed with live fluoroscopy and digital-subtraction angiography (DSA) to guide the AVS. Seventeen first attempts at AVS were performed with image registration and retrospectively compared with 15 first attempts without image registration performed earlier by the same 2 interventional radiologists. First-attempt AVS was considered successful when both adrenal vein samples showed representative cortisol levels. Sampling time, dose-area product (DAP), number of DSA runs, fluoroscopy time, and skin dose were recorded. Without image registration, the first attempt at sampling was successful in 8 of 15 procedures indicating a success rate of 53.3%. This increased to 76.5% (13 of 17) by adding CBCT and CE-CT image registration to AVS procedures (p = 0.266). DAP values (p = 0.001) and DSA runs (p = 0.026) decreased significantly by adding image registration guidance. Sampling and fluoroscopy times and skin dose showed no significant changes. Guidance based on registration of CBCT and previously acquired diagnostic CE-CT can aid in enhancing localization of the adrenal veins thereby increasing the success rate of first-attempt AVS with a significant decrease in the number of used DSA runs and, consequently, radiation dose required.

E-059 Guiding Sclerotherapy for Deep Lying Lesions using Advanced Angiographic Imaging Applications and MR-Fusion

BackgroundDeep head and neck lesions are challenging to treat using conventional guidance, such as ultrasound (US) and fluoroscopy. High impedance structures prevent the use of US, while fluoroscopy lacks resolution...

Intravascular Flow Detection During Transforaminal Epidural Injections: A Prospective Assessment

Background: Transforaminal epidural steroid injections (TFESI) are a mainstay in the treatment of spine pain. Though this commonly performed procedure is generally felt to be safe, devastating complications following inadvertent intra-arterial injections of particulate steroid have been reported. The use of digital subtraction angiography (DSA) has been suggested as a means of detecting intra-arterial needle placements prior to medication injection. Objective: To examine the efficacy of DSA in detecting intra-arterial needle placements during TFESI. Study Design: Prospective cohort study evaluating the impact of DSA on detecting intra-arterial needle placements during TFESI. Methods: We enrolled 150 consecutive patients presenting to a university-affiliated spine center with discogenic and/or radicular symptoms affecting the cervical, lumbar, and sacral regions. For each injection, prior to imaging with DSA, traditional methods for vascular penetration detection were employed, including the identification of blood in the needle hub (flash), negative aspiration of blood prior to injection, and live fluoroscopic injection of contrast. Once these tests were performed and negative for signs of intra-arterial needle placement, DSA imaging was utilized prior to medication administration for identification of vascular flow. Results: A total number of 222 TFESI were performed, 41 injections at the cervical levels (18.47%), 113 at the lumbar levels (50.9%), and 68 at the sacral levels (30.36%). Flash was observed in 13 injections performed (5.85% of the total number of injections): one (0.45%) in the cervical, 2 (0.9%) in the lumbar, and 10 (4.5%) in the sacral levels. In 11 TFESI blood aspiration was obtained (4.95% of all injections): 3 (1.3%) in cervical, 4 (1.8%) in lumbar, and 4 (1.8%) in sacral injections. Live fluoroscopy during contrast injection detected 46 (20.72%) intravascular flow patterns: 7 (3.1%) cervical, 17 (7.6%) lumbar, and 22 (9.9%) sacral. DSA identified an additional 5 intravascular injections after all previous steps had resulted in negative vascular penetration signs, which accounted for 2.25% of all injections. Limitations: This is a prospective, single-center study with a relatively small number of patients and no control group. Conclusion: DSA detected additional 5.26% intravascular needle placements following traditional methods. Our findings also support other studies that conclude TFESI are generally a safe procedure. We recommend that special attention should be paid to the sacral injections as vascular penetration was statistically higher than at other levels. Key words: Digital subtraction angiography, transforaminal epidural steroid injections

2D/3D registration of TEE probe from two non-orthogonal C-arm directions.

2D/3D registration is a well known technique in medical imaging for combining pre-operative volume data with live fluoroscopy. A common issue of this type of algorithms is that out-of-plane parameters are hard to determine. One solution to overcome this issue is the use of X-ray images from two angulations. However, performing in-plane transformation in one image destroys the registration in the other image, particularly if the angulations are smaller than 90 degrees apart. Our main contribution is the automation of a novel registration approach. It handles translation and rotation of a volume in a way that in-plane parameters are kept invariant and independent of the angle offset between both projections in a double-oblique setting. Our approach yields more robust and partially faster registration results, compared to conventional methods, especially in case of object movement. It was successfully tested on clinical data for fusion of transesophageal ultrasound and X-ray.

Backstop™ Gel to Prevent Stone Fragment Migration After Endourologic Lithotripsy: Initial Experience

Introduction and Objective: In this video, we present our initial experience with the use of the Backstop™ gel for preventing stone fragment migration after endourologic lithotripsy. Material and Methods: Two patients with stones in the urinary tract were treated endourologically for stone disease. One patient had a history of a non progressing proximal 5 mm right ureteral stone and the other had a 2.5 cm right lower pole stone. The Backstop gel (thermosensitive polymer) was used to prevent stone fragment migration during lithotripsy using either the holmium laser or the ultrasonic probe. A noncontrast CT scan was performed before and after surgery. Results: During right ureteroscopy, the Backstop gel was placed 2 cm away from the 5 mm stone lodged in the proximal ureter (between the renal pelvis and stone). Holmium laser lithotripsy was performed and basket extraction of stone fragments from the ureter was performed. During a right percutaneous nephrolithotripsy (PCNL), the Backstop gel was deployed in the proximal ureter just passing the ureteral pelvic junction. To help position the three french Backstop gel catheter, a five french Pollack catheter was placed into the ureter using the nephroscope and the Backstop gel applicator was passed into the Pollack catheter. Using live fluoroscopy, the exact position of gel deployment was secured. The Backstop gel prevented migration of stone fragments in both patients without complications. Postoperative CT scans of both patients confirmed stone-free status. Conclusions: The Backstop gel prevents retropulsion of stone fragments up to the kidney when performing ureteroscopic laser lithotripsy and prevents stone migration down the ureter when used before percutaneous nephrolithotripsy, decreasing the operative time. Runtime of video: 5 mins 19 secs