dcm_modify_object: 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/dcm_modify_object - from package: ctn

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

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