T H E E S C N E W S L E T T E R

inside this issue:Page 3Recent studies confirm effectiveness of virtual colonoscopy

Page 2CT Colonography

Page 5Meet our Radiologists

Page 8Competition - win a case of vintage Champagne

Page 7EBCT preventive screening -a GP’s perspective

CT Colonography: Technique and Status

Colorectal cancer (CRC) is the third most common malignancy in the UK

with approximately 30,000 new cases reported each year. In the UK the

lifetime risk of developing CRC is 1 in 18 in males and 1 in 20 in females.

The vast majority of cancers arise from benign adenomatous polyps, a

process which occurs over a 10-20 year period. The incidence of cancer

increases with polyp size, with a polyp greater than 1cm having a 10-50%

risk of developing malignancy. The long lead time from polyp to cancer

renders the condition preventable if the polyp can be detected and resected.

continued on page 2

by Dr Chris J Harvey BSc MBBS MRCP FRCR

WINTER07

page 2

administration of intravenous contrast. Scanning should be performed in

both supine and prone positions. This is to ensure that all segments of the

colon are well visualised as there may be positional collapse e.g the sigmoid

colon is commonly collapsed in the supine position but is well distended on

the prone view. Prior to the CT the patient follows a low residue diet for 48

hours and then one day before the CT scan patients undergo standard bowel

cleansing with purgatives. Immediately prior to the CT scan an intravenous

injection of 20mg of buscopan is administered to relax the colon and

prevent spasm. Rectal CO2 or air is then insufflated via a small Foley catheter

until a feeling of fullness is experienced. Adequate distension of the whole

colon is confirmed on a CT scanogram before the scan is commenced.

Scanning parameters vary but in a typical study would be performed at

3mm intervals, with overlap of slices. The data is then downloaded to

an independent workstation equipped with appropriate software for 3D

reconstruction. A computer generated retrograde intraluminal ‘fly through’

navigation from rectum to caecum can then be viewed and can be repeated

in the opposite direction.

The virtual colonoscopies (VC) are stored in a ‘cine loop’ format and can be

viewed directly from the workstation monitor. Image analysis is interactive,

and the radiologist can choose to view the rendered mucosa from any angle,

pass through the tightest stricture, and even cross the colonic wall into

adjacent structures. Virtual studies are usually examined in combination

with the standard axial images. The computer can also generate two-

dimensional images at cross sectional and orthogonal angles to the long

axis of the colon to aid interpretation.

Future developments are likely to include the use of oral contrast agents to

‘tag’ or label residual faeces and fluid with the aim of improving sensitivity

and specificity, while reducing the laxative regime. However the optimum

tagging/cathartic regimen is still controversial.

Another area of great interest is computer-aided detection (CAD) to

highlight areas of abnormalities, which the radiologist must then assess.

CAD has been shown to significantly increase sensitivity in the detection of

colonic abnormalities.

CT colonography in symptomatic patients and screening in asymptomatic individuals

Studies show that CT colonography surpasses barium enema and

approaches the sensitivity of conventional colonoscopy (3-5). Meta-analyses

show that CT colonography is both sensitive and specific for the detection

of large and medium polyps (Fig 1) and has a high reported diagnostic

accuracy for symptomatic cancer (Fig 2)(6). Results demonstrate a mean

sensitivity for the detection of cancer of 95.9%, sensitivity and specificity for

polyps greater than 1cm of 92.5% and 97.4%, respectively and for 5-9 mm

polyps of 86.4% and 86.1%, respectively.

Cost effectiveness and patient compliance are major determinants when

considering a feasible screening tool. Studies have shown that these are

Welcome to the Christmas edition of the European Scanning Centre newsletter. All of the team are delighted by the positive response we have received from the inaugural issue and hope you enjoy the latest edition.

In this issue, Dr Chris Harvey, Consultant GI Radiologist from the Hammersmith Hospital, discusses the pros and cons of virtual colonoscopy. Dr Alix Daniel then gives her perspective on using Electron Beam CT for preventive screening. We also put the spotlight on our radiological team, headed by Dr Sarah Howling, as well as our regular Ross’s Riddle.

In response to practitioners’ requests, we are happy to announce our new extended opening hours of 8am – 6pm Monday to Friday. We have also recently obtained recognition by AXA-PPP as a diagnostic imaging centre, which means we are now approved by all private insurance providers.

We welcome your feedback as always, but in the meantime we wish you a Merry Christmas and prosperous New Year.

Dr Paul Jenkins, MA MD FRCPMedical Director

CT Colonography: Technique and Status (continued from front cover)

From the Medical Director...

CT colonography was first described in 1994 and represents a fusion of thin

slice computed tomography of the large bowel with advanced techniques

for rendering three dimensional (3D) images to produce views of the colonic

mucosa, similar to those obtained during conventional colonoscopy, hence

its popular name of virtual colonoscopy. However, CT colonography also

provides exquisite 2D views of the colon in axial, coronal and sagittal planes.

It allows the whole colonic wall to be imaged rather than just the luminal

view as well as depicting extra-colonic abnormalities and the abdominal and

pelvic organs. CT colonography has evolved since 1994 and now has a strong

evidence based role in the investigation of symptomatic patients as well as a

screening tool for colorectal neoplasia in asymptomatic individuals. (1, 2)

Technique

A CT colon scan is performed during a single breath hold of 15-20 seconds

after bowel cleansing, optimal colonic distension, bowel paralysis and

page 3

favourable for CT colonography. Currently flexible sigmoidoscopy and faecal

occult blood tests are favoured as screening tools for the NHS whilst results

of larger CT colonography trials are awaited.

Radiation dose

Radiation dose remains a concern in mass VC screening. The effective dose

equivalent for multidetector (MD) CT colonography varies according to the

protocol performed. A recent study of simulated radiation dose in 64-slice

CT colonography demonstrated a dose range of 2.5-5.7mSv for males and

2.9-6.4mSv for females (a chest x-ray gives a dose of 0.06mSv, the annual

background radiation dose is 2.5-3mSv in the UK and the mean dose for a

barium enema is 7mSv) (7). Preliminary studies have suggested that a protocol

adjustment resulting in a dose reduction to 0.7mSv and 1.7mSv does not

impair sensitivity of detecting significant polyps (≥1cm) because of the

high contrast resolution between luminal air and bowel wall(8, 9). However,

the detection of extracolonic abnormalities will be reduced because of the

decrease in contrast resolution making noise a bigger problem.

Advantages of CT colonography compared to conventional colonoscopy

Although conventional colonoscopy is still considered the gold standard

for the detection of colonic neoplasia, a UK audit showed an overall caecal

intubation rate of only 56%(10) and expert back to back colonoscopies have

been shown to miss 24% of adenomas (11) but the majority of these were

less than 5mm in size. CT colonoscopy offers several advantages over the

conventional approach (Table 1).

continued on page 4

Recent results from two large screening trials demonstrate virtual

colonoscopy (VC) to be as sensitive in colonic polyp detection

compared to more invasive fibre-optic colonoscopy (OC). The US

National CT Colonography Trial performed on 2,531 asymptomatic

participants demonstrated an impressive per-patient sensitivity for

VC of 90% for adenomas 1cm or larger in diameter, a sensitivity

similar to OC.

The second study, published in the New England Journal of Medicine

(October 4, 2007), involving 6,283 subjects found comparable

detection rates between VC and OC for advanced adenomas (3.2%

and 3.4%, respectively) in two demographically similar asymptomatic

patient groups referred by the same primary care providers.

Interestingly, VC detected more cancers compared to OC, and

contrary to expectations, VC was also more effective at detecting

flat colonic polyps.

In both studies, the detection of

significant lesions by VC, which

required subsequent OC was 7.9%

and 8.3%, leading both study

investigators to claim that VC was

a suitable and often preferable

alternative to OC for colorectal

cancer screening.

Principal investigator Dr. Daniel Johnson from the Mayo Clinic hoped

that the results would encourage more individuals over 50 years of

age to get screened. “I think we can say that CT colonography is

similar to the performance of colonoscopy for large adenomas 1cm

or larger, as well as those intermediate adenomas 5-10mm in diameter.

I think it’s reasonable to consider broader application of this relatively

non-invasive imaging modality, which hopefully will enhance

compliance with colorectal cancer screening guidelines.”

Recent studies confirm effectiveness of virtual colonoscopy

Table 1: Advantages and disadvantages of CT virtual colonoscopy over traditional fibreoptic colonoscopy

Advantages• Quicker

• Safer - minimal risk of perforation; 0.03% vs. 0.13%

• No need for sedation

• Non-invasive

• Much higher success rate in visualising the caecum (>95%)

• Allows visualisation of entire colonic mucosa in any plane regardless of strictures/obstruction

• Visualises extracolonic structures

• Allows immediate staging of any cancer

• Non-operator dependent

Disadvantages

• Radiation exposure

• Cannot perform immediate polypectomy/biopsy

• Poor detection of ‘flat’ polyps (also with conventional colonoscopy)

page 4

Conclusion

CT colonography is a non-invasive,

safe, quick, well tolerated and

non-operator dependent sensitive

technique for examining the entire

colon. Its sensitivity and specificity

for colonic neoplasia exceeds that of

barium enema and approaches that

of conventional colonoscopy. It can

accurately indicate which patients

need to proceed onto a conventional

colonoscopy or polypectomy.

Further research is warranted to

fully assess its impact in terms

of a screening tool, acceptability,

availability and cost benefit.

References

1. Harvey CJ et al Eur Radiol 2001; 11: 1612-1625.

2. Tolan D et al. Clin Rad 2007; 62: 819-827.

CT Colonography: Technique and Status (continued from page 3)

Fig 1a.

Fig 1b.

Fig 2a.

3. Rockey D et al. Lancet 2005; 365: 305-311.

4. Pickhardt P et al. NEJM 2003; 349: 2191-200.

5. Cotton P et al. JAMA 2004; 291: 1713-9.

6. Halligan S et al. Radiology 2005; 237: 893-904.

7. Luz O et al. Eur Rad 2007; 17: 616-621.

8. Florie J et al. Eur Radiol 2007 June (Epub).

9. Innaccone R et al. Eur Radiol 2003; 13: 1297-1302.

10. Bowles C et al. Gut 2004; 53: 277-283.

11. Rex D et al. Gastroenterology 1997; 112: 24-28.

12. Yee J et al. Radiology 2005; 236: 519-526.

13. Burling D et al. Radiology 2006; 239: 464-471.

Figure Legends

Fig. 1a. - 64 year-old man with

rectal bleeding. The axial CT shows a

1.5 cm sigmoid polyp (arrow).

Fig 1b. - The same polyp is depicted

in axial, coronal and sagittal

muliplanar reformats as well as

3D. Its position in the colon is also

shown on the ‘fly through’ which

gives its distance from the anal

margin. The polyp was successfully

resected at colonoscopy and was

confirmed as a benign adenoma.

Fig 2a. - 58 year-old man with a

change in bowel habit. A colon

cancer is seen at the hepatic flexure

(arrow on 3D image) and is seen

as an applecore lesion on axial CT

image (bottom left image).

Dr Chris J Harvey BSc MBBS MRCP

FRCR Consultant Radiologist,

Hammersmith Hospital, London

The European Scanning Centre is delighted to announce

that we are now covered by AXA PPP insurance for

diagnostic imaging. We are also covered by all other

major insurers including:

BCWA BUPA

Clinicare Norwich Union

Pru Health WPA

European Scanning covered by AXA PPP

Consulting Room now availableLarge, recently refurbished consulting room available to rent at 68 Harley Street. For further information, please contact Dr Paul Jenkins on:020 7436 5755

New Opening HoursMonday - Friday 8:00am - 6:00pm

We are pleased to announce that the European Scanning Centre has extended its opening hours to better meet the needs of our referring doctors.

page 5

SPOTLIGHT... on our Radiologists

Why did you choose a career in radiology? I was inspired by Dr Mike Reubens who was a radiologist working at the London Chest Hospital and who always seemed so calm and happy sitting in his darkened room. I have also always been a bit of a gadget girl with regard to technology and liked the idea of peeping inside people and trying to piece together a set of clues.

Where did you train and how did your training prepare you for a career in radiology? My medical training was at The Royal Hospital, although I am not sure that this really did prepare me for my radiology career as technology really has marched on. We did not even have MRI scanners back then and a CT head scan took 20 minutes not 3 seconds as it does now. I continued my radiology training at UCLH with a chest fellowship in Vancouver.

What branch of radiology do you specialise in? My specialist interest is chest and cardiac imaging. In the last few years I have also gone a little northwards and now do dedicated thyroid and FNA lists.

What is your position at ESC and how long have you worked there? I am Director of Imaging and have been a Consultant at ESC for the last 4 years, heading up what I think is a fantastic team of radiologists and radiographers. In my NHS capacity, I am also the lead radiologist at the Whittington Hospital.

What role does the radiologist play in a patient’s day at ESC? Although the radiologist is often tucked away in that calm dark room, their responsibility starts with checking the patient is having the appropriate test to answer the clinical question and that it is safe to do so. We detail how we would like CTs and MRIs to be performed and with ultrasounds and biopsies we are hands on. We review the imaging before patients leave to check we have everything we need before composing the final report. If there are any rare complications we deal with them.

Once a patient is scanned, how and where are their images reported? Images are transferred in a few minutes to the powerful workstation

in our office. We then reconstruct them in multiple planes and do fly-throughs as necessary before dictating the final report.

How do the patients and referring clinicians receive the reported images? In essence, in any way they want! Some ask to be rung with the results, others prefer to have their reports faxed and others posted. One learns individual preferences and what each would want to know about fast.

How important is it for the radiographers and radiologists to work as a team? We are so lucky to have such a slick team that work brilliantly together, a bit like a grand prix pit team. It means that the radiographers feel confident to query any of our decisions or to suggest tweaks so as to get the best possible images to report. I remember my first night on call in 1992 was with these same radiographers and it is wonderful to be back with them as a team again.

How do you ensure that you provide a superior clinical service? Simple: We all aim to provide the service that we would wish a relative or colleague to receive.

What are the most technically difficult scans to report on? CT coronary angiograms as we have to look through about 800 images

Interview with ESC’s Director of Imaging, Dr Sarah Howling MB BS MRCP FRCR

and reconstruct along multiple vessels.

What do you enjoy most about working at ESC? It is wonderful to walk into such a happy place where I do not have the same volume of red tape and targets to meet as in the NHS. I can focus on my job and do what I am best at, which is hugely satisfying.

Where do you think radiology is going in the next 5 years? MRI is likely to get more functional and CT will develop in terms of quality of imaging and computer aided review. CT will also have an increasing cardiac role and radiologists will work more closely with cardiologists.

What do you see as the biggest challenges facing the field? Radiation dose certainly. There is increasing concern how this might affect future generations, as some of the doses we are generating on multidetector CT scans are really quite high.

What are the qualities of a good radiologist?Affable, time efficient, experienced, specialised and with a good eye. They need to be a good communicator, available and keen to stay up to date. They also need to give sensible further advice and have a good clear voice so as to keep their secretary happy.

Dr Christopher Harvey BSc MBBS MRCP FRCR

Chris is a Consultant Radiologist at the Hammersmith Hospital where

he leads their ultrasound service. He was integral to the early development of CT colonography in the UK from which he has multiple publications and years of expertise. He is our principle GI specialist but is also adept in all cross-sectional modalities and carotid ultrasound.

“I enjoy working as part of an innovative team”

Dr Christopher Schelvan BSc MBBS MRCP FRCR

Chris is a Consultant Radiologist at St Mary’s Hospital. He has numerous publications and is

Honorary Senior Lecturer at Imperial College. He has particular expertise in body cross-sectional imaging using his extensive experience in CT, MRI and ultrasound.

“ESC has an outstanding collection of staff who provide a friendly, efficient and top notch clinical service to patients and referring doctors. I’m proud to be part of the team”

Dr Jeevan Kumaradevan MB ChB MRCP FRCR

Jeevan is a Consultant Radiologist at the Whittington Hospital where he leads the

urology and vascular intervention radiology services. He trained at the Royal Free Hospital and undertook a prestigious Fellowship in Perth, Australia. He is reputed as being able to guide a needle into virtually anything and is renowned for his helpful nature. He provides our urological expertise.

“It is very satisfying to work as part of a highly select team, that aims to provide the highest possible quality of service to our referring clinicians and their patients.”

page 6

New StaffWe are delighted to announce

the recent appointments of

Julie White and Maria Sweeney

as our new radiology secretaries.

Both Julie and Maria will be

responsible for typing reports and

ensuring they are promptly

delivered to our referring doctors.

We are also happy to welcome

back Inder Bull, our Sales and

Marketing Manager, from

maternity leave. Inder looks

forward to working with you

all again in the near future.

Thursday 24th January 2008 from 6 - 8.30pm

Cavendish Conference Centre, 22 Duchess Mews, London W1

Due to popular demand, we have rescheduled and expanded our symposium programme on CT screening. The symposium will now include five talks on such topics as screening for coronary artery disease, lung cancer, colorectal cancer and functional abdominal imaging.

2 CPD points awarded.

Delegate spaces are available at £25 per person but early registration is advisable as numbers are limited. You can register using our online registration form at www.europeanscanning.com, by faxing the enclosed registration form or by contacting Caroline Metcalf on020 7436 5755.

Symposium on CT screening

Julie White

Maria Sweeney

How to refer patientsMany practitioners have asked for clarification on our booking

process. We hope you find the following guide helpful.

Patients can be referred to us in one of 3 ways:

1 Post/fax us a personalised letter on your headed paper

2 Post/fax us a completed ESC scan request form (available online at www.europeanscanning.com or by request

over the telephone)

3 Call us on 020 7436 5755 A completed scan request form can be faxed or sent with the

patient, by way of written confirmation.

In all cases, we will contact your patient directly to arrange a prompt

and convenient appointment.

Our team will work with you to tailor the ESC service to your

practice and preferences e.g. how, when and where you want

your patients’ reports delivered.

page 7

EBCT scanning has been part of both

my health screening activities and my

daily work as a general practitioner

over the past 4 years. It has helped

me to achieve personalised and

tailored medical prevention at a

level, which goes beyond my initial

expectations.

In terms of the EBCT heart scan, I

have been routinely proposing this

scan to low to medium risk patients

(5-20% risk in non-diabetic patients).

This has helped in several ways: first,

to detect high risk patients (who

were initially considered as mild-

moderate risk); second, to support my

recommendation for treatment with

a statin, when indicated, and third, to

reassure people who were suffering

from atypical chest pain but found to

be at low risk.

High-risk patients have gone on

to undergo further stress testing

and when indicated, subsequent

angioplasty. They are now on

“secondary preventive treatment” and

EBCT preventive health screening - a GP’s perspective

are all participating actively in the

management of their condition. One

of my patients, the husband of a chief

executive of a large company, was

reluctant to take a statin for his high

cholesterol, despite a family history of

coronary heart disease (CHD). He was

reluctant, because he felt well, was

exercising 4 times a week, and really

did not like the idea of taking a tablet

every single day of his life. The EBCT

scan revealed an elevated Agaston

score of 623 and a subsequent

exercise ECG was abnormal.

He underwent an angioplasty with

stenting of the anterior descending

coronary artery. Since then he

remains well, is taking his medicine

on a daily basis and exercises 5 days

a week.

I am also very impressed with the

way in which calcium scoring has

enabled low-medium risk patients to

engage in their preventive treatment

at an individual level. Prior to using

this technology, I was struggling to

persuade patients to take their blood

pressure tablets or statins regularly.

Having had an EBCT scan definitely

helps patients to understand the

link between blood pressure or

cholesterol and risk of heart attacks.

I have also referred low risk patients,

with atypical chest pain. A good

example of this type of referral was

one of my lady patients, aged 52,

who unfortunately lost her husband

the year before from complications

resulting from valve surgery. She

complained of atypical chest pain,

and I suspected this was part of

the bereavement process. She had

an exercise ECG, which came back

normal, but she still complained. I

referred her then for a heart scan.

This revealed a calcium score of zero.

This reassured her, and if I may say,

cured her from those chest pains.

EBCT scan technology can also be

used for screening for colorectal

cancer, or lung disease. I do not

have much experience in lung cancer

detection, and so I will comment only

on colon cancer screening and the

use of EBCT technology.

Confident of the now well-

established high sensitivity and

specificity of EBCT colon scans, I have

been using this technology alongside

conventional colonoscopy. All my

patients over 50 years of age or with

a family history of colon cancer are

offered either of the techniques.

EBCT colonoscopy has been mostly

used for repeat colonoscopy, or

for people on anticoagulants or

because of the patient’s personal and

informed choice.

A few weeks ago, a new patient, who

was asymptomatic, but was willing

to have a full executive medical,

underwent a virtual colonoscopy.

This revealed a large tumour of 3 cm.

He was subsequently colonoscoped

and operated on. Histology revealed

a Dukes A adenocarcinoma of the

sigmoid colon with no spread.

As you will understand, after having

incorporated the use of EBCT

scanning in my activities 4 years

ago, I am still enthusiastic about it. I

have to nonetheless admit that prior

to using this technology I have had

concerns, like many practitioners I

suppose. My main concern was to

end up doing, on occasion, more

harm than good. I do not like for

example to have a result back with an

incidental finding of a lesion in the

lung, kidney or liver, which could be

malignant, but for which the patient

has to wait sometimes 6 months for

a repeat scan and a definitive answer.

Despite my concerns, I have not

received any patient complaint about

this draw back of the technology. I

have indeed felt that my patients

accept this, as a minor inconvenience

which is acceptable as part of the full

process.

Dr Alix DanielGeneral Practitioner99 Harley Street

page 8

Ross’s Riddle

?In each issue 6 bottles of vintage Champagne will be offered to one lucky reader whose correct entry is drawn at random. Entries to be submitted by Friday 29th February, via email to: caroline.metcalf@europeanscanning.com The answer & name of the winner will be announced in the next edition.

Riddle 24 of Santa’s reindeer have to cross a narrow bridge in the dark. They have one torch between them, which must be used on the crossings. One or two can cross at a time but not more than two. One of them can cross in 1 minute, one in 2 minutes, one in 4 minutes and one in 10 minutes. What is the shortest elapsed time for them all to cross the bridge?

Moans without stonesA 21 year old female, engineering student, presented with a 2

year history of severe epigastric pain. The symptoms progressively

worsened, so that she was unable to continue her studies. The pain was

sharp and precipitated by eating. Endoscopy was reported to show a

small ulcer and an initial urease test was positive. Despite appropriate

antibiotic and high dose proton pump therapy, her symptoms persisted.

Further gastroenterological opinions suggested a psychosomatic

disorder, before a general physician investigated for gallbladder

dysmotility. Though previous imaging with abdominal ultrasound, CT

and MRCP confirmed normal anatomy and absence of any abnormality,

the gallbladder dynamic ultrasound stimulation test (DUST) at ESC (a

baseline scan followed by serial ultraound studies of the gallbladder

and common bile duct over an hour, after ingestion of a Mars

bar and 250ml of hot chocolate) demonstrated a markedly atonic

gallbladder (Fig 1). The fat stimulus precipitated a severe episode of her

symptoms, which were completely resolved by subsequent laparoscopic

cholecystectomy. Histology confirmed chronic acalculous cholecystitis.

Case Study • Case Study • Case Study

Electron Beam Computed Tomography (EBCT)

Abdominal & Pelvic Scan

Angiography (carotid artery, coronary and

peripheral)

Bone Mineral Density

Brain

Heart Scan (coronary artery calcium)

Lung Scan

Renal Tract

Sinuses

Virtual Colonoscopy

UltrasoundAbdominal Aorta

Abdomen & Pelvis

Carotid Doppler

Echocardiography

FNA Thyroid

Gallbladder (static and dynamic)

Leg Veins

Prostate (trans-abdominal)

Prostate (trans-rectal)

Renal Tract

Testes

Thyroid Gland

X-rayWe offer a complete

X-ray service

MRIBrain

Carotid Arteries

Elbows

Feet

Fingers

Musculo-skeletal

Neck

Shoulder

Spine

European Scanning Centre68 Harley StreetLondon W1G 7HE

Tel: 020 7436 5755Fax: 020 7436 5756

www.europeanscanning.com

European Scanning Centre

Scans

She is now resuming her

studies and has had no further

abdominal symptoms.

Comment: Mr Marcus Reddy,

Consultant GI surgeon, St.

George’s Hospital. Gallbladder

dysmotility is an under diagnosed

cause of abdominal pain. Patients

in whom routine investigations

have failed to elucidate a cause,

especially when biliary symptoms

are suspected, should undergo a

dynamic ultrasound stimulation

test. This test can demonstrate

the abnormal reponse of the

gallbladder and/or CBD to a large

fatty stimulation and also allows

correlation of symptoms with this

physiological stimulus.

Answer to Ross’s Riddle 1You have two strings, which will burn for one hour each, but they burn in an unpredictable way so that you cannot be sure that half the string would burn, say, in half an hour. Using the strings, how can you time exactly 45 minutes?You light both ends of one string and one end of the second string. When the first string burns out exactly half an hour has passed. You immediately light the other end of the second string and that will complete its burning in another 15 minutes, making 45 minutes in all.

The first correct answer drawn out of a hat was that from Dr Di Holdright, Consultant Cardiologist at The Heart Hospital, London.

Many congratulations from everyone at ESC to our lucky winner!

Patients

Time (minutes)

00 5 10 30 45 60

5

10

15

20

25

30

Gal

lbla

dder

vol

ume

(ml)

Normals (Kishk et al AJR 1987)

Fig 1