diff --git a/controller/relay-image.go b/controller/relay-image.go
index a7941ba5..8ee07670 100644
--- a/controller/relay-image.go
+++ b/controller/relay-image.go
@@ -27,7 +27,7 @@ func isWithinRange(element string, value int) bool {
 
 func relayImageHelper(c *gin.Context, relayMode int) *OpenAIErrorWithStatusCode {
 	imageModel := "dall-e-2"
-	requestSize := "1024x1024"
+	imageSize := "1024x1024"
 
 	tokenId := c.GetInt("token_id")
 	channelType := c.GetInt("channel")
@@ -45,29 +45,34 @@ func relayImageHelper(c *gin.Context, relayMode int) *OpenAIErrorWithStatusCode
 		}
 	}
 
+	// Size validation
+	if imageRequest.Size != "" {
+		imageSize = imageRequest.Size
+	}
+
 	// Model validation
 	if imageRequest.Model != "" {
-		// Check if model is supported
-		if _, ok := common.DalleSizeRatios[imageRequest.Model]; !ok {
-			return errorWrapper(errors.New("model not supported"), "model_not_supported", http.StatusBadRequest)
-		}
-
 		imageModel = imageRequest.Model
 	}
 
-	// Size validation
-	if imageRequest.Size != "" {
-		requestSize = imageRequest.Size
+	imageCostRatio, hasValidSize := common.DalleSizeRatios[imageModel][imageSize]
+
+	// Check if model is supported
+	if hasValidSize {
+		if imageRequest.Quality == "hd" && imageModel == "dall-e-3" {
+			if imageSize == "1024x1024" {
+				imageCostRatio *= 2
+			} else {
+				imageCostRatio *= 1.5
+			}
+		}
+	} else {
+		return errorWrapper(errors.New("size not supported for this image model"), "size_not_supported", http.StatusBadRequest)
 	}
 
 	// Prompt validation
 	if imageRequest.Prompt == "" {
-		return errorWrapper(errors.New("prompt is required"), "required_field_missing", http.StatusBadRequest)
-	}
-
-	// Number of generated images validation
-	if isWithinRange(imageModel, imageRequest.N) == false {
-		return errorWrapper(errors.New("invalud value of n"), "number_of_generated_images_not_within_range", http.StatusBadRequest)
+		return errorWrapper(errors.New("prompt is required"), "prompt_missing", http.StatusBadRequest)
 	}
 
 	// Check prompt length
@@ -75,6 +80,11 @@ func relayImageHelper(c *gin.Context, relayMode int) *OpenAIErrorWithStatusCode
 		return errorWrapper(errors.New("prompt is too long"), "prompt_too_long", http.StatusBadRequest)
 	}
 
+	// Number of generated images validation
+	if isWithinRange(imageModel, imageRequest.N) == false {
+		return errorWrapper(errors.New("invalud value of n"), "n_not_within_range", http.StatusBadRequest)
+	}
+
 	// map model name
 	modelMapping := c.GetString("model_mapping")
 	isModelMapped := false
@@ -111,20 +121,7 @@ func relayImageHelper(c *gin.Context, relayMode int) *OpenAIErrorWithStatusCode
 	ratio := modelRatio * groupRatio
 	userQuota, err := model.CacheGetUserQuota(userId)
 
-	sizeRatio := 1.0
-
-	if ratio, ok := common.DalleSizeRatios[imageModel][requestSize]; ok {
-		sizeRatio = ratio
-		if imageRequest.Quality == "hd" && imageRequest.Model == "dall-e-3" {
-			if requestSize == "1024x1024" {
-				sizeRatio *= 2
-			} else {
-				sizeRatio *= 1.5
-			}
-		}
-	}
-
-	quota := int(ratio*sizeRatio*1000) * imageRequest.N
+	quota := int(ratio*imageCostRatio*1000) * imageRequest.N
 
 	if consumeQuota && userQuota-quota < 0 {
 		return errorWrapper(errors.New("user quota is not enough"), "insufficient_user_quota", http.StatusForbidden)