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PubMed1989

Compton spectroscopy in the diagnostic x-ray energy range. I. Spectrometer design.

The optimal design of a Compton spectrometer for measuring photon energy spectra from x-ray tubes in a clinical laboratory is analysed. The demands are: (i) coherent and multiple scattering distort the measurements and must be avoided; (ii) the measuring time should be as short as possible to avoid unnecessary wear on the x-ray tube; and (iii) the impairment in energy resolution due to the scattering geometry should be kept minimal. A scattering angle of 90 degrees is advocated. Scatterers (of low-atomic-number material) in the shape of long circular rods (0.5-4 mm diameter, 20-40 mm long) are preferable to scattering foils. Use of a short focus-scatterer distance (approximately 200 mm) is to be preferred compared to using a large detector area (greater than or equal to 4 mm diameter) in order to establish a sufficiently high count rate in the detector. Short focal distances and a 90 degrees scattering angle are advantages in measuring energy spectra in the gantry of CT machines where the available space is limited. To limit the geometrical energy broadening to less than 1 keV, the spread in scattering angles of registered photons must not exceed 1-2 degrees for incident photon energies of 100-150 keV.

Algorithms↗
PubMed2003

Lung density distribution in dynamic CT correlates with oxygenation in ventilated pigs with lavage ARDS.

BACKGROUND: Fast dynamic computed tomography (dCT) has been used to assess regional dynamics of lung inflation and deflation processes. The aim of this study was to relate ventilation-induced changes in lung density distribution, as measured over several respiratory cycles by dCT, to oxygenation and shunt fraction in a lavage acute respiratory distress syndrome model. METHODS: Six anaesthetized pigs underwent pressure-constant ventilation (FIO2=1.0, inspiratory:expiratory ratio=1:1) before and after induction of lung damage by saline lavage. Mean airway pressure (Paw) was varied (8, 13, 18, 23, 28, 33, and 38 cm H2O) in random order. At each Paw level, dCT acquisitions were performed over several respiratory cycles (Somatom Plus4, Siemens; supradiaphragmatic transverse slice; thickness=1 mm; temporal resolution=100 ms). During scanning at each Paw, arterial and mixed venous blood were obtained for blood gas analysis and shunt calculation. In each CT image, fractional areas (FA) of defined density ranges representing ventilated lung and atelectasis were determined by planimetry using dedicated software. The FA data of individual 100 ms scans were averaged over several respiratory cycles, and expressed as mean FA in percentage of total lung area at each Paw. For atelectatic lung parenchyma a quantitative relationship of the respective mean FA to shunt fraction was studied using regression analysis. RESULTS: Under steady-state conditions, mean FA of atelectasis correlated linearly with the calculated shunt fraction (healthy lungs, r=+0.76; lavaged lungs, r=+0.89). There is a non-linear relationship between mean FA of ventilated lung parenchyma and mean FA of atelectasis with PaO2. CONCLUSIONS: We conclude that dCT allows assessment of the effects of ventilator adjustments and resultant Paw; changes upon lung aeration and oxygenation rapidly, and with good spatial and temporal resolution. This may benefit patients with acute lung injury, whose ventilatory pattern may be optimized as early as during their first diagnostic workup.

Animals↗
PubMed2006

Practice parameters for the use of continuous and bilevel positive airway pressure devices to treat adult patients with sleep-related breathing disorders.

Positive airway pressure (PAP) devices are used to treat patients with sleep related breathing disorders (SRBD) including obstructive sleep apnea (OSA). Currently, PAP devices come in three forms: (1) continuous positive airway pressure (CPAP), (2) bilevel positive airway pressure (BPAP), and (3) automatic self-adjusting positive airway pressure (APAP). After a patient is diagnosed with OSA, the current standard of practice involves performing full, attended polysomnography during which positive pressure is adjusted to determine optimal pressure for maintaining airway patency. This titration is used to find a fixed single pressure for subsequent nightly usage. A task force of the Standards of Practice Committee of the American Academy of Sleep Medicine reviewed the available literature. Based on this review, the Standards of Practice Committee developed these practice parameters as a guideline for using CPAP and BPAP appropriately (an earlier review and practice parameters for APAP was published in 2002). Major conclusions and current recommendations are as follows: 1) A diagnosis of OSA must be established by an acceptable method. 2) CPAP is effective for treating OSA. 3) Full-night, attended studies performed in the laboratory are the preferred approach for titration to determine optimal pressure; however, split-night, diagnostic-titration studies are usually adequate. 4) CPAP usage should be monitored objectively to help assure utilization. 5) Initial CPAP follow-up is recommended during the first few weeks to establish utilization pattern and provide remediation if needed. 6) Longer-term follow-up is recommended yearly or as needed to address mask, machine, or usage problems. 7) Heated humidification and a systematic educational program are recommended to improve CPAP utilization. 8) Some functional outcomes such as subjective sleepiness improve with positive pressure treatment in patients with OSA. 9) CPAP and BPAP therapy are safe; side effects and adverse events are mainly minor and reversible. 10) BPAP may be useful in treating some forms of restrictive lung disease or hypoventilation syndromes associated with hypercapnia.

Adult↗
PubMedDate not supplied

The application of photographic reducers to autoradiographically intensified radiographs.

In autoradiographic intensification of underexposed images by the method of Askins, the lower densities are intensified by a much larger factor than the higher densities, thus decreasing the contrast of the intensified image. However, when the underexposed, developed, and processed image radiograph) is treated in a subtractive photographic reducer (potassium ferricyanide-sodium thiosulfate mixture) prior to activation with 35S thiourea, the fog is decreased greatly, thereby increasing the contrast of the intensified image. Of the six underexposed radiographys, involving both bone phantoms and various body regions studied after autoradiographic intensification, five were consistently rated adequate for their diagnostic certainty in comparison to the corresponding optimally exposed radiographs.

Autoradiography↗
PubMed1987

Fine needle aspiration of the lung: a pathologist's perspective.

Fine needle aspiration of the lung is gaining wide acceptance as a fast, accurate, safe, and inexpensive method of diagnosing lung lesions. It provides information that eliminates the need for or helps guide surgery. If used optimally, pulmonary fine needle aspiration has a diagnostic accuracy approaching open biopsy with minimal and minor morbidity. Since fine needle aspiration has closely linked radiology and pathology, communication and understanding between these areas is of increasing importance.

Biopsy, Needle↗
PubMed2003

Diagnosis of blunt cerebrovascular injuries.

PURPOSE OF REVIEW: Blunt cerebrovascular injuries (BCVI) are being increasingly recognized. The optimal criteria for screening, and the best diagnostic test, remain a matter of controversy. This review analyzes the available literature to propose management guidelines for the diagnosis of BCVI. RELEVANT FINDINGS: A number of centers are screening asymptomatic patients for BCVI. The criteria vary from center to center. The incidence of injuries diagnosed is proportional to the breadth of screening criteria. Noninvasive diagnostic modalities such as duplex ultrasonography, computed tomographic angiography, and magnetic resonance angiography have been proposed as screening tools. Although they are all capable of identifying many injuries, prospective comparisons reveal inaccuracies. SUMMARY: Screening for BCVI is appropriate. Institutions should adopt formal criteria, recognizing that more restrictive criteria are likely to miss injuries. Noninvasive modalities must be used with caution, because they have been found to be inferior to arteriography.

Angiography↗
PubMed2004

Prevalence and impact of extracolonic findings in patients undergoing CT colonography.

BACKGROUND: CT colonography (virtual colonoscopy) is a new technique being offered to patients as a noninvasive method of imaging the colon. The aims of this study were to prospectively determine the prevalence of extracolonic findings in patients undergoing CT colonography, as well as to determine the clinical significance and consequences of these findings. METHODS: Two-hundred and fifty patients who were referred for colonoscopy for clinically indicated reasons underwent CT colonography using low-dose radiation (50 mAs) immediately prior to conventional colonoscopy. A single radiologist reviewed the CT images for extracolonic pathology, and findings were classified as having high, moderate, or low clinical significance. Electronic medical records were reviewed to assess what follow up diagnostic tests, if any, were performed. RESULTS: A total of 136 extracolonic findings were detected in 83 (33.2%) of the 250 patients. Of these 136 findings, 17 (12.5%) were highly significant, 53 (38.9%) were moderately significant, and 66 (48.5%) were of low significance. The most common highly significant lesions were solitary lung nodules in 3 patients, mesenteric lymphadenopathy in 3, adrenal masses in 2, low attenuation liver lesions consistent with metastases in 2, and bone metastases in 2 patients. Fourteen of the 17 (82.4%) highly significant findings were new findings, and in 11 the extracolonic abnormalities resulted in further diagnostic testing. None of the patients with moderate or low significance lesions underwent further testing. CONCLUSIONS: Low-dose CT colonography can detect highly significant extracolonic findings. Although extracolonic lesions were common, only a small proportion of patients required further diagnostic testing. Additional studies to determine the optimal radiation dose, cost-effectiveness, and legal implications of detecting extracolonic findings are warranted.

Aged↗
PubMed2005

Contemporary minimally invasive approaches to the management of acute cholecystitis: a review and appraisal.

Acute cholecystitis is one of the most common emergency admissions in surgical practice. This review appraises the available evidence from the English-language literature regarding the minimally invasive approaches to the management of this condition. The following aspects of care are reviewed and appraised: (1) the diagnostic criteria for acute cholecystitis, (2) the optimal timing for cholecystectomy (early, delayed, or interval surgery), (3) the optimal approach to cholecystectomy (laparoscopic versus open), (4) the role of intraoperative cholangiography, and (5) the management of patients unfit for surgery.

Cholangiography↗
PubMed1988

Management of serious alloimmunization in pregnancy.

In the past 40 years, tremendous advances in the treatment of hemolytic disease have been made. The perinatal mortality has been reduced considerably. Rh immunoprophylaxis has decreased the incidence of Rh immunization to around 6 per 100,000 live births. Nevertheless, treatment of severe hemolytic disease is still essential. Increased reliability of diagnostic procedures have made early detection and optimal treatment of hemolytic disease possible. Treatment by plasmapheresis is still controversial. Although believed to be beneficial by some authors, conclusive evidence of its efficacy has not been obtained. With preterm induction of birth at 32 weeks of gestation, the chances for survival are 95%. Improvement of techniques and the use of modern real-time ultrasound equipment have made intrauterine intraperitoneal transfusion, in experienced hands, a relatively safe and successful procedure. Intravascular transfusion appears beneficial in early pregnancy. Combination of both techniques will probably be the answer for the future. The development of neonatal intensive care facilities has made a major contribution to the survival of children with haemolytic disease. The relative low incidence of haemolytic disease has made it imperative that treatment should take place in centers where experience and special skill are available.

Female↗
PubMed2004

Videodermatoscopy enhances the ability to monitor efficacy of scabies treatment and allows optimal timing of drug application.

BACKGROUND: Videodermatoscopy (VD) is a noninvasive diagnostic tool that has recently been advanced as an alternative technique for the diagnosis of scabies, based on studies showing its ability to detect mites in vivo with results comparable to those obtained by traditional skin scraping. OBJECTIVE: In this study we evaluated a group of patients undergoing topical treatment with a thermosensible foam containing 0.165% pyrethrins and 1.65% piperonyl butoxide to determine whether VD would enhance monitoring of the clinical response to treatment and indicate the optimal timing of drug application. MATERIALS AND METHODS: Twenty patients (12 M, 8 F; age 1-65 years) affected by scabies (diagnosis confirmed by VD), and who were treatment naïve, were included in the study. The foam was applied to the entire body once a day at bedtime for two consecutive days. To detect treatment response, VD evaluation of two targeted skin sites for each patient was performed at baseline and at 12, 24, 36 and 48 h. A video microscope system equipped with a zoom lens that allowed skin observation with incident light at magnifications ranging from x 20 to x 600 was used. RESULTS: In all patients, VD showed active mite migration within burrows at 12 h. At 24 h, there was no evidence of active mite migration, and a majority of patients reported that itching had subsided. At 48 h, the mites were no longer visible in appreciable amounts by VD, and an amorphous material, probably resulting from mite decomposition, was detectable at one end of an empty burrow in the majority of patients. Skin scraping at 48 h, followed by standard microscopic observation, also showed only mite remnants in all patients. None of the 20 patients showed signs of infestation by VD at targeted skin sites at a 2-week post baseline follow-up visit. CONCLUSIONS: VD enhances the monitoring of clinical response to treatment and allows optimal timing of drug application. This may be particularly important in minimizing risk of overtreatment, reducing the potential for side-effects, and enhancing patient compliance.

Administration, Topical↗
PubMed2005

Subcutaneous Rosai-Dorfman disease: is surgical excision justified?

Rosai-Dorfman disease in soft tissue without nodal disease has been recognized as a distinct clinicopathologic entity. It may represent a diagnostic challenge and the natural history and optimal treatment has not been well clarified. We investigated a patient in whom Rosai-Dorfman disease was confined to the subcutis of the abdominal wall and recurred after incomplete excision. Complete resolution was achieved by wide surgical excision with negative margins. Pathologic examination confirmed the diagnosis of extranodal Rosai-Dorfman disease. The patient is disease-free after 1 year of follow-up. Despite the possibility that spontaneous remission may occur, our results suggest that when anatomically feasible, complete excision can be a treatment option for persistence or recurrence of exclusively extranodal disease. Larger case series and longer follow-up are needed to assess the long-term efficacy in these patients.

Abdominal Wall↗
PubMed2005

Variations in performance characteristics of commercial enzyme immunoassay kits for detection of antineutrophil cytoplasmic antibodies: what is the optimal cut off?

BACKGROUND: Previous studies have shown considerable variation in diagnostic performance of enzyme linked immunosorbent assays (ELISAs) for measuring antineutrophil cytoplasmic antibodies (ANCA) specific for proteinase 3 (PR3) and myeloperoxidase (MPO). OBJECTIVE: To analyse the performance characteristics of different commercially available direct ANCA ELISA kits. METHODS: ELISA kits for detecting PR3-ANCA and MPO-ANCA from 11 manufacturers were evaluated. Serum samples were taken from patients with Wegener's granulomatosis (15), microscopic polyangiitis (15), other vasculitides (10), and controls (40). RESULTS: were compared with data obtained by indirect immunofluorescence (IFT). The diagnostic performance of the tests was analysed and compared by receiver operating characteristic (ROC) curve analysis.Results: Applying the manufacturers' cut off resulted in great variation in sensitivity of the commercial PR3-ANCA kits for diagnosing Wegener's granulomatosis (ranging from 13.3% to 66.7%), and of the MPO-ANCA kits for diagnosing microscopic polyangiitis (ranging from 26.7% to 66.7%). Specificities were relatively constant (from 96.0% to 100%). IFT was superior to all ELISAs (C-ANCA for Wegener's granulomatosis: sensitivity 73.3%, specificity 98%; P-ANCA for microscopic polyangiitis: sensitivity 86.7%, specificity 98%). The sensitivities of PR3-ANCA and MPO-ANCA ELISA kits were increased by lowering the cut off values. This reduced specificity but increased overall diagnostic performance. CONCLUSIONS: The low sensitivity of some commercial kits reflects the high cut off levels recommended rather than methodological problems with the assays. Comparative analyses using sera from well characterised patients may help identify optimum cut off levels of commercial ANCA ELISA tests, resulting in better comparability of results among assays from different manufacturers.

Adult↗
PubMedDate not supplied

Endoluminal MR imaging of the rectum and anus: technique, applications, and pitfalls.

Anorectal diseases (e.g., fecal incontinence, perianal and anovaginal fistulas, anorectal tumors) require imaging for proper case management. Endoluminal magnetic resonance (MR) imaging has become an important part of diagnostic work-up in such cases. Optimal endoluminal MR imaging requires careful attention to patient preparation, imaging protocols, and potential pitfalls in interpretation. Comfortable positioning and the use of an antiperistaltic drug are vital for adequate patient preparation. Selected sequences and imaging planes are used in imaging protocols tailored for specific diseases. In fecal incontinence, three-dimensional sequences allow detailed demonstration of the anal anatomy and related defects. In perianal and anovaginal fistulas, longitudinal imaging planes help determine the superior extent of the abnormality. In anorectal tumors, T1-weighted turbo spin-echo MR imaging can help detect extension into the perirectal fat and T2-weighted turbo spin-echo MR imaging is used to optimize contrast between tumor and the rectal wall. Off-axis and radial imaging planes are used in all anorectal diseases to minimize partial volume effects. Potential pitfalls include various parts of the normal anal anatomy mimicking sphincter defects, veins and hemorrhoids mimicking fistulas and abscesses, and overhanging tumor mimicking more extensive tumor. Adequate patient preparation combined with proper technique and a knowledge of potential pitfalls will allow optimal endoluminal MR imaging of the rectum and anus.

Anus Diseases↗
PubMed1981

Cardiac infarction injury score: an electrocardiographic coding scheme for ischemic heart disease.

A multivariate decision-theoretic electrocardiogram (ECG) classification scheme called Cardiac Infarction Injury Score (CIIS) was developed using ECGs of 387 patients with myocardial infarction (MI) and 320 subjects without infarction. The most accurate and stable classification was achieved by using a combination of eight binary (single threshold), three ternary (two thresholds), and four ECG features measured on a continuous scale. For practical visual coding of ECGs, the CIIS coding procedure uses a checklist containing 12 items measured from the conventional 12-lead ECG. The CIIS test results indicate that, in comparison with conventional ECG criteria for MI used in clinical trials, the diagnostic accuracy can be considerably improved by optimizing feature and threshold selection and by multivariate analysis. The CIIS detected MI with a sensitivity of 85% and a specificity of 95%. Using a higher severity level, a specificity of 99% was achieved, with a sensitivity of 71%. One of the primary uses of the CIIS is coding of significant worsening of the ECG with new coronary events from annually recorded ECGs in clinical trials and epidemiologic studies.

Adult↗
PubMed1980

Transbronchial lung biopsy in sarcoidosis. An approach to determine the optimal number of biopsies.

In order to determine if the diagnostic yield of the transbronchial lung biopsy in sarcoidosis is dependent upon the number of biopsies, a study was designed to examine individual specimens from 6 biopsies in patients with Stage II sarcoidosis. It was found that the probability of obtaining a positive specimen per biopsy was 46%, and this percentage remained constant for each biopsy. The diagnostic yield followed a logarithmic curve, gradually increasing from 1 through 4 biopsies until about 90% of true positive diagnoses were obtained, then approaching a plateau with successive biopsies. We therefore recommend that 4 transbronchial lung biopsies are sufficient to diagnose stage II sarcoidosis in the majority of patients with diffuse lung disease.

Adolescent↗
PubMed2005

Effects of type and level of training on variation in physician knowledge in the use and acquisition of blood cultures: a cross sectional survey.

BACKGROUND: Blood culture (BCX) use is often sub-optimal, and is a user-dependent diagnostic test. Little is known about physician training and BCX-related knowledge. We sought to assess variations in caregiver BCX-related knowledge, and their relation to medical training. METHODS: We developed and piloted a self-administered BCX-related knowledge survey instrument. Expert opinion, literature review, focus groups, and mini-pilots reduced > 100 questions in multiple formats to a final questionnaire with 15 scored content items and 4 covariate identifiers. This questionnaire was used in a cross-sectional survey of physicians, fellows, residents and medical students at a large urban public teaching hospital. The responses were stratified by years/level of training, type of specialty training, self-reported practical and theoretical BCX-related instruction. Summary scores were derived from participant responses compared to a 95% consensus opinion of infectious diseases specialists that matched an evidence based reference standard. RESULTS: There were 291 respondents (Attendings = 72, Post-Graduate Year (PGY) = 3 = 84, PGY2 = 42, PGY1 = 41, medical students = 52). Mean scores differed by training level (Attending = 85.0, PGY3 = 81.1, PGY2 = 78.4, PGY1 = 75.4, students = 67.7) [p < or = 0.001], and training type (Infectious Diseases = 96.1, Medicine = 81.7, Emergency Medicine = 79.6, Surgery = 78.5, Family Practice = 76.5, Obstetrics-Gynecology = 74.4, Pediatrics = 74.0) [p < or = 0.001]. Higher summary scores were associated with self-reported theoretical [p < or = 0.001] and practical [p = 0.001] BCX-related training. Linear regression showed level and type of training accounted for most of the score variation. CONCLUSION: Higher mean scores were associated with advancing level of training and greater subject-related training. Notably, house staff and medical students, who are most likely to order and/or obtain BCXs, lack key BCX-related knowledge. Targeted education may improve utilization of this important diagnostic tool.

Blood↗
PubMed1996

Image quality and safety after iodixanol in intravenous urography; a comparison with iohexol.

A double-blind, randomized phase III study compared intravenous urography in 100 adult patients receiving iodixanol 320 mgI ml-1 (Visipaque) with 99 patients receiving iohexol 350 mgI ml-1 (Omnipaque). The aim of the study was to investigate differences in image quality between a non-ionic dimeric contrast medium (CM) and a non-ionic monomer at 40 ml per patient and 60-100 ml per patient volume levels. There were no statistically significant differences between iodixanol and iohexol with respect to overall diagnostic information, which was found to be optimal in 86% and 79%, respectively. Immediately after the injection, the renal border was better delineated with iohexol than with iodixanol (p = 0.0001). Marked papillary blush occurred more often in the iodixanol group (16%) than in the iohexol group (0%), as did visualization of the collecting ducts (24% vs 5%) (p = 0.001). The incidence of adverse events was similar and low for both contrast media. In patients who received the higher doses of CM (60-100 ml), the frequency of discomfort was significantly lower after iodixanol than after iohexol (p = 0.006). We conclude that, in intravenous urography, iodixanol provides at least as good image quality as does iohexol. Iodixanol may cause less discomfort than iohexol, in particular when larger volumes of CM are injected.

Adult↗
PubMed2004

Patient radiation doses during invasive cardiac procedures categorised by clinical code.

Patient radiation doses delivered during invasive fluoroscopic cardiology procedures at the University Hospital of North Staffordshire during a 3 year period from November 1999 to August 2002, and comprising 6189 patient records, have been analysed. Cases have been stratified using classification codes from the Office of Population Census and Surveys (OPCS-4 codes), allowing representative doses to be assessed for 34 distinct types of cardiac radiological procedure. In addition, local guidance levels have been derived for the eight most common procedures. This work represents one of the largest and most detailed published studies of patient radiation dose during cardiac procedures, and should assist in meeting the IR(ME)R regulations requirement for establishment of diagnostic reference levels, and in enabling dose optimization of individual exposures.

Cardiac Surgical Procedures↗