Diapositiva

Document Sample
Diapositiva Powered By Docstoc
					                                                                      A Sensor Based On Plastic Scintillator for Alpha, Beta
                                                                           and Gamma Monitoring in Liquid Effluents
                                                                                         A.Tarancón1, J.F.García2 and G. Rauret1
                                                  1Departament de Química Analítica, Facultat de Química. Universitat de Barcelona. Av/ Diagonal 647, 08028 Barcelona
                                                  2Departament de Pintura, Facultat de Belles Arts. Universitat de Barcelona. C/ Pau Gargallo 4, 08028 Barcelona (Spain)

                                                                                E-mail: jfgarcia@apolo.qui.ub.es, alex.tarancon@ub.edu

INTRODUCTION                                                                                                                                                                                SENSOR DESCRIPTION AND OPERATION
On-line radioactivity monitoring in liquid effluents is an increasing                                                                                                                       The sensor patented is composed of two parts: Receptor and Transductor.
need according to the present international regulations. Classical                                                                                                                          Receptor is made of plastic scintillator. It is divided in two concentric cylinders:
activity determination procedures include the sequence of sampling,                                                                                                                         the internal ALFA-BETA DETECTOR and the external GAMMA DETECTOR. A
chemical treatment, measurement and data treatment. These steps                                                                                                                             modified 1414 Liquid Scintillation detector was used as transducer. A peristaltic
are man-power consuming, generate a great amount of waste and                                                                                                                               pump introduce the effluent into the sensor. Two bundles of optical fibers connect
introduce an important delay between the potential pollution event                                                                                                                          each part of the sensor with the transducer. Both detector were not measured
and its detection and quantification.                                                                                                                                                       simultaneously.

To overcome these limitations, we have developed a                                                                                                                                              SIGNAL DETECTED IN THE ALFA-
RADIOCHEMICAL SENSOR (PATENT PENDING Nº:P200500480)
for liquid effluents capable to send information about the specific
                                                                                                                                                                                                BETA DETECTOR: BKG+ γ +β + α
activity and volume of a contamination episode to a remote position,
on line and continuously. The sensor developed is capable to detect
and quantify the contamination pulses of alpha, beta and gamma                                                                                                                                    SIGNAL DETECTED IN THE
emitters of different volumes and activity levels included in a
continuous stream.                                                                                                                                                                                GAMMA DETECTOR: BKG+ γ


SENSOR SIGNAL CARACTERIZATION                                                                                                                                                              QUALITY PARAMETERS
 Different pulse volumes (P.V.) (0.2ml to 60ml) of 90Sr90Y, 134Cs
 and 240Pu were loaded into the sensor (flow = 0.5ml/min)                                                                                                                                                               P.V.                                      Time             Efficiency                            Background L.O.D.
                                                                                                                                                                                                                        (ml)                                       (s)                 (%)                                  (Bq)    (Bq/ml)
 SIGNAL PROFILE (0.2, 1, 4, 10, 14 and 20ml)                                                                            SPECTRA                                                             90SR90Y   in ALPHA-          0.2                                       10                  5.5                                    0.61                3.0
                        140                                                                                                                                                                     BETA DETECTOR
                                                                                                                                                                                                                         60                                       1200                117                                     0.80              9.1·10-2
                        120                                                                                                                           ++ :134Cs (alpha
                                                                                                                                                                     -beta)
                                                                                                      0.07
 Eff(%) or Counts(Bq)




                                                                                                                                                                                                240Puin ALPHA-
                        100                                                                                                                           ___:240Pu   (alpha
                                                                                                                                                                       -beta)                                            0.2                                       10                 0.13                                    0.49                9.4
                                                                                         Counts(Bq)




                                                                                                                                                      ----: 90Sr/ Y (alpha
                                                                                                                                                                90       -beta)                 BETA DETECTOR
                        80                                                                            0.05                                            ***:137Cs (gamma)
                                                                                                                                                                                                                         60                                       1200                 2.8                                    0.56                1.6
                                                                                                                                                                                                134Cs
                                                                                                                                                                                                    in GAMMA
                        60
                                                                                                                                                                                                                         0.2                                       10                0.034                                    0.17                75.9
                        40                                                                            0.03                                                                                        DETECTOR
                        20
                                                                                                                                                                                                                         60                                       1200                 1.2                                    0.13                0.77
                        0                                                                             0.01

                            0   50   100 150 200 250 300 350                                             0           100                               200            300         400       LIMIT OF DETECTION (L.O.D) WILL IMPROVE DRASTICALLY IF
                                        Time (s)                                                                                                      Channels                              ALPHA-BETA DETECTOR AND GAMMA DETECTOR ARE
(B-A) Parameter is obtained by applying the second derivate to                                                                                                                              MEASURED IN COINCIDENCE
the signal profile: δ2Bq/δV2=0

 ACTIVITY DETERMINATION OF UNKNOWN SAMPLES
The Sensor was calibrated to modelize the relationship between detection efficiency and the volume loaded (P.V.) versus de (B-A) parameter. Then it
was applied to quantify the activity an the volume of a serie of unknown contamination pulses of different volume and activity
                                                ACTIVITY QUANTIFICATION                                                     VOLUME QUANTIFICATION                                                                             ACTIVITY QUANTIFICATION                                             VOLUME QUANTIFICATION
                                                                                                                                                                                                                                                                                        7 ml                                                      7 ml
                                                                                                          8 ml
                                                                                                                                                                                                                                    Relative Error (%)




          90Sr90Y
            in the                                                10                                                                          10                                         8 ml                                                   10                                                              15
                                                                                                                             Relative Error (%)




                                                                                                                                                                                                                                                                                       12 ml
                                                                                                                                                                                                                                                                                               Relative Error (%)
                                                 Relative Error (%)




                                                                                                         14 ml                                                                          14 ml                                                                                                                                                    12 ml
      ALPHA-BETA                                                                                                                                                                                        134Csin the                                                                                             10
       DETECTOR                                                       5                                                                           5                                                     ALPHA-BETA                                       5

                                                                                                                                                                                                         DETECTOR                                                                                                    5


                                                                                                                                                  0                                                                                                      0                                                           0
                                                                      0
                                                                          Activity    Activity Activity                                                 Activity Activity           Activity                                                                  Activity Activity Activity                                 Activity    Activity   Activity
                                                                          3 Bq/ml    12 Bq/ml 21 Bq/ml                                                 3 Bq/ml 12 Bq/ml             21 Bq/ml                                                                  25 Bq/ml 141 Bq/ml 338 Bq/ml                               25 Bq/ml 141 Bq/ml 338 Bq/ml


                                                ACTIVITY QUANTIFICATION                                                    VOLUME QUANTIFICATION                                                                                   ACTIVITY QUANTIFICATION                                          VOLUME QUANTIFICATION
                                                                                                              7 ml                                                                       7 ml                                                                                           7 ml                                                     7 ml
                                                                  35                                                                         25                                                                                                 20                                                              10
                                             Relative Error (%)




                  240Pu                                                                                                                                                                 12 ml
                                                                                                                                                                                                                           Relative Error (%)




      in the                                                                                                                                                                                                                                                                           12 ml                                                    12 ml
                                                                                                                       Relative Error (%)




                                                                                                             12 ml
                                                                                                                                                                                                                                                                                                Relative Error (%)




                                                                  30
                                                                                                                                             20
                                                                                                                                                                                                         134Cs                                  15
 ALPHA-BETA                                                       25
                                                                  20                                                                         15
                                                                                                                                                                                                             in the
  DETECTOR                                                        15
                                                                                                                                             10
                                                                                                                                                                                                          GAMMA                                 10                                                                   5

                                                                  10
                                                                      5                                                                           5
                                                                                                                                                                                                         DETECTOR                                  5

                                                                      0                                                                           0                                                                                                0                                                                 0
                                                                          Activity Activity Activity                                                   Activity Activity Activity                                                                            Activity   Activity    Activity                              Activity   Activity   Activity
                                                                          97 Bq/ml 262 Bq/ml 282 Bq/ml                                                97 Bq/ml 262 Bq/ml 282 Bq/ml                                                                           94 Bq/ml 383 Bq/ml 542 Bq/ml                                95 Bq/ml 383 Bq/ml 542 Bq/ml


 Relative errors increase when pulses lower than 5ml are quantified.


CONCLUSIONS                                                                                                                                                                                                      BIBLIOGRAPHY
                                                                                                                                                                                                                 - Patent Applications nº P200500480: Sensor Radioquímico para
The radiochemical sensor can be applied to the DETERMINATION ON-                                                                                                                                                 fluidos. A. Tarancón, J.F. García y G. Rauret
LINE, REMOTELY, AND CONTINUOUSLY OF ALPHA, BETA, AND                                                                                                                                                              - Development of a radiochemical sensor for liquid effluents. Part
BETA-GAMMA RADIONUCLIDES included in liquid effluents.                                                                                                                                                           I. A. Tarancón, J.F. García y G. Rauret. Analytica Chimica Acta 538
                                                                                                                                                                                                                 (2005) 233-239
Relative errors for 90Sr/90Y and 134Cs in the alpha-beta receptor are
                                                                                                                                                                                                                 - Development of a radiochemical sensor for liquid effluents. Part
lower than 10% for contamination volumes higher than 5 ml. For 240Pu                                                                                                                                             II. A. Tarancón, A. Padró, J.F. García y G.Rauret. Analytica Chimica
relative errors are less than 15%. For 134Cs in the gamma receptor                                                                                                                                               Acta 538 (2005) 241-249
similar values were obtained. RESULTS WILL IMPROVE WITH NEW
                                                                      ACKNOWLEDGEMENTS: The authors thanks the CICYT for
DESIGNS ADAPTED TO SPECIFIC PROBLEMS.                                 Financial support: PPQ2002-00264

Dr. Pratt: A clinical-team meeting of the obesity-medicine specialist,
nutritionist, and psychologist concluded that this patient was a suitable
candidate for bariatric, or weight-loss, surgery. The term bariatric comes
from the Greek word "baros," meaning "weight," and refers to the
treatment of weight disorders. Many different surgical procedures have
been tried during the past 50 years, but there are three major categories in
current use: restrictive operations (gastroplasties with the use of adjustable
gastric bands), malabsorptive operations (biliopancreatic diversions), and
gastric bypasses.
Each can be performed either laparoscopically or in an open
fashion. The standard types of gastric bypass do not carry the risk
of clinically significant protein malnutrition that is associated with
biliopancreatic-diversion procedures.
Weight-loss surgery provides the best long-term results for
patients with moderate (class II) or severe (class III) obesity who
have not responded to more conservative approaches.11,12 It is
generally reserved for patients with a body-mass index greater
than 40 or for those with a body-mass index greater than 35
whose obesity is complicated by one or more major diseases.
This patient met the criteria for this approach, since she had a
body-mass index of 52 and several major complications and was
unable to maintain weight loss by other means.
The overall morbidity and mortality associated with gastric bypass
surgery are approximately 10 percent and less than 1 percent,
respectively.13,14 Early postoperative complications of laparoscopic
gastric bypass surgery include wound infections (incidence, 3
percent), anastomotic leak (2 percent), bowel obstruction (2 percent),
gastrointestinal hemorrhage (2 percent), and pulmonary embolus
(less than 0.5 percent). Late complications include bowel obstruction
(3 percent) and stomal stenosis (5 percent)13; both of these problems
are more common after laparoscopic procedures than after open
procedures.
Although reported in less than 1 percent of cases,7 anastomotic ulcers
have been one of the most common late postoperative complications in
my experience. In patients who have gastric bypass surgery, there is often
improvement or resolution of coexisting diseases such as diabetes,15
hypertension, hyperlipidemia, and sleep apnea,12 as well as improved
quality of life.7,14 For this patient, my colleagues and I believed that the
risks of continued obesity outweighed those of bariatric surgery and its
potential complications.
Laparoscopic Roux-en-Y gastric bypass was recommended,
because this procedure is associated with the best long-term
outcomes.14,16 This operation includes a restrictive procedure and a
short-limb gastroduodenal bypass (Figure 1). It does not result in
protein-calorie malabsorption, but it appears to induce
neurohumoral effects that result in decreased hunger, accelerated
postprandial satiety, and diminished emotion-based or reward-
based eating.2 The physiological and molecular mechanisms of
these effects remain poorly understood.
In the current case, preparation for surgery involved the full
multidisciplinary team. The preoperative nutrition program included
an individual session of nutrition counseling with a dietitian and a
group education session to familiarize the patient with the
postoperative diet protocol. The diet to be followed after gastric
bypass surgery is advanced in a staged approach (Table 5).
Psychological counseling was instituted to assist the patient in
making the behavioral changes that would be required after surgery.
The preoperative medical evaluation included a thorough
assessment of the operative risks and the need for perioperative
management of coexisting diseases, with discussion among the
obesity-medicine physician, anesthesiologist, and surgeon to
optimize her care.
The operation took about three hours. The surgical team first gained access
by placing two 12-mm ports and three 5-mm ports through the abdominal
wall in the upper abdomen — one for a camera, one for the liver retractor,
one for stapling devices, and the other two for graspers to manipulate the
stomach and intestines. The stomach was first divided by staplers across the
cardia, creating a 30-ml proximal gastric pouch (Video Clip 1 in the
Supplementary Appendix, available with the full text of this article at
www.nejm.org). We then created a 100-cm Roux limb by dividing the
intestines, stapling a jejunojejunostomy (Video Clip 2 in the Supplementary
Appendix), and passing the limb behind the colon and stomach (Video Clip
3 in the Supplementary Appendix).
Finally, this limb was stitched to the pouch in a double-layer anastomosis
1.5 cm in diameter (Video Clip 4 in the Supplementary Appendix).
Because the liver appeared fatty, a wedge-biopsy specimen of the liver
was obtained. Postoperatively, an amidotrizoic acid (Gastrografin)
swallow examination confirmed that the gastrojejunal anastomosis was
intact and without leak. The patient was discharged on the third hospital
day while following a stage 1 diet (Table 5).
Pathological Discussion
Dr. Fiona Graeme-Cook: The specimen obtained by liver biopsy
revealed hepatocellular steatosis with a very few foci of ballooning
degeneration; the portal tracts showed slight proliferation of the bile
ductules with minimal chronic inflammatory infiltrate (Figure 2A).
Glycogenated hepatocellular nuclei were scattered. These findings are
consistent with the presence of nonalcoholic fatty liver disease,
without evidence of steatohepatitis, fibrosis, or cirrhosis.
In the presence of insulin resistance, high levels of circulating
insulin lead to high levels of free fatty acids within the liver,
increasing the synthesis of triglycerides. Although the mechanism is
not completely understood, hepatocytes accumulate fat, manifested
as hepatocellular steatosis. This is the most common finding in the
liver in patients with severe obesity, present in more than 75 percent
of cases.
The additional feature of glycogenated nuclei is also a marker
for insulin resistance and hyperglycemia. Steatohepatitis may
complicate steatosis, possibly as a result of excessive -
oxidation of fatty acids by hepatocellular mitochondria. The
resultant oxidative stress is thought to lead to peroxidation of
lipids, resulting in hepatocyte necrosis, an influx of
mononuclear inflammatory cells, and eventually, fibrosis and
cirrhosis (Figure 2B). 17,18
Discussion of Outcome
Dr. Kaplan: During the early postoperative period, the patient's most
prominent symptom was constipation, which was probably a result of mild
dehydration. The mobilization of stored fat by lipolysis consumes
prodigious amounts of water, and fluid requirements are high during the
first several months after surgery. During the first few weeks, patients are
closely monitored for dehydration, which may be manifested as
constipation, lethargy, or light-headedness. The use of diuretics or other
antihypertensive agents often must be reduced or stopped altogether in the
immediate postoperative period.
This patient's blood pressure remained normal, and the lisinopril was
discontinued without adverse effect. Her blood sugar levels became
normal within two days after surgery, despite the discontinuation of
insulin and metformin. This rapid improvement in insulin sensitivity
within several days after surgery is typical, and many patients require
little or no therapy for their diabetes during this time. To avert
potentially life-threatening hypoglycemic episodes, her blood glucose
levels were monitored frequently and insulin and sulfonylureas were
avoided.
Ten days after surgery, she had lost 9.1 kg. Three months after the
operation, she was eating three meals and two snacks daily and had
lost 27.2 kg. Six months after surgery, she had lost 37.2 kg and was
eating most foods without having symptoms. Participation in
postoperative programs of nutrition education and cognitive
behavioral therapy appears to minimize both short-term
complications related to nutritional issues and subsequent weight
gain.10,11
Beginning six months after surgery, the patient participated in a monthly
program for surgical support and education, which provides ongoing
support and counseling. Her weight decreased by 54.4 kg, to 70.3 kg,
during the first 12 months after surgery. Excess skin with ptosis in the
lower abdomen was treated with abdominoplasty 15 months after the
weight-loss surgery. She later regained approximately 4.5 kg, and her
weight then stabilized at 74.8 kg for the next year.
Nutritional Outcome
Two years after surgery, the patient's body-mass index was 30, down from
52, and her energy expenditure was estimated to be about 1800 kcal per
day, down from 2500 kcal per day. She ate three meals a day and did not
routinely eat snacks. She experienced satiety with half-normal portions of
food, and her hunger returned about five hours after each meal. She
tolerated all types of food, although she avoided concentrated
carbohydrates at the beginning of each meal as a way of preventing the
dumping syndrome (i.e., rapid gastric emptying). She did not have any
change in her food preferences. She walked 4.8 km a day and reported
enjoying exercise for the first time.
Medical Outcome
Two years after surgery, the patient's diabetes improved but did not
completely resolve. She no longer required insulin, and her metformin
dose decreased from 850 mg taken three times daily to 500 mg taken
twice daily. Her levels of hemoglobin A1c and urinary microalbumin fell
(Table 1). Her diabetic retinopathy did not progress. Her sleep apnea,
hypertension, and folliculitis resolved. Her lumbar back pain and
sciatica improved substantially. Her hyperlipidemia remained well
controlled with the use of a lower dose of atorvastatin than she was
taking before the surgery, and there was no progression of her coronary
artery disease.
A deficiency of micronutrients is common after gastric bypass surgery.
We regularly assessed the patient's levels of iron, calcium, vitamin B12,
vitamin D, and vitamin K. Iron deficiency developed approximately 10
months after surgery (Table 1). It was treated successfully with oral
ferrous bisglycinate and polysaccharide iron supplementation. Before
surgery, she had been found to have a vitamin B12 deficiency, which
occurs in a small number of patients with obesity who have followed
many diet programs. Intranasal vitamin B12 supplementation was begun
before the operation and was continued afterward, and two years later she
had normal levels of vitamin B12 (Table 1).
Secondary hyperparathyroidism from malabsorption of calcium
and vitamin D occurs in more than 60 percent of patients after
gastric bypass. Metabolic bone disease is common and must be
screened for and treated. This patient took prophylactic
supplementation with an oral calcium preparation (1000 mg of
elemental calcium per day), and her levels of calcium, vitamin D,
and parathyroid hormone have remained normal.
Psychological Outcome
Six weeks after the operation, the patient recognized feelings of loss related
to being unable to overindulge in food. She commented, "You fixed my
stomach, but I need to fix my head," alluding to the need to focus on
psychological triggers for eating that could no longer be satisfied by food.
Twelve weeks after surgery, she reported feeling "great." She was excited
about her increased energy, and the Beck Depression Inventory score fell to
3, within the range of minimal depressive symptoms, and it remained at that
level thereafter. She stopped taking fluoxetine.
Two and a half years after the gastric bypass surgery, both her self-
confidence and her self-esteem have increased. She is more assertive
in her relationships, with positive results.
Dr. Pratt: This case illustrates the importance of a multidisciplinary
team that includes an obesity-medicine specialist, a nutritionist, a
psychologist, and a surgeon to ensure optimal medical and
psychological results from weight-loss surgery.1,10,19 Although this
patient was able to initiate exercise on her own, it is important to
include a physical therapist or trainer when needed. Although her
obesity was not cured, since her body-mass index remained elevated
(at 30), the team viewed this case as having a successful outcome.
Dr. A. Benedict Cosimi (Surgery): How would you assess whether the
patient's psychological issues were solved or complicated by the surgery?
This patient considered her weight a protective shield. How did she feel
when this shield disappeared?
Dr. Vineberg: Instead of using the weight as a protection, she worked
to establish appropriate boundaries with people in her life, so that she
could maintain appropriate emotional distance that did not depend on
the physical or emotional distance caused by her size.
Dr. Kaplan: It is not clear whether the protection that she felt the excess
weight provided was a primary or a secondary event. If you are
shunned in society because of obesity, you may then use the weight as
an excuse not to interact with people.
Dr. Carlos Fernández-del Castillo (Surgery): The adjustable gastric band has
been approved by the Food and Drug Administration for use in the United
States. I anticipate that its application is an easier operation than bypass. Why
was it not used here?
Dr. Pratt: The early experience with the adjustable gastric band in
the United States showed a high rate of reoperation,20 and
definitive studies of long-term outcomes are not yet available. To
achieve an optimal outcome, the band has to be adjusted every two
to six months by the addition or removal of saline. This
dependence on frequent follow-up visits suggests that success with
this procedure may be more dependent on voluntary behavior than
the success observed after gastric bypass.
Dr. Jay Vacanti (Pediatric Surgery): Can you comment on the use of
surgery in the management of pediatric obesity?
Dr. Pratt: Obesity in adolescents is being treated surgically in several
centers around the country, including the Weight Center.21 Although the
pediatric program here focuses primarily on behavioral and medical
approaches, gastric bypass surgery has been used to treat a few teenagers
with severe obesity and obesity with medical complications, such as type
2 diabetes mellitus or obstructive sleep apnea, who have not been
responsive to other interventions. Recent studies have shown that
resolution of diabetes is most likely in patients who have had it for less
than five years, so waiting to perform surgery in children with type 2
diabetes may be more dangerous in the long term than performing the
surgery.22

				
DOCUMENT INFO