niftidump: 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/niftidump - from package: vtk-dicom-tools

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

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