I used the latest source code to build niftyrec with CUDA GPU acceleration for mac OSX (10.6.8). Unfortunately, I got an unspecified error when executing any of the demo files that include GPU acceleration (Matlab R2012a). For example, running et_demo_mlem returned:

>> et_demo_osem
Creating synthetic sinogram..
Error using et_project_mex
niftyrec: ERROR - unspecified error.

Error in et_project (line 91)
sinogram = et_project_mex(activity, cameras, attenuation, psf,
use_gpu, background, background_attenuation,
truncate_negative_values);

Error in et_demo_osem (line 56)
ideal_sinogram = et_project(phantom, cameras, attenuation, psf,
GPU);

Apparently, there is a problem with the mex file? The demo file runs fine with GPU acceleration turned off.

I used the CUDA 4.2 toolkit and SDKs to compile the code, and also installed the CUDA 4.2 driver on my mac with OSX 10.6.8 and a NVIDIA Quadro 4000 GPU (see details below).

>> gpuDevice
Properties:
Name: 'Quadro 4000'
Index: 1
ComputeCapability: '2.0'
SupportsDouble: 1
DriverVersion: 4.2000
MaxThreadsPerBlock: 1024
MaxShmemPerBlock: 49152
MaxThreadBlockSize: [1024 1024 64]
MaxGridSize: [65535 65535]
SIMDWidth: 32
TotalMemory: 2.1470e+09
FreeMemory: 973713408
MultiprocessorCount: 8
ClockRateKHz: 950000
ComputeMode: 'Default'
GPUOverlapsTransfers: 1
KernelExecutionTimeout: 1
CanMapHostMemory: 1
DeviceSupported: 1
DeviceSelected: 1