PydicomReader dimension mismatch vs. pydicom

[oseymour]

Describe the bug
I get different dimensions when loading with the LoadImage transform and pydicom, even when specifying reader="PydicomReader". The DICOM file is a multi-frame ultrasound file. Unfortunately, I can't share it here because this is for work.

To Reproduce
Running pydicom.dcmread(path_to_file).shape returns (61, 748, 982, 3). This is the expected result.

Running LoadImage(image_only=True, reader="PydicomReader").shape returns torch.Size([748, 61, 982, 3]). I see the same behavior without specifying reader.

Expected behavior
The arrays should have the same dimensions.

Screenshots
N/A

Environment

Ensuring you use the relevant python executable, please paste the output of:

================================
Printing MONAI config...
================================
MONAI version: 1.4.0
Numpy version: 1.26.4
Pytorch version: 2.5.1+cpu
MONAI flags: HAS_EXT = False, USE_COMPILED = False, USE_META_DICT = False
MONAI rev id: 46a5272196a6c2590ca2589029eed8e4d56ff008
MONAI __file__: C:\Users\<username>.HCAD\Downloads\carotid_multiframe_model\.venv\Lib\site-packages\monai\__init__.py

Optional dependencies:
Pytorch Ignite version: NOT INSTALLED or UNKNOWN VERSION.
ITK version: NOT INSTALLED or UNKNOWN VERSION.
Nibabel version: 5.3.2
scikit-image version: NOT INSTALLED or UNKNOWN VERSION.
scipy version: NOT INSTALLED or UNKNOWN VERSION.
Pillow version: 11.0.0
Tensorboard version: 2.18.0
gdown version: NOT INSTALLED or UNKNOWN VERSION.
TorchVision version: NOT INSTALLED or UNKNOWN VERSION.
tqdm version: 4.67.1
lmdb version: NOT INSTALLED or UNKNOWN VERSION.
psutil version: 6.1.0
pandas version: NOT INSTALLED or UNKNOWN VERSION.
einops version: NOT INSTALLED or UNKNOWN VERSION.
transformers version: NOT INSTALLED or UNKNOWN VERSION.
mlflow version: NOT INSTALLED or UNKNOWN VERSION.
pynrrd version: NOT INSTALLED or UNKNOWN VERSION.
clearml version: NOT INSTALLED or UNKNOWN VERSION.

For details about installing the optional dependencies, please visit:
    https://docs.monai.io/en/latest/installation.html#installing-the-recommended-dependencies


================================
Printing system config...
================================
System: Windows
Win32 version: ('10', '10.0.19045', 'SP0', 'Multiprocessor Free')
Win32 edition: Enterprise
Platform: Windows-10-10.0.19045-SP0
Processor: Intel64 Family 6 Model 186 Stepping 3, GenuineIntel
Machine: AMD64
Python version: 3.12.3
Process name: python.exe
Command: ['C:\\Users\\<username>.HCAD\\AppData\\Local\\Programs\\Python\\Python312\\python.exe', '-c', 'import monai; monai.config.print_debug_info()']
Open files: [popenfile(path='C:\\Windows\\System32\\en-US\\KernelBase.dll.mui', fd=-1)]
Num physical CPUs: 10
Num logical CPUs: 12
Num usable CPUs: 12
CPU usage (%): [45.3, 3.3, 55.0, 0.0, 2.7, 2.0, 2.0, 12.7, 8.0, 1.3, 3.3, 6.7]
CPU freq. (MHz): 1800
Load avg. in last 1, 5, 15 mins (%): [0.0, 0.0, 0.0]
Disk usage (%): 76.7
Avg. sensor temp. (Celsius): UNKNOWN for given OS
Total physical memory (GB): 31.4
Available memory (GB): 17.4
Used memory (GB): 14.0

================================
Printing GPU config...
================================
Num GPUs: 0
Has CUDA: False
cuDNN enabled: False
NVIDIA_TF32_OVERRIDE: None
TORCH_ALLOW_TF32_CUBLAS_OVERRIDE: None

And since it's not printed out above, the pydicom version I'm using is 3.0.1.

Additional context
Add any other context about the problem here.

[KumoLiu]

Hi @oseymour, thanks for reporting this.
You can set swap_ij=False in the LoadImage function. By default, this value is set to True to ensure the outputs are consistent with other readers.

MONAI/monai/data/image_reader.py

Line 399 in e1e3d8e

swap_ij: whether to swap the first two spatial axes. Default to ``True``, so that the outputs