qnifti2dicom: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/qnifti2dicom - from package: qnifti2dicom

You may install the required package with command apt-get install {package}

Error in other languages:
qnifti2dicom: bevel nie gevind nie
qnifti2dicom: comandă negăsită
qnifti2dicom: comando não encontrado
qnifti2dicom: commande introuvable
qnifti2dicom: command not found
qnifti2dicom: käsku ei ole
qnifti2dicom: không tìm thấy lệnh
qnifti2dicom: komanda nerasta
qnifti2dicom: Kommando nicht gefunden.
qnifti2dicom: kommandot finns inte
qnifti2dicom: komut yok
qnifti2dicom: nie znaleziono polecenia
qnifti2dicom: níor aimsíodh an t-ordú
qnifti2dicom: no se encontró la orden
qnifti2dicom: no s'ha trobat l'ordre
qnifti2dicom: opdracht niet gevonden
qnifti2dicom: parancs nem található
qnifti2dicom: perintah tidak ditemukan
qnifti2dicom: príkaz nenájdený
qnifti2dicom: příkaz nenalezen
qnifti2dicom: команда не найдена
qnifti2dicom: командата не е открита
qnifti2dicom: 命令找不到
qnifti2dicom: コマンドが見つかりません