Bernd Hofmann

Hybrid simulation with loosely coupled system dynamics and agent-based models for prospective health technology assessments

Due to the ageing of the world population, the demand for technology innovations in healthcare is growing rapidly. All stakeholders (e.g., patients, healthcare providers and health industry) can take profit of innovative products, but the development degenerates often into a time consuming and cost-intensive process. Prospective Health Technology Assessment (ProHTA) is a new approach that combines the knowledge of an interdisciplinary team and uses simulation techniques to indicate the effects of new innovations early before the expensive and risky development phase begins. In this paper, we describe an approach with loosely coupled system dynamics and agent-based models within a hybrid simulation environment for ProHTA as well as a use-case scenario with an innovative stroke technology. The project ProHTA is a part of the Centre of Excellence for Medical Technology and is supported by the German Federal Ministry of Education and Research (BMBF), project grant No. 01EX1013B.

Benefit of 1.5-T intraoperative MR imaging in the surgical treatment of craniopharyngiomas

BackgroundAs low-field magnetic resonance imaging (MRI) has very limited significance for intraoperative control of total tumor removal (TTR), we examined the influence of 1.5-T MRI, incorporating higher resolution into the intraoperative strategy of craniopharyngioma surgery.MethodsSurgery with intraoperative imaging was performed in 25 selected patients in whom tumor resection was anticipated to be difficult according to pre-operative findings.ResultsIntraoperative MRI confirmed the intended extent of tumor removal in 15 patients (14 TTRs, one intended incomplete removal, while a second procedure was scheduled due to complex shape). Misinterpretation was false positive or negative in one patient each. The extent of removal was not achieved as expected in eight patients (expectation: seven TTRs, one incomplete removal). In three patients, the expected TTR was achieved by resuming surgery. In another case, that goal was accomplished by performing an unscheduled second procedure. In total, by using intraoperative imaging, the rate of TTR was increased by 16% (four patients), leading to 80% in the entire series. Compared with the literature, the rate of new ophthalmologic and endocrine deficits is acceptable; the rate of other surgical complication is slightly higher but not directly caused by intraoperative imaging.ConclusionIntraoperative 1.5-T MRI provides benefits because of good early prediction of TTR (sensitivity, positive predictive value: 93.8%; specificity, negative predictive value: 88.9%) and a low rate of false-positive results. Moreover, extended resection of remnants visualized is enabled and helps to increase the rate of TTR but does not exclude recurrence.

Hormone receptor expression in craniopharyngiomas: a clinicopathological correlation.

BACKGROUNDExtensive neurosurgical resection of craniopharyngiomas often requires lifetime hormonal substitution. OBJECTIVEWe investigated the effect of the hormone receptor expression of insulinlike growth factor-1, growth hormone–releasing hormone receptor, growth hormone, progesterone, estrogen (ER-1, ER-β), and leptins (Ra6.4, Ra12.1, Rb) on tumor recurrence, size, and proliferation using clinical, histopathological, and molecular genetic analysis. PATIENTS AND METHODScDNA expression analysis was obtained in a cohort of 20 patients suffering from a craniopharyngioma to systematically determine the expression of above-mentioned receptors. In addition, 51 tumor samples were available to immunohistochemically investigate the extent and distribution of estrogen and progesterone receptors. In 18 tumor specimens, both experimental paradigms could be performed. RESULTSAll hormone receptors under study, including leptins, were detectable in craniopharyngiomas with reverse-transcription polymerase chain reaction but did not reach significance regarding the tested parameters. However, a correlation was observed between tumor size and cell proliferation indexes, as well as with cDNA expression levels of ER-1 and growth hormone receptors. CONCLUSIONThe present preliminary data point to a correlation between estrogen and growth hormone receptor expression and proliferation indexes with tumor size in craniopharyngiomas. Because of the small cohort of tumors, these data require expansion and validation. This is the first report about leptin expression in this tumor entity. These findings should prompt careful consideration of hormonal replacement therapy regimens in patients with tumor remnants and evidence of respective receptor expression.

System Dynamics and Agent-Based Simulation for Prospective Health Technology Assessments

Healthcare innovations open new treatment possibilities for patients and offer potentials to increase their life quality. But it is also possible that a new product will have negative influences on patient’s life quality, if it has not been checked before. To prevent latter cases three already established methods can be used in order to assess healthcare technologies and to inform regulatory agencies. But these tools share a common problem. They can only be applied when a product is already developed and high costs have been already produced. This work describes Prospective Health Technology Assessment. This approach uses hybrid simulation techniques in order to learn about the impacts of a new innovation before a product has been developed. System Dynamics is used to perform high-level simulation and Agent-Based Simulation allows to model individual behavior of persons.