New CT protocols show promising results in pulmonary embolism assessment. High-pitch dual-source CT (DSCT) at 100 kV provides radiation dose savings for pulmonary CTA. High-pitch DSCT at 100 kV maintains diagnostic image quality for pulmonary CTA. Dual energy CT uses more radiation but also provides lung perfusion evaluation. Whether the additional perfusion data is worth the extra radiation remains undetermined.
We examined transient and steady-state responses of the pulmonary circulation to hypoxia in isolated pig lungs perfused with autologous blood. Responses were quantified by the pulmonary artery pressure at a flow of 1 l/min (Ppa1) read directly from pressure-flow recordings. Alveolar carbon dioxide tension was constant at 38 Torr and alveolar oxygen pressure (PAO2) was varied between 670 and 0 Torr. When PAO2 was lowered progressively every 10 min, the relation between PAO2 and Ppa1 was sigmoidal, with maximum constriction occurring at a PAO2 of 0 Torr; however, if Ppa1 was allowed to reach a steady state at each level of PAO2, the relation was reproducibly and reversibly biphasic. Ppa1 increased as PAO2 decreased from 670 to 60 Torr, was maximum and stable at PAO2 between 60 and 30 Torr, and decreased as PAO2 was lowered from 30 to 0 Torr. As a result, steady-state Ppa1 at PAO2 greater than or equal to 200 Torr was similar to that at PAO2 = 0 Torr. When PAO2 was changed from 200 Torr to a constant lower level, Ppa1 required 20-30 min to achieve a steady state at PAO2 greater than or equal to 25 Torr and 40-50 min at PAO2 of 10 and 0 Torr. With the latter, the responses consisted of vasoconstriction followed by marked vasodilation. Thus pulmonary vasomotor tone was a complex function of both PAO2 and time. Attempts to explain the pulmonary vascular response to hypoxia must take these complexities into account.
Advances in computerized and imaging technology permit both students and doctors to depict the anatomy of the human pelvis more realistically than with previous methods. Further refinements outline fine pelvic structures, such as the nerve plexus, which may as a result be spared during major pelvic surgery, thus preserving the function of the bladder neck and urethra. Dynamic computerized tomography or magnetic resonance imaging, coupled with three-dimensional depiction of the lower urinary tract and its adjacent structures, enable visualization of the whole lower urinary tract and the pelvic floor musculature in both continent and incontinent women. In patients with a reconstructed lower urinary tract computer-assisted image processing shows the postoperatively altered topographical anatomy. This may be clinically useful for interpretation of unexpected findings with conventional imaging modalities, postoperative morbidity, and surgical planning of a lower abdominal reoperation. Examples of our own work regarding the innervation of female pelvic organs, dynamic depiction of the bladder and pelvic floor musculature during straining in normal and incontinent women, and the situation of female patients after undergoing an anterior pelvic exenteration with subsequent orthotopic neobladder procedure, are given. In addition, the data of these patients have been compiled for virtual reality endoscopy, which is useful for patient consent and for teaching residents, students and nurses.
The aim of this pilot study in 54 patients was to improve the visualization of the anatomy and postoperative changes in the pelvic topography after bilateral ureteroileal urethrostomy, using surface rendering of electron beam CT (EBCT) data for the 3D display. Fifty-four patients (39 men and 15 women) were scanned with an EBCT unit between 3 and 110 months after performing orthotopic ureteroileal urethrostomy ("Hemi-Kock") or ureteroileal rectosigmoidostomy. Various parameters and spatial viewing points were used in the 3D reconstruction, which was performed interactively on external workstations with commercially available software. The anti-reflux nipple was visualized as a distinct structure in all patients. In 8 patients with an interval of more than 12 months between surgery and CT, the pouch had developed an ovoid shape almost indistinguishable from the original bladder. The segmented data sets were partly animated to display the anatomy as virtual endoscopy. Three-dimensional depiction and virtual endoscopy of the neobladder using EBCT are a new way of imaging the postoperative anatomy. Its clinical efficacy in the diagnosis of inconclusive postoperative morbidity, especially voiding problems, and planning of necessary therapy have to be the subject of further evaluation.
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