Increase In Patient Dose Research Articles

Similar Clinical Outcomes in Patients with Systemic Juvenile Idiopathic Arthritis and Adult-Onset Still's Disease Treated with Canakinumab: Bayesian and Population Model-Based Analyses.

IntroductionSystemic juvenile idiopathic arthritis (sJIA) and adult-onset Still’s disease (AOSD) represent pediatric and adult variants of the Still’s disease continuum. To determine whether clinical outcomes between patients with sJIA and AOSD were similar, Bayesian and population model-based analyses were conducted on endpoints from studies of canakinumab in both patient populations. The objective was to further support the efficacy of canakinumab in patients with AOSD.MethodsA Bayesian analysis of endpoints from a study of canakinumab in AOSD was conducted borrowing information from five pooled sJIA studies using a robust meta-analytic predictive (MAP) approach. Similarity of clinical outcomes across populations was fulfilled if the AOSD study posterior median fell within the 95% predicted credible interval for the outcome of interest, based on the pooled sJIA data. Population model-based analyses (pharmacokinetic [PK] and PK/pharmacodynamic [PKPD]) were conducted to compare the pharmacokinetics and exposure–response relationships between populations.ResultsThe AOSD study posterior medians for adapted American College of Rheumatology (ACR)30 response, continuous adapted ACR response, number of active joints, C-reactive protein, and absence of fever were within the 95% credible interval for the prediction of the MAP analysis from the pooled sJIA data, supporting the similarity in outcomes between patient populations. PK analysis demonstrated comparable exposure across sJIA age groups and patients with AOSD. PKPD relationships were consistent across patient populations. Analyses indicated that no therapeutic benefit can be expected from a dose increase in patients with AOSD.ConclusionThe analyses presented support the similarity of clinical outcomes following treatment with canakinumab in patients with sJIA and AOSD.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40744-021-00422-9.

Assessment of Thyroid Cancer Risk After Cervical Computed Tomography: The Impact of Bismuth Shielding

Background: Computed tomography (CT) is vastly applied in X-ray procedures because of its high quality in detecting the anatomical structures of the body. However, it leads to an increase in patient dose, resulting in carcinogenesis. In the head and neck CT, the thyroid is the most important at-risk organ. The aim of this study was to estimate thyroid cancer risk in cervical CT with and without a bismuth shield. Materials and Methods: After obtaining permission from the authors, data related to the thyroid dose of patients undergoing cervical CT in the study by Santos et al (2019) were used, and then thyroid cancer risk was calculated for different ages at exposure in male and female patients using the biological effects of the ionizing radiation (BEIR) VII model. Results: Using bismuth shielding reduced thyroid dose by 37% and 39% in male and female phantoms, respectively. Thyroid cancer estimation demonstrated that the risk was nearly two-fold in females compared to males. Finally, bismuth shielding reduced 40% of cancer risk, and it decreased in both genders by increasing age at exposure. Conclusion: According to our findings, excess relative risk (ERR) up to 0.06% was associated with cervical CT. Although ERR amounts were low, the effect of radiation on thyroid cancer risk should not be neglected. Accordingly, it is suggested that future trials use bismuth shielding to reduce thyroid cancer risk.

Initial data from an experiment to implement a safe procedure to perform PA erect chest radiographs for COVID-19 patients with a mobile radiographic system in a “clean” zone of the hospital ward

IntroductionWith the current Covid-19 pandemic, general wards have been converted into cohort wards for Covid-19 patients who are stable and ambulant. A 2-radiographer mobile radiography team is required to perform bedside Chest X-rays (CXR) for these patients. Hospital guidelines require both radiographers to be in full Personal Protective Equipment (PPE) throughout the image acquisition process and the mobile radiographic unit needs to be disinfected twice after each case. This affects the efficiency of the procedure and an increase usage of limited PPE resources. This study aims to explore the feasibility of performing mobile chest radiography with the mobile radiographic unit in a “clean” zone of the hospital ward. MethodsAn anthropomorphic body phantom was used during the test. With the mobile radiographic unit placed in a “clean” zone, the phantom and the mobile radiographic unit was segregated by the room door with a clear glass panel. The test was carried out with the room door open and closed. Integrated radiation level and patient dose were measured. A consultant radiologist was invited to review and score all the images acquired using a Barco Medical Grade workstation. The Absolute Visual Grading Analysis (VGA) scoring system was used to score these images. ResultsA VGA score of 4 was given to all the 40 test images, suggesting that there is no significant differences in the image quality of the images acquired using the 2 different methods. Radiation exposure received by the patient at the highest kV setting through the glass is comparable to the regular CXR on patient without glass panel at 90 kV, suggesting that there is no significant increase in patient dose. ConclusionThe result suggests that acquiring CXR with the X-ray beam attenuating through a glass panel is a safe and feasible way of performing CXR for COVID-19 patients in the newly converted COVID wards. This will allow the mobile radiographic unit as well as one radiographer to be completely segregated from the patient. Implications for practiceThis new method of acquiring CXR in an isolation facility set up requires a 2-Radiographer mobile radiography team, and is applicable only for patients who are generally well and not presented with any mobility issues. It is also important to note that a clear glass panel must be present in the barriers set up for segregation between the “clean” zone and patient zone in order to use this new method of acquiring CXR.

Efficacy of switching to bilastine, a histamine H1 receptor antagonist, in patients with chronic spontaneous urticaria (H1-SWITCH): study protocol for a randomized controlled trial

BackgroundChronic spontaneous urticaria (CSU) is characterized by the spontaneous appearance of wheals, angioedema, or both for > 6 weeks. Continuous treatment with H1-antihistamines is used as a first-line treatment for CSU. However, H1-antihistamine treatment leads to absence of symptoms in less than 50% of patients with CSU. Although Japanese guidelines for the diagnosis and treatment of urticaria recommend an increase in the H1-antihistamine dose or a switch to other H1-antihistamines, there is no evidence supporting a switch to other H1-antihistamines in patients with refractory CSU who are unresponsive to H1-antihistamines at the licensed dose.MethodsWe will conduct a multicenter, open-label, non-inferiority, randomized, parallel, comparison study to determine if the efficacy of bilastine 20 mg is not inferior to that of a twofold H1-antihistamine dose increase in patients with refractory CSU who are unresponsive to H1-antihistamines at the licensed dose. This study will be performed at 15 academic hospitals in Japan, and the administration period (increasing the H1-antihistamine dose twofold vs. switching to bilastine 20 mg) will be 7 days. Participants (n = 150) will be randomized to either an increased H1-antihistamine dose or a switch to bilastine 20 mg at a 1:1 ratio. The primary endpoint, mean of the total symptom score of 5–7 days after the intervention, will be evaluated. The secondary objective is to determine if the safety of bilastine 20 mg regarding somnolence is superior to that of a twofold dose increase of H1-antihistamines. This will be measured by a change in the Japanese version of the Epworth Sleepiness Scale from baseline to 7 days after starting the intervention.DiscussionThis multicenter, open-label, non-inferiority, randomized, parallel, comparison study will be, to our knowledge, the first well-designed clinical study to evaluate the efficacy of a switch to other H1-antihistamines in patients with refractory CSU who are unresponsive to H1-antihistamines at the licensed doses. This trial will provide evidence of the efficacy and safety of bilastine when treatment is switched in patients with refractory CSU who are unresponsive to H1-antihistamines at the licensed dose.Trial registrationJapan Registry of Clinical Trials (jRCT), jRCTs051180105. Registered on 8 March 2019.

Relationship of faecal calprotectin and long-term outcomes in Finnish patients with Crohn’s disease: retrospective multi-centre chart review study

Background and Aims: A retrospective non-interventional, multi-centre patient chart review study was conducted to investigate the association of faecal calprotectin (FC) 1 year (±2 months) after biological therapy initiation with composite event-free survival (CEFS) consisting of surgical procedures, corticosteroid initiation, treatment failure or dose increase in patients with Crohn’s disease (CD). In addition, the correlations of FC and other tests of disease activity were assessed.Materials and methods: Data on Finnish CD patients initiating a biological therapy between 2010 and 2016, were collected. The association of FC and CEFS was analysed with Kaplan-Meier and Cox proportional hazard modelling. The correlations were tested with Pearson’s test.Results: Biological therapy was initiated in 186 patients, of which 87 (46.8%) had FC results available at 1 year and 80 had follow-up exceeding 14 months. The characteristics of patients with and without FC results were similar. Patients with elevated FC (>250 µg/g) had a significantly increased risk of experiencing composite event (HR 3.4, 95% CI: 1.3–8.9; p = .013) when compared to patients with normal FC (FC ≤ 100). No such risk was observed in patients with intermediately increased FC level (100 µg/g < FC ≤ 250 µg/g) (HR 2.2 (95% CI: 0.8–6.2; p = .120). FC value had significant positive correlation with CRP, HBI and leukocyte values when measured at similar timepoints.Conclusions: Elevated level of FC approximately 1 year after the initiation of biological therapy was associated with an increased risk of either surgical procedures, corticosteroid initiation, treatment failure or dose increase (i.e. composite outcome) in patients with CD.

P6238Predictive factors for alirocumab dose increase in patients with hypercholesterolaemia and high cardiovascular risk: from the ODYSSEY COMBO I and II trials

P6238Predictive factors for alirocumab dose increase in patients with hypercholesterolaemia and high cardiovascular risk: from the ODYSSEY COMBO I and II trials

Predictive factors for alirocumab dose increase in patients with heterozygous familial hypercholesterolaemia

Aim: Alirocumab (a PCSK9 inhibitor) is prescribed at 75 and 150 mg doses every 2 weeks (Q2W). Data from the ODYSSEY FH I and II studies were used to explore determinants for alirocumab dose increase and compare LDL-C reduction at 24 weeks in patients with heterozygous familial hypercholesterolaemia (HeFH) who did and did not require dose increase.

Diagnostic Reference Levels of Adults CT-Scan Imaging in Cameroon: A Pilot Study of Four Commonest CT-Protocols in Five Radiology Departments

CT-scan is the most irradiating tool in diagnostic radiology. For 5% - 10% of diagnostic X-ray procedures, it is responsible for 34% of irradiation according to UNSCEAR. Patients radiation protection must therefore be increased during CT-scan procedures. This requires the rigorous application of optimization principle which imposes to have “diagnostic reference levels”. Objective: The aim of this study was to determine the diagnostic reference levels (DRLs) of the four most frequent CT-scans examinations of adults in Cameroon. Material and Method: It was a cross-sectional pilot study carried out from April to September 2015 in five health facilities using CT-scan in Cameroon. The studied variables were: patients age and sex, type of CT-scan examination (cerebral, chest, abdomino-pelvic, lumbar spine), Used of IV contrast (IV﹣/ IV+), acquisition length, time of tube rotation, voltage (kV), mAs, pitch, thickness of slices, CTDIvol and DLP. For each type of examination, at least 30 patients were included per center, consecutively on the randomly predetermined days. The DRL for each type of examination was defined as the 75th percentile of its PDL and CTDIvol. Results: Of the 696 examinations, 41.2% were cerebral, 26.9% abdomino-pelvic, 17.7% lumbar spine and 14.2% chest. The mean age of patients was 52 ± 15 years [20 - 90 years], 58.9% were 50 years and older. The sex-ratio was 1.26 (55.9% males). The CT machines were 4, 8 and 16 multidetectors. The 75th percentile of DLP or DRLs [standard deviation] was: [1150 ± 278 mGy·cm], [770 ± 477 mGy·cm], [720 ± 170 mGy·cm] and [715 ± 187 mGy·cm] respectively for cerebral, lumbar spine, abdominopelvic and chest CT-scans. Taking in consideration the number of detectors, the 75th percentile of the Dose-Length product decreased with the increase number of detectors for cerebral examinations but was the highest with 16 MDCT for the abdominopelvic, lumbar spine and chest CT-scans. For the chest and lumbar spine examinations, there was a significant increase in patient-dose with the increase in the number of detectors. Conclusion: Our DRLs values lie between the norms of some European countries and those of some African countries. There is remarquable variation in dose for the commonest CT-scans examinations in Cameroon, requiring then an optimization process from these determined DRLs and establishment of national DRLs. Special attention to optimization should be paid when using 16 MDCT.

SU-E-I-34: Evaluating Use of AEC to Lower Dose for Lung Cancer Screening CT Protocols

Purpose: The National Lung Screening Trial mandated manual low dose CT technique factors, where up to a doubling of radiation output could be used over a regular to large patient size range. Recent guidance from the AAPM and ACR for lung cancer CT screening recommends radiation output adjustment for patient size either through AEC or a manual technique chart. This study evaluated the use of AEC for output control and dose reduction. Methods: The study was performed on a multidetector helical CT scanner (Aquillion ONE, Toshiba Medical) equipped with iterative reconstruction (ADIR-3D), AEC was adjusted with a standard deviation (SD) image quality noise index. The protocol SD parameter was incrementally increased to reduce patient population dose while image quality was evaluated by radiologist readers scoring the clinical utility of images on a Likert scale. Results: Plots of effective dose vs. body size (water cylinder diameter reported by the scanner) demonstrate monotonic increase in patient dose with increasing patient size. At the initial SD setting of 19 the average CTDIvol for a standard size patient was ∼ 2.0 mGy (1.2 mSv effective dose). This was reduced to ∼1.0 mGy (0.5 mSv) at an SD of 25 with no noticeable reduction inmore » clinical utility of images as demonstrated by Likert scoring. Plots of effective patient diameter and BMI vs body size indicate that these metrics could also be used for manual technique charts. Conclusion: AEC offered consistent and reliable control of radiation output in this study. Dose for a standard size patient was reduced to one-third of the 3 mGy CTDIvol limit required for ACR accreditation of lung cancer CT screening. Gary Arbique: Research Grant, Toshiba America Medical Systems; Cecelia Brewington: Research Grant, Toshiba America Medical Systems; Di Zhang: Employee, Toshiba America Medical Systems.« less

Abstract P1-03-02: CYP2D6 intermediate metabolizers includes patient groups with distinct metabolic activity

Abstract Background: Tamoxifen is a selective estrogen receptor modulator that is the most commonly used and cost effective hormonal agent for pre-menopausal hormone-receptor positive breast cancer patients. CYP2D6 activity phenotype, which is classified by genotype, predicts the extent of metabolic activation of tamoxifen to endoxifen. We previously reported that increasing the daily dose to 40 mg/day in intermediate metabolizers (IMs), but not poor metabolizers (PMs), achieves target endoxifen concentrations, defined as that of extensive metabolizers (EMs) on 20 mg/day. There was substantial endoxifen variability in the IM phenotype group, which is composed of several discrete diplophenotypes (EM/IM, EM/PM, IM/IM, IM/PM). We enrolled a second, larger cohort of patients in order to determine whether these diplophenotypes should be combined into a single IM phenotype or segregated. Methods: 380 patients on tamoxifen ≥ 4 months and not on potent CYP2D6 inhibiting medications enrolled in Lineberger Comprehensive Cancer Center (LCCC) trial 0801. Genotyping was performed using the Amplichip® CYP450 test (Roche Diagnostics) for CYP2D6, followed by systematic assignment of phenotype based on diplophenotype. Tamoxifen was increased from 20 to 40 mg/day in PMs and IMs. Endoxifen concentrations in IM diplophenotypes were compared with EM/EMs and PM/PMs at baseline and at 4 months (after dose increase in patients with IM and PM phenotypes). Results: After exclusion of UM patients and patients missing endoxifen data at baseline and/or 4 months, 295 patients were included in this analysis. At baseline the EM/IM patients had similar endoxifen level to the EM/EM patients while the IM/IM and IM/PM patients had similar levels to the PM/PMs. After 4 months on 40 mg/day the endoxifen concentrations in EM/IM patients were significantly greater than EM/EMs; EM/PM and IM/IM patients were similar to EM/EMs; but IM/PM patients remained significantly lower than EM/EMs and similar to PM/PMs (See Table 1 for results). Conclusions: The large group of patients currently defined as CYP2D6 intermediate metabolizers is comprised of four distinct CYP2D6 diplophentoypes. The most metabolically active diplophenotype (EM/IM) are very similar to EM/EMs while the least active diplophenotype (IM/PM) are similar to PM/PMs. A more accurate CYP2D6 activity classification system may be necessary if genetic association testing and genotype-guided therapy are pursued. Endoxifen Level at Baseline and 4 Months by CYP2D6 Diplophenotype Baseline Endoxifen 4-Month Endoxifen DiplophenotypenMedian (SD)P-val vs. EM/EMP-val vs. PM/PMMedian (SD)P-val vs. EM/EMP-val vs. PM/PMEM/EM11038.67 (6.01)NAp=0.00018.23 (5.09)NAp=0.007EM/IM2568.02 (4.75)p=0.09p=0.00213.11 (9.38)p&amp;lt;0.0001p&amp;lt;0.0001EM/PM2745.72 (4.45)p=0.0001p=0.028.91 (5.28)p=0.42p=0.003IM/IM2174.29 (4.10)p=0.001p=0.266.52 (5.53)p=0.27p=0.24IM/PM2323.90 (3.17)p&amp;lt;0.0001p=0.485.82 (3.47)p=0.0009p=0.77PM/PM3133.33 (2.89)p=0.0001NA6.08 (2.57)p=0.007NA1Diplophenotype classified as extensive metabolizer phenotype, continued on 20 mg/day. 2Diplophenotypes classified as intermediate metabolizer phenotype, changed to 40 mg/day. 3Diplophenotype classified as poor metabolizer phenotype, changed to 40 mg/day. Citation Format: Daniel L Hertz, Anna C Snavely, Howard L McLeod, Christine M Walko, Joseph G Ibrahim, Steven Anderson, Karen E Weck, Peter Rubin, Oludamilola Olajide, Susan Moore, Rachel Raab, Daniel R Carrizosa, Steven Corso, Gary Schwartz, Jeffrey M Peppercorn, James P Evans, Zeruesenay Desta, David A Flockhart, Lisa A Carey, William J Irvin Jr. CYP2D6 intermediate metabolizers includes patient groups with distinct metabolic activity [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-03-02.

SU-E-I-32: Sterile Radiation Reduction Gloves May Be Contraindicated in Fluoroscopically Guided Interventions.

Sterile radiation reduction gloves have been widely used in the past decade to provide modest decreases in operator hand dose when the hands are placed in the field of view (FOV). While multiple publications have quantified the potential dose reduction from the use of such gloves, possible effects on the patient have not yet been assessed. The aim of this study was to determine if radiation reduction gloves can Result in a significant increase in patient dose and increased risk of radiation induced skin injury when used in interventional radiology. The effect of radiation reduction gloves when used in the FOV was determined by measurement of patient entrance exposure rate (EER) for a variety of patient sizes and varying operating and magnification modes. EERs were measured with no glove in the FOV, with one glove and, to replicate the actions of many dose-conscious radiologists, with double gloves in the FOV. Compared to an ungloved hand, the use of a single radiation reduction glove near the center of the FOV results in a 2-fold average increase in patient EER. The use of double radiation reduction gloves results in a 3-fold average increase in EER. In both cases, this increase was only weakly dependent on the size of the patient and on the operating and magnification modes used. In fact, patient thicknesses ranging from 6-14 inches and operating modes ranging from low-dose fluoroscopy to DSA produced less than a 20% deviation from the increases in EER quoted above. When used in the FOV, radiation reduction gloves can substantially increase patient EER. This increase in patient dose, when compared with the relatively small published reduction in extremity dose provided to the operator, may make their use contraindicated in cases where radiation induced skin injury is a possible risk.

Step back from the patient: Reduction of radiation dose to the operator by the systematic use of an automatic power injector for contrast media in an interventional angiography suite

During arterial interventional procedures, power injectors allow the operator to step back from the patient or exit the angiography suite during digital subtraction angiography (DSA) acquisitions. Increasing the distance to the radiation source reduces exposure to the operator and staff. To systematically investigate the effect of increasing the distance between the radiation source and the operator during DSA acquisitions in a daily clinical setting, regarding radiation exposure to the operator and patient, as well as the duration of the procedure using a power injector to deliver contrast media. Patients scheduled for arterial interventional procedures in the pelvis or lower extremities were consecutively included. In phase one (duration 6 weeks, 44 patients) contrast media were injected manually. In phase two (duration until the total dose area product [DAP] was equal to phase 1, 41 patients) the operator used a power injector and exited the suite whenever possible. Patient, procedure, and examination data were recorded. Collective dose to the operator's collar, lead apron, and hands was recorded using thermo luminescent dosimetry (TLD). Our results showed a dose reduction of 50% to the operator's hands, lead apron, and thyroid collar when using a power injector during DSA, with no significant increase in DAP or procedure time when performing pelvic procedures. For lower extremity procedures there was a small but significant increase in procedure time and DAP. Pelvic procedures yielded substantially higher DAP than lower extremity procedures during both phases. Utilization of a power injector, thus allowing the operator to step back from the patient, facilitates a radiation dose reduction to the operator of approximately 50% with no significant increase in patient dose or procedure time during pelvic procedures.

Antiscatter grid use in pediatric digital tomosynthesis imaging

The objective of this study was to assess the effect of antiscatter grid use on tomosynthesis image quality. We performed an observer study that rated the image quality of digital tomosynthesis scout radiographs and slice images of a Leeds TO.20 contrast‐detail test object embedded in acrylic with and without a grid. We considered 10, 15, 20 and 25 cm of acrylic to represent the wide range of patient thicknesses encountered in pediatric imaging. We also acquired and rated images without a grid at an increased patient dose. The readers counted the total number of visible details in each image as a measure of relative image quality. We observed that the antiscatter grid improves tomosynthesis image quality compared to the grid‐out case, which received image quality scores similar to grid‐in radiography. Our results suggest that, in order to achieve the best image quality in exchange for the increase in patient dose, it may often be appropriate to include an antiscatter grid for pediatric tomosynthesis imaging, particularly if the patient thickness is greater than 10 cm.PACS number: 87.57.‐s

THE DEVIATION OF LIVER DOSE IN REAL PATIENTS FOR THORACIC COMPUTED TOMOGRAPHY SCANS: A NEW APPROACH TO INDIVIDUAL DOSIMETRY WITH METHODS OF RADIOTHERAPY TREATMENT PLANNING

The increasing use of computed tomography (CT) in diagnostic imaging is associated with a relevant increase in patient dose and requires CT dose optimization. Anthropomorphic phantoms and mathematical patient models have been developed to improve the dosimetry in diagnostic imaging. Nevertheless, the doses calculated in these models and the ones individual patients can receive may differ considerably. In particular, the assessment of organ doses is problematic when organs and tissues receive only a partial exposure. A typical example for this situation is the exposure of the liver within a thoracic CT. To evaluate the impact of the field boundary and the liver volume on the individual organ dose, 50 CT scans from 25 male and 25 female patients between the ages of 27 to 87 were analyzed in this study with the volumetric tools of a treatment planning system for radiotherapy. The relative volume of the liver within a thoracic CT was assessed and compared to results from dosimetry methods using standardized patient models. The differences between an individual dose and the results from standardized patients are considerable. The fraction of the liver volume within a thoracic CT with a standard lower boundary extends from 48-92%, resulting in a possible dose difference of up to a factor of 1.7. Results from mathematical phantoms can underestimate the liver dose by more than a factor of 2.6. From the determined data, correction factors for the dosimetry of the liver using standard programs can be derived.

An automatic and accurate x‐ray tube focal spot/grid alignment system for mobile radiography: System description and alignment accuracya)

A mobile radiography automatic grid alignment system (AGAS) has been developed by modifying a commercially available mobile unit. The objectives of this article are to describe the modifications and operation and to report on the accuracy with which the focal spot is aligned to the grid and the time required to achieve the alignment. The modifications include an optical target arm attached to the grid tunnel, a video camera attached to the collimator, a motion control system with six degrees of freedom to position the collimator and x-ray tube, and a computer to control the system. The video camera and computer determine the grid position, and then the motion control system drives the x-ray focal spot to the center of the grid focal axis. The accuracy of the alignment of the focal spot with the grid and the time required to achieve alignment were measured both in laboratory tests and in clinical use. For a typical exam, the modified unit automatically aligns the focal spot with the grid in less than 10 s, with an accuracy of better than 4 mm. The results of the speed and accuracy tests in clinical use were similar to the results in laboratory tests. Comparison patient chest images are presented--one obtained with a standard mobile radiographic unit without a grid and the other obtained with the modified unit and a 15:1 grid. The 15:1 grid images demonstrate a marked improvement in image quality compared to the nongrid images with no increase in patient dose. The mobile radiography AGAS produces images of significantly improved quality compared to nongrid images with alignment times of less than 10 s and no increase in patient dose.

Computertomographische Längsschnitte des Körperstammes, rekonstruiert aus Standardquerschichten

Reduction in scan times and advances in the field of image reconstruction have made it possible to reconstruct the trunk from sequential coronal sections. For this purpose 8 mm cuts without overlap are suitable. There is consequently no increase in patient dose or in the scan time. Longitudinal sections can be reconstructed by a dedicated computer in about 10 minutes and cross sections can be evaluated in more detail. The longitudinal reconstructions provide better demonstration of organs and space-occupying lesions in their craniocaudal extent. This extension of the diagnostic spectrum is of value to the diagnostician and particularly to radiotherapists and surgeons during treatment planning.

TU-D-304A-04: The Influence of CT Resolution On Volume Definition and Image Quality in SRS and SBRT Simulation

Purpose: To determine the influence of resolution of the CT scan (including sub‐millimeter slice thickness) on volume definition and image quality in stereotactic radiotherapy and body radiotherapy simulation. Method and Materials: A novel low‐contrast gel phantom was fabricated with spiculated tumor‐like volumes approximately 2, 5, 8, and 20cc in size. The phantom was scanned using a Philips Brilliance BigBore 16‐slice CT scanner. First, a scan was taken using our standard clinical protocol employing a 16×1.5mm collimator and reconstructed slice thickness of 3mm. Next, a scan was taken with the sub‐millimeter collimator (16×0.75mm) and reconstructed with slice thicknesses of 0.75mm and 3mm for comparison. Contours of the structures were drawn using a specific CT number range in Eclipse. Digitally reconstructed radiographs(DRRs) were exported for evaluating image quality and the standard deviation (SD) was calculated for four uniform, non‐background regions. Results: The difference in measured volume decreased with increasing tumor size when comparing the standard clinical scan and both sub‐millimeter scans. Measured volume varied from 4–16% for volumes less than 10cc when comparing the 0.75mm and clinical scan. The 3mm reconstructed sub‐millimeter scan showed smaller but significant volume differences (>5%). The 16×0.75mm scan increased the CTDIdose by 9.4% versus the clinical protocol scan. Small spicules in the tumors resulted in greater measured volume in the 0.75mm scan. These features were easier to visualize in the 0.75mm DRR, however, SD values were larger than both 3mm scans (15–69%). Conclusion:Tumor size and shape are important considerations in choosing slice thickness for stereotactic radiotherapy simulation. As expected, slice thickness has larger effects on smaller targets. DRR feature sensitivity improved with the 0.75mm scan, but an increase in noise was observed. Our results show that sub‐millimeter slice thickness is useful in SRT for smaller target volumes despite a small increase in patient dose.

IVIg dose increase in multifocal motor neuropathy

In this prospective, non-randomized 6-month observational study we evaluated the efficacy of intravenous immunoglobulin (IVIg) dose increase in patients with multifocal motor neuropathy (MMN). Diagnosis according to AAEM criteria, repetitive IVIg treatment for at least one year, persistent paresis and conduction block, stable symptoms and findings for at least six months were inclusion criteria. Nine patients (7 men) were identified and approved to standardized increase of IVIg dose. Patients were monitored using clinical scores and electrophysiological studies. Dose was increased from a baseline of 0.5 g/kg per month [mean, range: 0.1-1.1], given at variable intervals [4-12 weeks] to 1.2 g/kg per month given over 3 consecutive days planned for 6 cycles. If the patients' motor function did not improve after two cycles they entered step two: Dose was increased to 2 g/kg per month given over 5 consecutive days. The increased dose was maintained for 6 months. Assessments were performed by the same investigator, not involved in the patient's management, at baseline, after 2 and after 6 months. Following dose increase, motor function significantly improved in 6 patients (p = 0.014), 2 patients entered step two, 1 patient withdrew due to absent efficacy. Higher doses of IVIg caused more side effects, however, transient and rarely severe (p = 0.014). IVIg dose increase may improve motor functions in patients with stable MMN on long-term IVIg therapy independent of baseline dose. Improvement of motor function was associated with shorter disease duration (p = 0.008), but not with degree of muscle atrophy (p = 0.483). The treatment strategy to try to find the lowest effective dose and the longest tolerated interval might lead to underdosing in the long-term in many patients.

Correlation of image quality with exposure index and processing protocol in a computed radiography system

The correlation of image quality with the exposure index (EI) and the processing protocol was investigated in a Kodak computed radiography (CR) system using clinical radiographs and a water phantom containing an aluminium and a copper step-wedge. The phantom was exposed to different dose levels and the acquired images were processed using four clinical protocols. The quality of these images was evaluated in terms of image brightness, contrast and noise. In clinical radiographs, there was no straightforward correlation of image quality with EI. In phantom images, higher EI values improved contrast and reduced noise but after a point this improvement does not justify the implied increase in patient dose. Image brightness, contrast and noise were also strongly dependent on the processing protocol. To obtain the images of satisfactory quality with the Kodak CR system, a dose slightly higher than those used in 400 relative speed screen-film systems and a processing protocol designated for the specific radiographic examination are required.

SU‐FF‐I‐49: Daily Patient Dose From Kilo‐Voltage Cone‐Beam Computed Tomography: A Comparison Between XVI and OBI

Purpose: To make a comprehensive set of absolute dose measurements from the X‐ray Volumetric Imager (XVI®, Elekta Medical Systems) and the On‐Board Imager (OBI®, Varian Medical Systems) on cylindrical phantoms using a calibrated ion chamber. Method and Materials: Two cylindrical (acrylic) phantoms with diameters of 18 cm (head phantom) and 30 cm (body phantom) were used for all measurements. Each phantom has a hole in the center and 2 cm below the phantom surface. For the XVI unit, the four manufacturer‐supplied protocols were measured, namely, “head &amp; neck”, “prostate”, “pelvis”, and “pelvis — large”. The total mAs settings were also varied for each protocol to verify the dose linearity. For the OBI unit, full bow‐tie, half bow‐tie, and no bow‐tie filters were used in combination with the two scanning modes, namely, “full‐fan” and “half‐fan”. Results: For the XVI unit, the (isocenter) doses range between 0.1 and 2.2 cGy for the “head &amp; neck” and “prostate” protocol, respectively, and agree well with the “Nominal Scan Dose” supplied by the manufacturer. The measured doses were highly linear with the total mAs settings. For the OBI unit, the (isocenter) doses range between 0.9 and 8.5 cGy. In the full bow‐tie with the “full‐fan” mode, the head phantom central dose was 8.5 cGy. This is significantly larger than a similar protocol scan measured with the XVI unit (“head &amp; neck”). Half value layers were between 4.6 to 7.0‐mm‐Al for the two x‐ray units. Conclusion: A comprehensive series of dose measurements were made on the XVI and OBI CBCT imagers. It was observed that the OBI unit generally results in higher dose with up to 8.5 cGy measured with the head phantom. More studies are required to determine the increase in image quality expected from the increase in patient dose from the OBI unit.