prostate volume overlap on these patients was 89.9 ± 4.2%. 3DUS defined prostate volumes were on average 86.5 ± 12.8% of the CT contoured volumes as expected. The prostate was not visible on CT for all of the bilateral MHP patients and partially obscured for the unilateral MHP patient. The prostate was clearly visible on 5/5 MHP patients on US; the apex was in the shadow of the pelvic bone in one case. 3DUS image quality was sufficient to confidently perform US-US IGRT on all MHP and non-MHP patients studied. Conclusions: The fusion of CT and 3DUS can be successfully used to assist in contouring the prostate, with US offering enhanced tissue contrast that is complementary to CT. In patients with MHP, when CT artifacts obscure the prostate, 3DUS provides significant improvements to target visualization allowing confident target planning delineation as well as daily IGRT.Purpose/Objective(s): To evaluate intrafraction prostate displacement among patients externally immobilized in the prone position using real-time monitoring of implanted radiofrequency transponders. Materials/Methods: Seventeen patients had three electromagnetic transponders implanted transperineally with ultrasound guidance at least 1 week prior to obtaining a radiation planning CT scan and 2 weeks prior to the start of definitive external beam radiation therapy for organ-confined prostate cancer. All patients were treated in the prone position and stabilized with a thermoplastic immobilization device that was custom-fitted over the buttocks and abdomen. The Calypso Ò four-dimensional localization system was used to track prostate motion in all patients. Real-time measurement of transponder position was recorded for each patient treatment fraction at a frequency of 10 Hz. Seven hundred fifty-one fractions were available for analysis. These measurements were used to determine the duration and magnitude of displacement along the three primary directional axes (lateral, superior-inferior, and anterior-posterior) as well as the net vector displacement. Results: The study population had a mean age of 72.2 ± 7.0 years, body mass index of 28.5 ± 4.1 kg/m 2 , and prostate volume of 52.1 ± 26.3 cm 3 . The mean/median PSA and Gleason score were 7.3/5.6 ng/mL and 6.9/6, respectively. Averaged over all patients and treatment fractions, the calculated vector displacement of the centroid of the implanted transponders was offset from the treatment isocenter by $ 1 mm, $ 2 mm, $ 3 mm, and $ 4 mm for 81.2%, 38.0%, 13.9%, and 4.5% of the time, respectively. In the lateral dimension, the centroid was offset from the treatment isocenter by $ 1 mm, $ 2 mm, $ 3 mm, and $ 4 mm for 20.4%, 2.7%, 0.4%, and 0.06% of the time, respectively. In the superior-inferior dimension, the centroid was offset from the treatment isocenter by $ 1 mm, $ 2 mm, $ 3 mm, and $ 4 mm for 46.8%, 16.1%, 4.7%, and 1.5% of the time, respectively. In the anterior-posterior dimension, the centroid was offset from the treatment isocenter by $ 1 mm, $ 2 mm, $ 3 mm, and $ 4 mm for 44.1%, 13.4%, 3.0%, a...
We studied two young army recruits with erythrocytosis. One had a variant hemoglobin with high affinity for oxygen (hemoglobin Osler, also known as Fort Gordon and Nancy, beta 145 Tyr leads to Asp). The other had normal oxygen affinity and erythrocytosis of undetermined etiology. Both were asymptomatic. We studied exercise capacity on a cycle ergometer before and after hemodilution. In the subject with high oxygen affinity, hemodilution resulted in reduced maximal work and increased heart rate at every work level. In addition, minute ventilation and arterial lactic acid increased, while anaerobic threshold decreased, indicating diminished oxygen supply to tissues. In contrast, the subject with normal oxygen affinity had no significant changes in exercise performance after hemodilution. These results suggest that when blood oxygen affinity is high, loss of efficiency in tissue oxygenation can be expected after phlebotomy or hemodilution. Therefore, it may be useful to measure blood oxygen affinity and exercise performance in polycythemic subjects in whom such procedures are intended to ameliorate symptoms of hyperviscosity.
In hereditary pyropoikilocytosis (HPP), the red cell membrane skeletons exhibit a mechanical instability that can be correlated to defective self-association of spectrin heterodimers. To determine the underlying molecular defect, we have subjected HPP spectrin to limited tryptic digestion, followed by one- and two-dimensional separations of the peptides. Two of the HPP kindreds exhibited a marked decrease in 80,000- dalton peptide (previously identified as the spectrin dimer-dimer contact domain of the alpha-subunit) and a concomitant increase of the 74,000-dalton polypeptide (presumably derived from the 80,000-dalton domain) and a decrease in a 22,000-dalton polypeptide. We now report tryptic digests of two other HPP kindred that are characterized by a decrease or complete absence of the 80,000-dalton tryptic fragment, with a concomitant increase in fragments at 46,000 and 17,000 daltons. The 46,000-dalton fragment separated into multiple spots on isoelectric focusing, ranging in isoelectric point from 5.25 to 5.35, and the 17,000-dalton fragment focused to a single spot at 5.4. Minor fragments at 56,000 and 22,000 daltons were also decreased, while a 38,000-dalton fragment increased. Limited tryptic digestion of the separated alpha- and beta-subunits revealed that the 74,000-dalton fragment in the first group of patients and the 46,000-dalton fragment in the second group of patients were derived from the alpha-subunit. Both subtypes exhibited a similar defect of spectrin self-association, with 30%-38% of spectrin dimers in O degrees C extracts. The results indicate that at least two distinct forms of structurally defective spectrin may give rise to the clinical presentation of HPP.
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