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Radiation dose optimization in coronary angiography and percutaneous coronary intervention (PCI). II. Clinical evaluation.

In a previous part of this study, the fluoroscopy dose rate was reduced in a cardiac catheterization laboratory. The objectives of the present study were to evaluate the effects in a clinical population undergoing percutaneous coronary intervention (PCI) of the dose-reducing measures detailed previously. Kerma area-product (KAP) values were first recorded for 154 patients undergoing PCI. Then, the fluoroscopy KAP rate was reduced from 44 to 16 mGy cm(2)/s by increasing filtration and reducing the image intensifier dose request. After this optimization, KAP was recorded for another 138 PCI procedures. After adjustment for differing proportions of combined procedures (coronary angiography+PCI), the total KAP was reduced to 67% of the original value with a 95% confidence interval from 57 to 78%, statistically significant. The mean total KAP values were 93.6 Gy cm(2) before and 69.1 Gy cm(2) after optimization. The KAP for digital acquisition did not change significantly. It is possible to make a large dose reduction in PCI by reducing the fluoroscopy dose rate. This dose reduction is beneficial for both patients and staff.

Cardiac Catheterization↗

Evaluation of patient-absorbed doses during coronary angiography and intervention by femoral and radial artery access.

The aim of this study was to compare the radiation dose to patients during coronary angiography (CA) and coronary intervention (percutaneous transluminal coronary angioplasty, PTCA) by the femoral or radial artery access routes. A plane-parallel ionisation chamber, mounted on an under-couch X-ray tube (Siemens Coroskop TOP with an optional dose reduction system), recorded the dose-area product (DAP) to the patient from 40 coronary angiographies and 42 coronary interventions by the femoral route. The corresponding numbers for radial access were 36 and 24, respectively. Using a human-shaped phantom, conversion factors between maximum entrance surface dose and DAP were derived for CA and CA plus PTCA, respectively. The dose to the staff was measured with TL dosimeters for 22 examinations. Fluoroscopy time and DAP were significantly (p=0.003) larger using the radial access route for coronary angiography (7.5 min, 51 Gy cm2) than the corresponding values obtained from femoral access route (4.6 min, 38 Gy cm2). For CA plus PTCA the fluoroscopy time and DAP were larger for radial access (18.4 min, 75 Gy cm2) than for femoral access (12.5 min, 47 Gy cm2; p=0.013). In our experience, radial access did significantly prolong the fluoroscopy time and increase the patient doses.

Aged↗

Flat detectors and their clinical applications.

Diagnostic and interventional flat detector X-ray systems are penetrating the market in all application segments. First introduced in radiography and mammography, they have conquered cardiac and general angiography and are getting increasing attention in fluoroscopy. Two flat detector technologies prevail. The dominating method is based on an indirect X-ray conversion process, using cesium iodide scintillators. It offers considerable advantages in radiography, angiography and fluoroscopy. The other method employs a direct converter such as selenium which is particularly suitable for mammography. Both flat detector technologies are based on amorphous silicon active pixel matrices. Flat detectors facilitate the clinical workflow in radiographic rooms, foster improved image quality and provide the potential to reduce dose. This added value is based on their large dynamic range, their high sensitivity to X-rays and the instant availability of the image. Advanced image processing is instrumental in these improvements and expand the range of conventional diagnostic methods. In angiography and fluoroscopy the transition from image intensifiers to flat detectors is facilitated by ample advantages they offer, such as distortion-free images, excellent coarse contrast, large dynamic range and high X-ray sensitivity. These characteristics and their compatibility with strong magnetic fields are the basis for improved diagnostic methods and innovative interventional applications.

Absorption↗

Do flat detector cardiac X-ray systems convey advantages over image-intensifier-based systems? Study comparing X-ray dose and image quality.

The recent introduction of "flat-panel detector" (FD)-based cardiac catheterisation laboratories should offer improvements in image quality and/or dose efficiency over X-ray systems of conventional design. We compared three X-ray systems, one image-intensifier (II)-based system (system A), and two FD-based designs (systems B and C), assessing their image quality and dose efficiency. Phantom measurements were performed to assess dose rates in fluoroscopy and cine acquisition. Phantom dose rates were broadly similar for all systems, with all systems classified as offering "low" dose rates in fluoroscopy on standard phantoms. Patient X-ray dose rate and subjective image quality was assessed for 90 patients. Dose area product (DAP) rates were similar for all systems, except system C, which had a lower DAP rate in fluoroscopy. In terms of subjective image quality, the order of preference was (best to worst): system C, system A, system B. This study indicates that the use of an FD detector does not infer an automatic improvement in image quality or dose efficiency over II based designs. Specification and configuration of all of the components in the X-ray system contribute to the dose levels used and image quality achieved.

Angioplasty, Balloon, Coronary↗

A Nordic survey of patient doses in diagnostic radiology.

The aim of this study was to test the applicability of the guidance levels for patient doses cooperatively set by the radiation protection authorities in the five Nordic countries. The kerma-area product (KAP) for five conventional radiological examination types was obtained from several hospitals in each of the Nordic countries. The number of radiographic images and fluoroscopy time were also registered, and the mean values for each examination type and hospital were established based on a representative number of patients (40-100 kg). The results indicate that the situation is very similar in the five Nordic countries, even though some differences were identified. Most of the hospitals demonstrated lower doses than the proposed guidance levels for chest, probably explained by use of faster film/screen combinations during the past decade. An increased use of fluoroscopy for positioning was observed for radiographic examinations of lumbar spine and urography. Large variations in patient doses were found for barium enema depending on the use of fluorospot or 100-mm camera vs full-format film, the range in fluoroscopy times, dose rate, and field size. The guidance levels for lumbar spine (10 Gy x cm2), pelvis (4 Gy x cm2), urography (20 Gy x cm2), and barium enema (50 Gy x cm2) seem to reflect the present quality of X-ray equipment and examination techniques in the Nordic countries. The guidance levels for chest (1 Gy x cm2) should be lowered to 0.6 Gy x cm2.

Barium Sulfate↗

Impact of intracardiac echocardiography on radiation exposure during adult congenital heart disease catheter-based interventions.

BACKGROUND: Intracardiac echocardiography (ICE) is a widespread approach in many cardiovascular procedures in which it has the potential to reduce the fluoroscopy time and patients radiation exposure. We sought to assess the patient radiation exposure during transcatheter closure of interatrial communications with and without ICE-guidance. METHODS: In a prospective consecutive series of 25 consecutive patients who underwent transcatheter closure of interatrial communications between May and October 2005 with (15 patients) and without (10 patients) ICE-guidance in a single secondary care referral centre, we measured the dose-area product (DAP), the fluoroscopy dose-area product (FDAP), the total dose-area product (TDAP), and the mean procedural time. RESULTS: In patients underwent ICE-guided transcatheter closure procedure the mean fluoroscopy time, the mean DAP, mean FDAP, and mean TDAP resulted significantly lower than in control patients: 2.0 +/- 0.21 (range 1.6-2.2) versus 5.05 +/- 0.54 (range 4.2-5.8) minutes (P < 0.001) , 13.72 +/- 9.03 (range 11.36-14.63) versus 21.95 +/- 6.93 (range 20.90-23.93) Gycm2 (P < 0.001), 8.25 +/- 1.22 (range 6.60-9.50) versus 20.15 +/- 8.83 (range 18.90-20.93) Gycm2 (P < 0.001), and 29.33 +/- 1.51(range 27.16-31.00) versus 32.61 +/- 2.53 (range 29.20-35.55) Gycm2 (P < 0.01). On the contrary, the mean procedural time, was significantly higher in ICE-guided transcatheter closure patients: 30.2 +/- 2.45 (range 23-40) versus 24.5 +/- 2.45 (range 24-31) minutes (P = 0.03). CONCLUSION: The radiation exposure during ICE-guided transcatheter closure of interatrial communications in this group of patients was quite lower than that reported in literature for such procedures and compared favourably with radiation exposure of patients in whom the intervention was performed without ICE guidance.

Adult↗

Use of an ultrathin gastroscope to allow endoscopic insertion of enteral wallstents without fluoroscopic monitoring.

Self-expanding metallic stents are useful in relieving tumoral obstruction in the gastrointestinal tract. Endoscopic insertion is usually made through the working channel of a therapeutic endoscope. Fluoroscopy during insertion is thought to be mandatory in most cases. Endoscopists sometimes encounter problems in using or accessing fluoroscopy facilities. This study describes a method to insert, under certain circumstances, enteral Wallstents using only endoscopic control. An ultrathin gastroscope is used to pass severe tumoral strictures and place a guide wire beyond the stenosis. The ultrathin gastroscope is removed leaving the guide wire in place, which is then inserted in a retrograde fashion into a therapeutic colonoscope, allowing insertion of through-the-scope stents. Successful insertion was achieved in 5 malignant gastric outlet obstructions and in 6 rectosigmoid tumoral obstructions. In conclusion, in some cases using an ultrathin endoscope to place a guide wire beyond the stricture can be useful for endoscopic placement of Wallstents without fluoroscopy.

Adenocarcinoma↗

A logistic regression analysis of multiple noninvasive tests for the prediction of the presence and extent of coronary artery disease in men.

The incremental diagnostic yield of clinical data, exercise ECG, stress thallium scintigraphy, and cardiac fluoroscopy to predict coronary and multivessel disease was assessed in 171 symptomatic men by means of multiple logistic regression analyses. When clinical variables alone were analyzed, chest pain type and age were predictive of coronary disease, whereas chest pain type, age, a family history of premature coronary disease before age 55 years, and abnormal ST-T wave changes on the rest ECG were predictive of multivessel disease. The percentage of patients correctly classified by cardiac fluoroscopy (presence or absence of coronary artery calcification), exercise ECG, and thallium scintigraphy was 9%, 25%, and 50%, respectively, greater than for clinical variables, when the presence or absence of coronary disease was the outcome, and 13%, 25%, and 29%, respectively, when multivessel disease was studied; 5% of patients were misclassified. When the 37 clinical and noninvasive test variables were analyzed jointly, the most significant variable predictive of coronary disease was an abnormal thallium scan and for multivessel disease, the amount of exercise performed. The data from this study provide a quantitative model and confirm previous reports that optimal diagnostic efficacy is obtained when noninvasive tests are ordered sequentially. In symptomatic men, cardiac fluoroscopy is a relatively ineffective test when compared to exercise ECG and thallium scintigraphy.

Adult↗

Lateral transcranial radiography of temporomandibular joints. Part I: Validity in skulls and patients.

Left and right TMJs of 10 skulls and 15 patients (50 TMJs) were studied by means of OLTP and tomography to establish optimal condylar position in the glenoid fossae at maximum dental intercuspation. Two OLTP examinations of each joint were made and individualized by submental X ray and by fluoroscopy. A comparison of the recorded data showed fluoroscopy to give the better result. According to this study, OLTP individualized by fluoroscopy may be a useful tool in the determination of condylar position.

Adolescent↗

Assessment of bedside umbilical vein balloon septostomy using two-dimensional echocardiographic guidance in transposition of great arteries.

The effectiveness of "bedside" balloon atrial septostomy via the umbilical vein using 2-dimensional echocardiography was compared to the traditional femoral vein approach using fluoroscopy in a series of neonates with transposition of great arteries from March, 1984 to April, 1987. There were 7 neonates who had balloon septostomy performed at the "bedside" (Group I) compared to 13 who had the procedure performed in the catheterization laboratory (Group II). Group II consisted of 7 newborns who had elective femoral vein catheterization under fluoroscopy (Group IIA) and 6 who failed "bedside" umbilical vein balloon septostomy and subsequently had the femoral vein approach under fluoroscopy (Group IIB). Results showed that adequacy of balloon septostomy was not related to the approach used, with 4 of 7 in Group I and 9 of 13 in Group II with an adequate atrial tear and clinical response. The Delay time to septostomy (i.e. time elapsed from initial assessment to commencement of balloon septostomy) and Procedure time (i.e. time taken to complete the balloon septostomy) was significantly shorter for Group I (mean time = 0.7 hours and 0.26 hours respectively) compared with Group IIA (mean time = 2.6 hours and 1.8 hours) and Group IIB (mean time = 2.4 hours and 1.4 hours). Of note, there was no significant increase in Delay time between Group IIA and IIB.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization↗

Transesophageal echocardiographic guidance of transcatheter ventricular septal defect closure.

OBJECTIVES: This report describes transesophageal echocardiographic guidance of transcatheter closure of ventricular septal defects and its value as an adjunct to fluoroscopy and angiography in this procedure. BACKGROUND: Experience with transcatheter closure of ventricular septal defects has identified a diverse group of patients in whom it may be the procedure of choice. Although facilitating other interventional procedures, such as transcatheter closure of atrial septal defects, the value of transesophageal echocardiographic guidance for transcatheter ventricular septal defect closure has not been documented. METHODS: All patients who underwent ventricular septal defect closure with transesophageal echocardiographic guidance before November 1992 were included. Angiograms and echocardiograms were reviewed to evaluate device position and relation to valve tissue during placement and to assess residual flow after device implantation. The ability of transesophageal echocardiography to assess these variables was compared with fluoroscopy and angiography. RESULTS: Transesophageal echocardiographic guidance was used in 31 of the 83 catheterizations involving transcatheter ventricular septal defect closure performed between February 1990 and November 1992. Under transesophageal echocardiographic guidance, 45 devices were implanted: 23 in muscular ventricular septal defects, 17 in residual postoperative patch margin defects and 5 in other ventricular septal defects. Transesophageal echocardiographic guidance enhanced assessment of device position and proximity to valve structures and markedly improved assessment of residual flow. Assessment of residual flow with transesophageal echocardiography eliminated the need for multiple angiograms in some patients. Combining transesophageal echocardiography with fluoroscopy and angiography provided the most information. CONCLUSIONS: Transesophageal echocardiography facilitates transcatheter closure of ventricular septal defects by improving assessment of device position and effectiveness of closure. It is indicated when device placement is likely to be difficult or may interfere with valve structures or when multiple interventional procedures are anticipated.

Adolescent↗

Truly hybrid X-ray/MR imaging: toward a streamlined clinical system.

RATIONALE AND OBJECTIVE: We have installed an improved X-ray/MR (XMR) truly hybrid system with higher imaging signal-to-noise ratio (SNR) and versatility than our first prototype. In our XMR design, a fixed anode X-ray fluoroscopy system is positioned between the two donut-shaped magnetic poles of a 0.5T GE Signa-SP magnet (SP-XMR). This paper describes the methods for increased compatibility between the upgraded x-ray and MR systems that have helped improve patient management. MATERIALS AND METHODS: A GE OEC 9800 system (GE OEC Salt Lake City, UT) was specially reconfigured for permitting X-ray fluoroscopy inside the interventional magnet. A higher power X-ray tube, a new permanent tube mounting system, automatic exposure control (AEC), remote controlled collimators, choice of multiple frame rates, DICOM image compatibility, magnetically shimmed X-ray detector, X-ray compatible MR coil, and better RF shielding are the highlights of the new system. A total of 23 clinical procedures have been conducted with SP-XMR guidance of which five were performed using the new system. RESULTS: The 70% increased power for fluoroscopy, and a new 6 times higher power single frame imaging mode, has improved imaging capability. The choice of multiple imaging frame rates, AEC, and collimator control allow reduction in X-ray exposure to the patient. The DICOM formatting has permitted easy transfer of clinical images over the hospital PACS network. The increased MR compatibility of the detector and the X-ray transparent MR coil has enabled faster switching between X-ray and MR imaging modes. CONCLUSION: The improvements introduced in our SP-XMR system have further streamlined X-ray/MR hybrid imaging. Additional clinical procedures could benefit from the new SP-XMR imaging.

Equipment Design↗

Transesophageal echocardiography to guide pulmonary vein mapping and ablation for atrial fibrillation.

BACKGROUND: This study describes the use and outcomes of transesophageal echocardiography to guide atrial fibrillation (AF) ablation procedures. METHODS: Under general anesthesia, 25 patients with a history of AF underwent multiplane transesophageal echocardiography in conjunction with catheter placement under fluoroscopy. RESULTS: In this series, a combined fluoroscopic/echocardiographic approach obviated the need for angiographic imaging. Anatomic variation in pulmonary veins (PV) was common; the shortest distance between the ostia ranged from 2 to 11 mm. Individual PV diameters did not predict the presence of ectopic foci. The number of radiofrequency pulses delivered per vein was 2.6 +/- 2.3 (range: 0-10). Mean fluoroscopy time per procedure was 31 +/- 13 minutes and mean procedure time was 110 +/- 31 minutes. At follow-up, 68% of patients were free from AF. CONCLUSIONS: Transesophageal echocardiography enables identification and cannulation of the ostia and proximal branches of PV during AF ablation. Fluoroscopy, procedure times, and outcomes compare favorably with series using PV angiography and, as such, suggest that a controlled trial is warranted.

Adult↗

The learning curve in the training of percutaneous nephrolithotomy.

OBJECTIVES: To investigate the learning curve in the training of percutaneous nephrolithotomy (PCNL). METHODS: A total of 104 PCNL cases were included in this evaluation to define the learning curve of a surgeon with no previous experience at performing solo PCNL. Two parameters of expertise were reviewed, namely the operation and fluoroscopic screening times. The operation time was calculated as the beginning of access with the needle until the nephrostomy tube was placed and secured. PCNL procedures were analyzed in seven sets of 15 cases regarding the operation and fluoroscopy times, stone size, stone clearance rate, blood transfusion rate, and estimated blood loss. RESULTS: The mean operation time was 2.4 h for the first 15 patients. It decreased to a mean of 1.5 h for cases 46 through 60. No further decrease in the operation time was observed after case 60. The fluoroscopic screening time was a peak of 17.5 min in the first 15 cases, whereas it dropped to a mean of 8.9 min for cases 46 through 60. The decline in the mean fluoroscopy screening time continued in cases 61 to 104, but the decline was not significant. There was no significant difference in stone size, stone clearance rate, blood transfusion rate, and estimated blood loss among each set of cases. CONCLUSIONS: This study suggests that the surgical competence in PCNL can be reached after 60 cases. PCNL and fluoroscopy times drop to a steady-state level after performing 60 procedures.

Clinical Competence↗

Remote magnetic navigation for mapping and ablating right ventricular outflow tract tachycardia.

BACKGROUND: Navigation, mapping, and ablation in the right ventricular outflow tract (RVOT) can be difficult. Catheter navigation using external magnetic fields may allow more accurate mapping and ablation. OBJECTIVES: The purpose of this study was to assess the feasibility of RVOT tachycardia ablation using remote magnetic navigation. METHODS: Mapping and ablation were performed in eight patients with outflow tract ventricular arrhythmias. Tachycardia mapping was undertaken with a 64-polar basket catheter, followed by remote activation and pace-mapping using a magnetically enabled catheter. The area of interest was localized on the basket catheter in seven patients in whom an RVOT arrhythmia was identified. Remote navigation of the magnetic catheter to this area was followed by pace-mapping. Ablation was performed at the site of perfect pace-mapping, with earliest activation if possible. RESULTS: Acute success was achieved in all patients (median four applications). Median procedural time was 144 minutes, with 13.4 minutes of patient fluoroscopy time and 3.8 minutes of physician fluoroscopy time. No complications occurred. One recurrence occurred during follow-up (mean 366 days). CONCLUSION: RVOT tachycardias can be mapped and ablated using remote magnetic navigation, initially guided by a basket catheter. Precise activation and pace-mapping are possible. Remote magnetic navigation permitted low fluoroscopy exposure for the physician. Long-term results are promising.

Body Surface Potential Mapping↗

The use of computer navigation in performing minimally invasive surgery for intertrochanteric hip fractures--The experience in Singapore.

OBJECTIVE: Intertrochanteric hip fractures are very common and early mobilisation correlates with a better outcome. The ideal surgical procedure should protect the soft tissue envelope, thereby preserving blood supply and reducing blood loss. Furthermore, occupational exposure to fluoroscopy that is used in hip fracture fixation remains a concern amongst orthopaedic surgeons. Computer-aided surgery can help to reduce reliance on fluoroscopy. We therefore combined the principles of minimally invasive plate osteosynthesis (MIPO) and computer navigation to describe a new procedure. We also present our results using this technique of minimally invasive computer-navigated dynamic hip screw fixation (navMIS-DHS), and compare it to computer-navigated open DHS fixation (nav-DHS) and to conventional open DHS fixation (conv-DHS). MATERIALS AND METHODS: This paper has three parts. In the first part, we describe the procedure of navMIS-DHS in detail. In the second part, we present our initial retrospective pilot series of 35 cases. Amongst them we performed 5 navMIS-DHS, 3 nav-DHS and 27 conv-DHS. There were also two cases of conv-DHS deliberately performed with a mini-incision in an attempt to see if we could duplicate the 5 cm incision that we achieved with navMIS-DHS. All patients were followed up for a minimum of 6 months. In the third part, we performed a single surgeon prospective evaluation of navMIS-DHS versus conv-DHS involving 43 fractures in two arms. RESULTS: We were able to achieve reduction in fluoroscopy time. There was also reduction in opiate requirement post-operatively in the minimally invasive procedure. The incision sizes were also smaller. The prospective study also showed less wound-related complications in navMIS-DHS and a shorter time to ambulation. Implant positions were acceptable but we have also described how it may be improved. CONCLUSIONS: Navigated MIS-DHS, by virtue of less pain, better healing, earlier rehabilitation and potentially shorter hospital stay, would benefit both the patients and reduce the economic strain on the health care system. It is a safe and reproducible procedure. Technical difficulties are present and these need to be addressed with further modifications of technique, and instrumentation.

Aged↗

Diagnostic evaluation of foreign body aspiration in children: a prospective study.

AIM: The aim of this study was to evaluate the yield of clinical symptoms, signs, and radiological studies in the diagnosis of foreign body aspiration (FBA) in children. METHODS: During the 2-year study, we performed on all children admitted to the pediatric department for suspected FBA a protocol that included the following: thorough medical history, physical examination, radiological studies (chest x-ray and fluoroscopy), and rigid bronchoscopy by a senior otolaryngologist. The yield of these measures for the diagnosis of FBA was evaluated. RESULTS: Foreign bodies were found in 56 (57%) of the 98 children with suspected FBA. Thirty-three (59%) children were boys and 23 (41%) girls (P < .05), with a mean age of 24 months (range, 8-84 months). Main symptoms in the children with FBA were the following: choking (76.8%), prolonged cough (14.3%), dyspnea (3.6%), and nonresolving pneumonia (1.8%). Physical examination, chest x-ray, and fluoroscopy findings were abnormal in 80.4%, 67.9%, and 46.9% of the children with FBA, respectively. The diagnostic yield of physical examination and radiological studies increased 24 hours after the event of FBA. In 45.2% of the children with positive history but with normal findings from physical examination and radiological studies, foreign bodies were found. Of the children with "doubtful" history, physical examination, chest x-ray, and fluoroscopy findings were abnormal in 58%, 38%, and 12.5%, respectively. Foreign bodies were found in 9.5% of these children. CONCLUSION: Medical history is the key for the diagnosis of FBA. Choking followed by an acute episode of coughing is the most common presentation of FBA. The yield of physical examination and radiological studies in the diagnosis of FBA is relatively low but is increased when the presentation is delayed and when history is doubtful. If FBA is suspected, bronchoscopy should be performed.

Airway Obstruction↗

Accuracy of subacromial injection: anterolateral versus posterior approach.

Subacromial bursa injection is commonly performed via an anterolateral or posterior approach. No study has compared the accuracy rates of these approaches. Twenty cadaveric shoulders were injected with radiocontrast in the subacromial bursa via an anterolateral approach and twenty via a posterior approach. Ten shoulders were injected with methylene blue via each technique for dissection. The anterolateral approach was accurate by fluoroscopy in 18 shoulders (90%), but dissection of 10 shoulders revealed successful injection in only 6 (60%). The posterior approach was judged to be successful in 16 shoulders (80%), and dissection of 10 shoulders confirmed 8 injections (80%) were accurate. There was no significant difference in the accuracy by fluoroscopy (P=.38) or dissection (P=.33). The accuracy rates of the anterolateral and posterior approaches to subacromial bursa injections are not significantly different. The anterolateral approach may place injected material medial to the medial bursal boundary, and fluoroscopy may not accurately assess this placement.

Aged↗