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Byline: Ivar Astby (1), Ragnar Winther (2) Keywords: Stability; Granulopoiesis; Mathematical model Abstract: A class of mathematical models involving a convection-reaction partial differential equation (PDE) is introduced with reference to recovering human granulopoiesis after high dose chemotherapy with stem cell support. The stability properties of the model are addressed by means of numerical investigations and analysis. A simplified model with proliferation rate and mobilization rate independent of maturity shows that the model is stable as the maturation rate grows without bounds, but may go through stable and non-stable regimens as the maturation rate varies. It is also shown that the system is stable when parameters are chosen to approximate a real physiological situation. System characteristics do not change profoundly by introduction of a maturity-dependent proliferation and mobilization rate, as is necessary to make the model operate more in accordance with hematological observations. However, by changing the system mitotic responsiveness with respect to changes in cytokine level, the system is still stable but may show persistent oscillations much resembling clinical observations of cyclic neutropenia. Furthermore, in these cases, changes in the model feedback signal caused by, for instance, an impaired effective cytokine elimination by cell receptors may enforce these oscillations markedly. Author Affiliation: (1) Department of Informatics, University of Oslo, Box 1080, Blindern, 0316, Oslo, Norway (2) Centre of Mathematics for Applications (CMA) and Department of Informatics, 1080, Blindern, 0316, Oslo, Norway Article History: Registration Date: 01/01/2004 Received Date: 24/06/2003 Online Date: 05/07/2004

Byline: Patricia A. Lowry (1), M. Cristie Carstens (1) Abstract: Background Tracer-avid osseous lesions are usually considered to represent metastases in pediatric oncology patients. However, sites of minor, clinically occult, skeletal trauma may be mistaken for osseous metastases. Objective The objective of this study was to review our experience with skeletal scintigraphy in pediatrie oncology patients to determine specificity for metastatic disease. Materials and methods We reviewed 164 bone scans performed on 96 consecutive patients (ages 5 months to 23 years) at presentation with malignancy or during chemotherapy. Tumors included osteosarcoma (13), Ewing sarcoma (11), lymphoma (19), neuroblastoma (12), brain tumors (16), rhabdomyosarcoma (10), renal tumors (5), and miscellaneous neoplasms (10). Scintigraphic abnormalities were considered metastatic based on radiographie findings, subsequent tumor progression, or multiplicity of lesions. Lesions were considered benign when spontaneous resolution occurred without change in therapy or radiographs demonstrated a traumatic or other benign lesion. Results Of the 96 patients, 51 had normal studies or showed only the primary lesion. Of the 45 patients with abnormal scintigraphy, 16 (35 %) had metastases and 29 (65 %) had one or more focal benign lesions. These lesions included abnormalities due to stress/trauma (25), benign neoplasm (2), infection (3), disuse (6), surgery (10) and artifacts (4). Conclusion The majority of scintigraphic abnormalities have nonmalignant etiologies, most commonly stress reaction and trauma. In patients without known extraosseous metastases, one or two skeletal lesions should not be assumed to represent metastatic disease. Author Affiliation: (1) University of Texas Southwestern Medical Center and Children's Medical Center of Dallas, 1935 Motor Street, Dallas, Texas, USA (2) Department of Radiology, St. Christopher's Hospital for Children, Eric Avenue at Front Street, 19134, Philadelphia, PA, USA Article History: Registration Date: 28/03/2009 Received Date: 11/12/1995 Accepted Date: 28/06/1996 Article note: Presented at the 37th Annual Meeting of the Society for Pediatric Radiology, April 1994 in Colorado Springs, Colorado, USA.