Use the standard value to fit the model and get lower mass attenuation for muscle compared to water

[knowledgefold]

Thanks for the software package.

I used the standard value to fit the model and got lower mass attenuation for muscle compared to water. I'm not sure whether it is correct.

The code and result is as follows:

cal = ogo.calib.internal_calibration.InternalCalibration(adipose_hu=-100.0, air_hu=-1000,  muscle_hu=30.0, label_list=(91, 92，95)) 
cal.fit() 
for k, v in cal.__dict__.items():
    print(k, v)

I get the following result:

_is_fit True
_slope 0.0
_intercept 0.0
_r_value 0.0
_p_value 0.0
_std_err 0.0
_hu None
_rho None
_adipose_hu -93.6
_air_hu -1000
_blood_hu 0
_bone_hu 0
_muscle_hu 48.2
_label_list [91, 92, 95]
_effective_energy 81.5
_max_r2 0.9999999439945123
_adipose_mass_attenuation 0.17915999999999999
_air_mass_attenuation 0.16529249999999998
_blood_mass_attenuation 0.18171
_bone_mass_attenuation 0.22009499999999999
_muscle_mass_attenuation 0.181325
_K2HPO4_mass_attenuation 0.24678000000000003
_CHA_mass_attenuation 0.254625
_triglyceride_mass_attenuation 0.178105
_water_mass_attenuation 0.182725
_hu_to_mass_attenuation_slope 1.529679264097352e-05
_hu_to_mass_attenuation_intercept 0.18058958900895788
_hu_to_density_slope 0.0010120702691656547
_hu_to_density_intercept 1.0129157583654536
_voxel_volume 0

In which, _muscle_mass_attenuation is 0.181325 and _water_mass_attenuation is 0.182725. To my knowledge, _muscle_mass_attenuation should be larger than _water_mass_attenuation.