With the increasing emphasis on research and development in nano-scale subjects—including nanomedicine, nanofabrication, and the imaging of nano-scale structures in bioengineering, proteomics/genomics, and other emerging fields—facilities must be planned and designed to meet the complex physical requirements of highly sophisticated imaging and analysis equipment while efficiently meeting the needs of the scientists who use these instruments. In particular, the use of MRI, NMR, and SPECT-CT instrumentation, and the installation of nanofabrication clean suites raise challenging planning and design issues, including space planning, structural capacity, vibration and noise isolation, magnetic and radiofrequency shielding, and instrument quench exhaust. Here is a look at the issues and practical solutions.

Increasingly powerful MRIs
Nanomedicine research is one of the factors that has led to the evolution of more powerful MRIs, placing greater demands on facilities design. In particular, the evolution of more powerful magnets (where 1.5 tesla once was the norm, MRIs can now be 12 tesla) has created special requirements.

Photo of a technician performing an MRI scan on a patient in N.Y.’s Buffalo General Hospital. Photo: Patricia Layman Bazelon

First, the MRI suite requires careful facility space planning. Commonly these suites require an area of 92.9-m2 or more, comprising a 46.4-m2 instrument room, 23.2-m2 dedicated machine room and 13.9 to 18.5-m2 dedicated control room.

Structural engineering must take into account the weight of the instrument, which may exceed 4,535 kg. Today, a typical 13-cm thick poured concrete slab on grade is inadequate; successful installations require a 30 to 60-cm reinforced concrete slab. Therefore, the instrument ideally is placed on the ground floor or basement of the facility, which, in turn, further affects space planning.

Today’s MRIs typically require steel shielding to contain their strong magnetic field to prevent demagnetization of pacemakers, credit cards, etc., and to prevent objects made of ferrous metals from being drawn into the instrument. In addition, the structure of the building containing the instruments must be designed to prevent the transfer of noise from the MRI room to adjacent spaces. Typically this is achieved using staggered double-stud, insulated walls or by providing double walls with air gaps between walls; extending walls to the structure; as well as utilizing isolated slab design within the MRI instrument space and designing in-duct sound traps.

Copper radiofrequency (RF) shielding must be employed to prevent interference with the operation of the instrument by external RF waves and shielding must be extended to include air handling ducts, pipes, and conduits. The instrument must be isolated from the sources and effects of vibration, including elevators and street traffic. This is achieved by effective location of the room within the building, a heavier, isolated slab, and use of isolators on the magnet itself. Finally, the magnet room must be designed with an effective, rapidly acting emergency quenching exhaust system in case of an unexpected, rapid loss of the super cooling media of the instrument, typically liquid nitrogen and helium under pressure.

Designing for NMR imaging
More and more research facilities are being designed to house state-of-the-art nuclear magnetic resonance (NMR) instruments to facilitate three-dimensional imaging of the physical topology of genes, proteins, and other structures. Over the past 20 years, the R&D world has observed the evolution of NMR from 300 MHz to 900 MHz, and everybody is talking about “the next level.” Typically, at each successively greater power level of instrumentation, the result is clearer data, allowing more precise imaging.

NMR instruments require careful space planning. In particular, planning must take into consideration both the horizontal and vertical magnetic field of the NMR instrument, starting from the basic question of whether the researcher is planning on a “self-shielding” instrument or a non-shielded instrument. If the instrument is self-shielded, its physical size is much larger, but its external magnetic field is contained within its perimeter. Non-shielded magnets are physically smaller, but their potentially hazardous, strong magnetic fields may have radii of 3 to 4.6 m or more surrounding the instrument. Safe containment of the magnetic field above the 5-gauss limit for an unshielded NMR instrument requires provision of a large open space of up to 7.6 m in dia around the magnet or, in some cases, heavy steel plate shielding around the perimeter of the instrument room including the ceiling.

Depending on the power of the instrument, the vertical field may extend 2 to 3.6 m above and below the magnet. Thus a minimum 5.4-m floor-to-floor height may be recommended to isolate the magnetic field from overhead ductwork and other building systems, as well as to prevent intrusion of the magnetic field into occupied labs on the floor above. A cost-effective solution is to place the magnet in a pit excavated below the ground floor to gain more height at the location of the magnet. Of course, an alternative may be to purchase a self-shielded instrument.

Sufficient radio frequency isolation for NMR instruments is generally less of an issue than it is for MRI instruments because the NMR can be shimmed to compensate for potentially disruptive environmental RF sources. Generally a 15- to 20-cm thick, isolated slab on grade may be sufficient, unless the facility is subject to significant vibration. Nevertheless, the instrument suite should be located away from corridors, streets and elevators, and other pathways of large, moving metal parts.

A technician examines a cryostat apparatus on an 800 MHz NMR instrument located at the Univ. of Kansas Structural Biology Building in Lawrence. Photo: Courtesy of Gould Evans, Photography by Michael Spillers Photography.

Other instrument requirements
SPECT-CT, ultrasound equipment, and gamma cameras are instruments that have less intensive planning, design, and construction requirements:
• Location of a SPECT-CT is fairly flexible, but cost-effective space planning locates this instrument proximate to other instruments requiring a thicker concrete slab.
• Ultrasound equipment requires more power and data outlets.
• Gamma cameras should be located within the radiochemistry lab or in an adjacent room. These require lead shielding of the walls and doors from floor level to about 2 m.

All of the spaces described above require seamless vinyl flooring to prevent migration of spills.

It is worth mentioning that use of focused-ion-beam instrumentation is sometimes a consideration in R&D facilities. These instruments have the greatest vibration-proofing requirements. In practice, they may require a 60-cm separate slab on the ground floor, which is isolated from the rest of the slab, and a dedicated pier that extends to bedrock below the facility. Therefore, facility owners would do well to plan new facilities to accommodate this technology if there is a reasonable chance it will be introduced in the future.

Core lab planning and design
In general, planning of today’s R&D facilities must balance cost with user convenience. The more precise the instrument, the more important it is to have a vibration-resistant environment. Therefore, a basement or ground floor tends to be the least expensive place to locate MRI, NMR, and SPECT-CT instruments. However, these have now become core labs for R&D activities of many scientists across many disciplines. Thus researchers increasingly demand core labs to be proximate to their primary research labs, that is, distributed throughout the building, rather than only on the ground floor.

A cost-effective solution requires identification of a “core zone” through the building, stacked vertically, with a heavier structural design, for example, four structural bays in the core of the building that are controlled to a 1,000-microinch level, with the remainder of the building controlled to a 2,500-microinch level or less, as appropriate.

Special needs of nanofabrication
Clean room environments for nanofabrication activities, whether they are Class 100, 1,000 or Class 10,000, have special requirements. In nanofabrication facilities, space planning for the sequential move from lower to higher cleanliness levels and vibration control are key issues. Prefabricated, pre-engineered 3.3- to 4.2-m tall clean-room suites with built-in air handling and air filtration capabilities are often utilized in R&D facilities to allow maintenance of clean environments.

Ideally, facilities which house these components should provide for a minimum 5.4 to 6-m floor-to-floor height to allow all the building systems to pass overhead and still maintain access to the clean suite plenum from above. Moreover, the structure should be designed to control vibration typically in the 1,000 microinch or lower range. Therefore, an isolated slab on grade condition may be ideal, away from vibration sources such as elevators or mechanical rooms.

Today’s focus on nanotechnology requires effective facility planning and design to meet the physical needs of precision instrumentation while balancing issues of user convenience. As in all R&D facilities planning, it is critical that the design team—from lab planners to architects and engineers—review the operating parameters and location of the owner’s proposed instrumentation and activities carefully with the owner. Then a proper cost-benefit analysis of the potential provision of highly-controlled environments for the instrumentation can be carefully assessed with the owner from a mutually-informed viewpoint.

Thomas Harvath,
AIA Principal Science Technology Practice, Cannon Design
Punit Jain,
LEED Associate Vice President, Cannon Design