present invention also describes analogous apparatus for penetrating radiation measurements on biological tissue samples application_number US 59713605 A description fig1 illustrates and apparatus suitable for in vitro irradiation of a tissue sample e g a breast tissue sample that has been obtained from a biopsy the apparatus comprises a penetrating radiation in this example x ray beam source 2 that directs a beam of x ray radiation onto the tissue sample 4 being examined a series of detectors 6 8 10 12 14 are arranged below and above the sample 4 to detect both transmitted and scattered x ray radiation in use the source and detector arrangement is scanned across the full length of the tissue sample as indicated by arrow u2018 s u2019 whilst the sample is held stationary the incident beam can be a slit form beam having a width into the page as illustrated in fig1 sufficient to extend across the full width of the sample alternatively the beam may be narrower e g a pencil form beam and be scanned laterally across the sample at each step in the longitudinal direction looking in more detail at the detector arrangement illustrated in fig1 it can be seen that below the sample 4 there are two of pairs of detectors 8 10 arranged to detect scattered radiation 16 18 and a single detector 6 for detecting transmitted radiation 14 the detectors 8 are for detecting ultra low angle scatter around 1 degree the detectors 10 are for detecting wider angle scatter of about 5 to 8 degrees in the present example above the.