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PubMed1992

Fleischner Lecture. Imaging the respiratory system in the first few years after discovery of the X-ray: contributions of Francis H. Williams, M.D.

Imaging of the respiratory system developed with exceptional rapidity in North America during the spring of 1896, after Roentgen's discovery of X-rays in November 1895, largely because of the efforts of a unique physicians, Francis H. Williams. With great zeal, this pioneer used fluoroscopy for early detection of tuberculosis and other life-threatening chest disorders. By the summer of 1896, he had accumulated more than 100 volumes containing tracings of clinical chest fluoroscopy. As a result of his extensive clinical experience, his dedication to patients' welfare, and his sense of scientific inquiry, several inventions and many landmark clinical observations were made in the first few years after the discovery of the X-ray. These included (1) the invention of a "densitometer" for standardized measurements of relative X-ray attenuation of the lung, (2) the invention of a "seehear" device to correlate auscultative findings and fluoroscopic observations, (3) the recognition that fluoroscopy was more accurate than percussion for estimating mediastinal displacement, (4) the discovery that clinically occult tuberculosis and congestive heart failure could be detected with fluoroscopy, (5) the documentation that unilateral chest disease caused decreased ipsilateral ventilatory compliance and increased contralateral ventilation, (6) the identification of the classical imaging characteristics of tuberculosis, pneumonia, pneumothorax, tension pneumothorax, pleural effusion, hydropneumothorax, emphysema, congestive heart failure, and air trapping. In April 1896, Dr. Williams described the "air bronchogram" in a radiograph of a patient with pneumonia.

History, 19th Century↗
PubMed2000

Evaluation and management of mechanical dysfunction in continent colonic urinary reservoirs.

PURPOSE: We analyze a group of patients who presented with mechanical dysfunction of the reservoir and/or efferent limb of a continent colonic urinary diversion, and establish an evaluation and management algorithm. MATERIALS AND METHODS: A total of 16 patients with a mean age of 58 years and 1 or more symptoms related to continent colonic urinary diversion were evaluated. Presenting symptomatology included difficult catheterization in 8 cases (50%), disabling incontinence in 8 (50%) and recurrent urinary tract infections in 6 (37.5%). All patients had normal, nonobstructed, nonrefluxing upper tracts and none presented with stone disease. Urological evaluation consisted of catheterization, fluoroscopy and urography of the pouch, retrograde urography of the external limb and urodynamics (enterocystometrogram and outlet pressure profilometry). RESULTS: Of the 8 patients with difficulty with catheterization 4 had stomal stenosis, 2 had an elongated and redundant external limb, and 2 had a false passage. Diagnosis was established by the inability to catheterize, fluoroscopy of the pouch and retrograde urography. Disabling incontinence occurred in 8 patients, including 7 who presented with an incompetent outlet and 2 with high pressure intestinal contractions of the reservoir. The aforementioned abnormalities were diagnosed by a combination of retrograde urography, urography of the pouch and urodynamics. Recurrent symptomatic urinary infections were observed in 5 patients of the previous groups and in another with an hourglass reservoir, which was primarily diagnosed by urography of the pouch. Surgical correction in 15 patients included outlet reinforcement, reservoir revision, stomal or external limb revision and conversion to a urinary conduit. Surgical treatment was successful in 14 of 15 patients (93%). CONCLUSIONS: Catheterization difficulty requires retrograde urography to define possible anatomical abnormalities (false passage, conduit elongation) if catheterization and fluoroscopy of the pouch do not demonstrate stomal stenosis. Urinary incontinence benefits from enterocystometry and outlet pressure measurement to determine reservoir and external limb function. Recurrent urinary tract infections not related to ureteral obstruction or reflux requires fluoroscopy of the pouch and external limb to determine abnormalities in patients with detubularization and localization of areas of urine pooling.

Adult↗
PubMed1999

Continuous transesophageal echocardiographic (TEE) monitoring during port-access cardiac surgery.

BACKGROUND: Since the introduction of the closed-chest minimally invasive heart surgery using the Port-Access system a variety of monitoring techniques including fluoroscopy, transesophageal echocardiography (TEE) and invasive pressure measurements have been described. We investigated whether or not single TEE is feasible for perioperative monitoring of the placement, localization and proper function of the endovascular cardiopulmonary bypass (CPB) devices. METHODS: Fifty-one patients (35 mitral valve repair or replacement [MVR], 8 coronary artery bypass grafting [CABG], 5 atrial septal defects [ASD] and 3 left atrial myxoma) were subjected to Port-Access surgery (PAS). Intraoperative Omniplane-TEE (2D- and color-flow Doppler techniques) was used as the leading monitoring device for correct positioning of the endopulmonary vent catheter and the venous cannula, and for the visualization of the guide wire and the endoaortic occlusion catheter (Endoclamp). After balloon inflation, its proper positioning and function during endo-aortic occlusion, sufficient delivery of cardioplegia into the coronary ostia, absence of leakage flow and adequate venting were controlled. Left and right radial artery catheters as well as aortic root pressure measurements served as controls. Additional fluoroscopy was used as standby device. RESULTS: In 46 patients (90.1%) sufficient perioperative monitoring was provided by single TEE. In five cases additional intermittent fluoroscopy was necessary for correct positioning of the guide wire (CABG) and the Endoclamp (three MVR and one ASD). Dislocation of the Endoclamp into the left ventricle was observed once but was successfully corrected by TEE guidance. Weaning from CPB and de-airing were easily guided with TEE. We did not observe balloon-mediated aortic injury or aortic valve dysfunction, and myocardial recovery from CPB was uneventful. All cases of MVRs showed sufficient results (68% without evidence of regurgitation, 32% showed residual mitral valve incompetence of less than grade II). Neither perivalvular leakage (MV-replacement) nor shunt- (residual ASD) flow were detectable. CONCLUSIONS: We recommend single TEE as a safe and effective on-line imaging device for monitoring the endovascular CPB system during PAS. Fluoroscopy with its potential risk for the patients and the staff due to x-ray exposure should only be used in the presence of peripheral vascular disease or when echocardiographic imaging is insufficient.

Cardiopulmonary Bypass↗
PubMed2001

Sizing of atrial septal defects to predict successful closure with transcatheter cardioSEAL device.

We conducted this retrospective study to compare methods for measuring atrial septal defects and to identify factors affecting echocardiographic measurement of such defects before transcatheter closure with the CardioSEAL'Septal Occluder. We reviewed the records of patients considered for device placement at our institution from January 1997 to April 1999. Atrial septal defect size was measured by transthoracic and transesophageal echocardiography; the stretched diameter was measured during catheterization by fluoroscopy and transesophageal echocardiography. The stretched-diameter fluoroscopic measurement was used for device size selection. Analysis of variance was used to calculate the effect of size, age, and size-by-age interaction. Thirty-one patients (3.3 to 72 years of age) underwent transthoracic and transesophageal echocardiography One patient was excluded from catheterization because of a 25-mm septal defect as indicated by transesophageal echocardiography (our maximum diameter, 15 mm). Thirty patients underwent transcatheter stretched-diameter sizing; 5 were excluded from device implantation because of defects >20 mm by stretched-diameter fluoroscopy (4) or septal length insufficient for device support (1). Implantation was successful in 23/25 patients; 2/23 had a residual shunt. In patients with available results (26/30), the stretched diameter was the same whether measured by stretched-diameter fluoroscopy or transesophageal echocardiography (P=0.007 R square=0.963). Compared with stretched-diameter fluoroscopy, precatheterization transthoracic and transesophageal echocardiography underestimated defect size by a mean of 22% and 13.2%, respectively. When data from those same tests were compared in defects of < or =0 mm and > 10 mm, transthoracic and transesophageal echocardiography were reliable predictors (P=0.003 and P=0.05, respectively) of stretched-diameter size in defects < or =0 mm.

Adolescent↗
PubMed2004

Patient radiation doses and references levels in interventional radiology.

PURPOSE: To set Diagnostic Reference Levels (DRLs) in interventional radiology by means of dose area product (DAP) measurements and the grouping of homogeneous procedures, and to quantify the associated errors in the DRL estimates. To evaluate the Mean Effective Doses per single procedure. MATERIALS AND METHODS: Interventional radiology procedures were divided into four main groups: neuroradiological, vascular, extravascular and paediatric. Neuroradiological and vascular procedures were further divided into diagnostic and interventional procedures. Starting from DAP and total fluoroscopy time measurements in 1,256 patients, the DRLs were determined for 17 procedures, together with an estimate of their uncertainty. The correlation between fluoroscopy time and DAP was assessed. Mean effective dose estimates were obtained from measured DAP values and from the analysis of the dosimetric data reported in the literature for similar procedures. RESULTS: The main features of DAP distributions are long high-dose tails, indicating asymmetric distributions, together with a large interquartile range. Rounded third-quartile values of DAP distributions showed a large range in the procedures taken into consideration. Values of 147, 198, 338 Gy cm(2)were obtained for supra-aortic angiography, cerebral angiography and embolization. Values of 86-101 and 459-438 Gy cm(2)were obtained for diagnostic and interventional vascular procedures on the lower limbs and on the abdomen, respectively. Values of 25-33 Gy cm(2)were obtained for retrograde cystourethrographies and ERCP, and values of 62-158 Gy cm(2)were obtained for nephrostomy and percutaneous transhepatic cholangiography. The correlation between total fluoroscopy time and the DAP values was poor. Mean effective dose estimates showed lower values for extravascular procedures (4.8-28.2 mSv), intermediate values for neuroradiological procedures (12.6-32.9 mSv) and higher values for vascular procedures involving the abdomen (36.5-86.8 mSv). DISCUSSION: DAP values were generally higher in vascular than in extravascular procedures. In generally, interventional vascular procedures show higher DAP values than the corresponding diagnostic procedures, with the exception of the abdominal region where the values were similar. Extravascular procedures with percutaneous access show significantly higher DAP values than those with endoscopic access. Total fluoroscopy time is a poor predictor of patient doses in interventional radiology. CONCLUSIONS: The systematic recording of DAP values, together with adequate grouping of similar procedures makes it possible to establish stable DRLs on a local basis and to carry out dosimetric evaluations, although on a statistical rather than individual basis. Patient radiation doses during interventional radiological procedures may be high, particularly when the abdominal region is involved.

Humans↗
PubMed1964

MEDICAL RADIATION TO CHILDREN WITH CONGENITAL HEART DISEASE.

A retrospective analysis was made of the source of medical radiation received by 25 children who were investigated by cardiac catheterization techniques and followed in the Cardiac Outpatient Clinic of the Health Centre for Children, Vancouver General Hospital. The source of radiation was analyzed. The r dose per year received from plane films averaged 0.05 r, from cardiac fluoroscopy 6.7 r, and from catheterization and angiocardiography studies 1.58 r per year. In six of the 25 children, radiation doses to the thorax exceeded the LD(50) for adult humans. In these six patients 95.8% of the radiation received was during cardiac fluoroscopy. Routine fluoroscopy for the radiological re-evaluation of pediatric patients with congenital heart disease should be replaced by plain chest radiographs.

Adult↗
PubMed1999

Radiation exposure to children during coil occlusion of the patent ductus arteriosus.

The risks of excessive exposure to ionizing radiation are well described and measures are routinely taken to limit such exposure to both patient and personnel in the catheterization laboratory. Coll occlusion of the patent ductus arteriosus (PDA) as well as other more complex pediatric interventions has raised concern regarding radiation exposure, particularly as minimally invasive surgical techniques are being developed which lack such exposure risk. In eight consecutive patients, aged 0.7-7 years (median, 2.3 years), coil occlusion of a PDA was performed and surface entrance radiation dose determined by thermoluminescent dosimetry (TD). Total cumulative doses (PA + lateral dose) were also calculated for each patient. Entrance and cumulative dose was likewise measured in 12 patients undergoing standard diagnostic catheterization (DC) and in 5 consecutive patients undergoing pulmonary balloon valvuloplasty (PBV). The groups were comparable in age, weight, and body surface area (BSA). Total cumulative dose in the PDA patients was 97 +/- 25 mGy (mean +/- SE). There was no significant difference between the three groups in entrance dose absorbed at each location or in total cumulative dose. The mean total fluoroscopy time in the PDA occlusion group was significantly less than that of the PBV group (10.1 +/- 1.81 min vs. 19.3 +/- 2.29 min, P < 0.05) but was comparable to the DC group (13.2 +/- 1.5 min, P = NS). When the subjects were analyzed collectively, no correlation between fluoroscopy time and measured entrance dose was observed. The strongest correlates of total cumulative dose were patient weight (r = 0.67, P < 0.001) and BSA (r = 0.62, P = 0.001). Patients undergoing coil occlusion of a PDA are not exposed to increased radiation entrance dose compared to those undergoing standard DC and PBV. Furthermore, surface entrance radiation dose as determined by TD varies according to patient size for a given fluoroscopy time.

Body Height↗
PubMed1999

Reuse of catheters for percutaneous transluminal coronary angioplasty: effects on procedure time and clinical outcomes.

In July 1996, because of concern regarding the possible transmission of Creutzfeldt-Jakob disease, the province of Quebec stopped the reuse of percutaneous transluminal coronary angioplasty (PTCA) catheters. Prior to this time, PTCA balloon catheters were used a maximum of four times and guide catheters a maximum of two times in the cardiac catheterization laboratory at our institution. After this time, only new catheters were used. In order to examine the effects of catheter reuse on duration of PTCA procedures and clinical outcomes, we compared 53 consecutive patients undergoing PTCA prior to 21 July 1996 with 54 consecutive patients undergoing PTCA after that time. A total of 81 men and 26 women underwent PTCA (average age, 64 +/- 12 years). There were no significant differences between the single-use and reuse groups with respect to baseline characteristics. There were also no significant differences in the numbers of PTCA catheters used (97 vs. 103, P = NS) or angiographic success rates (88% vs. 83%, P = NS). There was a trend for total procedure time and fluoroscopy time to be slightly longer for single-use compared with reuse cases (49.2 vs. 45.7 min and 19.7 vs. 16.8 min, respectively; P = NS for both comparisons). However, after controlling for case severity and the use of stents, there were no significant differences in total procedure time or fluoroscopy time between the two groups. We found little evidence to suggest that the reuse of PTCA catheters is associated with longer total procedure time or fluoroscopy time. We conclude that if catheter reuse is not found to be associated with infectious disease transmission, its widespread use should be considered. Cathet. Cardiovasc. Intervent. 48:54-60, 1999.

Aged↗
PubMed1993

Radiation exposure: comparison of rapid exchange and conventional over-the-wire coronary angioplasty systems.

The growth of coronary angioplasty has resulted in increased fluoroscopy time to patients, staff, and physicians. Rapid exchange-type catheters have purported to reduce fluoroscopy time and procedure time compared to conventional over-the-wire systems. Of 150 consecutive patients, 54 were treated solely with rapid-exchange catheters and 84 were treated solely with over-the-wire catheters. Excluding 12 cases treated with fixed wire or combination catheters, the following data were found: [table: see text] Overall procedural success was obtained in 98.5% (136/138) of patients, 1.5% (2) requiring emergency coronary artery bypass graft surgery. A significant 35% reduction in fluoroscopy time and 13% reduction in procedure time were found when rapid-exchange catheters were used, with identical success rates, number of balloons used per case, and complication rates compared to over-the-wire catheters. Rapid-exchange catheters should be considered as part of an overall effort to reduce radiation exposure in the interventional cardiology laboratory.

Angioplasty, Balloon, Coronary↗
PubMed2006

Randomized comparison of operator radiation exposure during coronary angiography and intervention by radial or femoral approach.

Controversial data have been published on the amount of radiation exposure during radial coronary procedures. We hypothesized that in the current era, high-volume operators with optimal technique would not be exposed to higher radiation doses during radial procedures. A total of 297 patients undergoing cardiac catheterization (195 elective diagnostic coronary angiograms and 102 elective coronary interventions) were prospectively assigned in a random fashion to the radial access (RA) or femoral access (FA). All procedures were performed by the same operator with vast experience in radial procedures and standard measures for radiation protection were used. Operator radiation exposure was measured with an electronic radiation dosimeter attached to the breast pocket of the operator on the outside of the lead apron and estimates of the ambient dose equivalent were derived. For coronary angiograms, fluoroscopy time (2.8 +/- 2.1 vs. 1.7 +/- 1.4 min; P < 0.001) and dose-area product (15.1 +/- 8.4 vs. 13.1 +/- 8.5 Gy x cm(2); P < 0.05) were increased by 18% and 15%, respectively, for RA vs. FA. Operator radiation exposure was 100% higher for the RA compared to the FA (64 +/- 55 vs. 32 +/- 39 microSv; P < 0.001). For coronary interventions, fluoroscopy time (11.4 +/- 8.4 vs. 10.4 +/- 6.8 min; P = NS) and dose-area product (46.3 +/- 28.7 vs. 51.0 +/- 29.4 Gy x cm(2); P = NS) for RA and FA were not statistically different. However, operator radiation exposure was increased by 51% for the RA compared to the FA (166 +/- 188 vs. 110 +/- 115 microSv; P < 0.05). This study demonstrates that the radial approach is burdened with a 100% increase in operator radiation exposure during diagnostic coronary catheterization procedures and a 50% increase during coronary interventions, provided that no special devices for radiation protection are used. Measurements of radiation dose, such as fluoroscopy time and dose-area product, substantially underestimate the disproportionate rise in radiation exposure. Special precautions are warranted to improve radiation protection during invasive coronary procedures via the radial approach.

Aged↗
PubMed2006

Guidewire navigation in coronary artery stenoses using a novel magnetic navigation system: first clinical experience.

The objective of this study was to investigate the efficacy of guidewire navigation across coronary artery stenoses using magnetic navigation system (MNS) versus conventional navigation. The MNS is a novel option to facilitate access to target lesions, particularly in tortuous vessels. In an experimental study using a challenging vessel phantom, magnetic-navigated guidewire passage has been reported to reduce fluoroscopy and procedure time significantly. Both magnetic and manual guidewire navigation were attempted in 21 consecutive diseased coronary arteries. The study endpoint was defined as an intraluminal wire position distal to the stenosis. Procedural success was defined as successful guidewire passage without procedural events. Procedure time, amount of contrast, fluoroscopy time, and radiation dose/area product (DAP) were evaluated. There were no procedural events related to either guidewire. Although the lesions attempted had relatively simple and straightforward characteristics, significantly shorter procedure and fluoroscopy time were observed for manual guidewire navigation compared to MNS (median, 40 vs. 120 sec, P=0.001; 38 vs. 105 sec, P=0.001, respectively). Contrast amount and DAP were higher in MNS than in conventional method (median, 13 vs. 9 ml, P=0.018; 215 vs. 73 Gym2, P=0.002, respectively). The magnetic wire did not cross in two vessels. Guidewire navigation using MNS presented a novel, safe, and feasible approach to address coronary artery lesions. Clinical studies are needed to evaluate the potential benefit of the MNS in more complex coronary lesions and tortuous anatomy.

Angioplasty, Balloon, Coronary↗
PubMed2002

Closed reduction and percutaneous fixation of anterior column acetabular fractures.

OBJECTIVE: The current standard treatment of anterior column acetabular fractures includes formal open reduction with internal fixation (ORIF) through a variety of anterior approaches. These approaches have been associated with significant blood loss, infection, lengthy operative times, and neurovascular complications. It therefore seems reasonable to consider less invasive alternatives to conventional treatment methods. A technique for percutaneous reduction and fixation of a particular acetabular fracture pattern is presented. Execution of this technique has been facilitated by the use of image-guided surgical navigation. MATERIALS AND METHODS: A retrospective review was performed on 23 patients who had suffered an acute anterior column fracture of the acetabulum (OTA 62-A3.2, 62-A3.3, 62-B3.2, 62-B3.3) managed with closed reduction and internal fixation using large-bore cannulated screws over an 11-year period. An additional three patients treated during the study period underwent formal ORIF with plates and screws after failure of attempted closed reduction, and were not included in this analysis. Eight of the 23 patients had an associated posterior hemitransverse fracture that was also managed with minimally invasive fixation. A variety of surgical navigation techniques were used to allow accurate percutaneous screw placement: CT-guided percutaneous fixation was performed in 10 patients (1990-1995); fluoroscopy alone was used in four patients (1995-1998); and computer-assisted virtual fluoroscopy was used in nine patients (1999-2002). Some fractures were nondisplaced but potentially unstable, and involved the superior weight-bearing dome; others required closed manipulation using Schanz-pin joysticks placed into the iliac wings and held in place with a temporary external fixator. One patient required a limited open reduction followed by percutaneous screw fixation. After confirmation of adequate reduction, one to three large-bore cannulated screws were placed percutaneously using previously defined safe trajectories. All patients were managed postoperatively with early mobilization and physical therapy. RESULTS: The average preoperative and postoperative displacements were 8.9 and 2.4 mm, respectively. No patient had a loss of reduction during healing. As experience was gained with the computer-assisted imaging, total fluoroscopy times were as little as 6 s, and were routinely kept below 45 s. None of the patients experienced infection, significant blood loss, or iatrogenic neurologic or visceral injury. No symptomatic heterotopic ossification was noted. Of those patients available for follow-up at a minimum of 2 years, the average HSS self-administered hip score was 91. CONCLUSION: We believe that our findings substantiate percutaneous reduction and internal fixation of anterior column acetabular fractures as a safe and effective alternative to formal ORIF, with a low anticipated complication rate and excellent outcome.

Acetabulum↗
PubMed1976

The role of metoclopramide in peroral jejunal biopsy: a controlled randomized trial.

Metoclopramide is known to enhance gastric emptying and stimulate duodenal and small-intestinal peristaltic activity. The effect of the drug on peroral jejunal biopsy was examined in a controlled, double-blind, randomized trial. Forty-nine patients (24 females and 25 males) who required jejunal biopsy for diagnostic purposes were admitted to the study. All the biopsies were performed by the same operator using the Quinton multipurpose suction biopsy tube and applying the same technique. Twenty-four patients ranging in age from 18 to 67 years (mean 44.5) received placebo intravenously (sodium metabisulfite), and 25 patients from 16 to 73 years old (mean 39.9) received 10 mg of metoclopramide intravenously prior to the jejunal intubation. Objective parameters of the study were (1) time in minutes required for the intubation at the biopsy site, ie, the area at the ligament of Treitz, and (2) fluoroscopy time. Intubation time in the placebo group was 22.3 +/- 1.9 min (mean +/- SEM) vs 11.3 +/- 1.4 min in the metoclopramide group (P less than 0.001). Fluoroscopy exposure time was 2.47 +/- 0.25 in the placebo group vs 1.40 +/- 0.12 min in the metoclopramide group (P less than 0.001). Subjective clinical evaluation of the operator's assessment of the procedure was based on a 0-4 scale (much easier = 0, easier = 1, average = 2, harder = 3, and much harder = 4). Metoclopramide administration resulted in a significantly easier performance of the procedure (P less than 0.001) but did not influence patient tolerance. Three patients who received metoclopramide and one receiving placebo developed mild to moderate drowsiness of short duration. The results of this controlled trial indicate that metoclopramide significantly shortens the time required for jejunal biopsy and reduces fluoroscopy exposure. Its regulatory action on gastrointestinal motility contributes to the easier performance of a valuable diagnostic procedure.

Adolescent↗
PubMed1992

Digital imaging in pediatric hospitals.

Thirty-nine of 65 children's hospitals in North America responded to a questionnaire regarding their use of digital fluoroscopy and computed radiography (CR) systems. Both digital modalities are very favorably rated by institutions that have them. Budget constraints limit purchases in the other institutions. Picture archiving and communication systems (PACS) networking is not the primary reason for installation of digital systems. Fourteen of 39 hospitals have digital fluoroscopy and another 9 plan installation within 12 months. The three most highly rated benefits of digital fluoroscopy were decreased radiation dose, immediate visualization of the acquired image on the monitor, and the ability to alter image contrast and density. Four of 39 hospitals have computed radiography. The three most highly rated benefits of computed radiography were more stable image quality, ability to alter contrast and density, and PACS networking.

Child↗
PubMed2001

[Navigation assisted by image conversion. An experimental study on pelvic screw fixation].

Within an experimental trial the new method of fluoroscopy based navigation was tested for percutaneous pelvic screw fixations. A regular C-arm was used and the navigation system developed by Medivision. In a first step appropriate C-arm projections were defined for five standardized screw positions. Then precision and fluoroscopy time of 60 screws in 6 artificial pelves were evaluated. For the sacroliacal screw in S1, S1 screw in S2, anterior column screw, posterior column screw and the supraacetabular ilium screw three to four appropriate projections were defined. These were all combinations of the known special pelvic views inlet/outlet and iliac/obturator. Using these standardized views the average fluoroscopy time was 6 seconds per screw. 51 screws (85%) were inserted correctly. In five cases there was a slight deviation without perforating the cortex, four times the cortex was perforated.

Acetabulum↗
PubMed2002

[Accuracy of fluoroscopic navigation of pedicle screws. CT-based evaluation of bone screw placement].

While the advantages of C-arm navigation in computer-assisted spine surgery are obvious, the accuracy of pedicle screw placement with virtual fluoroscopy still needs to be verified. The C-arm-based ION system (Medtronic Sofamor Danek) was used to navigate pedicle screw insertion in patients undergoing spinal surgery for various conditions. In a prospective study, a total of 160 screws were inserted in the first 30 consecutive patients since introduction of the system at our institution: 54 at the thoracic spine (highest level: TH4) and 106 at the lumbar spine. Computed tomography (CT) scans were performed postoperatively by two independent radiologists to control the accuracy of screw placement at the level of the pedicles after reconstruction of axial images according to Laine et al. The comparison of the calculated accuracy rate of pedicle screw placement using virtual fluoroscopy with reported results achieved with CT-based navigation shows similar results for virtual fluoroscopy and a remarkable increase of accuracy in comparison to reports on conventional pedicle screw placement.

Bone Screws↗
PubMed2002

[Effective in vivo radiation dose with image reconstruction controlled pedicle instrumentation vs. CT-based navigation].

UNLABELLED: There is a rapid increase of computer-assisted surgery (CAS) in the spine for insertion of pedicle screws. In contrast to the traditional technique using fluoroscopy, CT is the primary source for surgical navigation systems. PURPOSE OF THE STUDY: To compare organ and effective doses of fluoroscopy-controlled versus computer-assisted pedicle screw insertion under the aspect of risk reduction and number needed to treat. MATERIALS AND METHODS: In 20 consecutive cases of traditional pedicle screw instrumentation under fluoroscopic control the effective doses were recorded in vivo and the organ doses then calculated. Simulating a spiral CT necessary for the 3-D-model for navigation we defined a spiral CT protocol for the instrumented levels and calculated organ and effective doses from Monte Carlo Results from CT examinations. RESULTS: Organ doses were clearly higher for the CT model than in any of the fluoroscopic procedures in vivo. The mean effective dose for the CT model was fifteen times higher than the fluoroscopic dose: 7.27 mSv versus 0.48 mSv. CONCLUSIONS: In experienced hands open pedicle screw insertion in the thoracic and lumbar spine using fluoroscopy-control requires a fifteen times lower radiation dose than do CT scans necessary for computer-assisted surgery. Regarding the published small percentage of neurological complications in traditional screw insertion technique the use of computer-assisted surgery in pedicle screw insertion using CT scan should be limited to carefully chosen indications. The development of navigation systems based on other data sources than CT should be encouraged.

Adolescent↗
PubMed2003

Comparison of fixed-flexion positioning with fluoroscopic semi-flexed positioning for quantifying radiographic joint-space width in the knee: test-retest reproducibility.

OBJECTIVE: To compare fixed-flexion radiography of the knee with fluoroscopic semi-flexed radiography in terms of the reproducibility of measurements of minimum joint-space width (JSW) in the medial femorotibial joint. METHODS: Posteroanterior radiographs of the right knees of 18 normal volunteers were acquired with the patients standing on an upright fluoroscopy table, the feet externally rotated 10 degrees and the toes touching the vertical table. Knees were positioned and radiographed with two different techniques: (1) semi-flexed positioning under fluoroscopic guidance using a horizontal X-ray beam; and (2) fixed-flexion positioning, with the knees and thighs touching the vertical table, using 10 degrees caudal beam angulation without fluoroscopy. Foot maps were drawn in each case. Subjects were repositioned and radiographed twice using each technique. The posteroanterior beam angle that optimally projected the medial tibia plateau with the patient in the fixed-flexion position was also determined for each subject in a separate examination using fluoroscopy. Ten patients with osteoarthritis were also examined with the fixed-flexion technique using a conventional radiographic unit. Minimum medial joint-space width (JSW) in the medial femorotibial joint was measured manually with a graduated lens and also with a semi-automated computer algorithm. RESULTS: Reproducibility errors (root-mean-square SD) for manual and automated JSW measurement were 0.2 mm and 0.1 mm, respectively, for fluoroscopic semi-flexed positioning in volunteers; 0.3 mm and 0.1 mm, respectively, for fixed-flexion positioning in volunteers; and 0.2 mm and 0.1 mm, respectively, for fixed-flexion positioning in osteoarthritic patients. The optimal beam angle for visualizing the joint space was 9.0 degrees +/-3.6 degrees. CONCLUSION: Fixed-flexion, non-fluoroscopic radiography of the knee can provide reproducible JSW measurement using widely available X-ray equipment. This technique is more feasible for multicenter clinical studies and routine clinical use than are methods that rely on fluoroscopic alignment of the tibial plateau.

Adult↗