26-2-2010: Afstudeerder Jelmer Kranenburg wint 3e prijs bij landelijke scriptieprijs Innovaties In De Zorg

Jelmer Kranenburg bij beste 3 scripties van landelijke scriptieprijs Innovaties in de Zorg

26 februari 2010

Nadat Jesse van Elteren vorig jaar de scriptieprijs 2009 van Innovaties in de Zorg in ontvangst mocht nemen, viel ons dit jaar weer de eer te beurt met een nominatie in de top 3 met de scriptie van Jelmer Kranenburg.

Vanuit de Nederlandse hbo-en w.o.-instellingen waren er 52 afstudeerscripties genomineerd voor de hoofdprijs van € 2500,-. Onze eigen Jelmer Kranenburg greep uiteindelijk net naast de hoofdprijs, maar behaalde met een lovend juryrapport een knappe derde plek.

De MSc-afstudeerscriptie van Jelmer Kranenburg (student in de Production & Logistics Management track van het Industrial Engineering & Management master programma) is getiteld “The prospect of walk-in for the CT-department of AMC”. Jelmer’s afstudeerwerk betrof een studie in AMC (Amsterdam) naar de logistieke haalbaarheid van het “op inloop” organiseren van de CT-scanners voor electieve patiënten.

Jelmer werd vanuit AMC begeleid door promovendi Jasper van Sambeek en Nikky Kortbeek, en vanuit UT door Erwin Hans en Koos Krabbendam.

Lees verder de management samenvatting (in het Engels) van Jelmer’s scriptie…

Management Summary


This study reflects on the access system of the CT scan modality in Academic Medical Center in Amsterdam. Earlier research in this hospital has shown that short access times and the combination of multiple hospital appointments on the same day are preferred by patients over short waiting times. Enabling patients to visit the CT scan without an appointment, which is called walk-in, contributes to a higher patient service as access time is completely eliminated.

Problem description

The effects of introducing walk-in on logistical performance indicators as patient waiting time, resource utilisation and overtime are largely unknown, as minor quantitative research has been done regarding walk-in. The goal of this research is to investigate the logistical feasibility when implementing various degrees of walk-in at the CT scan modality.


Allowing walk-in inherently results in a non-stationary arrival pattern as demand fluctuates, both within as between days. As our process analysis phase shows that walk-in would not be possible for all patient types, we investigate ways to counteract for the non-steady behaviour by scheduling appointments during periods of low expected demand. We introduce several interventions in which the degree of walk-in is varied. Furthermore, we explore an intervention where inpatients are called in from the ward at times the expected waiting time for the CT scan is low. To quantify the input variables, patient data is acquired over the year 2008 and several time-stamp measurements were performed. A discrete-event simulation model is developed to explore the logistical performance of each intervention. The model is validated by performing independent-samples t-tests on access time and patient waiting time. An important principle is that we do not wish to affect waiting time for planned patients. This research took place in close cooperation with the radiology department of AMC, as well as the hospital Alysis in Arnhem.


The logistical performance of introducing walk-in for various interventions is shown in terms of average access time, waiting time, overtime, production and utilisation. Access times of planned patients have been shown to decrease in comparison with the current situation, indicating a more timely access for all patients since walk-in patients’ access times are eliminated completely. The current waiting time is 9 minutes on average. When introducing walk-in, waiting time for walk-in patients is determined to be 35 minutes on average, while planned patients’ waiting time decreases to between 4 to 8 minutes depending on the intervention chosen. On average no overtime exists, with a deviation of maximally 25 minutes from the planned closing time in 90% of the days. Utilisation is equal in the various interventions due to equal demand, but is shown to increase significantly when an increase of 10% in demand is attained under the same available capacity. Under a 10% growth and same capacity, the average waiting time of walk-in patients increases to approximately 42 minutes. The various interventions put forward proved particularly useful in eliminating the average overtime, and reduce the number of patients that are rejected or decide to go home because of high waiting times.

Conclusions and recommendations

Our context analysis shows, that walk-in for 100% of the patients is not feasible from a practical point of view, as some examinations require the presence of other medical specialists, because large preparation times are required, or simply because some patients will prefer to make an appointment. This research demonstrates that by introducing walk-in in combination with appointments, patient service can significantly be improved. It enables patients to combine multiple appointments on the same day, while lower access times for planned patients can be achieved. Simultaneously, the logistical performance indicators do not exceed the threshold values set. Calling-in inpatients from the ward at times of low expected waiting time reduces the number of rejections and patients that decide to leave because of high expected waiting times. In addition, we have shown that by introducing walk-in, the CT department is able to serve more patients under the same capacity, indicating a higher attainable efficiency. Further improvement of the results is possible, as the model currently imposes strict priorities on planned patients which might be loosened, and prudence is applied in the data analysis.

A few hospitals in the Netherlands have already implemented walk-in at their radiology department, or are starting a pilot aimed at doing so (Tweesteden in Tilburg, Alysis in Arnhem). This research provides the scientific guidelines for such a system, and creates a deeper understanding of the effects of introducing walk-in on patient logistics. The experience in practice provides several success factors. For a walk-in system to come to full fruition, broad support and clear communication from the radiology department at all levels is indispensable. The work process changes considerably, and the responsibility of laboratory workers and other directly involved in the process increases. Recent trials in other hospitals that are piloting walk-in however show that the work process is perceived as more dynamic and fun due to the increased responsibility and flexibility required.

The approach chosen, where walk-in and appointments are combined to balance non-stationary demand is new in the literature. It might find application in areas wider than healthcare alone, for example in call-centres and bank tellers.