R/mrs_read_ima.R

In spant: MR Spectroscopy Analysis Tools

read_ima <- function(fraw, verbose = FALSE, extra) {
  
  tags <- list(ascii_hdr = "0029,1120", spec_data = "7FE1,1010")
  res  <- dicom_reader(fraw, tags)
  
  vars <- read_siemens_txt_hdr(res$ascii_hdr, "vd", verbose)
  
  # works for CMRR MPRESS, but not CMRR sLASER
  if (!vars$rm_oversampling) vars$N <- vars$N * 2
  
  # calculate expected size of data points
  data_size <- vars$x_pts * vars$y_pts * vars$z_pts * vars$N * 2
  
  # note that for scans where oversampling is not removed there are actually
  # twice the number of points in the DICOM tag. However these points seem to
  # be garbage making this mode useless as half the time-domain data is lost.
  
  raw_pts <- readBin(res$spec_data, what = "double", n = data_size, size = 4L)
  
  # make complex
  data <- raw_pts[c(TRUE, FALSE)] + 1i * raw_pts[c(FALSE, TRUE)]
  
  data <- array(data, dim = c(vars$N, 1, 1, vars$z_pts, vars$y_pts, vars$x_pts, 
                              1))
  
  data <- aperm(data, c(7, 5, 6, 4, 3, 2, 1))
  
  # freq domain vector vector
  freq_domain <- rep(FALSE, 7)

  # get the resolution and geom info
  paras <- calc_siemens_paras(vars, TRUE)
  
  meta <- list(EchoTime = vars$te,
               FlipAngle = vars$flip_ang,
               SequenceName = vars$seq_fname,
               ChemicalShiftReference = 4.7 + vars$delta_freq,
               NumberOfTransients = vars$averages,
               Manufacturer = "Siemens")
  
  if (toupper(vars$seq_fname) == "%SIEMENSSEQ%\\SVS_SE") {
    meta <- append(meta, list(PulseSequenceType = "press"))
  }
  
  if (toupper(vars$seq_fname) == "%SIEMENSSEQ%\\SVS_ST") {
    meta <- append(meta, list(PulseSequenceType = "steam"))
  }
  
  mrs_data <- mrs_data(data = data, ft = vars$ft, resolution = paras$res,
                       ref = paras$ref, nuc = paras$nuc,
                       freq_domain = freq_domain, affine = paras$affine,
                       meta = meta, extra = extra)
  
  return(mrs_data)
}

#' Read a directory containing Siemens MRS IMA files and combine along the coil
#' dimension. Note that the coil ID is inferred from the sorted file name and
#' should be checked when consistency is required between two directories.
#' @param dir data directory path.
#' @param extra an optional data frame to provide additional variables for use
#' in subsequent analysis steps, eg id or grouping variables.
#' @param verbose output extra information to the console.
#' @return mrs_data object.
#' @export
read_ima_coil_dir <- function(dir, extra = NULL, verbose = FALSE) {
  
  # check the directory exists
  if (!dir.exists(dir)) stop("Error read_ima_coil_dir directory was not found.")
  
  # check it contains some files
  files <- list.files(dir, full.names = TRUE)
  if (length(files) == 0) stop("Error, read_ima_coil_dir files not found.")
  
  #warning("coil ordering is based on file name only.")
  
  files <- sort(files)
  mrs_list <- lapply(files, read_mrs, format = "dicom", verbose = verbose,
                     extra = extra)
  mrs_data <- append_coils(mrs_list)
  return(mrs_data)
}

#' Read a directory containing Siemens MRS IMA files and combine along the
#' dynamic dimension. Note that the coil ID is inferred from the sorted file
#' name and should be checked when consistency is required.
#' @param dir data directory path.
#' @param extra an optional data frame to provide additional variables for use
#' in subsequent analysis steps, eg id or grouping variables.
#' @param verbose output extra information to the console.
#' @return mrs_data object.
#' @export
read_ima_dyn_dir <- function(dir, extra = NULL, verbose = FALSE) {
  
  # check the directory exists
  if (!dir.exists(dir)) stop("Error read_ima_dyn_dir directory was not found.")
  
  # check it contains some files
  files <- list.files(dir, full.names = TRUE)
  if (length(files) == 0) stop("Error, read_ima_dyn_dir files not found.")
  
  #warning("coil ordering is based on file name only.")
  
  files <- sort(files)
  mrs_list <- lapply(files, read_mrs, format = "dicom", verbose = verbose,
                     extra = extra)
  
  mrs_data <- append_dyns(mrs_list)
  return(mrs_data)
}