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We introduce a new class of multiple description scalar quantizer (MDSQ), which will be referred to as the modified MDSQ (MMDSQ). The structure of MMDSQ is fundamentally different from the MDSQ proposed by Vaishampayan. Analysis shows that at high rates for sources with smooth pdfs, MMDSQ achieves the same performance as entropy-constrained MDSQ using a uniform central quantizer. Compared with MDSQ, MMDSQ features a more efficient central-side distortion tradeoff control mechanism, without requiring the design and implementation of a complicated index assignment scheme. The simple and efficient implementation of MMDSQ makes it suitable for image coding: It can be naturally incorporated into existing coders to form new multiple description coders. Such a system is constructed using an existing image coder, and the performance of the resulting system is compared to that of the same coder but using Vaishampayan's MDSQ. Simulation results on natural images reveal that the system based on MMDSQ outperforms that based on MDSQ.