Inter-comparison of radon detectors for one to four week measurement periods.

Seven different types of radon detectors (Atmos 12 dpx, RAD7, RStone, Sun Nuclear 1028, Ramon 2.2, Canary and CR-39) were compared for exposure periods of 1, 2, 3 and 4 weeks. The comparison was conducted under two conditions: (a) in a purpose-built radon chamber with an average radon concentration of 2560 Bq m(-3) (b) in a home environment with a radon concentration of 57 Bq m(-3), in both cases measured by the reference detector (Atmos 12 dpx) with a ±10% uncertainty range. In (a) 5 out of 8 detectors recorded radon concentrations within the Atmos uncertainty range and all detectors recorded within ±15%; in (b) 3 out of 9 detectors recorded within the Atmos uncertainty range and 6 out of 9 measured within ±20%, for a 4 week measurement. The results from this study show that radon surveys can be conducted for shorter periods than the recommended 3 months where a rapid indication is needed of whether the radon concentration is above the reference level, such as when assessing the concentration during and after remediation work.

Design and performance of a small-animal imaging system using synthetic collimation.

This work outlines the design and construction of a single-photon emission computed tomography imaging system based on the concept of synthetic collimation. A focused multi-pinhole collimator is constructed using rapid-prototyping and casting techniques. The collimator projects the centre of the field of view (FOV) through 46 pinholes when the detector is adjacent to the collimator, with the number reducing towards the edge of the FOV. The detector is then moved further from the collimator to increase the magnification of the system. The object distance remains constant, and each new detector distance is a new system configuration. The level of overlap of the pinhole projections increases as the system magnification increases, but the number of projections subtended by the detector is reduced. There is no rotation in the system; a single tomographic angle is used in each system configuration. Image reconstruction is performed using maximum-likelihood expectation-maximization and an experimentally measured system matrix. The system matrix is measured for each configuration on a coarse grid, using a point source. The pinholes are individually identified and tracked, and a Gaussian fit is made to each projection. The coefficients of these fits are used to interpolate the system matrix. The system is validated experimentally with a hot-rod phantom. The Fourier crosstalk matrix is also measured to provide an estimate of the average spatial resolution along each axis over the entire FOV. The 3D synthetic-collimator image is formed by estimating the activity distribution within the FOV and summing the activities in the voxels along the axis perpendicular to the collimator face.

Christopher Merrett's "Pinax rerum naturalium britannicarum" (1666): annotations to what is believed to be the author's personal copy.

In 1666, Christopher Merrett published "Pinax rerum naturalium britannicarum," this essentially being a catalogue of British plant localities known at the time together with a few other items of natural history. What is thought to be the author's personal annotated copy is held in the British Library. These annotations have been examined and the hand-writing compared to surviving examples known to be either of the author or of one of his sons and are now transcribed. Brief biographical notes relating to Merrett and to the background to his production of the "Pinax" are also given.

Wrist arthrodesis with excision of the proximal carpal bones using the Ao/ASIF wrist fusion plate and local bone graft.

We present our series of 17 patients who underwent wrist arthrodesis with excision of the proximal row carpal bones using the AO wrist fusion plate and local bone graft obtained from the excised proximal carpal row. All patients were evaluated using a questionnaire to assess pain, function, ability to perform an occupation and satisfaction with the procedure. The mean follow-up was 17 months, at which time all the fusions had united. Clinical outcome scores showed that 14 and 15 of the 17 patients achieved good or excellent results with regard to their current condition and clinical improvement, respectively. Four patients required secondary surgery, two for fractures and two for instability of the distal radio-ulnar joint unrelated to the wrist fusion.

A bait and switch hapten strategy generates catalytic antibodies for phosphodiester hydrolysis.

General base catalysis supplied by the histidine-12 (H-12) residue of ribonuclease (RNase) A has long been appreciated as a major component of the catalytic power of the enzyme. In an attempt to harness the catalytic power of a general base into antibody catalysis of phosphodiester bond hydrolysis, the quaternary ammonium phosphate 1 was used as a bait and switch hapten. Based on precedence, it was rationalized that this positively charged hapten could induce a counter-charged residue in the antibody binding site at a locus suitable for it to deprotonate the 2'-hydroxyl group of the anhydroribitol phosphodiester substrate 2. After murine immunization with hapten 1, mAb production yielded a library of 35 antibodies that bound to a BSA-1 conjugate. From this panel, two were found to catalyze the cyclization-cleavage of phosphodiester 2. Kinetic studies at pH 7.49 (Hepes, 20 mM) and 25 degreesC showed that the most active antibody, MATT.F-1, obeyed classical Michaelis-Menten kinetics with a Km = 104 microM, a kcat = 0.44 min-1, and a kcat/kuncat = 1.7 x 10(3). Hapten 1 stoichiometrically inhibits the catalytic activity of the antibody. MATT.F-1 is the most proficient antibody-catalyst (1.6 x 10(7) M-1) yet generated for the function of phosphodiester hydrolysis and emphasizes the utility of the bait and switch hapten paradigm when generating antibody catalysts for processes for which general-base catalysis can be exploited.

Radiologic placement of long-term central venous peripheral access system ports (PAS Port): results in 150 patients.

PURPOSE: The author reports experience with 150 peripheral access system ports (PAS Ports) placed in an interventional radiology suite. Complication rates from this series are compared with those of surgically placed tunneled catheters. The average cost of placement is compared with that of a surgically placed chest port. PATIENTS AND METHODS: Findings were retrospectively reviewed in 150 patients in whom the PAS Port catheter was implanted. The age range was 26-84 years (mean, 46 years). The diagnoses in these patients included cancer (n = 68), acquired immunodeficiency syndrome (n = 52), osteomyelitis (n = 21), and abscess (n = 9). Implantation with use of fluoroscopic guidance and "Cath-finder" technology is described. RESULTS: One hundred fifty ports have been indwelling for a total of 24,151 patient days (range, 40-220 days; mean duration, 161 days). Sepsis occurred in 3.3%, local infection in 5% (early infection 1%, late infection 4%), temporary catheter occlusion in 3.3%, postinsertion phlebitis in 7.3%, and venous thrombosis in 2%. The cost of radiologic PAS Port insertion averaged $1,488 versus $3,720 for surgical chest port insertion. CONCLUSION: PAS Port central venous catheter placement by an interventional radiologist in this series is safe and cost effective and compares very favorably with surgery. Radiologists will likely see increasing requests by referring physicians for radiologically placed catheters and ports in this era of cost containment.

Utilization of temporary muscle paralysis to eliminate CT motion artifact in the critically ill patient.

The intubated, critically ill patient often cannot suspend respiration long enough to eliminate severe computed tomographic (CT) motion artifact, even with current generation CT scanners. High quality, motion-free CT images were safely and easily obtained in two such patients using pancuronium bromide (Pavulon) to achieve muscle paralysis.

CT demonstration of pneumatosis intestinalis from bowel infarction.

A case is presented that illustrates the value of CT in detecting pneumatosis intestinalis prior to plain film findings.

Thoracic and lumbar spine fusion: postoperative radiologic evaluation.

A retrospective review of 206 consecutive thoracic and lumbar fusions revealed a variety of surgical procedures performed for instability and malalignment after severe trauma. Stabilization procedures included insertion of 103 Harrington distraction and 15 Harrington compression rods, 84 Weiss spings, six Luque rods, and 10 miscellaneous plates and wires as single or multiple devices in combination with anterior and/or posterior fusions. Complications of surgical fusion included nine unhooked rods, six fatigue fractures of rods and springs, five overdistractions of vertebrae, four cases of severe kyphosis, and two failures of reduction. A meaningful postoperative radiologic evaluation can be accomplished only when indications for surgical techniques, their radiologic appearance, and possible complications are known.

Reactions to intravenous contrast media. Part I: Severe and fatal cardiovascular reactions in a canine dehydration model.

Investigations into the nature of severe and fatal reactions to contrast media have been severely limited by their unpredictable occurrence in the clinical setting and the absence of suitable laboratory models. The authors report their experience with a canine dehydration model. Intravenous administration of 2 ml/kg of 76% sodium methylglucamine diatrizoate resulted in vomiting, shock, inappropriate slowing of the heart rate, and death. ECG findings indicated suppression of sinoatrial node automaticity, a decrease in the rate of atrioventricular conduction, and depression of myocardial contractility. These results suggest two possible mechanisms: (a) enhanced vagal tone as the result of stimulation of the vasomotor center of the medulla or (b) accentuation of direct contrast-induced myocardial toxicity.

Reactions to intravenous contrast media. Part II: Acute renal response in euvolemic and dehydrated dogs.

Growing concern about acute renal failure as the result of contrast agents prompted an investigation into the renal effects of intravenous contrast materials in euvolemic and dehydrated dogs. Bolus injection of hypertonic agents induced marked reductions in filtration fraction and glomerular filtration rate in both groups of animals; however, these changes were transient, returning to near-base-line values within 30 minutes after injection. The most striking differences between euvolemic and dehydrated animals appeared to be related to prerenal factors such as hypovolemia and contrast-induced hypotension.

Reappraisal of contrast media used to detect upper gastrointestinal perforations: comparison of ionic water-soluble media with barium sulfate.

Iodinated water-soluble compounds have been widely recommended as the most suitable contrast media for diagnosis of gastrointestinal perforations. However, the authors present 6 cases in which mucosal tears and transmural perforations of the upper gastrointestinal tract were either unrecognizable or inadequately shown during initial evaluation with methylglucamine diatrizoate. Re-examination with barium sulfate demonstrated the precise location and extent of the perforations. Reasons for the higher diagnostic yield of barium studies are explained on the basis of experimental and clinical observations.

Evaluation of the urethra in males with spinal cord injury.

Of 358 antegrade voiding urethrograms obtained in 200 males with spinal cord injury, the urethra was satisfactorily shown by 154 (77%), permitting evaluation of alterations related to cord damage, surgery, or iatrogenic trauma. In 105 cases the neurogenic urethra was normal, demonstrated only minor distension, or had a patulous appearance, in contrast to urinary tract changes such as a markedly neurogenic bladder, vesicoureteral reflux, and bladder calculi. In 49 patients, abnormalities included (a) changes related to surgical alleviation of sphincter dyssynergia; (b) iatrogenic changes such as diverticula strictures, undermining of the external sphincter ("spiral sign"), and intravasation of contrast material; and (c) pressure necrosis of the urethra. Some changes need no special treatment; others, such as pressure necrosis, require early recognition and prompt therapy.

Radiologic evaluation of surgical cervical spine fusion.

Preoperative, intraoperative, and postoperative radiologic evaluation of surgical cervical spine fusion plays an integral part in the management of cervical spine injuries. The radiographic anatomy of the basic types of anterior, posterior, and combined fusions and the indications for their performance are discussed. A retrospective review of 210 consecutive cervical spine fusions showed a 21.1% radiographic complication rate for anterior fusions and only 3.9% for posterior fusions. The high complication rate of anterior fusions is related to the performance of anterior fusion in the presence of unrecognized posterior instability. Radiographically identified complications must be correlated with the clinical neurologic examination in each case since the spectrum of radiographic complications may be compatible with a clinically satisfactory result.