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ABSTRACT: Purpose: CT can contribute over 50% of radiation dose in the whole body (WB) PET/CT scan. Tube current modulation (TCM) is a standard technique for reducing CT radiation dose to the patient by changing the tube current with the patient size, and is controlled by a very low-dose scoutscan, which assumes the patient is positioned at the center of the CT gantry opening. However, most patients are not positioned at the center due to practicality or to avoid claustrophobic or to reduce time of radiation exposure from the patient to the technologist. We study the impact of the AP and PA scout scans to the patient radiation exposure from CT. Methods: Ina retrospective study of 200 patients, each received two WB PET/CT scans: one with AP, and the other one with PA. The helical CT with TCM and PET acquisitions were identical in both scans. Separation of the two scans was about 10 months in average. The scans were performed on four GE PET/CT scanners: three 16- and one 64-slice with the same TCM settings. The 200patients were selected for the same scan coverage and similar body weight (difference = 3 kg). The tube current in each slice and average exposure tothe patient were recorded and compared. Results: The AP scout caused lower radiation dose on 94% of the patients. Both the tube current, and radiation exposure were reduced by 46±30 mA and 1.6±1.0 mGy, respectively. The effective radiation dose is reduced by 1.7±1.2 mSv. These results were statistically significant (p<0.00001). Conclusions: The AP scout caused significantly less radiation dose than the PA scout in the CT scan of the whole-body PET/CT scan. Care should be taken to select theorientation of the scout scan to achieve appropriate radiation exposure to the patient when TCM is applied.
Medical Physics 06/2012; 39(6):3621. · 2.83 Impact Factor
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A Faught,
S Kry, D Luo,
A Molineu,
D Bellezza,
R Gerber,
S Davidson,
W Bosch,
J Galvin,
R Drzymala,
R Timmerman,
J Sheehan,
M Gillin,
G Ibbott,
D Followill
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ABSTRACT: Purpose: To develop and evaluate a modified anthropomorphic head phantom for evaluation of stereotactic radiosurgery (SRS) dose planning and delivery. Methods: A phantom was constructed from a water equivalent, plastic, head-shaped shell. The original phantom design, with only a spherical target, was modified to include a nonspherical target (pituitary) and an adjacent organ at risk (OAR) (optic chiasm), within 2 mm, simulating the anatomy encountered when treating acromegaly. The target and OAR spatial proximity provided a more realistic treatment planning and dose delivery exercise. A separate dosimetry insert contained two TLD for absolute dosimetry and radiochromic film, in the sagittal and coronal planes, for relative dosimetry. The prescription was 25Gy to 90% of the GTV with >= 10% of the OAR volume receiving >= 8Gy. The modified phantom was used to test the rigor of the treatment planning process, dosimeter reproducibility, and measured dose delivery agreement with calculated doses using a Gamma Knife, CyberKnife, and linear accelerator based radiosurgery systems. Results: TLD results from multiple irradiations using either a CyberKnife or Gamma Knife agreed with the calculated target dose to within 4.7% with a maximum coefficient of variation of+/-2.0%. Gamma analysis in the coronal and sagittal film planes showed an average passing rate of 99.3% and 99.5% using +/-5%/3mm criteria, respectively. A treatment plan for linac delivery was developed meeting the prescription guidelines. Dosimeter reproducibility and dose delivery agreement for the linac is expected to have results similar to the results observed with the CyberKnife and Gamma Knife. Conclusions: A modified anatomically realistic SRS phantom was developed that provided a realistic clinical planning and delivery challenge that can be used to credential institutions wanting to participate in NCI funded clinical trials. Work supported by PHS CA010953, CA081647, CA21661 awarded by NCI. DHHS.
Medical Physics 06/2012; 39(6):3746-3747. · 2.83 Impact Factor
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ABSTRACT: L-selectin, a surface adhesion glycoprotein expressed on leukocytes, has a well-established role in mediating inflammation and lymphocyte recirculation. Recent evidence suggests that L-selectin may also influence hematopoiesis. We observed that a greater proportion of CD34+ cells express L-selectin in cord blood compared with adult bone marrow, and we hypothesized that L-selectin expression is associated with enhanced clonogenic properties. To test this, we compared CD34+/L-selectin+ cells with CD34+/L-selectin- cells in hematopoietic clonogenic assays. From CD34+/L-selectin+ cell cultures, we observed a 3-fold increase of d 12-14 colony-forming unit-granulocyte/macrophage and multipotent progenitor cells, and a 5-fold enhancement of primitive d 21 high proliferative potential colony-forming cells compared with the progeny of CD34+/L-selectin- cells. We conclude that CD34+ cord blood cells expressing L-selectin are enriched in their clonogenic activity compared with cell fractions lacking L-selectin expression.
Pediatric Research 07/1999; 45(6):867-70. · 2.70 Impact Factor
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ABSTRACT: Apoptosis mediates neutrophil (PMN) phagocytosis and is influenced by cytokines and the Fas/Fas ligand pathway. To determine whether apoptosis of cord blood PMN differs from those of adults, cultured PMN were evaluated by morphological analysis, flow cytometry (TUNEL assay), and DNA gel electrophoresis. In addition, we studied the effect of anti-Fas IgM or cycloheximide on induction of PMN apoptosis. Spontaneous apoptosis (24 h) was less in cord blood PMN (mean +/- SD; 29 +/- 9 vs. adults, 56 +/- 14%, P < 0.001). Treatment (6 h) with anti-Fas IgM induced less apoptosis in cord blood PMN (24 +/- 6 vs. adults, 63 +/- 7%, P < 0.001), as did treatment with cycloheximide (13 +/- 10 vs. adults, 55 +/- 16%, P < 0.01). These data suggest the pre-existence of proteins that inhibit apoptosis or the absence of those that promote apoptosis in cord blood PMN.
Journal of Leukocyte Biology 10/1998; 64(3):331-6. · 4.99 Impact Factor
