Numerical Simulation of Scalp Cooling to Prevent Chemotherapy–Induced Alopecia

One way of treating cancer is by chemotherapy. Side–effects of chemotherapy include hair loss. Cooling the scalp during treatment can reduce hair loss. For this cooling, a cap containing a cold fluid (cold cap) is used. However, the rate of success of this method varies strongly, because precise mechanisms of preservation are unknown. Temperature and perfusion are thought to play an important role in the hair preservative effect of scalp cooling. To gain more insight into these parameters, a computer model has been developed. With this, the influence of perfusion models is studied. The computer model comprises a head and cold cap, modeled with concentric shells representing brain, skull, fat, skin, hair and cold cap. Metabolism is temperature dependent and two relations from literature are used to model temperature dependent perfusion. Pennes’ bio–heat equation is used to determine the heat transfer in the head. Steady state temperatures without cold cap are calculated and used as basal temperatures for metabolism and perfusion. Then, a cold cap (T = -30 ̊C) is added and the development of temperature in time is calculated. For constant perfusion, a minimum skin temperature of 16.0 ̊C is reached after 476 seconds. When skin blood flow is set to zero, the minimum temperature drops a further 1.5 ̊C to 14.5 ̊C. For the perfusion models, the drop in skin temperature results in a decreased perfusion, down to a value ranging from 19% to 33% of base level. The thickness of the hair layer is of great importance for both perfusion and temperature. Reducing the thickness resulted in a decrease in temperature of 5.7 ̊C, and decreased relative perfusion by a further 0.10, indicating that chances of preserving hair are higher. For optimal protection against hair loss, the cold cap should fit the scalp as tightly as possible.