Reduce Patient Radiation Exposure Research Articles

FDG PET of the Brain in Pediatric Patients: Imaging Spectrum with MR Imaging Correlation

Positron emission tomography (PET) of the brain is an important problem-solving tool in pediatric neuroimaging, neurology, and neurosurgery. Fluorine 18 fluorodeoxyglucose (FDG) PET or dual-modality PET and computed tomographic (CT) imaging (PET/CT), with magnetic resonance (MR) imaging correlation, can be used to evaluate childhood epilepsy and pediatric brain tumors, areas in which PET adds value in patient management. FDG PET has been widely used in pediatric temporal lobe epilepsy, most commonly manifesting as mesial temporal sclerosis, which demonstrates hypometabolism at interictal PET and hypermetabolism during seizures. Recently, FDG PET has shown added value for patients with extratemporal epilepsy, in whom FDG PET can help identify cortical foci of interictal hypometabolism that are undetectable or difficult to detect with MR imaging. These findings can then guide additional investigations and surgery. FDG PET also enhances medical decision making in children with brain tumors, in whom FDG PET can be used to (a) improve the diagnostic yield of stereotactic biopsies by detecting metabolically active areas of tumor, (b) help guide the surgeon in achieving total tumor resection, and (c) increase detection of residual or recurrent tumor. Technologic advances in the past decade have allowed fusion of PET and MR images, combining the high resolution of MR imaging with the low-resolution functional capability of PET. As dual-modality integrated PET/MR imaging systems become available, CT coregistration for PET can be eliminated, thus reducing patient radiation exposure. Increasing familiarity with normal and abnormal appearances of FDG PET brain images correlated with MR images can enhance diagnostic yield and improve the care of children with epilepsy and brain tumors.

1046 Can Early Double Guidewire Technique Facilitate Common Bile Duct Cannulation and Reduce Post ERCP Pancreatitis? -Results of a Multicenter Prospective Randomized Controlled Trial: EDUCATION Trial-

decreases in mean DAP and mean Effective Radiation Dose. A significant decrease was also noted in the number of images. Prior to education, LVE had significantly a higher mean DAP and mean Effective Radiation Dose compared to HVE. Following education, no significant differences were seen between the two groups. None of the endoscopists reported any compromise in their ability to interpret and perform ERCP despite incorporating fluoroscopy best practices. Conclusion: Educating endoscopists in fluoroscopy best practices significantly reduces patient radiation exposure during ERCP. This benefit is more pronounced in LVE. All endoscopists (HVE and LVE) benefited from fluoroscopy education, allowing reduction in patient radiation exposure, without compromising their ability to interpret and perform ERCP.

2:18 PM Abstract No. 40 - Success of using saline flush for repositioning peripherally inserted central catheters

Purpose To evaluate a peripherally inserted central venous catheter (PICC) repositioning protocol involving use of vigorous saline flush technique for correction of malpositioned PICCs placed at bedside. Materials and Methods All episodes of PICC tip malposition on post-bedside placement CXR over a 12 month period were reviewed. Data were prospectively collected at time of repositioning flush technique. Our protocol for malpositioned PICC begins with fluoroscopic evaluation of the PICC. If the PICC is too long or short or if it is coiled within an arm vein, saline flush is not attempted. Otherwise, if malposition is confirmed, vigorous saline flush technique using a 3mL polycarbonate syringe is performed under fluoroscopic guidance. If unsuccessful, the patient is then prepped and an attempt is made to exchange the PICC over a wire. Results 94 patients were included. In 5 (5%) there was spontaneous repositioning of the catheter without need for intervention. In 25 other encounters, flush repositioning was not attempted. Of the remaining 64, 30 (47%) were successfully repositioned with saline flush (Table). In the successful cases, the mean number of flushes required to reposition the PICC was 3 (SD 2, range 1-6). Out of all of the catheters, 46 (including those PICCs that were not attempted to be flushed and those that failed flush) were successfully replaced over a wire, 8 required a new venous puncture, 3 were left as midline catheters due to inability to thread the catheter centrally and 2 were pulled back and secured with a box clamp because they were too long. Mean fluoroscopy time for successful repositioning using flush technique (0.8 minutes SD 1.0) was significantly less than for those requiring wire manipulation (4.1 minutes, SD 5.3) (p Conclusion Vigorous saline flush technique is effective for correction of roughly half of selected malpositioned PICCs. It can reduce patient radiation exposure. It is most likely to be successful if the PICC is not coiled and if the tip is in the ipsilateral internal jugular vein. Table 1

Abstract 277: Quality Initiative to Reduce Radiation Exposure and Detect Radiation Injury in the Congenital Cardiac Catheterization Lab

Background: The frequency and duration of cardiac catheterization for patients with complex congenital heart disease have increased as a result of the advances in technique and devices available. Increasing catheter interventions require efforts to reduce patient radiation exposure and improve detection of radiation burns. Follow-up protocols based on fluoroscopy time alone are often inadequate as surveillance measures to identify patients that develop radiation burns. Objective: The objective of this study was (1) to reduce the radiation exposure during cardiac catheterization and (2) to improve the quality of post cardiac catheterization radiation surveillance by the development of standardized dose dependent follow-up protocols. Methods: Quality initiatives introduced to reduce radiation exposure from July 2008 - July 2010 included (1) fluoroscopy frame rate reduction from 30 to 15 fps; (2) digital acquisition frame rate reduction from 30 to 15 fps for pts > 65kg; (3) Toshiba system upgrade superior noise reduction filter with high-quality fluoro-record capabilities. Quality initiatives for follow-up surveillance based on radiation exposure included (1) all patients exposed to a dose of ≥ 3000mGy received a letter explaining radiation risks and possible signs of radiation burns, as well as a phone call 1 week post procedure inquiring about possible signs of radiation burns or other skin changes; (2) all patients exposed to a dose of ≥ 6000mGy received 2 additional phone calls at 3 and 6 weeks post procedure; and (3) all patients exposed to a dose of > 9000mGy had a follow-up appointment with a cardiologist 4-6 weeks post procedure with skin assessment for radiation injury. Results: In 2008, there were 519 patients; median radiation exposure was 544 mGy (range 10-31519); median fluoroscopy time was 23 min (range 1-335); radiation burns N=4. In 2009, there were 495 patients; median radiation exposure was 439 mGy (range 0.4-15955); median fluoroscopy time was 24 min (range 0.1-192); radiation burns N=7. In 2010, there were 519 patients; median radiation exposure was 322 mGy (range 1.6-19196); median fluoroscopy time was 24 min (range 0.5-386); radiation burns N=4. In 2011, there were 572 patients; median radiation exposure was 220 mGy (range 1-11108); median fluoroscopy time was 23 min (range 0.3-201); radiation burns N=3. The median patient radiation exposure decreased by over 50% from 2008 to 2011 (p<0.001 ). Fluoroscopy times did not change significantly during the study period (p=0.9). Conclusions: Quality improvement initiatives aimed at reduction of cardiac catheterization radiation exposure and dose dependent follow-up protocols have been effective in reducing the radiation exposure and improving detection of radiation burns in patients with congenital heart disease undergoing cardiac catheterization.

Determination of Internal Target Volume From a Single Positron Emission Tomography/Computed Tomography Scan in Lung Cancer

The use of four-dimensional computed tomography (4D-CT) to determine the tumor internal target volume (ITV) is usually characterized by high patient radiation exposure. The objective of this study was to propose and evaluate an approach that relies on a single static positron emission tomography (PET)/CT scan to determine the ITV, thereby eliminating the need for 4D-CT and thus reduce patient radiation dose. The proposed approach is based on the concept that the observed PET image is the result of a joint convolution of an ideal PET image (free from motion and partial volume effect) with a motion-blurring kernel (MBK) and partial volume effect. In this regard, the MBK and tumor ITV are then estimated from the deconvolution of this joint model. To test this technique, phantom and patient studies were performed using different sphere/tumor sizes and motion trajectories. In all studies, a 4D-CT and a PET/CT image of the sphere/tumor were acquired. The ITV from the proposed technique was then compared to the maximum intensity projection (MIP) volume of the 4D-CT images. A Dice coefficient of the two volumes was calculated to represent the similarity between the two ITVs. The average ITVs of the proposed technique were 97.2% ± 0.3% and 81.0% ± 16.7% similar to the MIP volume in the phantom and patient studies, respectively. The average dice coefficients were 0.87 ± 0.05 and 0.73 ± 0.16, respectively, for the two studies. Using the proposed approach, a single static PET/CT scan has the potential to replace a 4D-CT to determine the tumor ITV. This approach has the added advantage of reducing patient radiation exposure and determining the tumor MBK compared to 4D-CT/MIP-CT.

Established and emerging dose reduction methods in cardiac computed tomography

Cardiac computed tomography (CT) is a non-invasive modality that is commonly used as an alternative to invasive coronary angiography for the investigation of coronary artery disease. The enthusiasm for this technology has been tempered by a growing appreciation of the potential risks of malignancy associated with the use of ionising radiation. In the spirit of minimizing patient risk, the medical profession and industry have worked hard to developed methods and protocols to reduce patient radiation exposure while maintaining excellent diagnostic accuracy. A complete understanding of radiation reduction techniques will allow clinicians to reduce patient risk while providing an important diagnostic service. This review will consider the established and emerging techniques that may be adopted to reduce patient absorbed doses from x-ray CT. By modifying (1) x-ray tube output, (2) imaging time (scan duration), (3) imaging distance (scan length) and (4) the appropriate use of shielding, clinicians will be able to adhere to the ‘as low as reasonably achievable (ALARA)’ principle.

Low voltage CTPA for patients with suspected pulmonary embolism

To test a low dose, low voltage protocol for the diagnosis of pulmonary embolism. 50 Patients with clinically suspected pulmonary embolism underwent CTPA with 80kVp and 295mAs (test group) on a 64-row MDCT scanner. These patients were compared to a similar group of 50 patients scanned on the same scanner with the 120kVp protocol with automatic tube current modulation (control group). All patients received 100-110ml of a 370mgI/ml solution at 4.5cm(3)/s. Scans were compared for quantitative imaging parameters (attenuation and standard deviation in the main, right and left pulmonary arteries, in a lobar and segmental pulmonary artery and in the aorta) and for dose parameters (CTDI and DLP), using an unpaired t-test. Phantom measurements were also performed for image quality parameters and radiation dose. Mean attenuation was significantly higher in the test group than in the control group in the main pulmonary trunk, in the right pulmonary artery, in the left pulmonary artery, in a lobar and segmental pulmonary artery and in the ascending aorta (all: p≤0.0001). Noise was significantly higher in the test group than in the control group, but contrast to noise ratio was not significantly different between the two protocols. Radiation dose was significantly lower in the test group than in the control group, as measured by CTDI, DLP and effective dose to organs (all: p<0.0001). The use of 80kVp for pulmonary CTA significantly reduces patient radiation exposure, and significantly increases contrast medium attenuation in the pulmonary arteries, with no effect on the diagnostic quality of the exams.

Cardiovascular Nuclear Imaging: Balancing Proven Clinical Value and Potential Radiation Risk

1162 Objectives In 1925 Blumgart demonstrated that he could measure serial blood levels of isotope activity to determine cardiac contractility through the measurement of “circulation time.” Todays modern SPECT cameras replace the cloud chambers of Blumgarts era, allowing us the opportunity to measure serial changes in isotope concentration needed to measure ischemia. This study determines the clinical utility of Blumgarts method using todays SPECT camera. Methods One hundred twenty individuals underwent diagnostic study measuring changes in sestamibi activity in eight regions of interest (ROIs) using a SPECT camera. Subjects were stressed and using Blumgarts method of measuring isotope scintillations, serial measurements were compared in each of the eight regions with results found on coronary angiography. Results Parabolic regression of stenosis from coronary angiography (figure 1) on changes in isotope activity were compared for each of the vascular territories. The result yielded an effect size of R(95%)=0.72 to 0.95, p=3.8x10-8. Conclusions Prior investigations suggested that changes in isotope distribution over time could be employed to more accurately measure ischemia. A thorough literature search and investigation and application of Blumgarts method of serial measurements of isotope scintillation, when applied using todays SPECT camera reveals that changes in sestamibi distribution can be accurately measured, allowing clinicians to employee SPECT cameras to obtain angiographic results, while improving diagnostic accuracy and reducing patient radiation exposure. Research Support CVISM sponsored

Vergleich der Bildqualität zweier unterschiedlicher mobiler 3-dimensionaler Röntgen-C-Bögen mit einem konventionellen CT bei der Darstellung relevanter Strukturen am knöchernen Becken

This study evaluated the image quality of two different cone beam CT scanners used in the operation theatre in pelvic trauma surgery in relation to their radiation dosage. Furthermore, the assumption that a higher dosage would result in better image quality was analysed by using the different acquisition scanner modes. We scanned the acetabulum (n=4) and iliosacral joints (n=4) of two human cadavers with a conventional CT and with two mobile cone beam CT scanners (Siemens Arcadis Orbic 3D and Ziehm Vision Vario 3D). With the two cone beam CT scanners (3D-BV), we used 6 different acquisition modes with different radiation dosages. The axial views of all scans were exported and blinded. Subsequently, the images were evaluated by 7 medical doctors with regard to identifiability of cortical structures (acetabular joint, fovea capitis femoris, cortical bone of the femur head, iliosacral joint, and sacral foramina), and the quality of the cancellous structure of the femur head. The evaluation was performed on axial views by using a defined five-point score. The interrater quality was statistically analysed according to Cohen with the kappa coefficient. In addition, the Wilcoxon test was used to identify significances between the 21 paired results of the evaluators. For determination of the signal-to-noise ratio, a Catphan 600 reference block with two different test elements (Teflon, PMP) was used. Overall, the image quality of the conventional CT scans received the best score. Comparing the two 3D cone beams, the image quality of the Siemens Arcadis Orbic 3D in high-dosage mode received the best score (median: 2.40), the Ziehm Vision Vario 3D in low-dose mode without large patient key received the lowest score (median: 3.16). The differences in the 21 paired results of the two different acquisition modes were significant in 17 cases (p < 0.05) but the size of difference when comparing the different acquisition modes was almost always small. The interobserver agreement in one acquisition mode was low (kappa 0.008-0.134). The overall evaluation results of the same acquisition mode diverged by up to 2 score points. We noted a higher signal-to-noise ratio in the high dosage mode than in the low dosage mode. When using intraoperative 3D imaging with the cone beam CT technique for pelvic injury, image acquisition in low-dose mode is adequate in terms of signal-to-noise ratio and image quality. The image quality does not correlate linearly with a higher radiation dosage. Therefore, the pelvic trauma surgeon using this technique is encouraged to gather his own experience with low dose modes thereby reducing patient radiation exposure.

Solid-State SPECT technology: fast and furious

This traditionaldesign uses a thallium-doped sodium iodine crystalwhich scintillates in response to gamma photons, pro-ducing weak flash of light, coupled with a set ofphotomultiplier tubes which detect the fluorescent flash.A parallel-hole collimator filters the incident gammarays so that only those traveling approximately parallelto a specified direction are allowed through. This designof the conventional gamma camera suffers from severalmajor limitations, compromising its performance. Thephoton energy resolution is limited due to the physicalcharacteristics of the NaI crystal and photomultipliers,while the spatial resolution is reduced due to the geo-metric characteristics of the collimator and limitednumber of photomultipliers. The sensitivity of thecamera system is very low since the low-energy high-resolution collimator attenuates the overwhelmingmajority ([99.9%) of the incident photons. Thesetechnological limitations lead to relatively a largeamount of administered radiation doses, and/or pro-longed imaging time. Furthermore, the photomultipliertube technology results in a large, bulky camera head,requiring large laboratory space and dictating inconve-nient patient position.A major aim in nuclear cardiology to date has beento achieve reducing patient radiation exposure andimaging time, while improving image quality and thusdiagnostic precision. The use of dual-detector SPECTcameras resulted in 50% or greater reduction in imagingtime, and the use of iterative reconstruction algorithmswith resolution recovery provided additional reductionin acquisition time, without compromising resolution.

SU‐GG‐J‐04: Determination of Tumor Volume Using a Joint Motion‐PVE Correction Technique in PET/CT Imaging

Objective: 4D‐CT has been used to determine the tumor volume (TV) for lung/thoracic radiation therapy treatment planning primarily due to its ability to detect the tumor motion extent and trajectory. However, 4‐D CT is usually characterized by high patient radiation exposure. The objective of this abstract is to propose and evaluate an approach that relies on a single static PET/CT scan than can determine the TV by simultaneously correcting for respiratory motion artifact and partial volume effect (PVE) thereby eliminating the need for 4D‐CT and reducing patient exposure.Materials and Methods: The proposed joint correction approach incorporates a model of motion blurring, PVE and object size/shape. A motion blurring kernel (MBK) is then estimated from the deconvolution of the joint model while the TV is derived from convolving the MBK by the object size/shape obtained from the CT image. To test this technique, two studies were performed using 2 spheres of different sizes moving in a 2cm 1D‐sinusoidal and 2D‐circular waveforms respectively. In both cases, a 4D‐CT and a PET/CT of the 2 spheres were acquired. For both studies, the TV from the proposed technique was compared to the maximum‐intensity projection (MIP) volume of the 4D‐CT. Also a Dice coefficient of the two volumes was calculated. Results: The TV of the proposed technique was on average 3% different from the MIP volume. The average Dice coefficient was 0.87. The motion trajectory derived from the proposed technique is continuous while that of the 4D‐CT is discrete. Conclusion: Using this approach, a single static PET/CT can replace a 4D‐CT to determine the TV. This approach also has the ability to determine the tumor motion extent and trajectory and has the added advantage of reducing patient radiation exposure and determining the tumor locale probability (or MBK) compared to 4D‐CT.

Effect of Reduced Radiation CT Protocols on the Detection of Renal Calculi

To determine the effect of reduced radiation (tube charge, measured as milliamperes per second) protocols on the sensitivity and specificity of multidetector computed tomography (CT) in the detection of renal calculi. This Health Insurance Portability and Accountability Act-compliant human cadaveric study was approved by the Department of Anatomic Pathology with strict adherence to the university policy for handling donor specimens. Three to five renal stones (range, 2.0-4.0 mm) were randomly placed in 14 human cadaveric kidneys and scanned with a 16-detector CT scanner at 100, 60, and 30 mAs while maintaining other imaging parameters as constant. Following acquisition, images were reviewed independently by two radiologists who were blinded to the location and presence of renal calculi. Interobserver agreement was measured with kappa statistics. The McNemar test was used to compare the sensitivity and specificity between different radiation settings for each reader. Specificity for both readers ranged from 105 (0.95; 95% confidence interval [CI]: 0.90, 0.99) to 109 (0.99; 95% CI: 0.95, 1.0) of 110 without significant differences between 30 and 60 mAs to the standard 100 mAs (P = .500 to >.999). Sensitivity ranged from 42 (0.74; 95% CI: 0.60, 0.84) to 48 (0.84; 95% CI: 0.72, 0.93) of 57, also without significant differences (P = .070 to >.999). When renal calculi detection rates were analyzed by size, 3.0-4.0-mm stones were detected well at all tube charge settings, ranging from 86%-90% (n = 21 for 3.0-mm stones) to 95%-100% (n = 19 for 4.0-mm stones). However, 2.0-mm stones were poorly detected at all tube charge settings (29%-59%; 5-10 of 17). Overall interobserver agreement for stone detection was excellent, with kappa = 0.862. Decreasing the tube charge from 100 to 30 mAs resulted in similar detection of renal stones while reducing patient radiation exposure by as much as 70%. Multidetector CT scanning parameters should be tailored to minimize radiation exposure to the patients while helping detect clinically significant renal stones.

An alternative method to match planned and achieved positions of implants, after virtual planning using cone-beam CT data and surgical guide templates – A method reducing patient radiation exposure (part I)

The present study describes a new method of evaluating the precision of surgically placed dental implants compared after virtual planning of implant positions using cone-beam computed tomography (CT) data and surgical guide templates. This method reduces radiation exposure for patients participating in scientific studies. Twenty-three implants in 10 patients with a unilateral free-end gap in the mandible (Kennedy Class II) were evaluated. After three-dimensional planning of implant position, the implant bed was prepared with a surgical guide template and transmucosal drilling. Preoperative cone-beam CT images were matched with postoperative images of the master cast with implant replicas. Deviations between planned and achieved positions were measured in position and axis. On average, the match between planned and placed implant axis was within 4.2 degrees (range, 0.0-10.0). The mean difference in distance at the implant shoulder was 0.9 mm (range, 0.0-4.5). The mean difference in distance at the implant apex was 0.6mm (range, 0.0-2.7) in the lateral/medial direction and 0.9 mm (range, 0.0-3.4) in the anterior/posterior direction. This alternative matching method provides reliable postoperative evaluation of differences in position and axis of planned and placed implants while reducing patient radiation exposure.

Linear Accuracy of Cone Beam CT Derived 3D Images

To compare the in vitro reliability and accuracy of linear measurements between cephalometric landmarks on cone beam computed tomography (CBCT) 3D volumetric images with varying basis projection images to direct measurements on human skulls. Sixteen linear dimensions between 24 anatomic sites marked on 19 human skulls were directly measured. The skulls were imaged with CBCT (i-CAT, Imaging Sciences International, Hatfield, Pa) at three settings: (a) 153 projections, (b) 306 projections, and (c) 612 projections. The mean absolute error and modality mean (+/- SD) of linear measurements between landmarks on volumetric renderings were compared to the anatomic truth using repeated measures general linear model (P < or = .05). No difference in mean absolute error between the scan settings was found for almost all measurements. The average skull absolute error between marked reference points was less than the distances between unmarked reference sites. CBCT resulted in lower measurements for nine dimensions (mean difference range: 3.1 mm +/- 0.12 mm to 0.56 mm +/- 0.07 mm) and a greater measurement for one dimension (mean difference 3.3 mm +/- 0.12 mm). No differences were detected between CBCT scan sequences. CBCT measurements were consistent between scan sequences and for direct measurements between marked reference points. Reducing the number of projections for 3D reconstruction did not lead to reduced dimensional accuracy and potentially provides reduced patient radiation exposure. Because the fiducial landmarks on the skulls were not radio-opaque, the inaccuracies found in measurement could be due to the methods applied rather than to innate inaccuracies in the CBCT scan reconstructions or 3D software employed.

Subjective evaluation of a novel method of dose reduction by optical re-exposure of conventional radiographs – A multi-observer region of interest evaluation in an animal model

A procedure previously been described that has an effect on the image quality and radiation dose of conventional radiographs already at the time of acquisition [Paech A, Schulz AP, Hahlbrauck B, Kiene J, Wenzl ME, Jürgens C. Physical evaluation of a new technique for X-ray dose reduction: measurement of signal-to-noise ratio and modulation transfer function in an animal model. Physica Medica 23 (2007):33–40]. This development is using X-ray sensitization by optical re-exposure. Aim of this study was to establish if the results of optical re-exposure measured with SNR and MTF also meant that the subjective quality of 50% dose-reduced and re-exposed radiographs of bony structures was equal or better than conventional full dose radiographs of the same area. Freshly slaughtered anterior shoulders of lambs served as the animal model. A comminuted fracture in the middle of the shaft was artificially produced. After taking a normal exposed reference image, dose-reduced, five underexposed images were prepared. These underexposed X-rays were then optically re-exposed for a defined period of time before development. The subjective changes in the image quality (information loss or gain) of the images were compared to the reference image and evaluated by 16 physicians with large experience in diagnosis of orthopedic radiographs. The evaluation of the observers scoring showed a significant decrease in the subjective image quality regarding the detail recognition in all images apart from the images re-exposed for 60 s. In conclusion, there is a possibility of reducing the collective radiation dose whilst keeping a high degree of diagnostic reliability. Film sensitization provides a technically simple and inexpensive procedure, which can be easily integrated into common film development processes and could considerably reduce patient radiation exposure as well as improve image quality and thus detail recognition.

Changes in Left Atrial and Pulmonary Venous Anatomy During Respiration

The possibility of integrating 3D models of the left atrium (LA) and pulmonary veins (PVs) in 3D mapping systems has recently provided a detailed anatomic reference for electrophysiologists performing atrial fibrillation (AF) ablations. Single-breathhold contrast-enhanced computed tomography (CT) or MRI images are reconstructed to a static 3D surface and registered to the LA geometry acquired by a roving catheter during the procedure. Respiratory changes in LA and PV anatomy, however, can reduce registration accuracy, especially when preprocedural CT images are acquired during inspiration.1 A 46-year-old man was referred for catheter ablation of drug-resistant paroxysmal AF. One day before the procedure, 64-slice cardiac CT was performed during both held inspiration and end-expiration. Images were not gated to the cardiac cycle to reduce patient radiation exposure. Nonrigid image registration2 between inspiratory and expiratory data sets with custom software resulted in a dynamic 3D (ie, 4D) sequence of the combined changes …

SU‐FF‐P‐07: Monitor and Reducing Patient Radiation Exposure From Fluoroscopically‐Guided Procedures in a Teaching Hospital

Purpose: Radiation dosimetry information from fluoro‐guided procedures was monitored timely for patient safety and for training of residents. Methods: Fluoro‐guided procedures were regularly conducted in our hospital‐based radiology core area (R/F rooms for GI, BE and other procedures), operating rooms, radiology special procedure suites, cardiac catheterization labs, and out‐patient clinics (ambulatory surgery, orthopedics, pain management, urodynomics, etc). Quality control and patient dosimety programs were managed by medical physicists. Results: Records on fluoro times/techniques for all procedures were reviewed on daily basis, and results discussed with respective attendings/residents who performed the procedure. Analysis of accrued data showed that all residents, after a learning period, were able to complete a general procedure in less than 5 minutes fluoro time. Interventional procedures were found to have some patient exposures at high radiation doses. Conclusions: Vigilant monitoring and closely interacting with practicing physicians and technologists were essential in helping to improve a physician's technique toward reducing fluoro times necessary. Additional attention was warranted to patient exposure in interventional procedures since some high doses were found.

Simultaneous PET/MR will replace PET/CT as the molecular multimodality imaging platform of choice

Suggestions for topics suitable for these Point/Counterpoint debates should be addressed to Colin G. Orton, Professor Emeritus, Wayne State University, Detroit: ortonc@comcast.net. Persons participating in Point/Counterpoint discussions are selected for their knowledge and communicative skill. Their positions for or against a proposition may or may not reflect their personal opinions or the positions of their employers.

Short communication: staff dose reduction during coronary angiography using low framing speed.

Radiation exposure of cardiac catheterization laboratory staff is a known occupational hazard, and efforts are made to obtain dose levels which are "as low as reasonably achievable". This study assessed the reduction in staff radiation exposure using cine framing at 12.5 f s-1 during coronary cineangiography, instead of 25 f s-1. Thermoluminescent dosemeters were used to measure equivalent dose at several sites for the operator, nurse assistant, and X-ray technician during 15 procedures at both frame rates. Patient-related and procedure-related variables were similar in the two groups of examinations. Mean equivalent dose absorbed (microSv) at the left side of the forehead was reduced by 61%, 60% and 36%, for the operator, nurse assistant and X-ray technician, respectively. With use of the lower frame rate similar reductions by 42%, 62% and 62% were measured at the thyroid level, and by 51%, 40% and 61% at the mid-thorax level. Cinefilming at low frame rates during coronary arteriography allows a substantial X-ray dose reduction at all body sites for all staff. Use of lower frame rates wherever possible is of special interest since it may also reduce patient radiation exposure.

Patient exposure requirements for high contrast resolution in digital radiographic systems.

The contrast resolution of modern digital radiographic equipment is primarily limited by quantum mottle. The derivation of the contrast resolution of a system as a function of radiation exposure is presented. Calculations based on this derivation show that achieving 0.8% contrast resolution (128 meaningful gray levels) with 1-mm spatial resolution may require a patient exposure of 1.7 rad (1.7 cGy) per image of a thick body part (20 cm tissue). Acceptable clinical studies often can be obtained with only 5% contrast resolution (20 meaningful shades of gray), but even this level of contrast may require a patient exposure of nearly 90 mrad (0.9 mGy) per image. A comparison of three commonly used methods of reducing patient radiation exposure (pulsed imaging, temporal averaging, and recursive filtering) shows that, in theory, a pulsed system achieves the highest contrast resolution for the same total exposure.