Further pieces of information...
The original image DICOM as reported by ImageJ includes:
0010,0020 Patient ID: CC11
0010,0030 Patient's Birth Date: 19520XXX
0010,0040 Patient's Sex: Z
0010,0020 Patient ID: CC11
after running clear on 0010,0020 and 0010,0030 imageJ shows:
0010,0020 Patient ID:
0010,0030 Patient's Birth Date:
0010,0040 Patient's Sex: M
0010,0020 >Patient ID: CC11
and DICOMBrowser shows a null entry for 0010,0020
If I run with delete 0010,0020 instead of clear, imageJ shows:
0010,0030 Patient's Birth Date:
0010,0040 Patient's Sex: M
0010,0020 >Patient ID: CC11
and DICOMBrowser doesn't show any 0010,0020 field in the result,