dcmgpdir: 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/dcmgpdir - from package: dcmtk

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

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