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- Nyman, Ulf, et al.
(författare)
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Patient-circumference-adapted dose regulation in body computed tomography. A practical and flexible formula
- 2005
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Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 46:4, s. 396-406
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To illustrate that the attenuation formula based on monochromatic radiation in homogeneous objects may be used for dose regulation in body computed tomography (CT) based on patient circumference and using a simple cloth measuring tape. Material and Methods: Based on the attenuation formula for monochromatic radiation, the following Microsoft Excel equation was derived: mAs(x)=mAs(n)* EXP(( 0.693/ HVT)*(empty set(x)-empty set(n))/ PI()), where mAs(x) (milliampere second) in a patient with circumference Ox is calculated based on the nominal mAs(n) set for a reference patient with the circumference On with regard to indication, scan protocol, and available CT scanner. The HVT=half-value thickness ( object thickness change in cm affecting mAs setting by a factor of 2) resulting in the least mAs difference compared with published studies investigating the mAs needed for constant image noise in abdominal CT phantoms at 80 140 kVp was evaluated. Clinically recommended HVT values were applied to 20 patients undergoing abdominal CT using 130 effective mAs and 94 cm circumference as nominal settings, and an HVT of 9 cm. Results: The object-sized dependent mAs for constant image noise at 80 - 140 kVp in 10 47 cm diameter abdominal phantoms ( 31 - 148 cm in circumference) differed, with few exceptions, by no more than 10% from those obtained with our formula using an HVT of 3.2 - 3.8 cm. An HVT of 9 cm in the patient study resulted in the same image noise patient circumference relation as a phantom study using a "clinically adapted mAs'' resulting in an acceptable noise according to diagnostic requirements. Clinical experiences recommend an HVT of about 8 cm for abdominal CT and 12 cm in thoracic CT. Changing the kVp from 120 to 80, 100, or 140 requires a mAs change roughly by factors of 4, 2, and 0.6, respectively, for constant image noise. Conclusion: Until fully automatic automatic exposure control systems have been introduced, applying the formula in a computer program provides the radiologist with an easy, quick, flexible, and practical instrument for reasonably good patient-sized adjusted exposure levels in clinical practice.
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- Olofsson, Christina, et al.
(författare)
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A multicenter clinical study of the safety and activity of maleimide-polyethylene glycol-modified Hemoglobin (Hemospan) in patients undergoing major orthopedic surgery.
- 2006
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Ingår i: Anesthesiology. - : Ovid Technologies (Wolters Kluwer Health). - 0003-3022 .- 1528-1175. ; 105:6, s. 1153-63
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Hemospan (Sangart Inc., San Diego, CA), a polyethylene glycol-modified hemoglobin with unique oxygen transport properties, has successfully completed a phase I trial in healthy volunteers. Because adverse events are expected to increase with age, the authors conducted a phase II safety study of Hemospan in elderly patients undergoing elective hip arthroplasty during spinal anesthesia. METHODS: Ninety male and female patients, American Society of Anesthesiologists physical status I-III, aged 50-89 yr, in six Swedish academic hospitals were randomly assigned to receive either 250 or 500 ml Hemospan or Ringer's acetate (30 patients/group) before induction of spinal anesthesia. Safety assessment included vital signs and Holter monitoring from infusion to 24 h, evaluation of laboratory values, and fluid balance. The hypothesis to be tested was that the incidence of adverse events would be no more frequent in patients who received Hemospan compared with standard of care (Ringer's acetate). RESULTS: Three serious adverse events were noted, none of which was deemed related to study treatment. Liver enzymes, amylase, and lipase increased transiently in patients in all three groups. There were no significant differences in electrocardiogram or Holter parameters, but there was a suggestion of more bradycardic events in the treated groups. Hypotension was less frequent in the treated patients compared with controls. CONCLUSIONS: In comparison with Ringer's acetate, Hemospan mildly elevates hepatic enzymes and lipase and is associated with less hypotension and more bradycardic events. The absence of a high frequency of serious adverse events suggests that further clinical trials should be undertaken.
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