dctopgx: 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/dctopgx - from package: dicom3tools

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

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