does backprojection by interpolating between the bins. More...

#include "stir/recon_buildblock/BackProjectorByBinUsingInterpolation.h"

Inheritance diagram for stir::BackProjectorByBinUsingInterpolation:

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Public Member Functions
	BackProjectorByBinUsingInterpolation (const bool use_piecewise_linear_interpolation=true, const bool use_exact_Jacobian=true)
	The constructor defaults to using piecewise linear interpolation and the exact Jacobian.

	BackProjectorByBinUsingInterpolation (shared_ptr< const ProjDataInfo > const &, shared_ptr< const DiscretisedDensity< 3, float >> const &image_info_ptr, const bool use_piecewise_linear_interpolation=true, const bool use_exact_Jacobian=true)
	The constructor defaults to using piecewise linear interpolation and the exact Jacobian. More...

void	set_up (const shared_ptr< const ProjDataInfo > &proj_data_info_ptr, const shared_ptr< const DiscretisedDensity< 3, float >> &density_info_ptr) override
	Stores all necessary geometric info. More...

const DataSymmetriesForViewSegmentNumbers *	get_symmetries_used () const override
	Gets the symmetries used by this backprojector. More...

void	use_exact_Jacobian (const bool use_exact_Jacobian)
	Use this to switch between the exact Jacobian and an approximate Jacobian (valid for s << R).

void	use_piecewise_linear_interpolation (const bool use_piecewise_linear_interpolation)
	Use this to switch between ordinary linear interpolation and piece-wise linear interpolation in the axial direction.

BackProjectorByBinUsingInterpolation *	clone () const override

Public Member Functions inherited from stir::RegisteredParsingObject< BackProjectorByBinUsingInterpolation, BackProjectorByBin >
std::string	get_registered_name () const override
	Returns Derived::registered_name.

std::string	parameter_info () override
	Returns a string with all parameters and their values, in a form suitable for parsing again.

Public Member Functions inherited from stir::BackProjectorByBin
	BackProjectorByBin ()
	Default constructor calls reset_timers()

void	back_project (DiscretisedDensity< 3, float > &, const ProjData &, int subset_num=0, int num_subsets=1)
	project whole proj_data into the volume More...

virtual void	back_project (const ProjData &, int subset_num=0, int num_subsets=1)
	projects the viewgrams into the volume it adds to the data backprojected since start_accumulating_in_new_target() was last called.

void	back_project (const RelatedViewgrams< float > &)
	projects the viewgrams into the volume it adds to the data backprojected since start_accumulating_in_new_target() was last called.

void	back_project (const RelatedViewgrams< float > &, const int min_axial_pos_num, const int max_axial_pos_num)
	projects the specified range of the viewgrams and axial positions into the volume it adds to the data backprojected since start_accumulating_in_new_target() was last called.

void	back_project (const RelatedViewgrams< float > &, const int min_axial_pos_num, const int max_axial_pos_num, const int min_tangential_pos_num, const int max_tangential_pos_num)
	projects the specified range of the viewgrams, axial positions and tangential positions into the volume it adds to the data backprojected since start_accumulating_in_new_target() was last called.

virtual void	start_accumulating_in_new_target ()
	tell the back projector to start accumulating into a new target. This function has to be called before any back-projection is initiated.

virtual void	get_output (DiscretisedDensity< 3, float > &) const
	Get output This will overwrite the array-content of the argument with the result of all backprojections since calling `start_accumulating_in_new_target()`. Note that the argument has to have the same characteristics as what was used when calling `set_up()`.

void	set_post_data_processor (shared_ptr< DataProcessor< DiscretisedDensity< 3, float >>> post_data_processor_sptr)
	Set data processor to use after back projection.

Public Member Functions inherited from stir::TimedObject
void	reset_timers ()
	reset all timers kept by this object

void	stop_timers () const
	stop all timers kept by this object More...

void	start_timers (bool do_reset=false) const
	start all timers kept by this object More...

double	get_CPU_timer_value () const
	get current value of the CPU timer (since first use or last reset)

double	get_wall_clock_timer_value () const
	get current value of the wall-clock timer (since first use or last reset)

Public Member Functions inherited from stir::ParsingObject
	ParsingObject (const ParsingObject &)

ParsingObject &	operator= (const ParsingObject &)

void	ask_parameters ()

bool	parse (std::istream &f)

bool	parse (const char *const filename)

Static Public Attributes
static const char *const	registered_name = "Interpolation"
	Name which will be used when parsing a BackProjectorByBin object.

Additional Inherited Members
Static Public Member Functions inherited from stir::RegisteredParsingObject< BackProjectorByBinUsingInterpolation, BackProjectorByBin >
static BackProjectorByBin *	read_from_stream (std::istream *)
	Construct a new object (of type Derived) by parsing the istream. More...

Static Public Member Functions inherited from stir::RegisteredObject< BackProjectorByBin >
static BackProjectorByBin *	read_registered_object (std::istream *in, const std::string &registered_name)
	Construct a new object (of a type derived from Root, its actual type determined by the registered_name parameter) by parsing the istream. More...

static BackProjectorByBin *	ask_type_and_parameters ()
	ask the user for the type, and then calls read_registered_object(0, type) More...

static void	list_registered_names (std::ostream &stream)
	List all possible registered names to the stream. More...

Protected Types inherited from stir::RegisteredObject< BackProjectorByBin >
typedef BackProjectorByBin (	RootFactory) (std::istream *)
	The type of a root factory is a function, taking an istream* as argument, and returning a Root*.

typedef FactoryRegistry< std::string, RootFactory, interfile_less >	RegistryType
	The type of the registry.

Protected Member Functions inherited from stir::BackProjectorByBin
virtual void	actual_back_project (const RelatedViewgrams< float > &, const int min_axial_pos_num, const int max_axial_pos_num, const int min_tangential_pos_num, const int max_tangential_pos_num)
	This actually does the back projection. There are two versions of this code to enable backwards compatibility. More...

virtual void	check (const ProjDataInfo &proj_data_info) const
	check if the argument is the same as what was used for set_up() More...

virtual void	check (const ProjDataInfo &proj_data_info, const DiscretisedDensity< 3, float > &density_info) const
	check if the arguments are the same as what was used for set_up() More...

Protected Member Functions inherited from stir::ParsingObject
virtual bool	post_processing ()
	This will be called at the end of the parsing. More...

virtual void	set_key_values ()
	This will be called before parsing or parameter_info is called. More...

Static Protected Member Functions inherited from stir::RegisteredObject< BackProjectorByBin >
static RegistryType &	registry ()
	Static function returning the registry. More...

Protected Attributes inherited from stir::BackProjectorByBin
bool	_already_set_up

shared_ptr< DiscretisedDensity< 3, float > >	_density_sptr
	Clone of the density sptr set with set_up()

shared_ptr< DataProcessor< DiscretisedDensity< 3, float > > >	_post_data_processor_sptr

shared_ptr< const ProjDataInfo >	_proj_data_info_sptr
	ProjDataInfo set by set_up()

Protected Attributes inherited from stir::ParsingObject
KeyParser	parser

Detailed Description

does backprojection by interpolating between the bins.

This implementation uses incremental backprojection

Two versions of interpolation are implemented:

ordinary linear interpolation
piecewise linear interpolation in the axial direction

The former is an implementation of "Incremental beamwise backprojection using geometrical symmetries for 3D PET reconstruction in a cylindrical scanner geometry" M L Egger, C Joseph, C Morel, Phys. Med. Biol. (1998) 43 3009-3024 http://dx.doi.org/10.1088/0031-9155/43/10/023

For the latter, see the extended abstract for 3D99 "On various approximations for the projectors in iterative reconstruction algorithms for 3D-PET", K. Thielemans, M.W. Jacobson, D. Belluzzo. Available on the STIR web-site.

The piecewise linear interpolation is only used when the axial voxel size is half the axial_sampling of the projection data (for the segment in question).

Warning

This implementation makes various assumptions (for optimal speed):

voxel_size.x() = voxel_size.y()
arc-corrected data
voxel_size.z() is either equal to or half the axial_sampling of the projection data

When the bin size is not equal to the voxel_size.x(), zoom_viewgrams() is first called to adjust the bin size, then the usual incremental backprojection is used.

Bug:: Currently this implementation has problems on certain processors due to floating point rounding errors. Intel *86 and PowerPC give correct results, SunSparc has a problem at tangential_pos_num==0 (also HP stations give problems).

Constructor & Destructor Documentation

◆ BackProjectorByBinUsingInterpolation()

stir::BackProjectorByBinUsingInterpolation::BackProjectorByBinUsingInterpolation	(	shared_ptr< const ProjDataInfo > const &	proj_data_info_ptr,
		shared_ptr< const DiscretisedDensity< 3, float >> const &	image_info_ptr,
		const bool	use_piecewise_linear_interpolation = `true`,
		const bool	use_exact_Jacobian = `true`
	)

The constructor defaults to using piecewise linear interpolation and the exact Jacobian.

Deprecated:: Use set_up() instead

References stir::BackProjectorByBin::set_defaults(), and stir::BackProjectorByBin::set_up().

Member Function Documentation

◆ set_up()

void stir::BackProjectorByBinUsingInterpolation::set_up	(	const shared_ptr< const ProjDataInfo > &	proj_data_info_ptr,
		const shared_ptr< const DiscretisedDensity< 3, float >> &	density_info_ptr
	)

overridevirtual

Stores all necessary geometric info.

Note that the density_info_ptr is not stored in this object. It's only used to get some info on sizes etc.

Implements stir::BackProjectorByBin.

References stir::error(), stir::VoxelsOnCartesianGrid< elemT >::get_voxel_size(), stir::round(), and stir::BackProjectorByBin::set_up().

◆ get_symmetries_used()

const DataSymmetriesForViewSegmentNumbers * stir::BackProjectorByBinUsingInterpolation::get_symmetries_used ( ) const

overridevirtual

Gets the symmetries used by this backprojector.

Warning: This BackProjectorByBin implementation requires that the RelatedViewgrams data are constructed with symmetries corresponding to the current member. Using another DataSymmetriesForViewSegmentNumbers object will likely crash the program.

Implements stir::BackProjectorByBin.

References stir::error().

The documentation for this class was generated from the following files:

/home/sirfuser/devel/STIRdistrib/STIR/src/include/stir/recon_buildblock/BackProjectorByBinUsingInterpolation.h
/home/sirfuser/devel/STIRdistrib/STIR/src/recon_buildblock/BackProjectorByBinUsingInterpolation.cxx
/home/sirfuser/devel/STIRdistrib/STIR/src/recon_buildblock/BackProjectorByBinUsingInterpolation_3DCho.cxx

Public Member Functions