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

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

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