and a request for appointment is considered one day earlier to the date on which the investigation is desired and a time slot is allotted randomly to the calling patient according to the free time slot availability Ap pointment requests more than one day in advance are rare, and even if such requests arrive, the patients are usually advised to call just a day before the desired appointment date. In other words, an advanced access policy is adopted. Thus, it may be assumed that the present scheduling horizon is one day. Usually, less than 18 calls are received in advance (including requests from inpatients) i.e., all the 18 slots are not filled up in advance. However, there are some unscheduled arrivals (walk-ins), i e., some patients directly come on the day of investigation and request for an appointment slot. These are usually those patients who had consultations the same day with physicians at clinics associated with the hospital and try to have their investigation performed on the same vis Also there are no-shows among the scheduled free, the walk-in patient is allotted a Otherwise, the patient asked to wait for a no-show or to come later by taking a prior appointment. Although these walk-in patients have lower prior ity of being served than the scheduled patients, it is desirable to serve as many walk-in requests as possible.The MRI machine keep functioning until all the scheduled patients get their investigations done or until 8 pm (whichever is later). A schematic representation of the patient flows represented by arrows) in the MRI system is shown in Fig. 2