Anteroposterior Abdomen Research Articles

Towards the establishment of national diagnostic reference levels for abdomen, KUB, and lumbar spine x-ray examinations in Sri Lanka: a multi-centric study

Diagnostic reference levels (DRLs) and achievable doses (ADs) provide guidance to optimise radiation doses for patients undergoing medical imaging procedures. This multi-centre study aimed to compare institutional DRLs (IDRLs) across hospitals, propose ADs and multi-centric DRLs (MCDRLs) for four common x-ray examinations in Sri Lanka, and assess the potential for dose reduction. A prospective cross-sectional study of 894 adult patients referred for abdomen anteroposterior (AP), kidney-ureter-bladder (KUB) AP, lumbar spine AP, and lumbar spine lateral (LAT) x-ray examinations was conducted. Patient demographic information (age, sex, weight, BMI) and exposure parameters (tube voltage, tube current-exposure time product) were collected. Patient dose indicators were measured in terms of kerma-area product (PKA) using a PKA meter. IDRLs, ADs, and MCDRLs were calculated following the International Commission on Radiological Protection guidelines, with ADs and MCDRLs defined as the 50th and 75th percentiles of the median PKA distributions, respectively. IDRL ranges varied considerably across hospitals: 1.42–2.42 Gy cm2 for abdomen AP, 1.51–2.86 Gy cm2 for KUB AP, 0.83–1.65 Gy cm2 for lumbar spine AP, and 1.76–4.10 Gy cm2 for lumbar spine LAT. The proposed ADs were 1.82 Gy cm2 (abdomen AP), 2.03 Gy cm2 (KUB AP), 1.27 Gy cm2 (lumbar spine AP), and 2.21 Gy cm2 (lumbar spine LAT). MCDRLs were 2.24 Gy cm2 (abdomen AP), 2.40 Gy cm2 (KUB AP), 1.43 Gy cm2 (lumbar spine AP), and 2.38 Gy cm2 (lumbar spine LAT). Substantial intra- and inter-hospital variations in PKA were observed for all four examinations. Although ADs and MCDRLs in Sri Lanka were comparable to those in the existing literature, the identified intra- and inter-hospital variations underscore the need for dose reduction without compromising diagnostic information. Hospitals with high IDRLs are recommended to review and optimise their practices. These MCDRLs serve as preliminary national DRLs, guiding dose optimisation efforts by medical professionals and policymakers.

Development and Validation of a Deep-Learning-Based Algorithm for Detecting and Classifying Metallic Implants in Abdominal and Spinal CT Topograms.

To develop and validate a deep-learning-based algorithm (DLA) that is designed to segment and classify metallic objects in topograms of abdominal and spinal CT. DLA training for implant segmentation and classification was based on a U-net-like architecture with 263 annotated hip implant topograms and 2127 annotated spine implant topograms. The trained DLA was validated with internal and external datasets. Two radiologists independently reviewed the external dataset consisting of 2178 abdomen anteroposterior (AP) topograms and 515 spine AP and lateral topograms, all collected in a consecutive manner. Sensitivity and specificity were calculated per pixel row and per patient. Pairwise intersection over union (IoU) was also calculated between the DLA and the two radiologists. The performance parameters of the DLA were consistently >95% in internal validation per pixel row and per patient. DLA can save 27.4% of reconstruction time on average in patients with metallic implants compared to the existing iMAR. The sensitivity and specificity of the DLA during external validation were greater than 90% for the detection of spine implants on three different topograms and for the detection of hip implants on abdominal AP and spinal AP topograms. The IoU was greater than 0.9 between the DLA and the radiologists. However, the DLA training could not be performed for hip implants on spine lateral topograms. A prototype DLA to detect metallic implants of the spine and hip on abdominal and spinal CT topograms improves the scan workflow with good performance for both spine and hip implants.

Proposed Institutional Diagnostic Reference Levels in Computed and Direct Digital Radiography Examinations in Two Teaching Hospitals

Background: The detectors of both computed radiography (CR) and direct digital radiography (DR) have a wide dynamic range that could tolerate high values of exposure factors without an adverse effect on image quality. Therefore, this study aims to assess patient radiation dose and proposes institutional diagnostic reference levels (DRLs) for two teaching hospitals in Ghana.Materials and Methods: CR and DR systems were utilized in this study from two teaching hospitals. The CR system was manufactured by Philips Medical Systems DMC GmbH, while the DR system was manufactured by General Electric. The entrance skin doses (ESDs) were calculated using the standard equation and the tube output measurements. Free-in-air kerma (μGy) was measured using a calibrated radiation dosimeter. The proposed institutional DRLs were estimated using 75<sup>th</sup> percentiles values of the estimated ESDs for nine radiographic projections.Results and Discussion: The calculated DRLs were 0.4, 1.6, 3.4, 0.5, 0.4, 1.1, 1.0, 1.2, and 1.7 mGy for chest posteroanterior (PA), lumbar spine anteroposterior (AP), lumbar spine lateral (LAT), cervical spine AP, cervical spine LAT, skull PA, pelvis AP, and abdomen AP, respectively in CR system. In the DR system, the values were 0.3, 1.6, 3.1, 0.4, 0.3, 0.7, 0.6, 0.9, and 1.3 for chest PA, lumbar spine AP, lumbar spine LAT, cervical spine AP, cervical spine LAT, skull PA, pelvis AP, and abdomen AP, respectively.Conclusion: Institutional DRLs in nine radiographic projections have been proposed for two teaching hospitals in Ghana for the first time. The proposed DRLs will serve as baseline data for establishing local DRLs in the hospitals and will be a valuable tool in optimizing patient doses.

Organ Dose and Radiation Exposure Risk: A Study Comparing Radiation Dose Using Two Software Packages

With the rapid development of X-ray equipment, assessing the patient’s radiation dose has become an important issue. This study uses DoseCal and PCXMC software to estimate the effective dose (ED) for 510 adult patients undergoing abdomen anteroposterior (AP) and chest anteroposterior/posteroanterior (AP/PA) X-ray examinations in Najran, Saudi Arabia. This study reported our experience with DoseCal and PCXMC software in calculating the ED and organ doses in abdomen and chest X-ray diagnostics. The mean ED values calculated using DoseCal were 0.051, 0.115, and 0.045 mSv for Abdomen AP, chest AP, and PA, respectively. Further, the mean ED calculated using PCXMC is 0.062, 0.132, and 0.047 mSv for Abdomen AP, chest AP, and PA, respectively. The dose results calculated by PCXMC were higher than DoseCal; however, we strongly recommended the dose surveyors utilize PCXMC because it uses the most recent tissue weighting factors (WTs) and offers a risk calculation.

DETERMINATION OF ENTRANCE SURFACE DOSE FOR THREE COMMON PLANAR DIAGNOSTIC X-RAY EXAMINATIONS.

Patient dose during diagnostic radiography procedures primarily depends on the entrance surface dose (ESD) and the exposure area. The purpose of this study was to determine ESD for five common diagnostic X-ray examinations using dose area product and X-ray tube output. The ESDs were estimated in a sample of 340 patients using normalised X-ray output from Philips-PrimaryDiagnost digital X-ray machine equipped with digital flat panel scintillator detector. The resultant mean ESDs for chest postero-anterior/lateral, lumbar spine antero-posterior (AP)/lateral and abdomen AP were 0.49, 2.00, 5.74, 12.79 and 4.62mGy, respectively. The mean and third quartile ESD values of this study were significantly higher than the values found in the literature. This can be attributed to the lower tube potential (kVp) values and the higher tube current-time products (mAs). The methodology used here is a better option for low-resources countries for routine dose monitoring.

Optimisation of the AP abdomen projection for larger patient body thicknesses

IntroductionThis study aims to identify optimal exposure parameters, delivering the lowest radiation dose while maintaining images of diagnostic quality for the antero-posterior (AP) abdomen x-ray projection in large patients with an AP abdominal diameter of >22.3 cm. MethodologyThe study was composed of two phases. In phase 1, an anthropomorphic phantom (20 cm AP abdominal diameter) was repetitively radiographed while adding 3 layers (5 cm thick each) of fat onto the phantom reaching a maximum AP abdominal diameter of 35 cm. For every 5 cm thickness, images were taken at 10 kVp (kilovoltage peak) intervals, starting from 80 kVp as the standard protocol currently in use at the local medical imaging department, to 120 kVp in combination with the use of automatic exposure control (AEC). The dose area product (DAP), milliampere-second (mAs) delivered by the AEC, and measurements to calculate the signal to noise ratio (SNR) and contrast to noise ratio (CNR) were recorded. Phase 2 included image quality evaluation of the resultant images by radiographers and radiologists through absolute visual grading analysis (VGA). The resultant VGA scores were analysed using visual grading characteristics (VGC) curves. ResultsThe optimal kVp setting for AP abdominal diameters at: 20 cm, 25 cm and 30 cm was found to be 110 kVp increased from 80 kVp as the standard protocol (with a 56.5% decrease in DAP and 76.2% in mAs, a 54.2% decrease in DAP and 76.2% decrease in mAs and a 29.2% decrease in DAP and 59.7% decrease in mAs, respectively). The optimal kVp setting for AP abdominal diameter at 35 cm was found to be 120 kVp increased from 80 kvp as the standard protocol (with a 50.7% decrease in DAP and 73.4% decrease in mAs). All this was achieved while maintaining images of diagnostic quality. ConclusionTailoring the exposure parameters for large patients in radiography of the abdomen results in a significant reductions in DAP which correlates to lower patient doses while still maintaining diagnostic image quality. Implications for clinical practiceThis research study and resultant parameters may help guide clinical departments to optimise AP abdomen radiographic exposures for large patients in the clinical setting.

ESTIMATES OF PATIENT DOSES AND KERMA-AREA PRODUCT MONITORING IN DIGITAL RADIOGRAPHY.

The application of the kerma-area product (PKA) meter is increased rapidly in dosimetry. This study presents measurements of PKA in adherence to the International Atomic Energy Agency protocol for 300 adult patients in digital radiographic procedures. Effective doses (ED) were calculated from PKA measurements and conversion coefficients (E-103/PKA) obtained from the International Commission on radiological protection 103. In skull posteroanterior (PA), skull lateral (LAT), cervical spine anteroposterior (AP), cervical spine LAT, chest PA, abdomen AP, lumbar spine AP, pelvis AP and lumbar spine LAT, the third-quartile PKA values were found to be 0.2, 0.28, 0.33, 0.19, 0.26, 0.95, 0.93, 0.96 and 3.15Gycm2, and estimated mean EDs were 0.005, 0.008, 0.056, 0.021, 0.037, 0.146, 0.165, 0.097 and 0.258mSv, respectively. The third-quartile PKA values were suggested as local diagnostic reference levels (LDRLs). Results were compared with the diagnostic reference levels (DRLs) of the UK, the European Commission, previously published LDRLs in Greece and China by Metaxas etal. and Zhang and Chu, respectively. The PKA (third-quartile) value for cervical spine AP was 120% higher than UK 2010 DRLs, lumbar spine LAT was 123% higher than LDRLs given by Metaxas etal. and chest PA was 160% higher than UK 2010 DRLs and 225% higher than Metaxas etal. provided LDRLs. The PKA results were lower than the UK, and two studies in Greece by Metaxas etal. except for chest PA, cervical spine AP and lumbar spine LAT showed the need for further optimization. The LDRLs reported in this study may further contribute to establishing future national DRLs.

A phantom study for the optimization of image quality and radiation dose for common radiographic examinations in digital radiography

Introduction: Phantom studies facilitate the implementation of radiation dose surveillance as a function of radiographic technical parameters for minimizing patient radiation dose. The evidence of such investigations can then be used to evaluate technical parameters used in the radiographic procedures to reduce radiation dose without compromising the image quality. Material and Methods: This experimental study was carried out using an anthropomorphic phantom and the Leeds test object. Computed radiographic system was utilized and the images were printed for objective evaluation. Dose-area-product (DAP) readings were obtained using a DAP meter for the technical parameters employed for the radiographic procedures. Results: The use of 0.2 mm additional copper filtration resulted in the lowest radiation doses for all four radiographic procedures (i.e. posteroanterior chest, anteroposterior abdomen and lumbar sacral spine projections). The highest tube potential appropriate to the body part being imaged, patient size, image receptor response and required information resulted in the minimum radiation dose to the patient without compromising the image quality. The focus to film distance utilized for the radiographic procedure must be in accordance with the focus to grid distance specified by the manufacturer when using the bucky to eliminate grid “cut-off.” Conclusion: The optimization of image quality and radiation dose can be accomplished by using a phantom and selecting the imaging parameters that yield an acceptable image quality with the lowest entrance surface dose while considering the adjustment for patient size.

The Prevalence and Treatment of Hip Dysplasia in Prader-Willi Syndrome (PWS).

Prader-Willi syndrome (PWS) is a genetic disorder with multisystem involvement. There are a number of associated orthopaedic manifestations, the most recognized of which is scoliosis. The aim of this study was to assess the prevalence of hip dysplasia and to investigate its treatment in patients with PWS. Following IRB approval, all patients seen at our institution's Prader-Willi multidisciplinary clinic were retrospectively reviewed. Only patients with an ultrasound, anteroposterior (AP) spine, AP abdomen, AP hip radiograph, and/or skeletal survey were included in the study. The presence of hip dysplasia was determined based on ultrasonographic and/or radiographic measurements performed by a single fellowship trained pediatric orthopaedic surgeon. A multivariable logistic regression analysis was used to test the association between patient demographics and the prevalence of hip dysplasia. Age at diagnosis, treatment type, and outcomes were recorded for patients that underwent treatment for hip dysplasia. Hip dysplasia was identified in 30% (27/90) of the patient population. Two of the 27 patients (7.4%) had normal films but had a history of resolved hip dysplasia. Prevalence was not associated with sex (P=0.7072), genetic subtype (P=0.5504), race (P=0.8537), ethnicity (P=0.2191), or duration of follow-up (P=0.4421). Eight of the 27 patients (30%) underwent hip treatment by Pavlik harness (2/8), Pavlik harness and closed reduction (1/8), closed reduction (3/8), open reduction (1/8), and unspecified hip surgery (1/8). The mean age at diagnosis was 2 months for the patients that were successfully treated for hip dysplasia (3/8) and 12 months for those who had residual dysplasia following the treatment (5/8). Our study demonstrates a higher prevalence of hip dysplasia in patients with PWS than previously documented. The age at which hip dysplasia develops remains unknown; therefore, we recommend an ultrasound screening for all infants with PWS at 6 weeks of age and subsequent radiographic studies at 1, 2, 5, 10, and 15 years of age to allow for early diagnosis and intervention. Level III-retrospective comparative study.

Estimating Entrance Skin Dose of Digital Radiography Examination Using Displayed Dose Area Product

Objective: To estimate entrance skin dose (ESD) of digital radiography (DR) examination using displayed dose area product (DAP)Material and Method: The functional relation between calculated ESD using x-ray tube output principle and displayed DAP were investigated. The displayed DAP was obtained from whole body phantom which underwent seven projections: skull anteroposterior (AP), skull lateral (Lat), chest posteroanterior (PA), abdomen AP, pelvis AP, lumbar spine AP and l umbar spine Lat. The estimating results were analyzed and compared with two other methods using one-way analysis of variance.Results: The high relation between the ESD calculated and the displayed DAP were founded with simple equation: ESD=0.0017.DAP+0.1546 (R2=0.88) The mean ESD estimated performed by DR examination with automatic exposure control (AEC) mode using our method, Mcparland method and Kisilewicz method were 1.07, 1.13 and 0.89 whereas without AEC mode were 3.25, 3.45 and 2.60 respectively. There was provided no statistically significant difference between our approach and two other methods (p-value>0.010).Conclusion: The displayed DAP can be used to estimate the ESD.

The abdominal radiation doses for paediatric patients undergoing X-ray examinations at southern Saudi Arabia.

This study aims to estimate radiation doses for paediatric patients undergoing abdominal X-ray examinations in Najran, Saudi Arabia, through evaluation of the entrance surface doses using DoseCal software. Two X-ray units were used at a paediatric referral hospital. A total of 216 patients were examined with an age range between 0 and 7years. The mean ESDs were found to be 0.042 and 0.101mGy, for abdomen anteroposterior (AP) and posteroanterior (PA) respectively. The results are useful to the National Centre for Radiation Protection in Saudi Arabia and other professional organizations elsewhere, to set up safety protocols to prevent paediatric patients from needless radiation and to establish diagnostic reference levels (DRLs).

Estimating pediatric entrance skin dose from digital radiography examination using DICOM metadata: A quality assurance tool.

To develop an automated methodology to estimate patient examination dose in digital radiography (DR) imaging using DICOM metadata as a quality assurance (QA) tool. Patient examination and demographical information were gathered from metadata analysis of DICOM header data. The x-ray system radiation output (i.e., air KERMA) was characterized for all filter combinations used for patient examinations. Average patient thicknesses were measured for head, chest, abdomen, knees, and hands using volumetric images from CT. Backscatter factors (BSFs) were calculated from examination kVp. Patient entrance skin air KERMA (ESAK) was calculated by (1) looking up examination technique factors taken from DICOM header metadata (i.e., kVp and mA s) to derive an air KERMA (k air) value based on an x-ray characteristic radiation output curve; (2) scaling k air with a BSF value; and (3) correcting k air for patient thickness. Finally, patient entrance skin dose (ESD) was calculated by multiplying a mass-energy attenuation coefficient ratio by ESAK. Patient ESD calculations were computed for common DR examinations at our institution: dual view chest, anteroposterior (AP) abdomen, lateral (LAT) skull, dual view knee, and bone age (left hand only) examinations. ESD was calculated for a total of 3794 patients; mean age was 11 ± 8 yr (range: 2 months to 55 yr). The mean ESD range was 0.19-0.42 mGy for dual view chest, 0.28-1.2 mGy for AP abdomen, 0.18-0.65 mGy for LAT view skull, 0.15-0.63 mGy for dual view knee, and 0.10-0.12 mGy for bone age (left hand) examinations. A methodology combining DICOM header metadata and basic x-ray tube characterization curves was demonstrated. In a regulatory era where patient dose reporting has become increasingly in demand, this methodology will allow a knowledgeable user the means to establish an automatable dose reporting program for DR and perform patient dose related QA testing for digital x-ray imaging.

Optimisation of performance for computed radiography in the West of Scotland

This paper describes experiences in the introduction of computed radiography systems to hospitals within the West of Scotland. Setting of automatic exposure control levels has enabled dose-area product values to be maintained at 160 cGy cm² for lumbar spine antero-posterior (AP), 250 cGy cm² for lumbar spine lateral, 210 cGy cm² for pelvis AP and 260 cGy cm² for abdomen AP. The study looks at dose levels achieved after 8 y in use and compares the dose levels found from surveys undertaken in 2007 and in 2010. The effects of raising tube potentials on image quality in terms of details and on contrast-to-noise ratio (CNR) were assessed. The results showed that CNR details seen in test images at tube potentials of 85-90 kV did not differ significantly from those with lower potentials and gave lower entrance surface doses.

Patient dosimetry during chest, abdomen, skull and neck radiography in SW Nigeria

The technique factors and X-ray output from the X-ray units of three Nigerian hospitals were obtained and used to calculate doses delivered to patients during chest, abdomen, skull and neck examinations. DoseCal software was used to calculate the entrance skin dose (ESD) and effective dose (E) based on the values of technique factors employed. The result obtained for inter-hospital comparison showed wide variation of mean hospital ESD, from a factor of 1.3 for chest posteroanterior (PA) in hospital 2 (H2) to a factor of 63 for the same chest X-ray projection in hospital 1 (H1). A comparison of ESD obtained in this work with established reference doses in the United Kingdom (UK 2005 review), International Atomic Energy Agency (IAEA), Community of European Commission (CEC), Ghana and Sudan shows that the values of ESD obtained in H1 for five examinations; namely: chest (PA) and lateral (LAT), abdomen anteroposterior (AP) and skull (PA and LAT) are higher. In H2, the dose value for chest PA is about 50% higher than that of UK but comparable with CEC and less than IAEA and Ghanaian values. The dose values obtained in H3 chest PA are higher than UK, IAEA and CEC values but comparable with that of Ghana. For abdomen AP, the dose is a factor of 1.2 less than IAEA and CEC values but greater than the UK, Ghanaian and Sudanese values by a factor of 2.1, 1.2 and 4.5, respectively. Reference data for abdomen LAT and neck AP were not available for comparison. Higher effective doses are being delivered to patients in chest PA (H1 and H3) and abdomen AP (H1) when compared with the range of values reported in the literature. This trend is an indication that patients examined are at higher health risks.

Estimation of patients' organ doses and conceptus doses from selected X-ray examinations in two Nigeria X-ray centres

In this study, organ and conceptus doses of patients undergoing chest, abdomen and skull radiograph examinations at two Nigeria X-ray centres, Niger State General Hospital (NGH) and Two-Tees (TTX), are reported. Air kerma was measured, and entrance surface dose (ESD) and half-value layer estimated for each set of tube potential (kV(p)), focus to skin distance and current-time product (mAs) used for each of the patients included in this study. Results show that the mean air kerma in the two centres are similar for the three projections considered in this study. Organ doses ranged from <0.01 to 2.18 mGy in NGH and from <0.01 to 1.29 mGy in TTX for examinations of the abdomen, from <0.01 to 0.20 mGy in NGH and from <0.01 to 0.13 mGy in TTX for examinations of the skull and from <0.01 to 3.90 mGy in NGH and from <0.01 to 1.96 mGy in TTX for examinations of the chest. Generally, no significant difference is seen between the organ doses of male and female patients. In NGH, organ doses are generally greater than those from TTX for the three examinations. The mean ESDs for examinations of the chest postero-anterior, abdomen antero-posterior (AP) and skull AP are, respectively, 5.37, 6.28 and 4.24 mGy in NGH, and 5.82, 5.33 and 4.76 mGy in TTX. The ESDs reported in this study, except for examinations of the chest, are generally lower than comparable values published in the literature. Conceptus doses were also estimated for female patients using normalised published conceptus dose data for abdomen examinations. The estimated conceptus doses were >1 mGy even when the conceptus was located 12 cm below the surface of the abdomen.

Valutazioni di dose al paziente tramite immagini DICOM per un apparecchio digitale diretto

The purpose of this work was to evaluate the statistical distribution of patient dose for different examinations by using the data stored in a DICOM image archive of a direct digital radiography system. An automatic procedure to extract dose data and exposure parameters from the image archives was implemented. During a 4.5-month period, 8,292 images were collected. Exposure parameters and the air kerma area product (P (KA)) stored in the image DICOM header were examined for each image. The entrance surface air kerma (K (a,e)), a quantity comparable to the current diagnostic reference levels (DRL), was estimated considering the P (KA) and the geometric parameters of each examination. P (KA) and K (a,e ) distributions showed highly variable values. The obtained K (a,e ) values were substantially lower than the DRL. DRL were more than six times the mean value of K (a,e ) distribution for the abdomen anteroposterior (AP) and lumbar spine lateral (LAT) projections, whereas the ratio was equal to 2.7 for posteroanterior (PA) chest examinations. The method adopted proved to be effective for characterising the dose of each examination by means of the statistical analysis of the dose quantities over extensive samples. The dose values obtained and the comparison with the DRL showed that this radiographic device allows substantial dose savings compared with estimations made for nondigital or for phosphor-based systems.

Estimation of Radiation Dose during Diagnostic X-Ray Examinations of Newborn Babies and 1-Year-Old Infants

Objective: It was the aim of this study to investigate radiation doses for commonly performed paediatric X-ray examinations (skull, chest, abdomen and pelvis) in public hospitals in Kuwait in order to establish national reference or guidance dose levels. Materials and Method: Exposure factors used for six commonly performed X-ray examinations – antero-posterior (AP) chest, lateral chest, AP abdomen, AP skull, lateral skull and AP pel vis – were obtained from various hospitals, and entrance surface doses (ESD) were measured using a Victoreen model 660 survey meter. Effective doses (E) and the corresponding risk of developing fatal malignancies were calculated using published conversion factors and methods recommended by the International Commission of Radiological Protection for newborn babies to 1-year-old infants. Results: The range of ESD values was 26– 668 µGy for newborn babies and 40–700 µGy for 1-year- old infants. The range of E values was about 4–150 µSv for the two age groups. The risk of developing long-term stochastic effects due to radiation exposure ranges between 0.6 and 23.4 per million. Conclusion: The range of ESD values, E values and risk of development of fatal malignancies obtained in this study can be used as a guide for the risk-benefit analysis of an X-ray examination for newborn babies and 1-year-old infants. Tube voltages used for these examinations should be kept above 60 kV, whenever possible, to minimise the radiation dose.

Abdominal muscle recruitment and PEEPi during bronchoconstriction in chronic obstructive pulmonary disease.

BACKGROUND: It has been recently shown that, when breathing at rest, many patients with severe chronic obstructive pulmonary disease (COPD) contract abdominal muscles during expiration, and that this contraction is...

Entrance doses during lateral lumbar spine and antero-posterior abdomen examinations: generator waveform dependence.

In North Trent, UK, an entrance dose survey of lateral lumbar spine and antero-posterior (AP) abdomen examinations has been carried out in 17 radiology departments. The survey comprised 294 lateral lumbar spine and 322 AP abdomen entrance dose measurements. The mean entrance doses were found to be approximately half of the relevant national reference entrance dose levels of 30 mGy and 10 mGy, respectively. The effect of generator waveform on entrance dose was studied by separating the generators into two types: "pulsating potential" (PP) generators and "constant potential" (CP) generators for each examination. PP generators comprised 23% of the total number of examinations. The mean entrance dose and radiographic exposure factors from CP generators were found to be significantly lower than those from PP generators. The use of CP type generators, together with low attenuation components can significantly reduce patient entrance doses for these examinations.

Intrinsic PEEP in patients with chronic obstructive pulmonary disease. Role of expiratory muscles.

Many patients with severe chronic obstructive pulmonary disease (COPD) contract the transversus abdominis (TA) muscle during expiration. The mechanical correlates of this contraction, however, are uncertain. In the present study, we have measured airflow, esophageal (Pes), and gastric (Pga) pressures, the anteroposterior (AP) diameter of the abdomen, and the electromyogram of the TA during resting breathing in 25 seated patients with severe COPD (FEV1 = 28 +/- 8% of predicted). Nine patients (Group I: FEV1 = 29 +/- 8% of predicted) in general had no TA activity during breathing, and 16 patients (Group II: FEV1 = 27 +/- 8% of predicted) had invariable phasic expiratory TA activity. In all patients of Group II, the decrease in abdomen AP diameter during expiration was associated with a gradual fall in Pga. In contrast, in 13 patients of Group II, the expiratory decrease in abdomen AP diameter was associated with a rise in Pga; this rise in Pga averaged 2.8 +/- 2.2 cm H2O. Furthermore, most patients had positive alveolar pressure at end-expiration, as shown by the time lag between the fall in Pes at the beginning of the inspiratory effort and the onset of inspiratory flow. However, whereas end-expiratory alveolar pressure averaged 2.4 +/- 2.2 cm H2O in Group II, it was only 0.8 +/- 0.6 cm H2O in Group I (p < 0.05). For the patient group as a whole, there was a close relationship between the rise in Pga during expiration and end-expiratory alveolar pressure (r = 0.87; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)