dcunrgb: 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/dcunrgb - from package: dicom3tools

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

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