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PART IV
Practical Aspects of
Radiopharmaceutical
Production and Use
Chapter 13
Automated Synthesis Modules for PET Radiochemistry
Laura Bruton and Peter J.H. Scott
Department of Radiology, University of Michigan, Ann Arbor, MI, 48109, USA

13.1 INTRODUCTION

The recent approval of several radiopharmaceuticals for positron emission tomography (PET) imaging by the United States Food and Drug Administration (FDA ) and other
regulatory agencies around the world has led to increases in annual PET scan numbers[1]. For example, millions of PET scans are now conducted in the US every year[2]
increased demand for access to short-lived PET radiopharmaceuticals has created a corresponding need for more ecient means for their production. For some radiochem­istry facilities, this requires the production of very large batches of one radiopharmaceu-
tical for distribution (see, for example,[3]), while other facilities need to produce multiple dierent research radiopharmaceuticals using a single synthesis module (for recent examples, see[4–7]). The eld of radiochemistry is thus constantly evolving to meet the
needs for increased starting amounts of radioactivity, and in the last couple of decades it has seen a move from manual radiochemistry to the use of automated synthesis mod-
ules (for reviews of new developments, see[8, 9]) supported by sophisticated software programs[10]. These modules are enclosed in hot cells and controlled by a computer
Handbook of Radiopharmaceuticals: Methodology and Applications, Second Edition. Edited by Michael R. Kilbourn and Peter J.H. Scott. © 2021 John Wiley & Sons Ltd. Published 2021 by John Wiley & Sons Ltd.
,
and the
from the outside, either using a preprogrammed synthesis sequence (timelist) that is
executed manually or totally under computer control. The modules are congured for
the synthesis and the hot cell is sealed in advance of delivery of radioactivity, thus signif-
icantly decreasing worker exposure. Radiochemistry synthesis modules need to be able
to deliver doses at a fast pace while maintaining compliance with radiation safety require­ments, especially when handling the very large amounts of radioactivity that some facil-
ities use today[3]. The daily synthesis and delivery of PET radiopharmaceuticals create
challenges for such systems, including short preparation times, compliance with pharma-
ceutical quality procedures, reproducibility, and reliability. Through the years, radiochem­istry synthesis modules have changed with the increasing pressure of these standards.
Compared to the early days of manually operated and hard-wired systems, modern computer-controlled radiopharmaceutical synthesis modules are more advanced in terms
of automation, eciency, and radiochemical yields, as well as the ability to meet the
increased demands of FDA-mandated current Good Manufacturing Practice (cGMP). This chapter provides an overview of radiopharmaceutical synthesis modules from the home-
made systems used in early PET centers when the rst edition of this book was published (2002) through to the new modules used today and concludes with thoughts on future directions for the eld.

13.2 EARLY RADIOCHEMISTRY SYNTHESIS MODULES

Figure 13.1 A tradi-
tional homemade radiochem­istry module. Source: Reprinted with permis­sion from Welch
etal. 1983[11],
copyright John Wiley and Sons.
The early radiopharmaceutical synthesis modules (for example, Figure13.1) were hard­wired systems where valves, uid movements through lines, gas ows, and temperature
438 Handbook of Radiopharmaceuticals
changes (heating and cooling) were controlled by manually activated electrical switches
that were located externally to lead shielding placed around the module[11]. If physical
movement of items was required, this could be done using the manipulator arms of a
hot cell. As automation was introduced in the 1980s, the components of the synthesis
apparatus began to be controlled using programmable logic controllers and, eventually, small computers; a unique intermediary application was the use of a computer-controlled robot to interact with, and control, an array of work stations that accomplished the
individual steps of a complex radiochemical synthesis (Figure13.2)[12].
By 1990, automated modules were increasingly common in many PET facilities. This
was mainly due to the manufacturing and reimbursement approval for [
18
cose ([
F]FDG), which was granted in the USA by the FDA and the Centers for Medicare
18
F]udeoxyglu-
and Medicaid (CMS), respectively. As FDG was the most important PET radiopharmaceu- tical that needed to be synthesized, there was a move to automate this process (see[13]). Many PET facilities acquired a Coincidence FDG synthesizer (Figure13.3), which had been commercially released in late 1998; that module was later acquired by General Electric (GE) and rebranded as the TRACERlab MX
[14]. The module introduced an impor-
FDG
tant new concept: the use of sterile, disposable, pre-assembled synthesis pathways and reagents (termed kits) dedicated to single radiopharmaceutical syntheses, such as
18
[
F]FDG. In the following years, GE and a number of third-party companies including Advanced Biochemicals (ABX) and Rotem Industries oered (and continue to oer) kits for making dierent radiopharmaceuticals on the TRACERlab MX
18
[
F]NaF, [18F]F-L-DOPA, [18F]uoroethyltyrosine, and [18F]uorthymidine. While the syn-
, including [18F]FDG,
FDG
thesis module is somewhat dated at this point, because of its very large install base, it
continues to be utilized extensively worldwide, and new reports of use of the TRACERlab MX
for the syntheses of radiopharmaceuticals such as [18F]uoromisonidazole[15],
FDG
Figure 13.2 An
early radiochem­istry module run using a computer­controlled robot. Source: Reprinted with permission
from Brodack etal. 1988[12], copy-
right Elsevier.
Chapter 13: Automated Synthesis Modules for PET Radiochemistry 439
Figure 13.3 Early
TRACERlab MX
FDG
cassette-based synthesis module. Source: Image courtesy of GE.
[18F]uoromethylcholine[16], [18F]PSMA-1007[17, 18], and [18F]uoroestradiol[19] con­tinue to be published. Most recently, with the increasing popularity of PET studies using gallium-68[20, 21], use of the TRACERlab MX module for synthesizing
68
Ga-labelled
tracers has also been disclosed[22].

13.3  MODERN CASSETTE-BASED MODULES

The design and development of synthesis modules have continued to evolve, leading
to the improved and more versatile modules that are in use today. For example, in the late 2000s, it became mandatory to prepare PET radiopharmaceuticals for clinical use according to cGMP. Building on lessons learned with early cassette-based systems such as the TRACERlab MX
control, use of information from sensors in pre-run diagnostics, post-run trouble-
shooting, trend analysis, and process documentation were introduced. For example, GE rened the TRACERlab MX into the FASTlab and, more recently, FASTlab 2 (Figure13.4a); other modules that have evolved from the TRACERlab MX include the NEPTIS (Figure13.4b) and the Trasis AllinOne (Figure13.4c) platforms. Cassette-based module systems were also introduced by Siemens (Explora), IBA (Synthera), and Scintomics (GRP Series). Similar to the TRACERlab MX, this new generation of synthesis modules was primarily developed for the preparation of [ PET radiopharmaceutical. To improve the control and use of the cassettes used with
these modules, they are frequently labeled with a barcode that, when read by the com-
puter, relays information as to which synthesis program should be executed. The use
of single-use cassettes is attractive from a cGMP perspective because it eliminates the
need for cleaning validation studies[23] and reduces errors during setup and operation. The use of these precongured sterile cassettes also enables quick transitions between
and incorporating cGMP principles, new features such as real-time
FDG
18
F]FDG, as it remains the most widely used
440 Handbook of Radiopharmaceuticals
(a) (b) (c)
Figure 13.4 Cassette-based synthesis modules. (a) GE FASTlab 2. Source: Image courtesy of GE Health-
care. (b) NEPTIS Perform. Source: Image courtesy of Optimized Radiochemical Applications (ORA). (c) Trasis AllinOne. Source: Image courtesy of Trasis.
syntheses. A common theme with all of these new synthesis modules is that they have been designed to address the challenges of a modern radiochemistry laboratory. Con-
scious of the space limitations many facilities have, manufacturers have designed many of
these new modules in a compact size that allows two (or more) units to t inside a single mini-cell. Moreover, cassettes have been developed for these new modules that include reagents and cartridges for multiple syntheses of a radiopharmaceutical (e.g. FDG),
enabling repeated batches to be prepared without the need to open a hot cell between
syntheses[24]. In addition to [
18
F]FDG, cassettes for these modules are also commercially
available for the production of other commonly used radiopharmaceuticals. Alternatively,
many of the systems can be adapted to prepare other radiotracers through the use of customizable cassettes, most often for the preparation of
18
F-labeled radiopharmaceu-
ticals[4, 5]; custom cassettes have also been developed for products labeled with other radionuclides, such as gallium-68[25].
13.4   FULLY AUTOMATED FIXED-
TUBING MODULES
The development of new PET radiopharmaceuticals is a very active area of research. Whereas cassette-based modules have become the industry standard for routine daily production of established PET radiopharmaceuticals such as [
18
F]FDG, they are not always suitable for the synthesis of new PET radiopharmaceuticals. For example, the majority of the modules have limited temperature and pressure tolerances due to the ttings, valves, and materials used to manufacture the cassettes. The systems are usually designed for
liquid-phase chemistry (
phase chemistry (e.g.
68
Ga and 18F ion reactions) and often not compatible with gas-
11
C). In addition, many modules have only one reaction vessel, which prohibits the synthesis of probes that need multi-reactor protocols (e.g. tracers prepared using radio-click chemistry; see[26]); however, newer systems such as the GE FASTlab 2 and Trasis AllinOne have two reaction vessels, which potentially allow the automation of
Chapter 13: Automated Synthesis Modules for PET Radiochemistry 441
more complex chemistry. For the most part, though, cassette-based systems are some­what limited in how much they can be recongured for novel radiochemistry, and new chemistry tends to be developed on fully automated xed-tubing modules such as the GE TRACERlab FX series (Figure13.5a), iPhase MultiSyn systems (Figure13.5b), Synthra radiopharmaceutical synthesizers (Figure13.5c), and Eckert & Ziegler Modular-Labs (Figure13.5d). There are systems available for conducting liquid-phase chemistry with
18
[
F]uoride (e.g.[6, 27, 28]) as well as gas-phase chemistry with [11C]CO2 or [11C]CH4[7].
Recent reports have also demonstrated compatibility with
68
Ga[29].
The new fully automated synthesis modules (Figure13.5) have gradually replaced the
early homemade remote systems (Figures13.1 and13.2). These synthesis modules con-
tain multiple interconnected parts, including modules for receiving radioactivity from a cyclotron (or generator); the synthesis component, which typically contains one or more reaction vessels and a heater; a vacuum pump for evaporating solvents; a semi-prepara­tive high-performance liquid chromatography (HPLC) purication system; and a module
for the reformulation of the puried radiopharmaceutical into a solution suitable for
Figure 13.5 Fully
automated xed-
tubing modules. (a) GE TRACERlab. Source: Image courtesy of GE. (b) iPhase F-18 Flex­Lab. Source: Image courtesy of iPhase Technologies. (c) PET radiosynthe­sizer. Source: Image courtesy of Synthra GMBH. (d) Modular­Lab. Source: Image courtesy of Eckert & Ziegler.
(a) (b)
(c) (d)
442 Handbook of Radiopharmaceuticals
intravenous injection. These xed-tubing machines are housed in hot cells and controlled
by a computer from outside, with a preprogrammed computerized timelist executed
manually or under full computer control. A radiotracer-specic program (Figure13.6) controls every step of the synthesis, from setting the parameters of the reaction (e.g. time, temperature) to the addition of reagents and solvents, purication, reformulation, and delivery of the nal product to a sterile vial. During the synthesis, information from
numerous components and detectors is sent to the interactive computer, allowing radio­chemists to see data such as temperature and pressure measurements in real time, as
well as track, trend, and troubleshoot syntheses after completion.
These synthesis modules are often provided by vendors with programs for preparing
standard radiolabeling precursors (e.g. [
11
C]MeI, [11C]MeOTf) as well as established radio­tracers, and such radiosyntheses are often accomplished using the basic conguration of the module. However, we and others have also shown that such modules can be easily recongured for dierent applications, including gas-phase reactions[30] and loop chem­istry[31, 32]. The basic module conguration is typically designed for the production of radiopharmaceuticals requiring HPLC purication but can be modied to incorporate purication by Sep-Pak cartridge (e.g. [
18
F]NaF, [11C]carfetanil, etc.) or a reformulation step when using non-injectable HPLC mobile phases. By way of example, in 2011, our group reported the synthesis of 7
18
F-labeled radiotracers and 12 11C-labeled radiotracers
using the TRACERlab FX platform[6, 7].
After a synthesis is completed, the module has to be cleaned and disinfected before
the next radiosynthesis. This is done by resetting the module to its basic conguration,
cleaning with sterile water, disinfecting with ethanol, and drying with acetone; the pro-
cess takes approximately 20 minutes. The time needed for cleaning and reset of the mod­ules, and possibly a cleaning validation[23], should be planned for, especially in a smaller lab setting. The need to open hot cells between syntheses to clean and recongure modules also potentially increases radioactivity exposure to sta. Moreover, although these systems can be recongured for dierent tracers, to maintain reproducible pro­duction conditions (and compliance with cGMP), constant reconguration is not always ideal. The need for more exible automation that matches the increasing demand for
the development of radiopharmaceuticals has led to the development of the new hybrid
modules and microuidic systems discussed next.

13.5  HYBRID MODULES

To overcome the limited nature of the cassette-based systems and the impact of recon-
guring xed-tubing modules on a routine basis, hybrid modules have been developed.
These modules aim to combine the simplicity of cassette-based systems with the ability
to handle high pressures and temperatures. For example, the Soe Biosciences ELIXYS FLEX/CHEM (Figure13.7) oers a three-reactor design suitable for both synthesis
development and routine production and is capable of accommodating complex multi-
pot radiochemistry[33–35]. The cassettes for this module include the uidic paths and
various reagent vial sizes, which enables a large number of probes to be produced within
Chapter 13: Automated Synthesis Modules for PET Radiochemistry 443
iso.
EtOH
NaCI
V8 V9
V7
HPLC
Pump
V31
Helium
V30
off
VENT.
0.2 μm
Strata
2
1
V16
NH2
V15
VENT.
Eluent
V22
V17
on
WASTE
0.2 μm
He
V21
HELIUM PRESSURE
V19
AIR PRESSURE
0.2 μm0.2 μm
V26
Load
WASTE
VENT.
0.2 μm
Pre-
cursor
Eluent
Inject
HILIC
UV Lamp
RDYTEMP.1
down
V24
V23
V18
stop
start
COOLING AIR
PRESSURE
V25
WASTE
off
on
STIRRERS
EXHAUST
Fluid
V1 V3V2 V4 V5 V6
GammaDep.
V12
V14
V20
18F SEPARATION
CARTRIDGE
V10
Auto Zero
UV Detector
He
up
NEEDLE
V13
V11
444 Handbook of Radiopharmaceuticals
FROM
TARGET
TRANS-
HEATER
FORMER
POWER
on
VACUUM
PUMP
off
Figure 13.6 Computer program for running a TRACERlab synthesis module. Source: Image courtesy of GE
Healthcare.