Such trees have considerable palaeoclimatic potential due to their longevity and landscape survival times, but are challenging to sample non-destructively.
A very practical consideration is that imaging can assess receptor expression at sites that are challenging to sample and assay, for example, bone metastases, where de-calcification can make assay of tumor gene products challenging.
Of note, it has been challenging to obtain lymph node biopsy samples from these patients and controls.
It is challenging to optimally sample the muscularis propria endoscopically for the diagnosis of muscle layer diseases, especially for motility disorders resulting from neuroenteric dysfunction.
The population biology of an organism so tightly associated with humans is challenging to study due to sampling bias, limited sampling sizes, human influence, and non-random sampling [5], [8], [15].
Owing to the relatively large sample area (∼2 × 2 cm) and limited imaging fields of view (<150 × 150 μm for CRM when working at 60× magnification), it is challenging to ensure precise sample navigation, reliable relocation of microscopic CRM ROIs for subsequent MSI, and proper alignment of imaged regions for precise spatial registry of the CRM and MSI data.
These calculations were determined at medical record level, since HCP encounters are nested within medical records and are challenging to compile into a sampling frame.
It is challenging to obtain sequential biopsy samples from patients with solid tumors and as such, surrogate tissues especially blood or cheek (buccal) cells can provide practical alternatives.
It is well established that FFPE tumour DNA samples are challenging to amplify and sequence due to damage resulting from the fixation process and due to sample heterogeneity.
It was challenging to determine how representative the samples were of target population.
