DRAFT Recommended Practice for Measurements and ...

1/29/98 122 C95.3-1991 Revision — 2 nd Draft
10/98 Draft
reconstructed 3-dimensionally using Spyglass Slicer TM software on the PC and
VoxBlast TM software on the Silicon Graphics workstation to ensure correct anatomical
placement of each tissue type. Each image was also checked for unknown pixel values
using Wave Advantag eTM software. To predict SAR values, the anatomical information
within each TIF image file was converted to PGM files and imported into a FDTD
mathematical model that used a look-up-table (LUT) containing permittivity values for
each tissue type.
Development of models suitable for FDTD dosimetric calculations, while straight forward,
is not trivial. MRI and CT scans provide voxel maps of density, but many of the tissues
have the same or similar densities, and many of the regions outside of the major organs
require a detailed understanding of anatomy to determine what tissue are present, e.g.,
fat, fluid, air. Even when some automatic tissue definition can be used, the bulk of the
task falls on manual tissue recognition by a trained anatomist. Moreover, since FDTD
calculations use the tissue dielectric properties, i.e., dielectric constant and conductivity,
and mass density at each voxel location, knowledge of these properties for
Table D1 RGB colors for 42 tissue types
Tissue Type RGB Value Tissue Type RGB Value
Air (External) 9, 24, 135 Intestine (Large) 255, 0, 134
Air (Internal) 0, 0, 0 Intestine (Small) 0, 255, 254
Bile 105, 25, 132 Kidneys 180, 0, 255
Bladder 0, 128, 0 Ligaments 50, 100, 200
Blood 0, 255, 146 Liver 73, 0, 255
Blood Vessel 200, 100, 200 Lung(Inner) 200, 112, 50
Body Fluid 100, 255, 0 Lung (Outer) 0, 117, 255
Bone (Cancellous) 170, 148, 12 Lymph 230, 99, 74
Bone (Cortical) 255, 0, 217 Mucous Membrane 182, 255, 0
Bone (Marrow) 128, 128, 128 Muscle 70. 255, 0
Cartilage 255, 255, 128 Nails (Toe and Finger) 60, 200, 0
Cerebral Spinal Fluid 208, 255, 0 Nerve (Spine) 0, 0, 255
Eye (Cornea) 65, 63, 120 Nerve (Brain) 245, 150, 160
Eye (Lens) 30, 50, 70 Pancreas 255, 0, 109
Eye (Retina) 80, 100, 70 Skin/Dermis 255, 0, 0
Eye (Sclera/Wall) 255, 220, 0 Spleen 255, 82, 0
Eye (Aqueous Humor) 159, 0, 255 Stomach 140, 70, 20
Fat 255, 112, 0 Testicles 113, 11, 11
Gall Bladder 200, 60, 70 Tooth 10, 180, 80
Glands 0, 87, 255 Perfect Conductor 150, 125, 0
Heart 0, 128, 128 2/3 Muscle 180, 170, 160
each voxel is also required. Properties of many of the tissues has been measured over a
wide frequency range [Gabriel, 1996; Stuchly and Stuchly, 1980; Geddes and Baker,
1967; Durney, et al., 1986]. All tissues are highly frequency dispersive, and some
tissues, e.g., bone, heart, skeletal muscle, demonstrate anisotropic properties at
frequencies below 1 MHz [Epstein and Foster, 1983]. Additional measurements of tissue
properties are on-going as there remains questions about variations in tissue properties
with individuals, age, health status, temperature, in vivo versus in vitro, etc.
Copyright © 1998 IEEE. All rights reserved. This is an unapproved IEEE Standards Draft,
subject to change.