With the rapid development of telemedicine and online diagnosis

more and more precious medical images have been transmitted through the open network

and the security problem of medical images has been taken much attention by many researchers.The integrity authentication of transmitted medical image is a key step in information protection.Watermarking technology is generally regarded as an effective method for integrity authentication.However

like other quality-sensitive images such as medical imagery

any slight distortions are not acceptable

because the distortion may cause wrong diagnosis.Therefore

using lossless watermarking method for medical image's tamper detection and recovery is a very important research field.Aiming at the existent algorithm's defects in region division and block's features chosen

a new lossless watermarking method based on quad-tree decomposition and linear weight interpolation is presented in this paper.First

the quad-tree decomposition is used to divide the original medical image into flexible size blocks with high homogeneity.Because this division method can reduce the length of feature value

much more information can be embedded.Then a new linear weight interpolation method is used to compute each block's features as watermark information in our method.Because in existent methods

the mean used of the block's pixels are used as recovery feature for each block

the tampered regions occurring in the low frequency region of an image(usually

the image's texture complex area)

it is not the best choice for restoring all tampered pixels with mean values

because it will reduce the quality of the recovered image.Finally

in order to reduce the embedding and extraction algorithm's complexity and enhance watermarking method's security

these features are embedded by using simple invertible integer transformation based on chaos.The introduction of chaos system improves the presented method's security.In order to test the presented method's validity

we test some performance properties including reversibility

embedding capacity

watermarked and recovered image's quality

and the detection accuracy rate.The experimental results show that the original image can be recovered with any distortion if the watermarked image was not been tampered

otherwise the tampered region can be localized and recovered with high similarity in the extracting procedure.Compared with the existent method

the embedding capacity is obviously prior to the similar method and the recovered image' quality using our method is about 20 dB higher.In addition

when the watermarked image is tampered to a large degree

the right detection rate and wrong detection rate is obviously better than the existent method.Since all the algorithms are open to the public

we introduce the logistic chaotic mapping to select the reference pixel's position in watermark embedding procedure.Due to the initial sensitivity and randomness

an adversary cannot obtain the correct watermark embedding positions easily if the initial parameters of logistic mapping are secret.Experimental results show that

compared with previous similar schemes

the presented method not only achieves high embedding capacity and good visual quality of restored image

but also has more accuracy for tampering detection.The presented method can be applied to realize medical image's integrity authentication and tampering detection.