Doubts about exercise in Lean Specialized Credential E-Learning

Hi, ASQ team.

I am studying the Lean Specialized Credential E-Learning and, in the subject OEE, in the case study topic, I am in doubt in two questions.

The scenario in the case study is:

Both hospitals in the Rolling Meadows healthcare system provide radiology services and use Magnetic Resonance Imaging (MRI) to generate detailed images. There is one MRI machine at each hospital. Recently, one hospital discovers that utilization of their MRI machine is almost 25% lower than the machine at the other hospital, and you are given the task of investigating why.

Over the past year, the Radiology Department with the under-utilized MRI machine accumulated the following data.

  • The Radiology Department is open weekdays, 12 hours/day. There are no downtimes for breaks or lunches, so patients flow through the department the entire 12-hour period.
  • There were 260 weekdays over the past year. The department was closed for 10 of those days due to holidays.
  • The MRI machine could not be used for a total of 1,187 hours due to the following reasons:
ReasonTime Loss (hrs.)# of Instances
Patient Table Mechanical Failure12912
Idle (No Patient Scheduled)381762
Helium Level Low482
Power Outage9326
Heat Exchanger Temperature Error25958
Coil Damage or Wear121
Power Up After Standby5652
Compressor Failure291
Blower Motor Failure121
Water Pump Failure241
LCD Screen Failure181
  • 3,158 patients were cycled through the MRI.
  • The ideal cycle time to process patients through the MRI, including setup and cleanup, is 20 minutes (0.33 hours or 3 people per hour).
  • There were 2,905 quality images and 253 poor-quality images taken by the MRI machine. Poor-quality images were due to artifacts (48 instances), patient movement (142 instances), technologist error (26 instances), and machine error (37 instances).

Based on your analysis of the accumulated data, answer the following questions related to the MRI machine’s overall equipment effectiveness.

My question: Why the target output is not 9,000 patients?

My understanding is that the target output is how many patients we could attend in the best cycle time? In this case, should be 250 days x 36 patients per day = 9,000 patients in the period. Also, I understood from the material that “running time” is a variable inside availability, not performance.


The second question is:

Because previous target output is considering running time, the performance ratio should be another one to me. It should be 3,158/9,000 = 35%


If we consider the running time in the calculation of target output, we are considering all the inefficiencies from the downtime table, which I understand that we “mask” the poor maintenance of the equipment. Am I right?

Please, appreciate any clarification here.

Thank you,

Claudio Genesini

2 Replies
Hi Claudio. I think you need to consider the 260 weekdays as the de department is open 12h/d weekdays. Then the target becomes 9360 and the result 34%. Is that the correct answer they give you? Hopefully?

The correct answers are 5,439 patients and 58% of performance rate. For any reason, the exercise is considering all inefficiencies in this result. Would it this calculation be correct?