Despite overwhelming successes in recent years, progress in the field of biomedical image computing still largely depends on the availability of annotated training examples. This annotation process is often prohibitively expensive because it requires the valuable time of domain experts. Additionally, this approach simply does not scale well: whenever a new imaging modality is created, acquisition parameters change. Even something as basic as the target demographic is prone to changes, and new

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... notated cases have to be created to allow methods to cope with the resulting images. Image labeling is thus bound to become the major bottleneck in the coming years. Furthermore, it has been shown that many algorithms used in image analysis are vulnerable to out-of-distribution samples, resulting in wrong and overconfident decisions [20, 21, 22, 23]. In addition, physicians can overlook unexpected conditions in medical images, often termed 'inattentional blindness'. In [1], Drew et al. noted that 50% of trained radiologists did not notice a gorilla image, rendered into a lung CT scan when assessing lung nodules. One approach, which does not require labeled images and can generalize to unseen pathological conditions, is Out-of-Distribution or anomaly detection (which in this context is used interchangeably). Anomaly detection can recognize and outline conditions that have not been previously encountered during training and thus circumvents the time-consuming labeling process and can therefore quickly be adapted to new modalities. Additionally, by highlighting such abnormal regions, anomaly detection can guide the physicians' attention to otherwise overlooked abnormalities in a scan and potentially improve the time required to inspect medical images. However, while there is a lot of recent research on improving anomaly detection [8, 9, 10, 11, 12, 13, 14, 15, 16, 17], especially with a focus on the medical field [4, 5, 6, 7], a common dataset/ benchmark to compare different approaches is missing. Thus, it is currently hard t [...]