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Analysis of the action of the restriction endonuclease AluI using three different comet assay protocols.

BACKGROUND AND PURPOSE: The comet assay offers the opportunity to measure the amount of DNA damage and the effectiveness of DNA repair in single cells. In a first part, experiments are presented comparing three different protocols of the comet assay technique with respect to the analysis of the induction of DNA damage after X-irradiation in isolated human lymphocytes and CHO cells. In a second part, the restriction enzyme AluI, an agent producing DNA double-strand breaks exclusively, was introduced into CHO cells by electroporation and the effects were analyzed using the different comet assay protocols. The experiments were carried out in order to test the assertion that comet assay techniques can measure different types of DNA damages at different pH conditions of lysis and electrophoresis. MATERIAL AND METHODS: Three different comet assay protocols were used for the analysis of DNA damage in lymphocytes and CHO cells. RESULTS: The results clearly indicate that among the three protocols the modified comet assay technique used by the authors showed the highest sensitivity in the radiotherapy-relevant dose range between 0 and 2 Gy. All three protocols were capable of detecting an effect by AluI. This effect, however, was clearly different from radiation effects. Whereas after radiation exposure all cell nuclei show a dose-dependent increase in DNA content in the comet tail, most of the cell nuclei were unaffected by an AluI uptake. Nevertheless, there was an effect by AluI that could be detected in all three assay versions: between 5% and 15% of the nuclei showed clearly abnormal comet morphologies. CONCLUSION: Neither the strictly alkaline nor the strictly neutral comet assay is applicable in the radiation dose range of about 2 Gy. The restriction enzyme results show that other factors than just DNA strand breaks contribute to DNA migration into the tail of the comets.

Animals↗

Low dose non-enhanced CT versus standard dose contrast-enhanced CT in combined PET/CT protocols for staging and therapy planning in non-small cell lung cancer.

PURPOSE: To evaluate low dose non-enhanced CT and standard dose contrast-enhanced CT in combined PET/CT protocols for staging and therapy planning of non-small cell lung cancer (NSCLC). METHODS: Retrospective analysis was performed of 50 consecutive patients with proven NSCLC who had been referred for primary staging (n=41) or restaging (n=9). All patients underwent a multi-phase PET/CT consisting of a low dose non-enhanced attenuation scan and an arterial and portal-venous contrast-enhanced CT scan followed by whole-body PET. Fused datasets of non-enhanced and contrast-enhanced PET/CT were compared per patient by using the TNM staging system, and per lesion regarding localisation, characterisation and delineation of tumour lesions. The staging results were validated either by histopathology or by clinical-radiological follow-up for >or=6 months. RESULTS: In 47/50 patients, the results of T staging did not differ between the two PET/CT protocols. Three patients could only be correctly classified as having T4 tumours after contrast application. Regarding N staging, both protocols yielded the same results. In M staging, there was only one patient with an improvement of the results as a result of contrast application. The lesion-based analysis of 92 sites showed no difference in the accuracy of lesion localisation and only one revision of lesion characterisation by contrast-enhanced PET/CT. The assessment of tumour delineation was altered by contrast application in 58/92 sites (p<0.0001). In 10/50 patients, contrast-enhanced PET/CT detected additional clinically important findings. CONCLUSION: In patients with advanced NSCLC, contrast-enhanced CT as part of the PET/CT protocol more accurately assessed the TNM stage in 8% of patients compared with non-contrast PET/CT. However, for planning of 3D conformal radiotherapy and non-conventional surgery, contrast-enhanced PET/CT protocols are indispensable owing to their superiority in precisely defining the tumour extent.

Adult↗

Effective doses in standard protocols for multi-slice CT scanning.

The purpose of this study was to assess the radiation exposure of patients in several standard protocols in multi-slice CT (MSCT). Scanning protocols for neck, chest, abdomen, and spine were examined on a Somatom Plus 4 Volume Zoom MSCT (Siemens, Erlangen, Germany) with changing slice collimation (4x1, 4x2.5, and 4x5 mm), and pitch factors (1, 1.5, and 2). Effective doses were calculated from LiF-TLD measurements at several organ sites using an Alderson-Rando phantom and compared with calculations using the weighted CTDI. Effective dose for MSCT of the neck was 2.8 mSv. For different protocols for MSCT of the chest, 7.5-12.9 mSv were found. In abdominal MSCT protocols, effective dose varied between 12.4 and 16.1 mSv. The MSCT of the spine may lead to 12 mSv. An excellent correlation between the effective dose as determined by LiF-TLD and the calculated effective dose using the weighted CTDI could be demonstrated; however, a difference of up to 30% (mean 14.3%) was noted. Standard protocols for MSCT as measured in this study showed effective doses of up to16 mSv. Phantom measurement data show a good correlation to estimations using the weighted CTDI.

Abdomen↗

Evaluation of different protocols for gene transfer into non-obese diabetes/severe combined immunodeficiency disease mouse repopulating cells.

PURPOSE: Although gene transfer with retroviral vectors has shown distinct clinical success in defined settings, efficient genetic manipulation of hematopoietic progenitor cells remains a challenge. To address this issue we have evaluated different transduction protocols and retroviral constructs in the non-obese diabetes (NOD)/severe combined immunodeficiency disease (SCID) xenograft model. METHODS: An extended transduction protocol requiring 144 h of in vitro manipulation was compared to a more conventional protocol requiring 96 h only. RESULT: While pretransplantation analysis of cells transduced with a retroviral vector, expressing the enhanced green fluorescent protein (EGFP) marker gene, demonstrated significantly higher overall transduction rates for the extended protocol (33.6 +/- 2.3 vs. 22.1 +/- 3.8%), EGFP expression in CD34+ cells before transplantation (4.0 +/- 0.9 vs. 11.6 +/- 2.5%), engraftment of human cells in NOD/SCID bone marrow 4 weeks after transplantation (4.5 +/- 1.7 vs. 36.5 +/- 9.4%) and EGFP expression in these cells (0 +/- 0 vs. 11.3 +/- 2.8%) were significantly impaired. When the 96 h protocol was used in combination with the spleen focus forming virus (SFFV)/murine embryonic stem cell (MESV) hybrid vector SFbeta11-EGFP, high transduction rates for CD45+ (41.0 +/- 5.3%) and CD34+ (38.5 +/- 3.7%) cells prior to transplantation, as well as efficient human cell engraftment in NOD/SCID mice 4 weeks after transplantation (32.4 +/- 3.5%), was detected. Transgene expression was observed in B-lymphoid (15.9 +/- 2.0%), myeloid (36.5 +/- 3.5%) and CD34+ cells (10.1 +/- 1.5%). CONCLUSION: Our data show that CD34+ cells maintained in cytokines for multiple days may differentiate and loose their capacity to contribute to the haematological reconstitution of NOD/SCID mice. In addition, the SFFV/MESV hybrid vector SFbeta11-EGFP allows efficient transduction of and gene expression in haematopoietic progenitor cells.

Animals↗

Comparison of different PCR protocols for the detection and diagnosis of Plasmodium falciparum.

An assessment of differing PCR protocols for the diagnosis of Plasmodium falciparum infection was performed on samples from an area of holoendemic malaria transmission in western Burkina Faso. The PCR protocols had generally high sensitivities (>92%) and specificities (>69%), but the negative predictive values (NPV) were moderate and differed widely among the PCR protocols tested. These PCR protocols that amplified either the P. falciparum pfcrt gene or the small subunit ribosomal DNA were the most reliable diagnostic tools. However, the moderate NPV imply that more than one PCR protocol should be used for diagnosis in holoendemic areas.

Adolescent↗

Duplex arteriography prior to femoral-popliteal reconstruction in claudicants: a proposal for a new shortened protocol.

The standard preoperative duplex arteriography (DA) from the aorta to the pedal vessels is time consuming and may be unnecessary in patients presenting with calf claudication alone. The feasibility of a shortened protocol was evaluated. Of 286 femoral-popliteal reconstruction based on DA during the last 4A years, 79 (28%) were primary operations for calf claudication. Eliminating the aortoiliac portion of the test except for the distal external iliac artery and limiting the scanning of the infrapopliteal vessels to one or two arteries in the leg would significantly shorten the exam. To confirm the adequacy of the inflow tract, we relied on the common femoral artery Doppler waveform analysis and the intraoperative graft pressure upon completion of the bypass. Of the 79 primary femoral-popliteal bypasses, 53 (67%) had triphasic common femoral artery waveform and the remaining 26 had monophasic or biphasic waveforms. Three (6%) of the 53 femoral-popliteal bypasses in the former group had significant pressure gradients measured intraoperatively and were treated with iliac angioplasties and stents for unsuspected stenoses in 2 cases and a covered stent for a common iliac aneurysm in 1 case. Three, two, and one infrapopliteal vessel runoff was observed in 24 (45%), 16 (30%), and 9 (17%) extremities, respectively. Four patients (8%) had significant stenoses (>50%) or occlusion of all three infrapopliteal arteries. Eighty-one percent of the patients would have completed the short protocol had we scanned the peroneal artery initially. An additional 8% would have required scanning of a second vessel (anterior tibial) and only 11%, scanning of all three infrapopliteal vessels. The time interval for completion of short-protocol DA was significantly less than the time for the standard DA (16.2 A+/- 5.2A min vs. 35.1 A+/- 10.6 min) ( p < 0.01). We believe that the proposed short DA protocol combined with intraoperative graft pressure measurements can be used in 94% of the patients who have a patent popliteal artery (>/= 7 cm). It is a totally noninvasive approach that is particularly suitable for vascular technologists and surgeons who wish to start utilizing DA instead of contrast arteriography prior to infrainguinal reconstructions. However, the short protocol does not avert the need for completion arteriography of the inflow arteries and readiness to perform endovascular procedures to correct lesions not suspected by common femoral artery waveform analysis.

Aged↗

A User-Friendly Protocol for Microinjection into Teleost Embryos to Study Gene Function.

Zebrafish (Danio rerio) and medaka (Oryzias latipes) are popular teleost models used in developmental biology and functional genomics. To achieve high-quality and reproducible microinjections, it is essential to have robust protocols for breeding, egg collection, and the precise delivery of genetic material. In this protocol, we present a comprehensive and optimized methodology for setting up breeding tanks under controlled photoperiod conditions to maximize egg yield while minimizing contamination. We provide detailed procedures for sex identification, pair selection, the use of grated breeding inserts, and methods to increase egg collection efficiency. We outline procedures for making injection gel beds, pulling needles, and calibration using one-microliter microcapillaries to achieve consistent nanoliter-scale injections. Our protocol outlines settings for the pico-liter injector that are optimized to deliver a precise amount per pulse with minimal variability. Finally, we demonstrate the application of these methods for gene knockdown using morpholino antisense oligonucleotides, gene knockout using CRISPR-Cas9, and gain-of-function mRNA overexpression experiments. Phenotypic assessments conducted at various developmental stages to evaluate gene-specific effects reveal consistent phenotypic outcomes between the morpholino and CRISPR-Cas9 approaches. This easy and comprehensive protocol enables efficient, precise, and scalable genetic manipulation of zebrafish and medaka embryos, thereby supporting advanced functional studies in developmental biology and disease modeling. To our knowledge, this is the first unified protocol for both zebrafish and medaka microinjection systems achieving 97.7% phenotype penetrance in CRISPR-Cas9 knockouts with precision together with a triple validation approach that confirms gene function across multiple techniques.

Animals↗

Detection of small vessels with electron beam computed tomographic angiography using 1.5 and 3 mm collimator protocols.

OBJECTIVES: To evaluate the effect of scanner collimation on the ability to detect small cardiac vessels using electron beam CT coronary angiography (EBA). MATERIALS AND METHODS: EBA scans from 40 patients who underwent study on two separate occasions with 3 mm (initial scan) and 1.5 mm (follow-up scan) collimation protocols were analyzed. Vessels of <2 mm in diameter were identified. RESULTS: The 1.5 mm collimation allowed 3-D visualization of 129 vessels<2 mm in diameter, while 3 mm collimation only allowed visualization of 89 vessels (p<0.001). The right coronary artery branches and distal LAD segments though were not displayed satisfactorily in almost half of the 3-D studies with either protocol. CONCLUSIONS: There was significant improvement in detection of small cardiac vessels with a 1.5 mm collimation EBA protocol compared to a 3 mm protocol. Both protocols though were insufficient for reliable visualization of the right coronary artery branches and distal LAD segments.

Coronary Angiography↗

The scheduling of repeat cesarean section operations: prospective management protocol experience.

There are benefits to patients and a busy obstetric service if repeat cesarean section operations are performed on a scheduled basis. Optimum management avoids prematurity and reduces the need for amniocentesis. Over a period of 20 months repeat cesarean sections were performed at Tripler Army Medical Center while a protocol with the following elements was used: (1) known last menstrual period; (2) landmarks: positive urine human chorionic gonadotropin test by 6 weeks, Doppler fetal heart tone by 12 weeks, date determination by examination before 10 weeks, fetoscope fetal heart tone by 20 weeks, and date determination by size before 30 weeks; (3) date determination by midtrimester sonogram(s); (4) normal third-trimester glucose screening; (5) biparietal diameter of 9.2 or 9.5 cm before scheduling. With two or more clinical landmarks and one date by sonogram or one landmark and date by two sonograms, elective repeat cesarean section was scheduled at 39 weeks if the biparietal diameter was greater than or equal to 9.2 cm (127). If dates by sonogram were less than dates by last menstrual period but greater than 1 week or if last menstrual period was unknown, dates by sonogram and landmarks corresponding to dates by sonogram were used to electively schedule, with biparietal diameters of 9.2 or 9.5 cm respectively required (28). If protocol criteria were not met or earlier delivery was indicated (e.g., vertical scar or diabetes), amniocentesis was performed (42), except when not possible, advisable, or refused when patients either elected labor (20) or were scheduled if three or more criteria for 40+ weeks were met (18). Of 225 patients (70.5%) scheduled by protocol (173), amniocentesis (34), or medical indication (18), 188 (58.9%) were delivered without labor. In the 147 patients (46.1%) delivered electively by protocol without labor or amniocentesis, there were no cases of respiratory distress syndrome and the mean birth weight was 3517 gm. With early care and better patient compliance nearly all repeat cesarean sections can be safely delivered electively with the use of this protocol.

Appointments and Schedules↗

EORTC guidelines for writing protocols for clinical trials of radiotherapy.

The concept of a Master Protocol for phase III studies was raised at the Steering Committee of the EORTC Radiotherapy Group, in order to make the work of the study coordinators easier, when writing protocols and to give them more homogeneity. The Master Protocol defines and clarifies in a logical order the different steps which must be taken when designing a randomized trial--from the rationale to the references. It pays particular attention to eligibility criteria, volumes of interest defined in agreement with ICRU Report 50 (gross tumor volume, clinical target volume, planning target volume and organs at risk), simulation procedure, treatment technique, normal tissue sparing, dose computation, equipment, dose specification (also in agreement with ICRU Report 50). Last but not least, the different procedures of quality assurance for protocols and patients are also defined (site visits, dummy run procedure, in vivo dosimetry, individual case review) to allow working plans to be made in advance. We are aware that this work is not exhaustive, but hope that the contents will be of help to those who are writing a protocol.

Clinical Trials as Topic↗

Development of a research-based protocol to rule out tuberculosis by means of continuous quality improvement techniques.

Centers for Disease Control and Prevention guidelines mandate that patients be kept in respiratory isolation until three negative results of acid-fast bacillus smears, obtained on three separate days, have been documented. This mandate, coupled with the increased prevalence of Tuberculosis and a limited number of isolation rooms, indicated that an effective system needed to be developed to avoid unnecessary time spent in isolation. When it was found that patients spent a mean of 6.6 days in isolation before three negative results of acid-fast bacillus smears were obtained, a quality improvement project was initiated by the department of medicine. A multidisciplinary group with representation from epidemiology, nursing, medicine, the microbiology laboratory, and respiratory therapy reviewed current practice and developed a protocol to rule out tuberculosis. The protocol, which incorporates gastric lavage and sputum induction, facilitates the collection and processing of specimens within a target of 4 days from the time of placement in isolation. The protocol was reinforced by traditional staff education and large posters displayed on nursing units for easy reference. The mean time spent in isolation to rule out tuberculosis was significantly decreased with the protocol to 4.9 days (p < 0.001). After implementation, 56.6% of patients were out of isolation within 4 days, compared with only 2.6% before the protocol's implementation. This represents both a significant cost saving and improved patient outcomes. Current efforts center on continuous maintenance and improvement of these gains.

Adult↗

Treatment planning for protocol-based radiation therapy.

Many protocol studies are conducted in which patients are assigned to alternative treatment regimens. Typically the dosimetric specifications will define the maximal and minimal target doses and maximal doses to specified critical normal structures, and the success of the study will depend upon the consistency and reliability with which these dose specifications are applied. We have investigated the use of dose-area histograms to ensure complete adherence to protocol dose specifications. A dose prescription is prepared that defines upper and lower target doses as well as normal tissue dose tolerance levels for all organs of interest. In addition, dose-volume histograms are derived which provide quantitative measures of the extent to which each dose limit has been met. This technique can be used during treatment planning to prevent protocol violations of pre-defined severity, or for retroactive correlation of local tumor recurrence and treatment-related morbidity with dose levels in the target and normal tissues. An example is presented for a protocol study of ca prostate, stages A and B, in which seven treatments were evaluated at the mid-plane for protocol violations.

Clinical Trials as Topic↗

The prognostic significance of race and survival from prostate cancer based on patients irradiated on Radiation Therapy Oncology Group protocols (1976-1985).

A number of studies have identified race as a prognostic factor for survival from prostate cancer. To evaluate the prognostic significance of race in a controlled setting, we evaluated 1294 patients treated on three prospective randomized trials conducted by the Radiation Therapy Oncology Group between 1976 to 1985. One-hundred and twenty (9%) of the patients were coded as black, while 1077 (83%) of the patients were coded as white. Protocol 7506 included 607 patients with clinical Stage T3-T4Nx or T1b-T2N1-2. Protocol 7706 included 484 patients with clinical Stage T1b or T2 who were node negative. Protocol 8307 included 203 Stage T2b-T4 patients with no lymph node involvement beyond the pelvis. Univariate and multivariate analyses were used to assess the possible independent significance of race and other prognostic factors, including Gleason score, serum acid phosphatase, nodal status, and hormonal status. Protocols 7706 and 8307 revealed that race was not of prognostic significance for disease-free or overall survival by either univariate or multivariate analysis. Univariate analysis of Protocol 7506 revealed that the median survival for blacks was somewhat shorter (5.4 years vs. 7.1 years, p = 0.02). This difference persisted after a multivariate analysis. A higher percentage of blacks treated on 7506 had an abnormally elevated serum acid phosphatase compared to whites (p = 0.006), and the time to distant failure tended to be shorter (p = 0.07). These findings suggest that blacks treated on 7506 may have had more extensive disease at presentation. Based on these prospective randomized trials, it is most likely that the lower survival noted for black Americans with prostate cancer reflects the tendency for blacks to present with more advanced disease. Differences in access to care, the quality of care received, and the impact of co-morbid conditions may explain the lower survival reported for black Americans elsewhere in the literature.

Black or African American↗

Establishing equivalence classes in preschool children with one-to-many and many-to-one training protocols.

The present study set out to assess if the different probabilities reported in the literature of obtaining equivalence after baseline training with MTO and OTM protocols could be attributed to individual differences and, if so, whether equivalence formation could be facilitated by using familiar stimuli as nodes. In Experiment 1, 16 preschool children were trained on four sets of 2-choice match-to-sample tasks, eight with a OTM protocol (A-B, A-C, A-D, A-E) and eight with a MTO protocol (B-A, C-A, D-A, E-A). For four OTM and four MTO children only abstract stimuli were used. The other four OTM children and four MTO children received the same training but with familiar stimuli as nodes. All children received tests for equivalence (first) and symmetry (second). In Experiment 2, eight children who served in Experiment 1 participated again, four who had passed the equivalence test, and four who had failed that test. All children received the same baseline training as in Experiment 1 but with the opposite type of nodes (abstract instead of familiar, and vice versa) and training protocol (MTO instead of OTM, and vice versa). The results showed that (a) the children's performances (training and testing) were not affected by the training protocol; (b) equivalence formation occurred more readily when being trained with all abstract stimuli than when familiar stimuli served as nodes; and (c) most children who passed or did not pass the equivalence test in Experiment 1 repeated their performance in Experiment 2, irrespective of the conditions that were used.

Adult↗

Interplay between plasma hormone profiles, sex and body condition in immature hawksbill turtles (Eretmochelys imbricata) subjected to a capture stress protocol.

We investigated plasma hormone profiles of corticosterone and testosterone in immature hawksbill turtles (Eretmochelys imbricata) in response to a capture stress protocol. Further, we examined whether sex and body condition were covariates associated with variation in the adrenocortical response of immature turtles. Hawksbill turtles responded to the capture stress protocol by significantly increasing plasma levels of corticosterone over a 5 h period. There was no significant sex difference in the corticosterone stress response of immature turtles. Plasma testosterone profiles, while significantly different between the sexes, did not exhibit a significant change during the 5 h capture stress protocol. An index of body condition was not significantly associated with a turtle's capacity to produce plasma corticosterone both prior to and during exposure to the capture stress protocol. In summary, while immature hawksbill turtles exhibited an adrenocortical response to a capture stress protocol, neither their sex nor body condition was responsible for variation in endocrine responses. This lack of interaction between the adrenocortical response and these internal factors suggests that the inactive reproductive- and the current energetic- status of these immature turtles are important factors that could influence plasma hormone profiles during stress.

Age Factors↗

Minimal sampling protocol for accurate estimation of urea production: a study with oral [13C]urea in fed and fasted piglets.

BACKGROUND & AIMS: An oral [13C]urea protocol may provide a simple method for measurement of urea production. The validity of single pool calculations in relation to a reduced sampling protocol was assessed. METHODS: In eight fed and five fasted piglets, plasma urea enrichments from a 10 h sampling protocol were measured following an intragastric [13C]urea bolus. Blood [13C]bicarbonate was measured to trace gut [13C]urea oxidation. Two-compartment and regression (single pool) computations were performed. Pool sizes were compared to urea distribution over total body water (TBW). Shorter protocol duration was tested in regression simulations. RESULTS: Differences in urea kinetics between fed and fasted piglets did not reach statistical significance. Mean (+/-SE) urea pool from TBW times plasma urea concentration was 2.2+/-0.16 mmol kg(-1). Two-compartment modelling yielded similar results for pool size (despite the oxidation of a small amount of urea tracer). Urea appearance rate was 306+/-18 micromol kg(-1)h(-1). Regression calculations overestimated urea appearance rate vs. compartmental model (P<0.05). When samples <2 h were discarded, results were comparable to compartmental calculations even if protocol length was 6 h (325+/-24 micromol kg(-1)h(-1), NS). CONCLUSIONS: Regression calculations using plasma enrichments sampled between 2 and 6 h after oral [13C]urea administration provide accurate rates of urea production, and are not affected by tracer oxidation.

Administration, Oral↗

Mapping and measuring addiction recovery: Recommended protocols through the PHENX toolkit.

BACKGROUND: Addiction "recovery" has served as a positive conceptual basis for major public health frameworks, communication strategies, and policies. With greater research interest and increasing explication of the recovery construct a multitude of measures have emerged, prompting a need to reach consensus on recommendations to enable better data harmonization and cross-study syntheses. The PhenX (consensus measures for Phenotypes and eXposures) Toolkit (www.phenxtoolkit.org) is a freely accessible catalog of validated protocols designed to promote data comparability across clinical, epidemiological, and genomic research, yet contained no recovery-specific measures. METHOD: In 2024, a Substance Use and Recovery Working Group (SURWG) followed a well-established and detailed PhenX consensus process to identify and recommend protocols suitable for recovery research. Protocols were chosen based on criteria including recovery specificity, brevity, psychometrics, scoring simplicity, and non-proprietary access. The broader scientific community (12 national/regional organizations) provided feedback (respondent N&#x2009;=&#x2009;86) on the SURWG's preliminary recommendation which was incorporated into final decisions. RESULTS: In 2025, the PhenX Toolkit released 15 new recommended protocols across three broad recovery elements: 1. Biopsychological (post-acute withdrawal; craving), 2. Socio-ecological (social relationships;social network characteristics; substance use goal; recovery identity; recovery capital), 3. Treatment and recovery services (Treatment and Recovery Services Use; Satisfaction; and Happiness in Recovery; Mutual-Help). CONCLUSIONS: This PhenX Toolkit SURWG process resulted in a new Substance Use Recovery Specialty Collection of recommended protocols with specific multidimensional applicability. As such, they provide the field with pre-vetted tools that researchers can employ with some confidence to enhance empirical efficiency and return on national research investment.

Humans↗

Optimal scanning protocol of multislice CT virtual intravascular endoscopy in pre-aortic stent grafting: in vitro phantom study.

OBJECTIVE: To investigate the optimal scanning protocol for multislice computed tomography angiography (MSCT) in pre-aortic stent grafting observed with virtual intravascular endoscopy (VIE). MATERIALS AND METHODS: The study was performed on a human abdominal aortic phantom which was housed in a perspex container, filled with contrast medium having CT attenuation similar to that used in the patient's abdominal CT scan. A series of scans were performed on a four-slice multislice CT scanner with the scanning protocols as follows: section thickness of 1.3, 3.2 and 6.5 mm, pitch value of 0.875, 1.25 and 1.75 with reconstruction intervals of 50% overlap. The degree of stair-step artifacts was measured at three different locations, superior mesenteric artery (SMA), renal ostium and the normal abdominal aorta. Standard deviation (S.D.) of the signal intensity measured on surface shaded images was used to determine the image quality. Radiation dose was also recorded in each scanning protocol. RESULTS: The VIE images showed that image quality was not dependent on pitch and section thickness in the visualization of renal ostium and SMA, whereas it was dependent on these two factors at the level of the normal aorta (p<0.05). It was noticed that when section thickness reached 6.5 mm the SMA and renal ostia became distorted. Radiation dose measured in 1.3 mm protocols was significantly higher that those measured in other section thicknesses (p<0.05). CONCLUSION: The scanning protocol of section thickness 3.2 mm, pitch 1.25 with a reconstruction interval of 1.6 mm was recommended as it allows optimal visualization of VIE images of aortic ostia, generation of fewer artifacts and less radiation dose.

Aorta, Abdominal↗