Search PubMed⌕ Search

Biomedical subjects

J C Hung

Publications and source records attributed to J C Hung.

At least 55 records · Page 3Linked to original sources
PubMed1995

Rapid radiochemical purity testing for [131I]m-iodobenzylguanidine.

The standard high pressure liquid chromatography (HPLC) method for determining radiochemical purity (RCP) of [131I]m-iodobenzylguanidine ([131I]mIBG) is cumbersome and time-consuming. A simplified and rapid separation method with the use of a reverse-phase extraction chromatography technique (i.e. Sep-Pak C18 [SPC] cartridge) is described. The new SPC system closely correlates (r = 0.99) to the standard HPLC method, and the time to complete the SPC analysis is less than 5 min.

3-Iodobenzylguanidine↗
PubMed1995

Generator eluate effects on the labeling efficiency of 99mTc-sestamibi.

Our nuclear pharmacy noted that 99mTc-sestamibi kits sometimes failed radiochemical purity (RCP) testing (i.e., RCP < 90%). All failed kits had been prepared with eluate from a newly arrived generator (ingrowth time > or = 72 h) which had been eluted > or = 6 h before the kit failure. The effects of 99mTc activity and eluate volume were then investigated to help explain the reason for the low RCP values. Our results demonstrated that higher failure rates of the 99mTc-sestamibi kits were noted when higher activities of 99mTc eluates were added, and the higher failure rates of the kits were associated with lower RCP values. In addition, higher kit failure rate and lower RCP values of the 5.55-GBq kits at 12 h postelution in comparison with the 11.1-GBq kits at 6 h (same eluate volume) indicated that the 99mTc activity and volume had a less detrimental effect on the 99mTc-sestamibi kit preparation than the 99mTc eluate age. The kit failures might be explained by the higher amount of 99mTc and the production of the free radicals during the long ingrowth time prior to generator elution. In conclusion, the use of a first elution from a long-ingrowth time generator at a later stage (i.e., 11.1 GBq at 6 h and 5.55 GBq at 12 h postelution) in preparation of a 99mTc-sestamibi kit is associated with a high rate of kit failure and should therefore be avoided.

Isotope Labeling↗
PubMed1995

Comparison of four alternative radiochemical purity testing methods for 99Tcm-sestamibi.

Four different methods for determining the radiochemical purity (RCP) of 99Tcm-sestamibi have been proposed to replace the recommended thin-layer chromatography (TLC) method, as the recommended method is inconvenient and time-consuming. The purpose of this study was to compare the recommended TLC method with the four proposed rapid QC methods for 99Tcm-sestamibi: (1) chloroform extraction (CE), (2) mini-paper chromatography with chloroform/tetrahydrofuran (1:1, v/v) (MPC), (3) Waters Sep-Pak alumina N cartridge with 100% ethanol (SPE), and (4) Waters Sep-Pak C18 cartridge with normal saline (SPNS). For RCP values ranging from 21.8 to 98.7% (n = 20), both the CE and SPNS methods produced falsely high RCP values (RCP difference: 14.1 +/- 23.5% for CE and 15.0 +/- 24.9% for SPNS). The MPC and SPE methods were in good agreement (r = 0.98 for MPC and 0.88 for SPE) with the recommended TLC method over the critical RCP range (i.e. 77.0-98.7%, n = 52) (RCP difference: -0.9 +/- 1.2% for MPC and -4.3 +/- 3.2% for SPE). None of the 99Tcm-sestamibi preparations that had been rejected (i.e. RCP < 90%) by the TLC method were accepted by either the MPC or SPE method. However, 4 of the 52 99Tcm-sestamibi preparations with acceptable RCP by the TLC method had unacceptable RCP by the MPC method, whereas 8 of the same 52 preparations were unacceptable by the SPE method.(ABSTRACT TRUNCATED AT 250 WORDS)

Chloroform↗
PubMed1995

In vitro evaluation of neutrophil viability after exposure to a hypotonic medium.

Separation techniques for radiolabelled leukocytes have inherent problems with contaminants (e.g. platelets and erythrocytes). Hypotonic lysis methods can eliminate the erythrocytes, but the question of neutrophil viability after an exposure to a hypotonic solution (i.e. sterile water) remains. Ficoll/ hypaque two-density gradient separation was performed on donor whole blood to obtain a pure neutrophil suspension. A timed sequence of water exposure was done for 5-100 s on the neutrophil preparations. The viability of these preparations was evaluated using flow cytometry and chemotaxis. The trypan blue staining method was used to document cell death. With water exposures ranging up to 100 s, 2.04 +/- 1.80% neutrophils exhibited cellular degradation by flow cytometry, and all samples demonstrated viable neutrophils by chemotaxis and trypan blue staining. The hypotonic medium exposure times for leukocyte separations should be less than 30 s for neutrophils to retain their viability by these in vitro techniques.

Cell Death↗
PubMed1995

Coeliac disease in children of West Indian origin.

Coeliac disease is uncommon in populations of non-European origin. Two English born West Indian children with coeliac disease are presented. The diagnosis should be considered in children of West Indian origin with chronic diarrhoea.

Celiac Disease↗
PubMed1995

Filtered technetium-99m-sulfur colloid evaluated for lymphoscintigraphy.

UNLABELLED: Several 99mTc-labeled radiopharmaceuticals have been developed for lymphoscintigraphy of the extremities. In the United States, however, these agents are not widely used clinically. This study evaluates the use of smaller particle sizes ( < 0.1 micron) of 99mTc-sulfur colloid (99mTc-SC) for lymphoscintigraphy. METHODS: The 99mTc-SC was prepared by kit, and the final preparation was filtered through a sterile 0.1-micron filter. The radiochemical purity (RCP) of the filtered 99mTc-SC was determined before administration. Nineteen patients with suspected lymphedema were injected with 18.5 MBq (500 muCi) filtered 99mTc-SC intradermally in each foot, and whole-body images were obtained immediately and 1, 3, 6 and 24 hr later. Local views over the inguinal or axillary lymph nodes were also obtained every 5 min for the first hour. RESULTS: The average RCP value was 93.4% +/- 4.2% (n = 19), and the RCP difference pre- and postfiltration of the 99mTc-SC preparation was -1.7% +/- 1.4% (n = 40). Evaluation of the particle size with the polycarbonate filter showed that 89.9% +/- 4.5% (n = 28) of particles were less than 50 nm, and the particle size was further determined by electron microscopy to be 38.0 +/- 3.3 nm (n = 202). The mean particle sizes of two peaks measured by laser light scattering techniques were 7.5 and 53.9 nm (major peak). Clinical studies with filtered 99mTc-SC demonstrated similar lymphoscintigrams compared with those obtained with 99mTc antimony sulfide colloid (99mTc-ATC). Filtered 99mTc-SC showed a faster transport rate to the inguinal lymph nodes and lower radiation dosimetry for liver, spleen and whole body compared with 99mTc-ATC. CONCLUSION: Filtered 99mTc-SC can be easily prepared and is readily available for routine clinical use in lymphoscintigraphic studies.

Antimony↗
PubMed1995

Effects of generator eluate age on the radiochemical purity of fractionated 99Tcm-MAG3.

The fractionation of US mercaptoacetyltriglycene (MAG3) cold kits provides an economical way of preparing 99Tcm-MAG3. However, our nuclear pharmacy noted that fractionated 99Tcm-MAG3 kits sometimes failed radiochemical purity (RCP) testing (i.e. RCP < 90%) when a 99Tcm eluate of older age was used. The purpose of this study was to evaluate the effects of eluate age on the radiochemical purity of fractionated 99Tcm-MAG3 kits. Each of four US MAG3 cold kits was initially diluted with 10 ml N2-purged 0.9% NaCl solution and subdivided into 10 aliquots of 1 ml MAG3 solution and overlayered with N2. The 40 fractionated MAG3 vials were immediately frozen at -20 degrees C for storage. Fractionated MAG3 kits were reconstituted with 1 ml of approximately 111 GBq 99Tcm eluate from a long-ingrowth generator (i.e. > or = 72 h) every hour during the 6 h post-elution period. The RCP of each 99Tcm-MAG3 preparation was determined using the recommended Sep-Pak C18 column chromatography 1, 2, 3, 4, 5 and 6 h post-reconstitution. All fractionated MAG3 kits prepared with 99Tcm eluates 4 h post-elution or less maintained an average RCP value of 96.3 +/- 2.5% (n = 144) throughout the 6 h evaluation period following preparation. However, 99Tcm eluates 5 and 6 h post-elution resulted in kit failure rates of 16.7% (1/6) with RCP = 89.3%, and 50% (3/6) with RCP = 88.2, 83.9 and 87.1%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography↗
PubMed1995

Single photon emission computed tomography.

Single-photon emission computed tomography is a well established functional imaging technique in epilepsy that aids precise noninvasive localization of the seizure focus required for surgical intervention in refractory seizures. Electroencephalography with video monitoring of seizures precedes more invasive evaluation, such as cortical or depth electrodes. Positron emission tomography studies in temporal lobe epilepsy are moderately sensitive, demonstrating ipsilateral hypometabolism. Ictal single photon emission computed tomography studies in temporal lobe epilepsy demonstrate transient intense hyperemia in the anterior temporal lobe structures. Peri-ictal images show persisting mesial temporal hyperperfusion with lateral hypoperfusion developing over the next 2 to 5 minutes to be replaced by significant hypoperfusion in the postictal phase. Interictal single photon emission computed tomography with ipsilateral hypoperfusion, suffers from reduced sensitivity and accuracy, whereas ictal and, to a lesser extent, peri-ictal and postictal single photon emission computed tomography are highly sensitive and accurate in localizing temporal lobe epilepsy. New iodinated neuroreceptor single photon emission computed tomography imaging agents hold promise in localizing the seizure focus (focally reduced uptake) without ictal injection, and also may elucidate underlying mechanisms inherent to epilepsy.

Cerebrovascular Circulation↗
PubMed1994

Modified radioiodination and quality control methods for [125I]sodium iothalamate.

[125I]Sodium iothalamate can be prepared by the isotope-exchange method with the use of a contrast medium preparation (i.e. iothalamate sodium injection, USP, 80%). The initial isolation and purification of iothalamate from the contrast medium solution for radioiodination is tedious and time-consuming (i.e. 1 1/2 h for purification and overnight for drying). The new method uses iothalamic acid to replace iothalamate sodium injection as a starting material and reduces the heating time and multiple acid-washing steps during radioiodination to expedite the radiolabelling process. The radiochemical purity (RCP) of [125I]sodium iothalamate obtained from the new method was 98.9 +/- 1.3% (n = 30) versus RCP value of 99.2 +/- 1.0% (n = 25) from the old method with no significant differences between the two groups of RCP values. An RCP chromatographical system to separate and migrate the radiochemical species of [125I]sodium iothalamate from the origin is described in this paper.

Iodine Radioisotopes↗
PubMed1994

The radiation dosimetry and normal value study of 99mTc-HMPAO-labeled leukocytes.

RATIONALE AND OBJECTIVES: Indium-111 (111In)-labeled leukocyte scanning has been used frequently in patients suspected of having infections. Recently, technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) has been used to label leukocytes. This study was undertaken to determine the distribution and dosimetry of 99mTc-HMPAO leukocytes in healthy subjects. METHODS: Five healthy volunteers had leukocytes labeled with 99mTc-HMPAO. After injection of the labeled leukocytes, whole body images and blood and urine samples were obtained at multiple time points. RESULTS: Visual interpretation of the images demonstrated significant bowel activity as early as 2 hours and increasing with time such that one the 8- and 24-hour images, the amount of bowel activity would preclude using 99mTc-HMPAO leukocyte scanning for abdominal processes. The dosimetry for this study is similar to that of other studies and is in an acceptable diagnostic range. CONCLUSIONS: 99mTc-HMPAO leukocyte studies are an acceptable alternative to 111In-labeled leukocyte studies in terms of dosimetry. Use of such studies in the abdomen should be limited to early images, usually before 2 hours, to avoid confusion with the normal route of excretion in the bowel.

Female↗
PubMed1994

Radiochemical purity testing for 99Tcm-exametazime: a comparison study for three-paper chromatography.

The standard radiochemical purity (RCP) determination uses a three-paper chromatography strip and solvent system (TP). The involvement of multiple strips for calculation of percentage primary, lipophilic 99Tcm-exametazime complex is tedious and time-consuming. The significant streaking of radioactivity on the ITLC/SG MEK strip of the TP method indicates that ITLC/SG MEK may not be an ideal system for RCP analysis of 99Tcm-exametazime. This study was undertaken to compare the standard TP method with two other proposed single-strip chromatography systems: Whatman 17 Chr paper with ethyl acetate (WE) and Gelman Solvent Saturation Pads paper with ether (GE). Our results showed that the solvent developing times (n = 55) and Rf values for TP, WE and GE were 130.4 +/- 9.0 s/0.5-1.0, 205.9 +/- 13.0 s/0.2-1.0 and 90.2 +/- 7.5 s/0.8-1.0, respectively. For RCP values ranging from 45.0 to 94.6% (n = 61), both WE and GE closely correlated with TP (r = 0.97 and 0.96). However, in the intermediate RCP range (i.e. 75-85%, n = 25), the false RCP acceptance rate (i.e. RCP > or = 80%) was 40% (10/25) for the WE method versus 4% (1/25) for the GE method. The GE method has the most clear separation of lipophilic 99Tcm-exametazime from other radiochemical impurities and offers the quickest RCP analysis for 99Tcm-exametazime with relatively accurate results.

Chromatography, Paper↗
PubMed1994

Evaluation of two commercial jet nebulisers and three compressors for the nebulisation of antibiotics.

Nebulised antibiotics have been shown to be beneficial in the treatment of lung infections in cystic fibrosis. Studies on the efficiency of nebuliser systems are constantly required in view of the large number of compressor/drug/nebuliser combinations which are possible and the development of new systems and drugs. Six combinations of three commercially available compressors were compared (PortaNeb 50 (Medic-Aid; 5.4-6.1 l/min), Turboneb (Medix; 8.3-9.1 l/min), and CR 60 (Medic-Aid; 7.3-7.8 l/min)) and two jet nebulisers (Microneb III (Lifecare) and System 22 Acorn (Medic-Aid)) for the nebulisation of colomycin, gentamicin, and ciprofloxacin. Aerosol droplet size, nebulisation time, and aerosol output were determined. Turboneb and CR 60 reduced the nebulisation time and produced higher proportions of 'respirable' (< 5 microns diameter) antibiotic aerosols. The residual volume of the Microneb III was lower than that of the System 22 Acorn. It was found that the Turboneb and CR 60, when coupled with either Microneb III or System 22 Acorn, were suitable for the nebulisation of all three antibiotics. Of the equipment tested, Turboneb coupled with Microneb III was the most efficient combination. Even with this combination, only around 50% of the nominal dose was released as respirable aerosol.

Administration, Inhalation↗
PubMed1993

Evaluation of 99Tcm nonspecific polyclonal IgG in the detection of rejection in a single lung transplant canine model.

Acute rejection is an important cause of graft failure in single lung transplantation, however, current noninvasive tests are neither sensitive nor specific for this diagnosis. The aim of this study was to determine whether 99Tcm-labelled human nonspecific polyclonal IgG (99Tcm-IgG) may serve as a marker for acute pulmonary rejection following allotransplantation in a dog model. Seventeen mongrel dogs were studied, including four controls and thirteen dogs which underwent surgery [right autotransplant recipient (n = 4), right unmodified allotransplant recipient (n = 5), and right immunosuppressed allotransplant recipient (n = 4)]. At 6 days following surgery, all dogs received 67Ga-citrate and 99Tcm-IgG. Two days later all dogs were sacrificed. Post-mortem examination revealed acute lung rejection in nine animals. No significant difference was found in the percentage uptake of both 99Tcm-IgG and 67Ga-citrate per gram of tissue between rejecting and nonrejecting transplanted lungs. In cases of moderate to severe rejection (n = 5), only 67Ga-citrate showed a significant difference (P = 0.03) in uptake between rejecting and contralateral native lungs, respectively. We conclude that 99Tcm-IgG does not accurately identify acute lung rejection in the early postoperative period.

Animals↗