Performance of the Tachyon Time-of-Flight PET Camera.

We have constructed and characterized a time-of-flight Positron Emission Tomography (TOF PET) camera called the Tachyon. The Tachyon is a single-ring Lutetium Oxyorthosilicate (LSO) based camera designed to obtain significantly better timing resolution than the ~ 550 ps found in present commercial TOF cameras, in order to quantify the benefit of improved TOF resolution for clinically relevant tasks. The Tachyon's detector module is optimized for timing by coupling the 6.15 × 25 mm2 side of 6.15 × 6.15 × 25 mm3 LSO scintillator crystals onto a 1-inch diameter Hamamatsu R-9800 PMT with a super-bialkali photocathode. We characterized the camera according to the NEMA NU 2-2012 standard, measuring the energy resolution, timing resolution, spatial resolution, noise equivalent count rates and sensitivity. The Tachyon achieved a coincidence timing resolution of 314 ps +/- ps FWHM over all crystal-crystal combinations. Experiments were performed with the NEMA body phantom to assess the imaging performance improvement over non-TOF PET. The results show that at a matched contrast, incorporating 314 ps TOF reduces the standard deviation of the contrast by a factor of about 2.3.

Growth kinetics of ω particles in ß-Ti matrix studied by in-situ small-angle x-ray scattering.

Nucleation and growth kinetics of nanoparticles of hexagonal ω phase in a body-centered cubic ß titanium matrix in single crystals of ß-Ti alloys were investigated by small-angle x-ray scattering measured in-situ during ageing at various temperatures up to 450 °C. The experimental data were compared with numerical simulations based on a three-dimensional short-range order model of nanoparticle self-ordering. The x-ray contrast of the particles is caused by an inhomogeneous distribution of impurity atoms (Mo, Fe and Al), whose density profile around growing nanoparticles was simulated by solving the corresponding diffusion equation with moving boundary conditions. From the analysis of the experimental data we determined the mean distance and size of the nanoparticles and confirmed the validity of the ∝ t1/3 growth law following from the Lifshitz-Slyozov-Wagner theory. From a detailed comparison of the experimental data with simulations we also assessed the diffusion coefficient of the impurity atoms and its activation energy.

[Posterior extensile approach to release a post-traumatic stiffness of the elbow]. / Extenzivní zadní prístup pri uvolnení poúrazové ztuhlosti loketního kloubu.

PURPOSE OF THE STUDY: Restriction of joint motion is a frequent complication in the treatment of elbow injury. Grade 4 elbow stiffness up to its ankylosis is a strong limiting factor in the patient's daily activities. The surgical release of a stiff elbow has been a rare procedure. It can be done using either isolated or combined approaches. The aim of the study is to present our experience with and the results of elbow arthrolysis using a posterior extensile approach to the joint. MATERIAL AND METHODS: Seven patients aged between 17 and 38 years with post-traumatic post-operative ankylosis, or grade 4 elbow stiffness were operated on. The average range of motion before surgery was 12.9° (range, 0° - 20°). The average interval between primary injury and arthrolysis was 21 months (range, 8 - 70 months). Clinical assessment before and after surgery was based on the Mayo Elbow Performance Score (MEPS). The average follow-up was 26 months (12 - 47). Arthrolysis was completed by application of an external fixator in four patients, by interposition arthroplasty in two patients, ulnar nerve transposition in five patients and radial head replacement in one patient. RESULTS The average MEPS score increased from 45.0 points (range, 30 - 65 points) to 87.9 points (range, 75 - 100 points). The average range of motion at the final follow-up was 99.3° (range, 65° - 135°). Most patients reported pain relief. There was no iatrogenic instability following surgery. Improvement was most marked in relation to joint function, as demonstrated by increase from an average score of 6.4 points (range, 0 - 15 points) before surgery to 24.3 points (range, 20 - 25 points) after surgery in the MEPS. DISCUSSION: Surgical treatment of an ankylosed elbow is not a common procedure in the majority of hospitals. The use of a posterior extensile approach, which preserves the extensor mechanism, to release the elbow joint has been reported only occasionally in the international literature. The results, however, seem to be good. On the other hand, removal of the olecranon is associated with a high complication rate. Operative release of the elbow with total joint replacement is an extreme option. CONCLUSIONS In grade 4 stiff elbow release, the posterior extensile approach to the elbow joint as described here allows us to have a good view of all articular compartments. It maintains continuity of the extensor apparatus of the elbow, which is the essential requirement for effective post-operative rehabilitation and therefore its great advantage. This approach is not associated with serious complications.

Optimization of a LSO-Based Detector Module for Time-of-Flight PET.

We have explored methods for optimizing the timing resolution of an LSO-based detector module for a single-ring, "demonstration" time-of-flight PET camera. By maximizing the area that couples the scintillator to the PMT and minimizing the average path length that the scintillation photons travel, a single detector timing resolution of 218 ps fwhm is measured, which is considerably better than the ~385 ps fwhm obtained by commercial LSO or LYSO TOF detector modules. We explored different surface treatments (saw-cut, mechanically polished, and chemically etched) and reflector materials (Teflon tape, ESR, Lumirror, Melinex, white epoxy, and white paint), and found that for our geometry, a chemically etched surface had 5% better timing resolution than the saw-cut or mechanically polished surfaces, and while there was little dependence on the timing resolution between the various reflectors, white paint and white epoxy were a few percent better. Adding co-dopants to LSO shortened the decay time from 40 ns to ~30 ns but maintained the same or higher total light output. This increased the initial photoelectron rate and so improved the timing resolution by 15%. Using photomultiplier tubes with higher quantum efficiency (blue sensitivity index of 13.5 rather than 12) improved the timing resolution by an additional 5%. By choosing the optimum surface treatment (chemically etched), reflector (white paint), LSO composition (co-doped), and PMT (13.5 blue sensitivity index), the coincidence timing resolution of our detector module was reduced from 309 ps to 220 ps fwhm.

[Minimally invasive and navigated implantation for total knee arthroplasty: X-ray analysis and early clinical results]. / Minimal-invasive und navigierte implantation von knietotalendoprothesen: radiologische analyse und frühe klinische ergebnisse.

Total knee arthroplasty (TKA) alignment is one of the most important factors in long-term prosthesis survival. Minimally invasive surgical (MIS) procedures are becoming more common. There may be an increased overall complication rate, especially component malpositioning, due to poor visualisation. The disadvantage of restricted visualisation in the less invasive technique can be compensated by a navigation system. This combined procedure is described in this paper. A total of 40 Search Evolution TKAs were implanted using OrthoPilot navigation in the standard manner, and 40 TKAs were implanted using MIS via a subvastus approach. Primary osteoarthritis of the third or fourth degree, without severe valgus deformity, was the indication. These patients were then selected at random as they came to the institution. The results were evaluated radiologically and clinically.Pain, range of motion, gait and function, and the entire clinical score 10 days after the operation were significantly better in the MIS-group. At 6 and 12 weeks postoperatively, these results were no longer statistically significant. Ideal radiological results were obtained in all cases. No differences in limb axis and component alignment were found after the operation between the navigated groups. MIS is technically very demanding. That is why it should be used only in carefully selected cases. Its advantages occur in the first weeks after the surgery. The long-term results must still be determined.

[Correlation of long-term clinical and radiological results after meniscectomies]. / Korelace dlouhodobých klinických a radiologických výsledku po meniskektomiích.

PURPOSE OF THE STUDY: Although surgical treatment of meniscus injuries has made great progress, meniscectomy remains the most frequently indicated intervention. The aim of this retrospective study was to evaluate the long-term radiological results of isolated subtotal and total meniscectomies and compare them with the clinical results. MATERIAL: The assessed group included 22 men and 8 women at an average age of 35 years; nine and 21 knees, respectively, were treated by isolated subtotal and total meniscectomy in the period from 1987 to 1989. The lateral meniscus was operated on in six knees and the medial meniscus in 24 knees. Patients with other injuries to the knee joint or with a systemic disease were not evaluated. The average follow-up was 16 years. The results were compared with the other, non-treated knee. METHODS: The results were assessed by means of the Lysholm scoring system which takes into account limping, support requirement, walking distances, instability, edema, stair ascent and descent, ability to squat and pain. Radiographic osteoarthritis of the knee was classified by the Kellgren and Lawrence system. A grade greater or equal to 2 was taken for a clear sign of arthritis. In addition, the anatomical axis of the lower extremity was evaluated. Anteroposterior projection of both knees under load was made in a standing position on long films and lateral projection was obtained separately on short films. RESULTS: The average Lysholm scores were 87 points (range, 41-100) and 91 points (range, 67-100) in the treated and non-treated knees, respectively. The outcome of meniscectomy was excellent in 14 (47 %), good in eight (27 %), satisfactory in five (16 %) and poor in three (10 %) knees. In 12 patients (40 %) the state of the treated knee was evaluated as being equal to that of the non-treated knee and in eight patients (27 %) it was even better. Osteoarthritis of the affected compartment was found in eight treated knees and that of the corresponding compartment on the opposite side in four knees. Grade 2 Kellgren- Lawrence radiographic changes were present in four, grade 3 in two and grade 4 in two knees treated by meniscectomy. The anatomic femoro-tibial angle differed between the treated and non-treated side, by 4 degrees on average (range, 2 degrees to 10 degrees ), in 13 (43 %) patients. DISCUSSION: Johnson et al. found at follow-up for about 17 years that osteoarthritis developed more often in the treated than in healthy contralateral knees (40 % as against 6 %). Tapper and Hoover reported that 45 % of men and 10 % of women were without subjective complaints at 10 to 30 years of follow up. In the relevant Czech literature, only Pasa et al. have recently paid attention to the development of lesions in knees treated by meniscectomy, but they have largely evaluated changes occurring after partial arthroscopic meniscectomies. CONCLUSIONS: The present study showed that osteoarthritis after subtotal or total meniscectomy developed in 27 % of the patients at an average follow-up of 16 years. In less than half of the patients, a deviation of the anatomical axis occurred in the treated lower extremity, as compared with the other healthy side. Lysholm scores worse in the treated than the non-treated knee were found in one third of the patients.However, a deviated knee joint axis and/or osteoarthritic lesions did not always correlate with deteriorated clinical findings.

Radiological study of tha after mini-incision technique.

Mini-incision procedures reduce perioperative blood loss, postoperative pain, time of the postoperative recovery, length of the surgical scar, and hospitalisation time. Implant malposition and poor stability are potential risks for compromising long-term results. Between September 2000 and February 2002 (18 months), 120 cemented primary total hip arthroplasties for primary osteoarthritis were performed at the authors institutions. In 60 of these cases selected at random, a posterolateral mini-incision up to 10 cm was used. Sixty other THAs were implanted through a standard posterolateral approach. The radiological measurements of the inclination and anteversion of the cup and stem position were performed and statistically evaluated by use of Mann-Whitney U and Bartlett tests. In the mini-incision group the average inclination angle was 42.3 (range 36 to 52) and the anteversion angle 13.6 (range 6 to 21). The femoral component coronal alignment was within 3 of neutral position in 54 cases (90.0 %). In the standard implanted group the average cup inclination angle was 42.4 (range 35 to 50) and anteversion angle 13.6 (range 8 to 24). Fifty-three stems (88,3 %) were implanted correctly. Statistical analysis found no significant difference in component position between the two groups. There are therefore no potential risks of compromising long-term results after the mini-incision procedure. The authors are encouraged to continue this technique. (Hip International 2005; 15: 98-101).

[Implantation of a non-cemented acetabulum with the use of a navigation system]. / Implantace necementované jamky s vyuzitím navigacního systému.

PURPOSE OF THE STUDY: To compare, on the basis of clinical and radiographic findings, the results of non-cemented acetabulum implantation involving the use of a CT-free navigation system with those of implantation without its use. MATERIAL: A total of 50 patients undergoing implantation of a non-cemented acetabulum in the period from April 2002 to September 2003 were evaluated. Twenty-five patients operated on without the navigation system were included in group 1 on a random basis and 25 patients treated with the use of the system constituted group 2. METHODS: Both groups were evaluated on the basis of clinical and X-ray findings. The radiographic measurement of acetabulular inclination was based on anteroposterior projection of both hips made on films on films equal in size. Anteversion of the acetabulum was assessed according to the Ackland system. The Merle d'Aubigne and Postel scores were used for clinical evaluation. The results were compared statistically. RESULTS: In group 1, the average inclination was 50.6 degrees (range, 38-62) and the average anteversion was 9.4 degrees (range, 3-18). In group 2, the values were 43.0 degrees (32-55) and 10.4 degrees (8-16) for the average inclination and anteversion, respectively. The difference in acetabular inclination between the two groups was statistically significant. When accuracy was evaluated, the difference in acetabular anteversion was statistically significant. DISCUSSION: The achievement of an optimal position of the acetabular component is one of the important factors for good, long-term outcomes of hip replacement. The optimal position that, as suggested by many authors, involves an inclination of 45 +/- 10 degrees and an anteversion of 15 +/- 10 degrees provides sufficient stability, low wear and a satisfactory range of motion in the hip joint. The results close to these values were achieved in the patients included in group 2. CONCLUSIONS: A comparison of the groups showed that the computer-assisted navigation system used in implantation resulted in an optimal position of the acetabular component.

[A rare shortening of the first metatarsus of the foot and its treatment with distraction arthrodesis]. / Vzácné zkrácení prvního paprsku nohy a resení distrakcní artrodézou.

Multiple toes may develop on the medial or lateral side of the forefoot or in its middle. This may involve duplication of only the distal phalanx or the whole hallux including the metatarsal. In a duplicated big toe, the phalanx to be maintained, because short muscles of the leg are attached to it, is usually localized medially. A rare case of dysplasia of the first metatarsus, following a resection indicated in childhood for a hallux triples, is described in a 20-year-old girl. In order to remove hallux insufficiency and an overloading of the middle metatarsals, the authors decided to carry out a one-stage prolongation of the first metatarsal, using an autologous tricorticcal graft collected from the pelvis and a dynamic compression plate. No surgical treatment of the middle metatarsals was indicated because a disproportionate, short foot would result. Both the subjective and objective status of the patient at 6 months after the operation showed that the non-standard prolongation procedure was correctly indicated and allowed for physiological loading of the foot and restoration of normal walking.

[The Weil osteotomy in metatarsalgia]. / Die Weil-Osteotomie bei Metatarsalgie.

AIM: The purpose of the prospective study is to evaluate the results of Weil osteotomy in painful overloaded central forefoot with dislocation of the MTP joint. METHOD: 19 left and 16 right feet underwent the Weil osteotomy. In 10 patients the procedure was performed on both feet. In 15 cases only one metatarsal was corrected (the 2 (nd) in 12 and the 3 (rd) in 3 cases), in 17 cases both the 2 (nd) and the 3 (rd) metatarsals and in 4 cases also with the 4 (th) one together. The simultaneous correction of hallux valgus was performed in 19 forefeet. The mean follow-up was 31 months (range, 19 to 41 months). RESULTS: All patients were satisfied with the result of the operation. The results were excellent in 29 cases (83 %) and good in 6 cases (17 %). The plantar callus disappeared in 27 feet (77 %) and decreased in 8 feet (23 %). In one patient the new callus formed under the head of the neighbouring metatarsal bone. The sufficient MTP joint reduction was found in 31 cases (89 %). CONCLUSION: It is possible with the Weil osteotomy to correct the metatarsal length accurately according to the preoperative planning. This results in the prevention of new callus formation under the neighbouring metatarsal head. Stable internal fixation allows the early mobilisation of the MTP joint.

Total knee arthroplasty implanted with and without kinematic navigation.

Between September 2000 and February 2002 we inserted 120 total knee arthroplasties. In 60 patients we used the standard technique, and in 60 patients we used the OrthoPilot navigation system. Postoperatively all patients had standing long radiographs of the lower extremity from the hip joint to the ankle. We considered the ideal value of the anatomic lateral tibiofemoral angle (LTFA) to be 174 degrees. In the standard group the mean value of LTFA was 174.9 degrees and in the navigation group 174.3 degrees. A deviation between 0 degrees and 2 degrees from the ideal value was seen in 42 cases in the standard group and in 53 cases in the navigation group. In the standard group 18 cases had a deviation of more than 2.1 degrees, whereas there were only seven cases in the navigation group with a deviation exceeding 2.1 degrees. There were no complications related to the use of the navigation system. The system affords a possibility to place femoral and tibial components precisely with less axis deviation than with the conventional technique.

[Indications for arthrodesis of the knee joint in modern orthopedics]. / Indikace artrodézy kolenního kloubu v moderní ortopedii.

INTRODUCTION: Indication for arthrodesis of the knee joint is nowadays most frequently failure of a total endoprosthesis, usually septic. A less frequent indication is purulent gonitis, frequently after corticoid administration, the condition after a complicated intraarticular fracture with subsequent arthritis or oncological disease of the bones in the area of the knee joint. MATERIAL AND METHODS: In the course of 2000 to 2002 at the authors' department 15 arthrodeses were implanted. In three cases the indication for arthrodesis was purulent gonitis, in three cases the condition after an open articular injury associated with infectious complications and in the remaining nine cases failure of an endoprosthesis of the knee, incl. seven caused by infection. The patients were three men and 12 women, mean age 64 years (30-75 years). For stabilization of the arthrodesis 9x external fixation was used, 5x plates and 1x intramedullary osteosynthesis. RESULTS: In all cases consolidation of the arthrodesis was achieved. In one case the external fixation had to be replaced by a system of two fixation devices and in one case correction of the axial position of the extremity was made. The presence of external fixation was perceived negatively in particular by female patients. DISCUSSION: Plate osteosynthesis and the use of external fixation devices are relatively quick, cheap and considerate methods of arthrodesis. External fixation must be used in acute virulent infections while plate osteosynthesis can be indicated in its absence. The characteristic of intramedullary fixation is similar, however special nails used for arthrodesis of the knee are several times more expensive than the previous types of stabilization. The advantage is the possibility to use a massive bone graft to fill the defect.

[Case report of extensive metallosis in extra-articular tissues after unicompartmental knee joint replacement]. / Prípad rozsáhlé metalózy mimokloubních tkání po unikompartmentální náhrade kolena.

The authors present a case of extensive metallosis of the knee joint resulting from the secondary abrasive wear of components of a unicompartmental alloplasty. Eight years after medial condyle replacement, an eighty-year-old patient presented with a break of the femoral component. This resulted in a rapid wear of tibial polyethylene and the development of secondary friction between two metal surfaces. The generation of a large number of metal particles produced an increase in the actual metal surface. This extensive articular metallosis affected not only intra-articular but also extraarticular tissues and the subchondral bone. Histological examination confirmed the presence of a large amount of opaque pigment in histiocytes. The condition was treated by total knee arthroplasty with resection of the posterior cruciate ligament (stabilizing plateau). The authors discuss the causes of metallosis development and its various types; they draw attention to the scarcity of literature data on this condition. Metallosis is a combined chemical and toxic reaction which, if the contact surface of a metal implant is large, may cause extensive damage to the surrounding tissue, the bone included.

PFC Modular Total Knee Replacement System - Middle Term Results.

Background. Total knee replacement, which is now the preferred solution for severe primary osteoarthritis, rheumatoid arthritis or posttraumatic osteoarthritis, is indicated in patients of various pathological changes and deformities. Every joint requires an individual treatment.
Material and method. We performed a prospective study of 500 cemented primary PFC modular total knee replacement implanted from 1991 to 2001, involving 350 prostheses (55 bilateral) in 295 patients with diagnosis of primary osteoarthritis, rheumatoid arthritis or posttraumatic osteoarthritis. The average age of our patients was 68,3 years (range 2,2-70,4 years). A survivorship curve was constructed based on revision surgery due to aseptic loosening.
Results. According to the Knee Society Clinical rating System, the results were excellent in 288 knees, good in 45 knees, poor in 13 knees and extremely poor 4 knees. We observed posterior dislocation of the tibial component in2 cases. In one patient we had to replace the implant in a two-stage procedure because of septic loosening.
Conclusions. The PFC total knee system seems to be a prosthesis of good quality, permitting, the solution of almost any problem that may arise in both primary and revision cases. We achieved good outcomes and high patient satisfaction.

Is plastic flow always controlled by dislocation mobility? An answer from in situ transmission electron microscopy straining tests.

In situ transmission electron microscopy (TEM) straining experiments are used to illustrate in two extreme cases the possible role of dislocation nucleation and exhaustion as a controlling factor in plastic flow. In the first example (FeAl intermetallic compounds), a thermally activated dislocation exhaustion is responsible for an anomalous stress-temperature dependence and an associated small strain rate sensitivity, the latter being evidenced during in situ experiments through unstable localized slip. The second example (heavily drawn pearlite) shows specific dislocation loop nucleation processes that may account for the Hall-Petch law breakdown characteristic of fine scale nanostructures.

[Surgical treatment of the ruptured achilles tendon.]. / Operacní lécba pretrzené Achillovy slachy.

The article deals with the issues of the rupture of Achilles tendon with a focus on its surgical treatment. On the group of 42 patients operated on between 1994 and 1999 with the average follow-up of 3 years and 9 months the authors analyze the epidemiology of this injury, i. e. its incidence by sex, age, causes etc. They also examine the influence of the presence of pretrauma complaints and the associated diseases. The results reflect both the subjective condition and the objective finding. Satisfaction of patients is expressed by a scale of seven subgroups. Achieved were 64,2 points out of the maximum number of 85. Clinical examination is focused mainly on the assessment of the standing on the toes or plan-tiflexion,Thompson test, range of motion and the presence of potential postoperative muscular hypotrophy. In the conclusion the authors discuss the influence of immobilization of the knee joint after the surgery on the strength of the regenerated tendon and mainly on the healing of the tendon in elongation which corresponds with the above mentioned clinical tests. Reduced plantiflexion was recorded in 26,2 % and the positive Thompson test in 21,4 % patients treated after the surgery by a foot-knee plaster fixation applied for 6 weeks. Key words: rupture of Achilles tendon, surgical treatment, results.

Intraoperative probes and imaging probes.

Intraoperative probes have been employed to assist in the detection and removal of tumors for more than 50 years. For a period of about 40 years, essentially every detector type that could be miniaturized had been tested or at least suggested for use as an intraoperative probe. These detectors included basic Geiger-Müller (GM) tubes, scintillation detectors, and even state-of-the-art solid state detectors. The radiopharmaceuticals have progressed from (32)PO(4)(-) injections for brain tumors to sophisticated monoclonal antibodies labeled with iodine-125 for colorectal cancers. The early work was mostly anecdotal, primarily interdisciplinary collaborations between surgeons and physical scientists. These collaborations produced a few publications, but never seemed to result in an ongoing clinical practice. In the mid 1980s, several companies offered basic gamma-detecting intraoperative probes as products. This led to the rapid development of radioimmunoguided surgery (RIGS) and sentinel node detection as regularly practiced procedures to assist in the diagnosis and treatment of cancer. In recent years intraoperative imaging probes have been developed. These devices add the ability to see the details of the detected activity, giving the potential of using the technique in a low-contrast environment. Intraoperative probes are now established as clinical devices, they have a commercial infrastructure to support their continued use, and there is ongoing research, both commercial and academic, that would seem to ensure continued progress and renewed interest in this slowly developing field.

Determination of erythromycin A by liquid chromatography and electrochemical detection, with application to salmon tissue.

The chromatographic performance of erythromycin A (EA) is improved significantly over that achieved on polymeric columns by using a sterically shielded octyldiisopropylsilica (Zorbax Rx-C8) column and a neutral mobile phase consisting of 5 mM aqueous sodium perchlorate-acetonitrile (50:50). This mobile phase facilitates electrochemical detection of EA at the 3-pmol level. Temperature control of both column and detection cell is important for minimizing detector noise and drift. A clean-up procedure, based on aminopropylsilica solid-phase extraction, allows the detection of EA in salmon flesh down to the 0.2-ppm level. Some of the metabolites of EA that retain the tertiary amine may also be detected by this method.

Analysis of paralytic shellfish poisoning toxins by automated pre-column oxidation and microcolumn liquid chromatography with fluorescence detection.

Periodate oxidation of the toxins responsible for paralytic shellfish poisoning (PSP) yields fluorescent purines suitable for trace analysis by reversed-phase LC. Mobile phases containing perfluorinated acids, such as heptafluorobutyric acid, as ion-pair agents were found to provide high capacity factors for the oxidized products. Gradient elution on a microbore column with large volume injections and fluorescence detection permitted the detection of femtomole quantities of PSP toxins. A fully automated pre-column oxidation procedure was developed for an LC autosampler system in order to improve precision and allow unattended analyses. The complete method was applied successfully to various samples, including shellfish and toxic phytoplankton.

Characterization of the oxidation products of paralytic shellfish poisoning toxins by liquid chromatography/mass spectrometry.

Periodate oxidation of the toxins responsible for paralytic shellfish poisoning (PSP) yields fluorescent products that are useful for trace analysis by reversed-phase liquid chromatography. Some toxins are oxidized to the same product, while others are transformed to a mixture of products; in all cases, the products are too unstable to be isolated preparatively. A mobile phase containing heptafluorobutyric acid as an ion-pair agent was developed to improve compatibility with liquid chromatography/mass spectrometry (LC/MS) analysis. Several LC/MS techniques were investigated: chemical ionization with the moving belt interface, atmospheric-pressure chemical ionization, thermospray, continuous-flow fast-atom bombardment, and ion-spray. Only LC/ion-spray MS was able to provide spectra of the oxidized products. The products were characterized as purines resulting from: (a) breakage of the C4-C12 bond and aromatization of the remaining rings (loss of 4 hydrogens); (b) partial elimination of a carbamoyl or N-sulfocarbamoyl side-chain (this is promoted by the presence of an N-1-hydroxy group); and (c) partial hydrolysis of an N-sulfocarbamoyl side-chain to a carbamoyl group.