dicom_filename: 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/lib/mrtrix/bin/dicom_filename - from package: mrtrix

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

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