Some ADNI3 DTI volumes do not match protocol descriptions

[bluju...@gmail.com]

Hi all,

I am processing DTI data from the ADNI3 phase. I downloaded the ADNI3_diffusion_gradient_table_info (link) files for each scanner. I compiled information from each file to understand how many volumes I should expect in each DTI dataset following dcm2niix conversion according to ADNI phase, scanner, and sequence:

ADNI 2 --> 5 b=0 + 41 b=1000 = 46 volumes
ADNI 3 GE --> 6 b=0 + 48 b=1000 directions = 54 volumes
ADNI 3 Philips Basic --> 1 b0 + 48 b=1000 + 5 b=2 = 54 volumes
ADNI 3 Philips Advanced --> 1 b0 + 32 b=1000 + 3 b=2 = 36 volumes
ADNI 3 Siemens Basic --> 7 b0 + 48 b=1000  = 55 volumes

ADNI 3 Siemens Advanced --> 13 b0 + 6 b=500 + 48 b=1000 + 60 b=2000 = 127 volumes 

Most of the NII converted images align with these expectations. However, I found about 100 datasets that do not. For example, there are 26 datasets that were acquired in ADNI3 using a Philips scanner that only have 33 volumes, rather than the expected 36 (see image IDs below). On the other hand, there are 64 datasets that were acquired in ADNI3 on Siemens scanners that have 31 volumes rather than 55. If the number of volumes in the converted datasets do not match what is expected (per the ADNI3_diffusion_gradient_table_info), would you recommend they be excluded from analysis? Any advice would be helpful.

Thank you!

Jenna

Philips Image IDs - 1010872, 871896, 860233, 926307, 922303, 1268413, 928487, 1068963, 841963, 960712, 1177163, 1079469, 938648, 873177, 880609, 1044569, 926586, 953559, 984882, 1050524, 1032579, 1058971, 1060005, 1063913, 1138756, 1129789

Siemens Image IDs - 925546, 845581, 1146969, 929046, 858513, 963765, 1274402, 899465, 949420, 848170, 909787, 969411, 872949, 984494, 974172, 907776, 949875, 947597, 958102, 899482, 1123773, 831861, 1004672, 839478, 844189, 851357, 923015, 887928, 939885, 895065, 911537, 907721, 1092350, 970016, 1264674, 945609, 948090, 961825, 966811, 1018481, 969045, 968286, 980923, 974702, 992774, 1011833, 1018188, 1037403, 1017013, 1039143, 1015832, 1060035, 1054703, 1047176, 1037966, 1064841, 1038951, 1032539, 1051060, 1080323, 1162717, 1176887, 1184042, 1226109

[Danielle J Harvey]

Hi Jenna,

 

I reached out to a contact in the ADNI MRI Core and got the following response:

 

the reason for those scanners have less volumes than expected are due to hardware limitations on some of the older Siemens and Philips systems.  The only way for those systems to run the DTI was to do less vols for the acquisition. 

 

That being said, the DTI data from those systems should still be useable, but if they wanted to ignore due to the hardware limitations of those systems that would be reasonable as well.

 

I hope that helps!

Danielle

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[Jenna Blujus]

Hi Danielle,

Thank you so much. This helps a lot.

Best,

Jenna Blujus