Quality management, quality assurance, and quality control in medical physics.

The historic and ongoing evolution of the practice, technology, terminology, and implementation of programs related to quality in the medical radiological professions has given rise to the interchangeable use of the terms Quality Management (QM), Quality Assurance (QA), and Quality Control (QC) in the vernacular. This White Paper aims to provide clarification of QM, QA, and QC in medical physics context and guidance on how to use these terms appropriately in American College of Radiology (ACR) Practice Parameters and Technical Standards, generalizable to other guidance initiatives. The clarification of these nuanced terms in the radiology, radiation oncology, and nuclear medicine environments will not only boost the comprehensibility and usability of the Medical Physics Technical Standards and Practice Parameters, but also provide clarity and a foundation for ACR's clinical, physician-led Practice Parameters, which also use these important terms for monitoring equipment performance for safety and quality. Further, this will support the ongoing development of the professional practice of clinical medical physics by providing a common framework that distinguishes the various types of responsibilities borne by medical physicists and others in the medical radiological environment. Examples are provided of how QM, QA, and QC may be applied in the context of ACR Practice Parameters and Technical Standards.

AAPM Medical physics practice guideline 15.A: Peer review in clinical physics.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines: Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. While must is the term to be used in the guidelines, if an entity that adopts the guideline has shall as the preferred term, the AAPM considers that must and shall have the same meaning. Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.

Left Ventricular Function Changes Induced by Moderate Hypothermia Are Rapidly Reversed After Rewarming-A Clinical Study.

OBJECTIVES: Targeted temperature management (32-36°C) is used for neuroprotection in cardiac arrest survivors. The isolated effects of hypothermia on myocardial function, as used in clinical practice, remain unclear. Based on experimental results, we hypothesized that hypothermia would reversibly impair diastolic function with less tolerance to increased heart rate in patients with uninsulted hearts. DESIGN: Prospective clinical study, from June 2015 to May 2018. SETTING: Cardiothoracic surgery operation room, Oslo University Hospital. PATIENTS: Twenty patients with left ventricular ejection fraction greater than 55%, undergoing ascending aorta graft-replacement connected to cardiopulmonary bypass were included. INTERVENTIONS: Left ventricular function was assessed during reduced cardiopulmonary bypass support at 36°C, 32°C prior to graft-replacement, and at 36°C postsurgery. Electrocardiogram, hemodynamic, and echocardiographic recordings were made at spontaneous heart rate and 90 beats per minute at comparable loading conditions. MEASUREMENTS AND MAIN RESULTS: Hypothermia decreased spontaneous heart rate, and R-R interval was prolonged (862 ± 170 to 1,156 ± 254 ms, p < 0.001). Although systolic and diastolic fractions of R-R interval were preserved (0.43 ± 0.07 and 0.57 ± 0.07), isovolumic relaxation time increased and diastolic filling time was shortened. Filling pattern changed from early to late filling. Systolic function was preserved with unchanged myocardial strain and stroke volume index, but cardiac index was reduced with maintained mixed venous oxygen saturation. At increased heart rate, systolic fraction exceeded diastolic fraction (0.53 ± 0.05 and 0.47 ± 0.05) with diastolic impairment. Strain and stroke volume index were reduced, the latter to 65% of stroke volume index at spontaneous heart rate. Cardiac index decreased, but mixed venous oxygen saturation was maintained. After rewarming, myocardial function was restored. CONCLUSIONS: In patients with normal left ventricular function, hypothermia impaired diastolic function. At increased heart rate, systolic function was subsequently reduced due to impeded filling. Changes in left ventricular function were rapidly reversed after rewarming.

Randomized, open-label, crossover trial comparing the pharmacokinetic profile of a novel oral aspirin solution and a chewed aspirin tablet.

OBJECTIVES: The primary objective of this study was to assess the pharmacokinetic profiles of acetylsalicylic acid (ASA) and salicylic acid (SA) after administration of two different formulations of aspirin under fasting and fed conditions. MATERIALS AND METHODS: The study was a randomized, open-label, parallel-group, 2-arm crossover study conducted at a single center. Healthy subjects were randomized to receive 300 mg of aspirin in either a 15-mL oral solution (pre-packaged vial containing powder and solvent that are combined at the time of administration) or a single solid tablet to be chewed and swallowed with 150 mL of water. Treatment visits were separated by a 10-day wash-out period. RESULTS: At 3 minutes, ASA concentrations for the oral solution fed state and fasting state arms exceeded those for the chewed tablet (fed 299 vs. 139 ng/mL; fasting 356 vs. 204 ng/mL). Compared to the chewed tablet, the mean plasma ASA concentration was 74% greater with the oral solution under fasting conditions, and 115% greater under fed conditions. Similarly, at 3 minutes, the mean SA plasma concentration with the oral solution under fed and fasting conditions exceeded those for the chewed tablet (fed 310 vs. 160 ng/mL; fasting 330 vs. 185 ng/mL). Under fasting conditions, the mean plasma ASA AUC0-last, with the oral solutions was 168,076.8 min.ng/mL compared to 163,726.3 min.ng/mL with the chewed tablet. Under fed conditions, the mean plasma ASA AUC0-last, with the oral solutions was 179,116.7 min.ng/mL compared to 164,704.3 min.ng/mL with the chewed tablet. CONCLUSION: This phase 1 study showed that use of an aspirin oral solution provided more rapid exposure to higher plasma concentration levels of ASA and SA than chewing a solid tablet.

Open chest and pericardium facilitate transpulmonary passage of venous air emboli.

BACKGROUND: Transpulmonary passage of air emboli can lead to fatal brain- and myocardial infarctions. We studied whether pigs with open chest and pericardium had a greater transpulmonary passage of venous air emboli than pigs with closed thorax. METHODS: We allocated pigs with verified closed foramen ovale to venous air infusion with either open chest with sternotomy and opening of the pleura and pericardium (n = 8) or closed thorax (n = 16). All pigs received a five-hour intravenous infusion of ambient air, starting at 4-6 mL/kg/h and increased by 2 mL/kg/h each hour. We assessed transpulmonary air passage by transesophageal M-mode echocardiography and present the results as median with inter-quartile range (IQR). RESULTS: Transpulmonary air passage occurred in all pigs with open chest and pericardium and in nine pigs with closed thorax (56%). Compared to pigs with closed thorax, pigs with open chest and pericardium had a shorter to air passage (10 minutes (5-16) vs. 120 minutes (44-212), P < .0001), a smaller volume of infused air at the time of transpulmonary passage (12 mL (10-23) vs.170 mL (107-494), P < .0001), shorter time to death (122 minutes (48-185) vs 263 minutes (248-300, P = .0005) and a smaller volume of infused air at the time of death (264 mL (53-466) vs 727 mL (564-968), P = .001). In pigs with open chest and, infused air and time to death correlated strongly (r = 0.95, P = .001). CONCLUSION: Open chest and pericardium facilitated the transpulmonary passage of intravenously infused air in pigs.

Modeling of kyphoplasty cement for accurate dose calculations.

We have determined the optimal method for modeling kyphoplasty cement to enable accurate dose calculations in the Eclipse treatment planning system (TPS). The cement studied (Medtronic Kyphon HV-R®) consists of 30% Barium, 68% polymethylmethacrylate (PMMA), and 2% benzoyl peroxide, formulated to be radiopaque with kV imaging systems. Neither Barium nor PMMA have a high physical density, resulting in different interaction characteristics for megavoltage treatment beams compared to kV imaging systems. This can lead to significant calculation errors if density mapping is performed using a standard CT number to density curve. To properly characterize the cement for dose calculation, we 3D printed a hemi-cylindrical container to fit adjacent to a micro-chamber insert for an anthropomorphic phantom, and filled the container with Kyphon cement. We CT scanned the combination, modeled the cement with multiple material assignments in the TPS, designed plans with different field sizes and beam geometry for five photon modes, and measured the doses for all plans. All photon energies show significant error in calculated dose when the cement is modeled based on the CT number. Of the material assignments we evaluated, polytetrafluoroethylene (PTFE) showed the best overall agreement with measurement. Calculated and measured doses agree within 3.5% for a 340-degree arc technique (which averages transmission and scatter effects) with the Acuros XB algorithm and PTFE as the assigned material. To confirm that PTFE is a reasonable substitute for kyphoplasty cement, we performed measurements in a slab phantom using rectangular inserts of cement and PTFE, showing average agreement of all photon modes within 2%. Based on these findings, we conclude that the PTFE material assignment provides acceptable dose calculation accuracy for the AAA and Acuros XB photon algorithms in the Eclipse TPS. We recommend that the cement be delineated as a structure and assigned the PTFE material for accurate dose calculation.

AAPM medical physics practice guideline 3.b.: Levels of supervision for medical physicists in clinical training.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines: (1) Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. (2) Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.

Safety and feasibility of dobutamine stress echocardiography in symptomatic high gradient aortic stenosis patients scheduled for transcatheter aortic valve implantation.

PURPOSE: We aimed to study the safety and feasibility of low-dose dobutamine stress echocardiography in a symptomatic high gradient aortic stenosis population scheduled for transfemoral transcatheter aortic valve implantation (TAVI) and to quantify left ventricular (LV) flow reserve. METHODS: Fifty patients underwent dobutamine stress echocardiography with 5 minutes increments of 5 µg/kg/min up to 20 µg/kg/min until the heart rate increased ≥20 beats/min from baseline or exceeded 100 beats/min. Other criteria for discontinuing the infusion were major adverse events: ventricular arrhythmia, persistent supraventricular arrhythmia, pulmonary edema, chest pain with significant ST-changes, or minor events: ST-changes, drop in systolic blood pressure >30 mmHg, mild chest pain, and/or dyspnea. LV flow reserve was defined as an increase in stroke volume ≥20% during the test. RESULTS: Of 50 patients, 45 completed the test according to protocol. No patient had major adverse event. Five patients experienced minor side effects: mild chest pain/dyspnea in three, self-terminating atrial flutter in one, and decrease in blood pressure in one. Significant LV flow reserve was observed in 20 patients (40%). CONCLUSION: Low-dose dobutamine stress test appeared safe and feasible patients with high gradient aortic stenosis, and showed LV flow reserve in a minority of them.

AAPM medical physics practice guideline 7.a.: Supervision of medical physicist assistants.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines: Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances. Approved by AAPM's Executive Committee May 28, 2019.

Hypofractionated Radiation Therapy for Localized Prostate Cancer: Executive Summary of an ASTRO, ASCO and AUA Evidence-Based Guideline.

PURPOSE: The aim of this guideline is to present recommendations regarding moderately hypofractionated (240-340 cGy per fraction) and ultrahypofractionated (500 cGy or more per fraction) radiation therapy for localized prostate cancer. METHODS AND MATERIALS: The American Society for Radiation Oncology convened a task force to address 8 key questions on appropriate indications and dose-fractionation for moderately and ultrahypofractionated radiation therapy, as well as technical issues, including normal tissue dose constraints, treatment volumes, and use of image guided and intensity modulated radiation therapy. Recommendations were based on a systematic literature review and created using a predefined consensus-building methodology and Society-approved tools for grading evidence quality and recommendation strength. RESULTS: Based on high-quality evidence, strong consensus was reached for offering moderate hypofractionation across risk groups to patients choosing external beam radiation therapy. The task force conditionally recommends ultrahypofractionated radiation may be offered for low- and intermediate-risk prostate cancer but strongly encourages treatment of intermediate-risk patients on a clinical trial or multi-institutional registry. For high-risk patients, the task force conditionally recommends against routine use of ultrahypofractionated external beam radiation therapy. With any hypofractionated approach, the task force strongly recommends image guided radiation therapy and avoidance of nonmodulated 3-dimensional conformal techniques. CONCLUSIONS: Hypofractionated radiation therapy provides important potential advantages in cost and convenience for patients, and these recommendations are intended to provide guidance on moderate hypofractionation and ultrahypofractionation for localized prostate cancer. The limits in the current evidentiary base-especially for ultrahypofractionation-highlight the imperative to support large-scale randomized clinical trials and underscore the importance of shared decision making between clinicians and patients.

Can we ablate liver lesions close to large portal and hepatic veins with MR-guided HIFU? An experimental study in a porcine model.

OBJECTIVES: Invasive treatment of tumors adjacent to large hepatic vessels is a continuous clinical challenge. The primary aim of this study was to examine the feasibility of ablating liver tissue adjacent to large hepatic and portal veins with magnetic resonance imaging-guided high-intensity focused ultrasound (MRgHIFU). The secondary aim was to compare sonication data for ablations performed adjacent to hepatic veins (HV) versus portal veins (PV). MATERIALS AND METHODS: MRgHIFU ablations were performed in six male land swine under general anesthesia. Ablation cells of either 4 or 8 mm diameter were planned in clusters (two/animal) adjacent either to HV (n = 6) or to PV (n = 6), with diameter ≥ 5 mm. Ablations were made using 200 W and 1.2 MHz. Post-procedure evaluation was made on contrast-enhanced MRI (T1w CE-MRI), histopathology, and ablation data from the HIFU system. RESULTS: A total of 153 ablations in 81 cells and 12 clusters were performed. There were visible lesions with non-perfused volumes in all animals on T1w CE-MRI images. Histopathology showed hemorrhage and necrosis in all 12 clusters, with a median shortest distance to vessel wall of 0.4 mm (range 0-2.7 mm). Edema and endothelial swelling were observed without vessel wall rupture. In 8-mm ablations (n = 125), heat sink was detected more often for HV (43%) than for PV (19%; p = 0.04). CONCLUSIONS: Ablations yielding coagulative necrosis of liver tissue can be performed adjacent to large hepatic vessels while keeping the vessel walls intact. This indicates that perivascular tumor ablation in the liver is feasible using MRgHIFU. KEY POINTS: • High-intensity focused ultrasound ablation is a non-invasive treatment modality that can be used for treatment of liver tumors. • This study shows that ablations of liver tissue can be performed adjacent to large hepatic vessels in an experimental setting. • Liver tumors close to large vessels can potentially be treated using this modality.

Reduced inflammatory response by transcatheter, as compared to surgical aortic valve replacement.

OBJECTIVES: The inflammatory response to on-pump cardiac surgery is well known. Systemic inflammatory response syndrome after transcatheter valve implantation (TAVI) has been reported. The objective of this study was to study the inflammatory response during TAVI, and compare with the response during surgical aortic valve replacement. METHODS: Eighteen patients undergoing transcatheter implantation, either by a transfemoral (n = 9) or transaortal (n = 9) approach were compared with eighteen patients admitted for surgical replacement. Blood samples per- and postoperatively were analysed for C3bc, terminal complement complex, myeloperoxidase, macrophage inflammatory protein-1ß, monocyte chemo-attractant peptide-1, eotaxin, IL-6 and troponin-T. All markers were measured at defined time points and the areas under the curve were compared. RESULTS: Activation of complement, granulocytes, monocytes and eosinophils were significantly lower in the transcatheter group as compared to the surgical group (<0.01). There was no difference in generation of troponin T and IL-6. A small difference in complement activation was observed between the transfemoral and transaortal placement of TAVI. There was no significant difference in clinical outcomes between the TAVI and surgical groups. DISCUSSION: Activation and release of inflammatory markers was significantly less during with TAVI as compared to SAVR, particularly for markers associated with extracorporeal circulation. TAVI and SAVR generated the same degree of IL-6 and troponin T, indicating that the burden on the myocardial tissue was the same. Clinical Trials: Gov ID: NCT03074838 Unique protocol ID: 2012/7919.

Development of clinically relevant QA procedures for the BrainLab ExacTrac imaging system.

PURPOSE: The aim of this study was to develop Quality Assurance procedures for the BrainLab ExacTrac (ET) imaging system following the TG 142 recommendations for planar kV imaging systems. MATERIALS AND METHODS: A custom-designed 3D printed holder was used to position the Standard Imaging QCkV-1 phantom at isocenter, facing the ET X ray tubes. The linac's light field (collimator at 45°) was used to position the phantom holder. The ET images were exported to ARIA where geometric distortion was checked. The DICOM images were analyzed in the PIPSpro software. The following parameters were recorded (technique 80 kV/2mAs): spatial resolution (Modulated Transfer Function (MTF) F50/F40/F30), contrast-to-noise ratio (CNR), and noise. A baseline was generated for future image analysis. Beam quality and exposure were measured using the Unfors R/F detector. Using a rod holder, the detector was placed at isocenter, facing each ET X-ray tube. The measurements were performed for all preset protocols ranging from cranial low (80 kV/6.3 mAs) to abdomen high (145 kV/25 mAs). The total exposure was converted to dose. RESULTS AND DISCUSSION: The image quality parameters were close for the two tubes. A common baseline was therefore generated. The average baseline values (both tubes, both images/tube) were 1.06/1.18/1.30, 1.32, and 67.3 for the MTF F50/F40/F30, noise, and CNR respectively. The procedure described here was used for another 24 sets. Using a positioning template and 3D printed phantom holder, experimental reproducibility has been acceptably high. The measured phantom dimensions were within 1 mm from the nominal values. The measured kV values were within 2% of the nominal values. The exposure values for the two tubes were comparable. The range of total measured dose was 0.099 mGy (cranial low) to 1.353 mGy (abdomen high). CONCLUSIONS: A reliable process has been implemented for QA of the ET imaging system by characterizing the system's performance at isocenter, consistent with clinical conventions.

AAPM-RSS Medical Physics Practice Guideline 9.a. for SRS-SBRT.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines: Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances. Approved by AAPM Professional Council 3-31-2017 and Executive Committee 4-4-2017.

Does therapeutic hypothermia during extracorporeal cardiopulmonary resuscitation preserve cardiac function?

BACKGROUND: Extracorporeal cardiopulmonary resuscitation (E-CPR) is increasingly used as a rescue method in the management of cardiac arrest and provides the opportunity to rapidly induce therapeutic hypothermia. The survival after a cardiac arrest is related to post-arrest cardiac function, and the application of therapeutic hypothermia post-arrest is hypothesized to improve cardiac outcome. The present animal study compares normothermic and hypothermic E-CPR considering resuscitation success, post-arrest left ventricular function and magnitude of myocardial injury. METHODS: After a 15-min untreated ventricular fibrillation, the pigs (n = 20) were randomized to either normothermic (38 °C) or hypothermic (32-33 °C) E-CPR. Defibrillation terminated ventricular fibrillation after 5 min of E-CPR, and extracorporeal support continued for 2 h, followed by warming, weaning and a stabilization period. Magnetic resonance imaging and left ventricle pressure measurements were used to assess left ventricular function pre-arrest and 5 h post-arrest. Myocardial injury was estimated by serum concentrations of cardiac TroponinT and Aspartate transaminase (ASAT). RESULTS: E-CPR resuscitated all animals and the hypothermic strategy induced therapeutic hypothermia within minutes without impairment of the resuscitation success rate. All animals suffered a severe global systolic left ventricular dysfunction post-arrest with 50-70% reductions in stroke volume, ejection fraction, wall thickening, strain and mitral annular plane systolic excursion. Serum concentrations of cardiac TroponinT and ASAT increased considerably post-arrest. No significant differences were found between the two groups. CONCLUSIONS: Two-hour therapeutic hypothermia during E-CPR offers an equal resuscitation success rate, but does not preserve the post-arrest cardiac function nor reduce the magnitude of myocardial injury, compared to normothermic E-CPR. Trial registration FOTS 4611/13 registered 25 October 2012.

Varian HDR surface applicators - commissioning and clinical implementation.

The purpose of this study was to validate the dosimetric performance of Varian surface applicators with the source vertically positioned and develop procedures for clinical implementation. The Varian surface applicators with the source vertically positioned provide a wide range of apertures making them clinically advantageous, though the steep dose gradient in the region of 3-4 mm prescription depth presents multiple challenges. The following commissioning tests were performed: 1) verification of functional integrity and physical dimensions; and 2) dosimetric measurements to validate data provided by Varian as well as data obtained using the Acuros algorithm for heterogeneity corrected dose calculation. A solid water (SW) phantom was scanned and the Acuros algorithm was used to compute the dose at 5 mm depth and at surface for all applicators. Two sets of reference dose measurements were performed, with the source positioned at (i) -10 mm and (ii) -15 mm from the center of the first nominal dwell position. Measurements were taken at 5 mm depth in a SW phantom and in air at the applicator surface. The results were then compared to the vendor's data and to the Acuros calculated dose. Relative dose measurements using Gafchromic films were taken at a depth of 4 mm in SW. Percent depth ionization (PDI) measurements using ion chamber were performed in SW. The profiles generated from film measurements and the PDI plots were compared with those computed using the Acuros algorithm and vendor's data, when available. Preliminary leakage tests were performed using optically stimulated luminescence dosimeters (OSLDs) and the results were compared with Acuros predictions. All applicators were found to be functional with physical dimensions within 1 mm of specifications. For scenario (ii) measurements taken in SW at 5 mm depth and in air at the surface of each applicator were within 10% and 4% agreement with vendor's data, respectively. Compared with Acuros predictions, these measurements were within 6% and 5%, respectively. Measurements taken for scenario (i) showed reduced agreement with both the vendor's data as well as the Acuros calculations, especially when using the 10 mm applicator. The full widths of the measured dose profiles were within 2 mm of those predicted by Acuros at the 90% dose level. The PDI plots and measured leakage dose were in good agreement with vendor's data and Acuros predictions. Based on the dosimetric results, a quality assurance program and procedures for clinical implementation were developed. Treatment planning will be performed using scenario (ii). The 10mm applicator will not be released for clinical use. A prescription depth of 4mm is recommended, to ensure full coverage at 3 mm and a minimum dose of 90% of prescribed dose at 4 mm depth.

Postoperatively increased serum alanine aminotransferase level is closely associated with mortality after cardiac surgery.

BACKGROUND: Hepatic biomarkers are often not assessed routinely after cardiac surgery. Alanine aminotransferase (ALT) has become the primary biomarker of any type of liver injury. Our purpose was to study the prognostic value of serum ALT in early and late mortality. METHODS: Patients subjected to any type of cardiac operation from January 1999 through December 2010 were studied. According to postoperative maximum ALT level, four groups were created: group 1 = ALT ≤ 50 U/L (n = 8,669), group 2 = ALT 50 to 150 U/L (n = 3,055), group 3 = ALT 151 to 500 U/L (n = 248), and group 4 = ALT > 500 U/L (n = 50). Cox multivariate modeling was used for survival analysis. RESULTS: Patients in groups 3 and 4 had increased 30-day mortality (hazard ratio [HR] = 8.07 [4.15-15.69], p < 0.001 and HR = 19.07 [9.88-36.80], p < 0.001, respectively). Late mortality was increased for group 4 after final adjustments (HR = 1.87 [1.18-2.95], p = 0.007). CONCLUSION: Elevated postoperative ALT level (above 150 U/L) is closely associated with early mortality after cardiac surgery. ALT level above 500 U/L implies a substantial liver dysfunction with a considerable negative association on both early and late survival.

Transcatheter aortic valve implantation and intraoperative left ventricular function: a myocardial tissue Doppler imaging study.

OBJECTIVE: Transcatheter aortic valve implantation in patients turned down for surgical aortic valve replacement is a high-risk procedure. Severe aortic stenosis is associated with impaired left ventricular longitudinal motion, and myocardial peak systolic velocity is a measure of left ventricular function in these patients. The present study aimed to quantify the acute changes in left ventricular function during the procedure by using myocardial tissue Doppler imaging and transthoracic cardiac output measurements. DESIGN: Prospective observational study. SETTING: Tertiary care university hospital. PARTICIPANTS: 40 patients with severe aortic stenosis scheduled for transcatheter aortic valve implantation. INTERVENTIONS: Transesophageal 4-chamber and 2-chamber echocardiograms were performed immediately before and ~15 minutes after valve implantation. Longitudinal myocardial peak systolic velocity was obtained by tissue Doppler imaging from 8 basal segments and averaged. Cardiac output was measured by the lithium dilution method, and systemic vascular resistance index and stroke volume were calculated. MEASUREMENTS AND MAIN RESULTS: Longitudinal myocardial peak systolic velocity improved immediately after valve implantation, from -2.3±0.8 to -3.0±1.1 cm/sec (p<0.001); this represented an average increase of 31%±33%. Cardiac output increased from 3.2±0.8 L/min to 3.6±0.9 L/min (15%±33%; p = 0.04). This was due to increased heart rate (59±9 beats/min to 72±12 beats/min; p<0.001) and not to an improved stroke volume. Systemic vascular resistance index was reduced from 2,937±984 dynes*sec/cm(5)/m(2) to 2,436±730 dynes*sec/cm(5)/m(2) (p = 0.003). CONCLUSION: Intraoperative echocardiography tissue Doppler imaging detected immediate improvement in left ventricular long-axis motion after transcatheter aortic valve implantation. The method provided detailed information not obtainable by routine hemodynamic monitoring.