OPTISON Again Featured at Echocardiography Conference; 12 Studies Presented as Part of "State-of-the-Art" Practices.

SAN DIEGO and ST. LOUIS--(BUSINESS WIRE)--June 16, 1999--

Molecular Biosystems, Inc. (NYSE:MB) and Mallinckrodt Inc. (NYSE:MKG) announced today that OPTISON(R), the only commercially available advanced-generation ultrasound contrast agent, is featured in a dozen scientific presentations delivered by researchers and clinicians at the 10th Annual Scientific Session hosted by the American Society of Echocardiography (ASE).

The symposium, held June 14 through 16 in Washington, D.C., is attended by more than 950 physicians and sonographers and focuses on state-of-the-art practices.

"The studies presented at this ASE conference describe in substantial numbers the everyday utility of OPTISON in the practice of Cardiology," said Dr. Howard Dittrich, MBI's Executive Vice President and a member of the American Society of Echocardiography. "We are extremely pleased to see this body of literature on the utility of OPTISON presented at such an important educational conference, a meeting that brings leading edge technology to practitioners in echocardiography."

OPTISON Being Studied Around the U.S.

The studies using OPTISON covered a number of areas. A list of the abstracts being presented at the ASE Scientific Session appears at the end of this news release. The research was conducted at many leading academic and clinical institutions, including Johns Hopkins School of Medicine (Baltimore), Children's Hospital (Pittsburgh) and Boston Children's Hospital (Boston); the University of Virginia (Charlottesville, VA); Mount Sinai Medical Center (New York); Case Western Reserve University at MetroHealth Medical Center (Cleveland); The Cleveland Clinic Foundation (Cleveland); Washington University School of Medicine (St. Louis); St. Louis University (St. Louis); Baylor College of Medicine, St. Luke's Episcopal Hospital and Texas Heart Institute (Houston); Stanford University (Stanford, Calif.); and the University of California (San Diego).

OPTISON, manufactured by MBI, is designed to improve ultrasound images by helping physicians to more clearly see the anatomy of the heart. Marketed by Mallinckrodt Inc. (NYSE:MKG) in the United States and Europe, OPTISON is being used in more than 1,600 institutions worldwide and continues to be the only available contrast agent of its kind.

MBI, based in San Diego, is a world leader in developing contrast agents for diagnostic imaging. Its innovative product, OPTISON, enables improved diagnosis of heart disease through clearer ultrasound images. For more information on Molecular Biosystems by fax, dial 888-329-4007 or visit its website at www.mobi.com

Based in St. Louis, Mallinckrodt Inc. has three healthcare product groups -- Imaging, Pharmaceuticals and Respiratory. The company operates in more than 100 countries and had fiscal 1998 net sales of $2.4 billion. The Mallinckrodt web site address is www.mallinckrodt.com.

This news release contains forward-looking statements that involve risks and uncertainties. Among the factors that could result in a materially different outcome are: the failure of OPTISON to gain market acceptance either in the U.S. or other markets; an adverse result in MBI's and Mallinckrodt's pending patent lawsuits or an adverse ruling by the PTO in the pending patent reexaminations; and other risk factors reported from time to time in MBI's and Mallinckrodt's filings with the Securities and Exchange Commission. -0-

           ABSTRACTS FOCUSING ON OPTISON BEING PRESENTED AT
                      1999 ASE SCIENTIFIC SESSION

1.   Accurate Qualitative Echocardiography is Achievable Using
     Harmonic Imaging with Contrast. T. Nahar, MD; L.B. Croft, MD; R.
     Shapiro, MD; E. Stern, MD; S. Buckley; A. Schussheim, MD; M.
     Henzlova, MD; J. Machac, MD; J. Doucette, Ph.D.; O. David; C.
     Soltero; D. Gainza; T. George; M.E. Goldman, MD; Mount Sinai
     Medical Center, New York.

2.   Is Non-Contrast Imaging a More Rapid and Convenient Alternative
     to Contrast Enhanced Fundamental Imaging. T. Nahar, MD; L.B.
     Croft, MD; R. Shapiro, MD; E. Stern, MD; S. Buckley; A.
     Schussheim, MD; M. Henzlova, MD; J. Machac, MD; J. Doucette,
     Ph.D.; O. David; C. Soltero; D. Gainza; T. George; M.E. Goldman,
     MD; Mount Sinai Medical Center, New York.

3.   Power Harmonic Doppler Can Eliminate 'Lateral Pseudodefects' Seen
     During Myocardial Perfusion Imaging with Contrast Echo. G.
     Venkataraman; A. Schussheim, MD; T. Nahar, MD; S. Buckley; E.
     Stern, MD; L.B. Croft, MD; A. Nahar; P. Santini; E. Fisher, MD;
     M.E. Goldman, MD; Mount Sinai Medical Center, New York.

4.   Clinical Impact of Second Harmonic Imaging and Left Heart
     Contrast in Echocardiographic Stress Testing. R.S. Finkelhor; M.
     Pajouh; A. Kett; R. Stefanski; G. Bosich; M. Youssefi; R. Bahler;
     Case Western Reserve University at MetroHealth Medical Center,
     Cleveland.

5.   Image Enhancement with Second-Generation Contrast Agents Improves
     Diagnostic Accuracy and Reduces Additional Testing. S.
     Thanigaraj, MD; J.E. Perez, MD; Washington University School of
     Medicine, St. Louis.

6.   Contrast Echo is Superior to Tissue Harmonics in Mechanically
     Ventilated Patients. M. Kornbluth, MD; D. Liang, MD, Ph.D.; P.
     Brown, RDCS; E. Gessford, RDCS; I. Schnittger, MD; Stanford
     University, Stanford, Calif.

7.   Contrast and Harmonic Imaging Improves Accuracy and Efficiency of
     Novice Readers for Dobutamine Stress Echocardiography. D.N.
     Rubin, MD; J.A. Odabashian, RDCS; M.J. Garcia, MD; L.M. King,
     RDCS; S. Lin, MD; J.K. Drinko, RDCS; A.J. Morehead, RDCS; C.R.
     Asher, MD; A.L. Klein, MD; J.D. Thomas, MD; The Cleveland Clinic
     Foundation, Cleveland.

8.   A Direct Comparison of the Value of Tissue Harmonic Imaging
     Versus Contrast Echocardiography for LV Endocardial Border
     Delineation. M. Taylor, MD; B. Cotter, MD; A. Raisinghani, MD;
     G.M. Strachan; K. McClure; J. Okun; O.L. Kwan, BS; D. Blanchard,
     MD; A.N. DeMaria, MD; University of California at San Diego.

9.   Intravenous OPTISON(R) Echocardiographic Contrast Dramatically
     Improves Inter-Observer Concordance of Ejection Fraction and
     Segmental Wall Motion Estimates. S. Damaraju, MD; S. Wilansky,
     MD; Y. Joseph, RVT; S. Maisey, RVT; W.K. Vaughn, Ph.D.; R.F.
     Stainback, MD; Baylor College of Medicine, St. Luke's Episcopal
     Hospital and Texas Heart Institute, Houston.

10.  Validation of a Novel Contrast Echocardiographic Technique for
     Quantification of Branch Pulmonary Artery Flow Distributions
     Following Surgery for Congenital Heart Disease. A.C. Lardo,
     Ph.D.; A. Iyengar, Ph.D.; P.J. del Nido, MD; S.A. Webber, MD;
     Johns Hopkins School of Medicine, Baltimore, MD; Children's
     Hospital of Pittsburgh, PA; Boston Children's Hospital, Boston.

11.  Myocardial Stress Perfusion Imaging During Continuous Infusion of
     OPTISON(R): Comparison with Single Photon Emission Computed
     Tomography. A. Barnstein, MD; J. Thorpe, RDCS; S. Moos, RDCS; J.
     Dent, MD; J. Sklenar, Ph.D., MD; S. Kaul, MD; University of
     Virginia, Charlottesville, Va.

12.  The Effect of Quantitative Perfusion on Sensitivity and
     Specificity of Dobutamine Contrast Echocardiography in
     Technically Difficult Patients. M. Dolan, MD; T, Kamala, MD; S.
     Puri, MD; J. Flanagan, RN; E. Havens, RDCS; L. McKinney, RN; J.
     St. Vrain, RDCS; K. Habenmehl, RDCS; M. Kern, MD; H. Goodgold,
     MD; A.J. Labovitz, MD; St. Louis University, St. Louis.