Case study: Lung cancer – Intermediate diagnostic imaging theory (draft)

Introduction

According to the World Health Organisation (WHO, 2018), lung cancer is the leading cause of cancer deaths in the world with 1.69 million deaths a year, surpassing the mortality rate of colorectal and breast cancer combined.  It is the third most common cancer in the UK with 46 700 new cases annually (Cancer Research UK, 2015). There are various risk factors associated with lung cancer with 90 % of cases caused by smoking. The poor mortality rate of lung cancer is due to two thirds of patients diagnosed when the cancer is at an advanced stage with no possibility of curative treatment. It is also attributed to poor prognosis, with only 5.5 % of cases being cured at the moment (National Institute for Health and Care Excellence, 2015).

The two main types of lung cancer are small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) with the latter being 87 % of cases. These classifications are important when determining suitable treatment method (Cancer Research UK, 2017).

This case study is based on a patient diagnosed with lung cancer and will follow their pathway from diagnosis, staging and treatment. It will focus on assessing the guidelines regarding diagnosis and treatment and the role of diagnostic imaging within this process. The discussion will be supported by evidence from relevant studies and clinical guidelines from the National Institute of Health and Care Excellence.

Diagnosis

The patient is a 70 – year old female who presented to her GP with shortness of breath that had lasted for three weeks. Upon examination, her heart rate was 104 which is high. Her chest was clear however blood test revealed that high concentration of C-reactive protein (CRP) which is an indication of tissue injury, inflammation or cell damage (Agassandian et al. 2014). The GP referred her for a chest x-ray to assess any presence of an infection within the chest.

The chest x-ray report revealed that the right hilum was bulky and the right paratracheal stripe was widened. There was no focal or lobar consolidation. The radiologist suggested computed tomography pulmonary angiogram for further investigation.

Staging

Treatment

References:

Agassandian, M., Shurin, G.V., Ma, Y., Shurin, M.R. (2014) C-reactive protein and lung diseases. The International Journal of Biochemistry & Cell Biology [online] 53 pp. 77-88 [Accessed 4 March 2018].

Cancer Research UK (2015) Lung cancer statistics. Available from: http://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/lung-cancer#heading-Zero [Accessed 4 March 2018].

Cancer Research UK (2017) Lung cancer: stages, types and grades. Available from: http://www.cancerresearchuk.org/about-cancer/lung-cancer/stages-types-grades/types [Accessed 4 March 2018].

http://www.cancerresearchuk.org/about-cancer/lung-cancer/stages-types-grades/types

National Institute of Health and Care Excellence (2015) Lung cancer in adults. Available from: https://www.nice.org.uk/guidance/qs17 [Accessed 4 March 2018].

World Health Organisation (2018) Cancer. Available from: http://www.who.int/mediacentre/factsheets/fs297/en/ [Accessed 4 March 2018].

To be added:

Royal College of Physicians (2017) National Lung Cancer Audit 2016. Available from: file:///home/chronos/u-3097ca33055b273b462fcbea4d46420d350bb6ce/Downloads/NLCA%202016%20Annual%20report_0_0.PDF [Accessed 4 March 2018].

Advertisements

Comparing the diagnostic efficacy of positron emission tomography (PET) and cardiac magnetic resonance (CMR) imaging in assessing myocardial viability in preparation for revascularisation

This last entry of the blog will be focusing on the imaging modalities utilised when assessing the viability of the myocardial tissue before revascularisation. I chose this topic because of my interest on the cardiovascular system and this would help me become familiar with the role of diagnostic imaging in the diagnosis and assessment of cardiovascular diseases. The term myocardial viability will be used to describe the myocardium with reversible contractile dysfunction in patient with coronary artery disease (CAD) (Allman, 2013).

Coronary artery disease is a condition where the arteries supplying blood to the heart muscle have narrowed due to gradual build-up of fatty material on their walls. This is known as atherosclerosis. It can cause a blockage in the coronary arteries which leads to the heart muscle not receiving oxygen-rich blood. If the blood flow is not re-established, it may lead to that part of the myocardium to die and is known as a heart attack (University Hospitals Birmingham NHS Foundation Trust, 2017). Some of the risk factors of CAD are diabetes, hypertension, smoking, lack of exercise, obesity and family history of CAD (NHS Choices, 2017).

The assessment of the viability of myocardium is essential in determining whether a patient is suitable for coronary revascularisation (Briceno et al. 2016; Allman, 2013; Anagnostopoulos et al. 2013). According to the European Society of Cardiology and the European Association for Cardio-Thoracic Surgery (ESC and EACTS, 2014), there are several different methods of myocardial revascularisation. These include coronary artery bypass graft (CABG), balloon angioplasty, and percutaneous coronary intervention with bare-metal stents (BMS) or drug-eluding stents (DES). Several imaging methods, such as single photon emission computed tomography (SPECT), positron emission tomography (PET), cardiac magnetic resonance (CMR) and echocardiography, are utilised in assessment of myocardial viability prior to revascularisation procedures. While these methods focus on determining the functionality of the tissue, it is important to note that there are also structural changes that occur due to prolonged lack of adequeate blood flow to the myocardium (Allman, 2013).

According to Anagnostopoulos et al. (2013) PET myocardial perfusion imaging (MPI) has sensitivity and specificity values around 90 %. It demonstrates metabolic and cellular functions to help differentiate viable myocardium from non-viable (Briceno et al. 2016). The technological advancements over the years have allowed PET to contribute significantly in the diagnosis and management of patients with coronary artery disease. Some of these advantages include determining prognosis for people with suspected or known CAD.  The findings are classed in to four categories; 1) normal flow/metabolism (viable), 2) mild matched reduction in flow/metabolism 3) severe matched defect, or 4) mismatch (reduction in resting flow but glucose is still utilised in tissue). All, except number three, have potential for the myocardium to be viable (Allman, 2013).

The limitation of PET is prominent when used with diabetic patients as the tracer (fluorodeoxyglucose) extraction is limited due to the tracers being insulin-sensitive. Additional imaging with PET would be required at a later stage after administrating insulin in order to have diagnostic images, which increases the radiation dose to the patient. This is important information because one of the risk factors for CAD is diabetes (Anagnostopoulos et al. 2013). However, according to Allman (2013) the risk is assessed according to the patient. This is because the benefit outweighs the risk for patients with low survival rate, while it is a significant concern for a relatively healthy patient undergoing viability assessment. Another strength of PET is that it produces images with high resolution allowing the differences of uptake between regions to be assessed. According to ESC and EACTS (2014), nuclear imaging methods, which includes PET, have been found to have high sensitivity values but have a lower sensitivity when used to assess contractile reserve of the tissue.

CMR works by assessing the concentration of gadolinium in the tissue. The contrast media gathers into the interstitial space of non-viable tissue and will remain there for a time. The accumulation also can demonstrate the thickness of scar tissue in the muscle. The area that is not enhanced is considered viable. CMR is also used to assess function such as wall motion and end-diastolic wall thickness. The latter is a very important indicator of functional recovery as it diminishes with decreasing wall thickness. The main limitation of CMR is that it is contra-indicated in patients with severe renal impairment and patients with implanted devices causing rhythm disturbance, device motion and heating of the lead (Allman, 2013). However, due to the lack of PET scanners there is an increase in the use of CMR when assessing myocardial viability (Timmer et al. 2017). Perhaps this is a positive aspect and further research into improving the sensitivity and specificity of CMR would be appreciated as it is non-ionising and would lessen the radiation dose patients may accumulate during their treatment. This is because coronary angioplasty is performed under fluoroscopic guidance, which is why non-ionising diagnostic test would be best for the patient. I had the opportunity to observe a coronary angioplasty procedure and it was a quite long and difficult case. Considering the length and the small area being imaged, the risk of radiation burn seems to be quite high.

According to Briceno et al. (2016) there is a lack of randomised control studies to strongly support the use of late contrast-enhanced CMR to predict the degree of functional recovery following revascularisation. However, there is no mention of this fact by Timmer et al. (2017) which reveals a need for studies with larger sample sizes to be conducted in order to fully assess the usefulness of CMR particularly as it is non-ionising.

This final blog is short because it is a very broad subject and I found it hard to understand all the aspects of imaging the myocardium. However with this exercise I have developed skills which have made me enjoy learning. I hope these blogs have been informative and enjoyable. I have found them to be educational and the improvement in my academic writing skills has boosted my confidence significantly.

Reference List:

Allman, K. (2013) Noninvasive assessment myocardial viability: Current status and future directions. Journal of Nuclear Cardiology [online] 20 (4) pp. 618-637 [Accessed 27 November 2017].

Anagnostopoulos, C., Georgakopoulos, A., Pianou, N., Nekolla, S.G. (2013) Assessment of myocardial perfusion and viability by Positron Emission Tomography. International Journal of Cardiology [online] 167 (5) pp. 1737-1749 [Accessed 27 November 2017].

Briceno, N., Schuster, A., Lumley, M., Perera, D. (2016) Ischaemic cardiomyopathy: pathophysiology, assessment and the role of revascularisation. Heart (British Cardiac Society [online] 102 (5) pp. 397-406 [Accessed 27 November 2017].

NHS Choices (2017) Coronary heart disease: causes. Available at: https://www.nhs.uk/conditions/coronary-heart-disease/causes/ [Accessed 01 December 2017].

The European Society of Cardiology, the European Association for Cardio-Thoracic Surgery (2014) 2014 ESC/EACTS Guidelines on myocardial revascularization. European Heart Journal [online] 35 pp. 2541-2619 [Accessed 30 November 2017].

Timmer, S., Teunissen, P., Danad, I., Robbers, L., Raijmakers, P., Nijveldt, R., van Rossum, A., Lammertsma, A., van Royen, N., Knaapen, P. (2017) In vivo assessment of myocardial viability after acute myocardial infarction: A head-to-head comparison of the perfusable tissue index by PET and delayed contrast-enhanced CMR. Journal of Nuclear Cardiology [online] 24 (2) pp. 657-667 [Accessed 27 November 2017].

University Hospitals Birmingham NHS Foundation Trust (2017) Coronary artery disease. Available at: https://www.uhb.nhs.uk/coronary-artery-disease.htm [Accessed 30 November 2017].

A comparison of MRI and plain film x-ray in imaging scaphoid fractures

This week’s blog will discuss and compare the diagnostic efficacy of magnetic resonance imaging (MRI) and plain film imaging in the diagnosis and management of scaphoid fractures. The discussion will be supported by evidence from appropriate literature and research.

According to the Royal College of Emergency Medicine (RCEM, 2013), scaphoid fractures account for nearly 90 % of all fractures involving carpal bones. They are also the most common type of carpal bone fractures in adolescents between the ages of 13-15, but uncommon in children under 10 years of age. The mechanism of injury is commonly a fall on an outstretched hand (FOOSH) resulting in the extreme dorsiflexion of the wrist (Geijer, 2013; Baldasarre and Hughes, 2013; Brooks and Hammer, 2013). They are difficult to diagnose and if left untreated, can result in significant complications, such as non-union and avascular necrosis (Bergh et al., 2014; Brooks and Hammer, 2013). These injuries often present as decreased range of movement in the wrist and tenderness in the anatomical snuffbox, which is the area where the scaphoid is situated. According to Geijer (2013) in nearly all cases of scaphoid fractures, combination of tests, such as snuff box tenderness, scaphoid compression and tenderness over scaphoid tubercle, have a specificity of 74-80 %. This combination of clinical tests was also used by Bergh et al. (2014) in their study. Depending on the type of injury, the treatment is either immobilisation of the wrist with a plaster cast or surgical intervention (Brooks and Hammer, 2013).

There is an agreement that the first line of investigation is conventional plain film radiography (Bergh et al. 2014; Baldasarre and Hughes, 2013; Brooks and Hammer, 2013; RCEM, 2013). However, this contradicts the guidance of the National Institute for Health and Care Excellence (NICE, 2016) which recommend the consideration of MRI as a first-line imaging method. There are different protocols regarding the projections or views taken in plain film imaging with suspected scaphoid fractures. For example, Brooks and Hammer (2013) mentioned three views with an additional view with the wrist in ulnar deviation. At my placement site, the protocol was five views while another student told me the protocol in their placement site was four views. The position of four views is also supported by the Bergh et al. (2014) as they used this protocol when conducting their study. While the focus of the study was on the use of MR, this information is important to include as evidence towards the use of fewer projections. They continue to say that the sensitivity of plain film imaging is 65-85 %. There is a significant difference between those values and the question arises whether other imaging modalities offer better diagnostic quality. This is supported by the RCEM (2013) statement that there is a lack of gold standard imaging modality to which other modalities can be compared to. Geijer (2013) presents plain film imaging as the best method in the initial diagnosis, and goes on to say that well-exposed PA and lateral wrist in a neutral position result in images with optimal diagnostic value. He also deviates from the protocols by recommending the use of 2-4 additional views of the scaphoid to supplement the two views. This means that the amount of views undertaken can vary from four to a maximum of six. This would indicate that the recommendation of NICE (2016) on the use of MRI is valid in order to reduce radiation dose. While Geijer (2013) does mention that the radiation dose is negligible, it is an important aspect to note, considering that the sensitivity is not sufficient to exclude the fracture completely at the time of injury as well as in the follow-up images (RCEM, 2013). The advantage of plain film imaging is that it is accessible, cost-effective and patient-friendly (Geijer, 2013; Baldasarre and Hughes, 2013).

RCEM (2013) collected data from several studies, which showed that MRI is excellent when it comes to detecting scaphoid fractures with sensitivity and specificity values at 98% and 99% respectively. It is also useful in providing information on soft tissue injuries as well as carpal and radial injuries. Baldasarre and Hughes (2013) assert that MRI is useful when plain film imaging produces negative results. They reported findings from a meta-analysis of 30 studies which concluded the sensitivity value to be 97.7 % and specificity value to be 99.8 %. This would support the notion that MRI should be first line of investigation instead of plain film. This is especially important as it is able to detect minor displacements which can be indication to proceed with surgical intervention. However, MRI is recognised as the best second line investigation method compared to CT and bone scintigraphy (RCEM, 2013).

Bergh et al. (2014) conducted a study in Norway at one site with a patient group consisting of patients between the ages of 18 and 49. There were no other details mentioned regarding their demographics. The inclusion criteria were all the patients that had sustained an acute wrist injury. The exclusion criteria were all the patients contra-indicated for MRI as well as those with obvious findings on plain film imaging such as dislocations and those with previous history of fractures and rheumatoid arthritis. After imaging 154 patients, the results revealed 13 occult fractures in the scaphoid, 40 occults fractures as well as 47 bone bruises in other bones in the wrist area. An occult fracture extends across the cross section of the bone while a bone bruise refers to the trabecular injuries resulting from the force of impact. They acknowledged the busy nature of the emergency department may have caused them to not have a bigger sample size and thus decreased the external validity of the study. They also focused heavily on the clinical test score that they used to assess patients prior to imaging and discussed its effectiveness in detail. Perhaps this is an area of development that could improve the diagnosis of scaphoid fractures.

The prominent limitation to the use of MR seems to be the cost and the length of the examinations compared to plain film x-ray. The difference in cost is significant with plain film imaging being £24 per patient while MRI scan is £200 per patient. It is also limited in access as it can be contra-indicated due to reasons such as pregnancy, claustrophobia and claustrophobia (Bergh et al. 2014; RCEM, 2013).

There needs to be adherence to the proper management and surveillance of scaphoid fractures due to the complications that may arise from them. The protocol of follow-up imaging after 10-14 days is recommended as these fractures can be visualised 10 days after injury (Baldasarre and Hughes, 2013). However imaging before this deadline can be seen as poor care as the patient is subjected to an unnecessary dose of ionising radiation. I had an experience of this during placement where a patient had been imaged too early following initial imaging and thus had to be scheduled for an x-ray again in line with the appropriate follow-up time. This could have been avoided had the radiographer checked previous images or perhaps even asked the patient whether they had any x-rays taken when the injury first occurred. This event highlighted the importance of checking previous images and discussing with the patient about their injury.

Reference List:

Baldasarre, R.L., Hughes, T.H. (2013) Investigating suspected scaphoid fracture. British Medical Journal [online] 346 (7904) [Accessed 27 November 2017].

Bergh, T.H., Lindau, T., Soldal, L.A., Bernardshaw, S.V., Behzadi, M., Steen, K., Brudvik, C. (2014) Clinical scaphoid score (CSS) to identify scaphoid fracture with MRI in patients with normal x-ray after a wrist trauma. Emergency Medicine Journal [online] 31 (8) [Accessed 27 November 2017].

Brooks, A., Hammer, E. (2013) Acute Upper Extremity Injuries in Young Athletes. Clinical Pediatric Emergency Medicine [online] 14 (4) p. 289 [Accessed 27 November 2017].

Geijer, M. (2013) Diagnosis of scaphoid fracture: optimal imaging techniques. Reports in Medical Imaging [online] 6 (1) [Accessed 27 November 2017].

National Institute for Health and Care Excellence (2016) Fractures (non-complex): assessment and management. Available at: https://www.nice.org.uk/guidance/ng38 [Accessed 27 November 2017].

Royal College of Emergency Medicine (2013) Guideline for the management of suspected scaphoid fractures in the Emergency Department. London: The Royal College of Emergency Medicine. Available at: https://www.rcem.ac.uk/docs/College%20Guidelines/5z25.%20Suspected%20Scaphoid%20Fractures-%20(Flowchart)%20(Sept%202013).pdf [Accessed 27 November 2017].

A comparison of radiation risk associated with Computed Tomography Pulmonary Angiography and pulmonary ventilation perfusion scan in pregnant patients with suspected pulmonary embolism

This blog will continue on the topic of pulmonary embolism (PE) and the focus will be on examining the radiation risk of computed tomography pulmonary angiogram (CTPA) and pulmonary perfusion/ventilation scan (V/Q) on pregnant patients. This topic interests me because the radiation protection measures are particularly rigorous with this patient group (Health Protection Agency, the Royal College of Radiologists and Society and College of Radiographers, 2009).

Venous thromboembolism (VTE) remains as the leading cause of maternal mortality in the developed countries (Simcox et al. 2015; Conti et al. 2014). VTE can develop at any stage of the pregnancy but the highest risk is during the period of six weeks right after giving birth called puerperium. A drop in the mortality rate, was recorded in the UK and Ireland from 2006-2008 compared to 2003-2005.  The reason for this was the change in national guidelines on assessment and treatment with focus on the financial implications of poor adherence to them (Simcox et al. 2015).

The path of diagnosis differs from non-pregnant patients. According to the National Institute for Health and Care Excellence (NICE, 2015) pregnant patients with suspected PE should be admitted immediately into the hospital, due to the ineffectiveness of normal diagnostic tests. The PE Wells score is not effective with pregnant patients, and the D-dimer test has a high rate of false positives as the levels are raised in a normal pregnancy, especially during the third trimester and the puerperium (Simcox et al. 2015). Diagnosis is challenging because the symptoms mimic the normal physiological changes experienced in pregnancy (Conti et al. 2014).

The Royal College of Obstetricians and Gynaecologists (2015) recommend an electrocardiogram (ECG) and a chest x-ray, as initial diagnostic imaging methods for PE in pregnancy. Chest x-ray is crucial in excluding other conditions with similar symptoms such as pneumothorax, pneumonia or pulmonary oedema with minimal radiation risk. The risk can be reduced with good positioning technique, accurate collimation, optimisation of exposure factors and application of protective equipment such as lead aprons. It is also important step as the findings help clinicians to decide between CTPA and a V/Q scan. If the x-ray findings include abnormalities then CTPA is the preferred method over a V/Q scan (Simcox et al. 2015; Conti et al. 2014).

The articles discussed here have all recognised the lack of research on the radiation risk to the foetus due to these procedures (Simcox et al. 2015; Conti et al. 2014; Shahir et al. 2010). They speculated that the issue here were the small sample sizes as well as the dose consideration to the mother and the foetus. According to the Health Protection Agency (HPA), the Royal College of Radiologists (RCR) and the Society and College of Radiographers (SCoR) (2009) the deterministic effects to the foetus include death, malformation and abnormal brain development, while the stochastic effects include induction of cancer and hereditary diseases in future offspring.

Shahir et al. (2010) conducted their study in the US with a sample size of 199 pregnant patients. There are no further details on the demographics however the patients were selected from a university hospital and a private hospital. 106 underwent a CTPA scan and 99 underwent a V/Q scan. The radiation dose to the foetus from CTPA was recorded to be around 0.1-0.66 mGy, which is higher than a V/Q scan which was 0.1-0.37 mGy. However, they mentioned that while these dose values are statistically significant, their effects have not been found to be clinically significant. There is a slight difference in these values according to HPA, RCR and SCoR (2009) which showed them to be 0.01- 0.1 mGy with the risk of childhood cancer being from 1 in 1,000,000 for CTPA , 1 in 100,000 for a ventilation scan and 1 in 10 000 for a perfusion scan. It is important to mention that there is a possibility of a risk to the foetal thyroid from iodine due to the contrast agent administered for CTPA. This risk has not been proven and further research is needed in this area (Simcox et al. 2015; Conti et al. 2014; Shahir et al. 2010).

Conti et al. (2014) found that for a low dose CTPA, there is an increased risk of breast cancer. This is probably due to the attenuation that occurs in the tissue as well as the sensitivity of the area to radiation. Simcox et al. (2015) explains that the use of bismuth shields for breasts reduces this risk by 20-40 %. They also explained that a V/Q scan is associated with a slightly higher foetal dose than CTPA (0.5 mGy and 0.1 mGy) but these values are very much below the threshold for congenital malformations (teratogenesis). Conti et al. (2014) continue to say that a V/Q scan is associated with lower absorbed dose to the breast tissue than CTPA. As far as foetal dose, there is a minimal increase in the risk of childhood cancer. Both CTPA and V/Q scan were recorded to have a foetal dose of 1-2 mSv. The absorbed dose for the foetus in the first trimester is 0.1-0.2 mGy for studies at 50 MBq. A V/Q scan is rarely associated with allergic reactions and the radioisotope administered (technetium 99m) is safe as far as renal function is concerned. The images produced are diagnostic with minimal variance of interpretation between different readers.

All of the above aspects are important to consider when choosing between these modalities. As far as accessibility goes, CTPA seems to be more accessible than a V/Q scan, as the latter requires radioisotopes to be ordered. However, according to Simcox et al. (2015) most hospitals in the UK will opt for the VQ scan, as it is associated with lower breast cancer risk and comparability to CTPA with regards to diagnostic value of images and similar negative predictive values. There is an emphasis on lead shielding during these procedures. Conti et al. (2014) include that use of lead shielding across the abdomen has been found to reduce foetal dose and reported to be as much as 10 % decrease. This is beneficial for my future practice as these measures minimise complications for both the mother and the foetus.

An unconventional safety measure was mentioned by Conti et al. (2014) where the foetus is shielded internally by an oral intake of barium. The mother swallows water with 40 % barium mixed in and the uterus is shielded due to the radionuclide attenuation to the bladder. The results demonstrated that foetal irradiation was reduced by as much as 90 %. However, the study they have quoted used phantoms and it was published in 2006 so perhaps there is further information on this subject. Further research is needed in this area for radiation safety purposes. It was also not accessible, so in order for me to understand it, I need further information and explanation on how it actually works.

During my first placement, I did note that the nuclear medicine department would order a few doses of radiopharmaceuticals to be used in V/Q scans for emergency cases. I can now appreciate this measure and understand that it can be used for suspected PE in pregnant patients. It is important information when considering which modality to choose, especially if CTPA is contraindicated due to contrast allergy or renal impairment (Simcox et al. 2015). I am not sure whether this is the protocol at every hospital however it would be beneficial to find it out for my next placement.

Both modalities have similar negative predictive values with CTPA being 98-99% and V/Q scan 100 % which makes them equal in diagnostic efficacy (Simcox et al. 2015; Conti et al. 2014; Shahir et al. 2010). The diagnostic quality is also comparable and especially V/Q scan is reported to have high specificity of 97 % and sensitivity of 77%. It also has 90 % positive predictive value which is used to justify the administration of anticoagulant treatment (Conti et al. 2014).

In conclusion the risk to the foetus is much smaller than the natural risk of childhood cancer. The ultimate choice of imaging method depends on local guidelines, availability, the patient and the judgement of the clinician.

 

 

Reference List:

Conti, E., Zezza, L., Ralli, E., Comito, C., Sada, L., Passerini, J., Caserta, D., Rubattu, S., Autore, C., Moscarini, M., Volpe, M. (2014) Pulmonary embolism in pregnancy. Journal of Thrombosis and Thrombolysis [online] 37 (3) pp. 251-270 [Accessed 23 November 2017].

Health Protection Agency, The Royal College of Radiologists and the Society and College of Radiographers (2009). Protection of Pregnant Patients during Diagnostic Medical Exposures to Ionising Radiation. Advice from the Health Protection Agency, The Royal College of Radiologists and the Society and College of Radiographers. London: Health Agency, The Royal College of Radiologists and the Society and College of Radiographers. Available at: https://www.rcr.ac.uk/publication/protection-pregnant-patients-during-diagnostic-medical-exposures-ionising-radiation [Accessed 26 November 2017].

National Institute for Health and Care Excellence (2015) Pulmonary embolism – Scenario: Managing suspected pulmonary embolism. Available at: https://cks.nice.org.uk/pulmonary-embolism#!scenario [Accessed 22 November 2017].

Royal College of Obstetricians & Gynaecologists (2015) Thromboembolic Disease in Pregnancy and the Puerperium: Acute Management. Available at: https://www.rcog.org.uk/globalassets/documents/guidelines/gtg-37b.pdf [Accessed 24 November 2017].

Shahir, K., Goodman, L. R., Tali, A., Thorsen, K.M., Hellman, R.S. (2010) Pulmonary Embolism in Pregnancy: CT Pulmonary Angiography Versus Perfusion Scanning. American Journal of Roentgenology [online] 195 (3) [Accessed 25 November].

Simcox, L.E., Ormesher, L., Tower, C., Greer, I.A. (2015) Pulmonary thrombo-embolism in pregnancy: diagnosis and management. Breathe: Practice-focused Education for Respiratory Professionals [online] 11 (4) pp. 282-289 [Accessed 23 November 2017].

The role of Computed Tomography Pulmonary Angiography in the diagnosis of pulmonary embolisms

This blog will discuss the use of computed tomography pulmonary angiography (CTPA) in patients suspected of having pulmonary embolism (PE) with evidence from relevant literature. It is an area of imaging that is of interest to me because I find the heart a fascinating organ to study.
PE is a blood clot in the blood vessels that carry blood from the heart into the lungs which can be deadly if not caught in time. The clot in the legs is known as deep vein thrombosis (DVT) (Morley et al, 2015). Symptoms include chest pain, shortness of breath and coughing up mucus or blood which can be caused by conditions such as cancer, heart failure, pregnancy and weakness in the wall of a blood vessel (NHS Choices, 2015). Other than CTPA, there are other diagnostic imaging procedures undertaken in order to diagnose PE in secondary care. These include chest x-ray, ventilation-perfusion scan, electrocardiography and lower limb compression venous ultrasound (National Institute of Health and Care Excellence, 2015a).
The National Institute for Health and Care Excellence (NICE, 2015b) guidelines say that patients suspected of having PE have CTPA immediately or are given anticoagulant therapy if it is not available immediately. In the case of pregnancy, contrast allergy or severe renal dysfunction the recommended pathway is ventilation-perfusion scan. This follows the review undertaken by Condliffe (2016), where first line investigation method after clinical examination was CTPA.
According to Walen et al. (2016) the specificity value of CTPA ranges between 81% and 98%, which makes it very valuable in excluding PE. However, the sensitivity values range from 60% to 100% which is a significant difference. The literature they have used as evidence is quite old, dating back to 1993. However, this is not discussed further as the aim of this study was to examine the diagnostic value of CTPA by influencing the behaviour of referrers. They explained that documenting Wells scores and D-dimer test scores on the request form increased the diagnostic yield from 23 % to 29.6 %. This is an important factor to consider. Research into diagnostic protocols of PE in the UK could be useful as this study was conducted in the Netherlands.
According to Mortensen and Gutte (2014) the sensitivity of CTPA was recorded to be 94 % and specificity value as 93 % using various sources as evidence. However, the authors have used sources that are over 10 years old. Considering this was published in 2014, it raises the question of whether they failed to include more up to date research to confirm these values. Furthermore, the diagnostic accuracy of CTPA is confirmed by Laugharne et al. (2013) using sources from 2005. This reveals a trend that would suggest more recent research has not been undertaken. They also mention that no CTPA examination was undiagnostic suggesting that the use is valid. While this study was conducted in the UK, it may not be applicable to the wider population as the sample included only elderly patients with the majority being female. They also justify the use of CT due to its availability in hospitals.
There was some debate on the topic of overdiagnosis and the impact on patients and healthcare providers. According to Wiener et al. (2013) small blood clots do not pose a significant risk and therefore do not need treatment. However this is challenged by Quantrill (2013), as he cites Wiener as acknowledging the drop in mortality by 3% after the introduction CTPA in diagnostic protocols. It is important to mention that Wiener used data on the trends in the US and this may not be generalisable to the UK or the rest of the world. Quantrill (2013) also points out that untreated PE can lead to severe health complications and death, highlighting the importance of offering treatment. The basis of Wiener’s (2013) argument is that the emboli are reabsorbed into the body without any clinical manifestations. Quantrill (2013) counters this by saying the effects of anticoagulation therapy is low enough to justify the benefit of giving it.
PE is treated with anticoagulant medicines and the amount of the medicine is measured regularly to check the dose is correct to prevent blood clots from reforming (NHS Choices, 2015).

 

Reference List:
Condliffe, R. (2016) Pathways for outpatient management of venous thromboembolism in a UK centre. Thrombosis Journal [online] 14 (1) [Accessed 14 November 2017].
Laugharne, M.J., Paravasthu, M., Preston, A., Hill, K.O. (2013) CT pulmonary angiography in elderly patients: Outcomes in patients aged > 85 years. Clinical Radiology [online] 68 (5) pp. 449-454 [Accessed 14 November 2017].
Mortensen, J., Gutte, H. (2014) SPECT/CT and pulmonary embolism. European Journal of Nuclear Medicine and Molecular Imaging [online] 41 (sup1) pp. 81-90 [Accessed 14 November 2017].
National Institute for Health and Care Excellence (2015a) Pulmonary embolism – Scenario: Managing suspected pulmonary embolism. Available at: https://cks.nice.org.uk/pulmonary-embolism#!scenario [Accessed 14 November 2017].
National Institute for Health and Care Excellence (2015b) Venous thromboembolic diseases: diagnosis, management and thrombophilia testing. Available at: https://www.nice.org.uk/guidance/cg144/chapter/Key-priorities-for-implementation [Accessed 14 November 2017].
Quantrill, S.J. (2013) Risk-benefit ratio favours all pulmonary emboli, no matter how small. The British Medical Journal [online] 347 (5121) [Accessed 14 November 2017].
Walen, S., de Boer, E., Edens, M.A., van der Worp, C.A.J, Boomsma, M.F., van den Berg, J.W.K. (2016) Mandatory adherence to diagnostic protocol increases the yield of CTPA for pulmonary embolism. Insights into Imaging [online] 7 (5) pp. 727-734 [Accessed 14 November 2017].
Wiener, R.S., Schwartz, L.M., Woloshin, S. (2013) When a test is too good: how CT pulmonary angiograms find pulmonary emboli that do not need to be found. The British Medical Journal [online] 347 (7915) [Accessed 14 November 2017].

 

Exploring imaging methods used in the detection of hepatocellular carcinomas

This week’s blog will focus on examining the detection of hepatocellular carcinoma (HCC) on patients with cirrhosis. It is inspired by last week’s lecture on imaging the hepato-biliary system.

According to The European Association of the Study of the Liver (EASL) (2012), HCC is the sixth most common cancer worldwide and the third most common cause of cancer related death. It develops from cells in the liver called hepatocytes hence why it is called a primary cancer. It is also more common in men than women and the risk increases with age, the peak being at the age of 70 (Cancer Research UK, 2015). Ethnicity is also a factor as the mean age of tumour manifestation is significantly younger within Asian and Black African population in the world. It also has a different pattern of occurrence in the world with the highest incidence rates found in East Asia, sub-Saharan Africa and Melanesia. 85 % of the cases in the world are found in these regions (EASL, 2012). Cirrhosis is a major risk factor, which is why adults with cirrhosis are offered 6-monthly surveillance for HCC (National Institute for Health and Care Excellence, 2017). Long-term survival is predicted by tumour stage at diagnosis, which is why early detection and accurate diagnosis is essential (Farrell et al. 2017; Cross et al., 2015).

Finding the best suited imaging technique for detection and characterisation of liver lesions on the background of cirrhotic liver is still a challenge (Kurucay et al. 2017). Farrell et al. (2017) did a review of the recall surveillance program for HCC detection in cirrhotic patients in a tertiary-referral centre in the UK. They acknowledge the lack of strong evidence for the efficacy of surveillance programs for HCC. This contradicts the guidelines published by the EASL (2012) which state it being cost-effective and helpful in excluding some patients from further surveillance. It is also not in line with NICE guidelines (2017) which recommend ultrasound surveillance, as HCC can remain asymptomatic while it advances. The reason behind the statement by Farrell et al. (2017) is most likely the lack of organisational support for surveillance programs and the poor provision of the service they found in their study. They continue to say that there is significant benefit to this program, provided they are given the same support as screening programs for other diseases such as breast and colon cancer (Farrell et al. 2017).

There is evidence in literature to say that accurate diagnosis requires contrast-enhanced CT and dynamic MRI with gadolinium (Kurucay et al. 2017; Hennedige and Venkatesh, 2012; EASL, 2012). While a biopsy was needed before, now radiological method is acceptable for diagnosis, provided there are imaging characteristics present (Hennedige and Venkatesh, 2012). This is ideal from patient management perspective as they do not need aftercare and are able to leave after the procedure.

The significant marker seems to be the vascular pattern of the tumour and this requires contrast-enhanced imaging methods (Hennedige and Venkatesh, 2012; EASL, 2012). The European Association of the Study of the Liver (2012) recommends the following guidelines in order to diagnose HCC. Lesions greater than 1 cm with a typical vascular pattern on dynamic contrast enhanced CT or MR should be treated as HCC. If a lesion has an atypical vascular pattern then further imaging is required for diagnosis. However, if a lesion is smaller than 1 cm with atypical vascular pattern then next step is to do a biopsy or an enhanced surveillance with MRI or CT. Lesions greater than 2 cm with atypical vascular patterns may be considered as HCC, provided the level of alpha-fetoprotein is above 200 ng/ml (AFP). High level of AFP is a strong indication of the presence of HCC.

Here, two articles discussing the diagnostic accuracy of CT and MRI for HCC, will be examined. The first one is a review by Kurucay et al. (2017), which examines the imaging parameters derived from perfusion CT (PCT) and gadoxetic acid-enhanced MRI in patients with HCC. The review was done in at one site in Germany with 36 cirrhotic patients with a diagnosis of HCC-suspected liver lesions. There were 67 lesions in total between the 36 patients. Perfusion CT quantified the blood flow within the liver with values for arterial liver perfusion (ALP), mean/max blood flow (BF), blood volume (BV), portal venous perfusion (PVP) and hepatic perfusion index (HPI). They found that HCC is associated with high HPI (> 96 %) and high values of BF in the tissue. Hennedige and Venkatesh (2012) agree with this, saying PCT quantifies arterial flow in the liver and can show the perfusion parameters, which differ significantly from between HCC tissue and normal liver parenchyma.

With regards to MRI, Kurucay et al. (2017) showed that six out of 67 HCCs were missed in T1 weighted images. 59 of the 67 lesions were detected in hepato-biliary phase images; 11 of the 67 lesions were missed on fat-saturated T2 weighted images. The conclusion showed that information from all applied imaging sequences were needed to equal the sensitivity of PCT. PCT also made clear the margins of the tumours, due to the high HPI value. Hennedige and Venkatesh (2012) agree and say that HCC has variable appearances on MRI. It seems to support the results found in the Kurucay et al (2017) study and can explain, why some lesions were missed in certain sequences. Hennedige and Venkatesh (2012) also add that diffusion-weighted imaging may be particularly useful in initial screening, as 70-95 % of lesions appear hyperintense.

The readers used in the study by Kurucay et al (2017) had the combined experience of more than 24 years in reading oncological CTs and MRIs. This was divided, with one reader having 4 years of experience and the other had more than 20 years. They may have done this to compare the effect of experience on lesion detection and characterisation, however they did not mention this in the article. It was mentioned that there were some disagreement with seven cases, however they were resolved in the end. The disagreement only occurred with the MRI scans and the steps that lead to the agreement were not explained. It would have been beneficial to include that information as it could be useful in managing reporting workload effectively within clinical imaging departments.

Kurucay et al. (2017) used only Siemens equipment with both CT and MRI, which suggests that results may differ between manufacturers. This means further studies need to be done with other equipment to compare their performance. The information is useful when departments consider purchasing new scanners. The MRI scanners used had different strength of magnets; one being 1.5 Tesla (T) and the other 3.0 T. This could have had an impact on the results as well. Also with regards to patient management the CT protocol was more patient-friendly, requiring only two scans with one injection of contrast. The MRI protocol included GRE T1-weighted, axial respiratory gated T2-weighted, diffusion weighted and fat suppressed T1 weighted VIBE sequences before the contrast was given. This was followed by four fat suppressed T1 weighted VIBE sequences. The time used is extensive and with issues experienced in these scans, such as claustrophobia and sensitivity to the noise of the machine, it is not the most patient friendly option. However, it is an recommended option because of the use of non-ionising radiation. The dose received from PCT varied between 9 and 14 mSv depending on the scan length. This is significant amount as it is around the range of CT scan of the whole spine, which is 10 mSv (Public Health England, 2011).

Sadly the 3 year survival rate of HCC can be as low as 10 %. Farrell et al. (2017) review showed that 16 of the 22 patients diagnosed with HCC died by June 2016. The review was conducted between 2009 and 2013. Low survival rates coupled with the rising incidence rates of HCC, shows the need for research in improving screening methods as well as diagnostic imaging technology for early detection (EASL, 2012).

 

 

Reference List:

Cancer Research UK (2015) Liver cancer – types. Available at: http://www.cancerresearchuk.org/about-cancer/liver-cancer/types [Accessed 09 November 2017].

Cross, T.J., Villaneuva, A., Shetty, S., Wilkes, E., Collins, P., Adair, A., Jones, R.L., Foxton, M.R., Meyer, T., Stern, N., Warshow, U., Khan, N., Prince, M., Khakoo, S., Alexander, G.J., Khan, S., Reeves, H., Marshall, A., Williams, R. (2015) A national survey of the provision of ultrasound surveillance for the detection of hepatocellular carcinoma. BMJ Journals [online] 7 (2) [Accessed 09 November 2017].

European Association for the Study of the Liver (2012) EASL Clinical Practice Guidelines on the management of hepato-cellular carcinoma. Available at: http://www.easl.eu/research/our-contributions/clinical-practice-guidelines/detail/management-of-hepatocellular-carcinoma-easl-eortc-clinical-practice-guidelines/report/4 [Accessed 12 November 2017].

Farrell, C., Halpen, A., Cross, T.J.S., Richardson, P.D., Johnson, P., Joekes, E.C. (2017) Ultrasound surveillance for hepatocellular carcinoma: service evaluation of a radiology-led recall system in a tertiary-referral centre for liver diseases in the UK. Clinical Radiology [online] 72 (4) p 338.e11 – 338.e17 [Accessed 12 November 2017].

Hennedige, T., Venkatesh, S.K. (2012) Imaging of hepatocellular carcinoma: diagnosis, staging and treatment monitoring. Cancer Imaging [online] 12 (3) pp. 530-547 [Available 12 November 2017].

Kurucay, M., Kloth, C., Kaufmann, S., Nikolau, K., Bosmuller, H., Horger, M., Thaiss, W.M. (2017) Multiparametric imaging for detection and characterization of hepatocellular carcinoma using gadodetix acid-enhanced MRI and perfusion-CT: which parameters work best? Cancer Imaging [online] 17 pp. 1-8 [Accessed 12 November 2017].

National Institute for Health and Care Excellence (2017) Liver disease quality standard [QS152]. Available at: https://www.nice.org.uk/guidance/qs152/chapter/Quality-statement-4-Surveillance-for-hepatocellular-carcinoma [Accessed 12 November 2017].

Public Health England (2011) Ionising radiation: dose comparisons. Available at: https://www.gov.uk/government/publications/ionising-radiation-dose-comparisons/ionising-radiation-dose-comparisons [Accessed 12 November 2017].

 

 

Imaging of conditions related to sickle cell disease (SCD)

This week’s blog will focus on exploring imaging methods used to identify conditions resulting from sickle cell disease (SCD).

According to National Institute for Health and Care Excellence (NICE, 2016) sickle cell disease is a mutation in the haemoglobin chain. This changes the shape of the red blood cell. These cells can then form clusters and block blood vessels. The shape of the red blood cells is designed to navigate blood vessels with efficiency and this mutation interferes with this process.

It is a genetic disease, which develops as a result of inheriting an abnormal haemoglobin variant from one parent and sickle haemoglobin from another. A person can also be a carrier of sickle cell trait by inheriting the sickle cell haemoglobin from one parent and a normal haemoglobin gene from the other. The highest prevalence is amongst people of Black African and Caribbean descent (NICE, 2016).

Sickle cell disease is diagnosed through tests such a full blood count, reticulocyte count, and blood film (NICE, 2016). This condition also causes a person to be susceptible to further health complications. These include dactylis, stress fracture and vertebral collapse among others (NICE, 2016; Almeida and Roberts, 2005).

The consideration for diagnostic imaging comes when looking at the effect of SCD on other organ systems. According to Almeida and Roberts (2005) bone involvement is one of the common presentations of SCD with conditions such as osteomyelitis. They also mention that diagnosing osteomyelitis with plain film x-rays is not useful as findings are non-specific. Imaging methods such as MRI are more useful especially with the use of contrast agent such as gadolinium. However, they assert that clinical observations and bone biopsy is relied on more than any single imaging method.

According to Bires et al. (2015), the imaging method deemed superior is radionuclide imaging (RNI). Although it is an American publication and guidelines may differ from those in the UK, it is helpful to mention the different methods used in other countries. It is specifically a three-phase bone scan with a sensitivity of over 90 percent. This is very good rate considering it identifies the condition within two days from the early onset of symptoms.

The use of RNI is corroborated by Dinh et al. (2008) and Almeida and Roberts (2005). The study by Dinh et al. (2008) discusses diagnosis of osteomyelitis underlying diabetic foot ulcers. They recognise the challenge of diagnosis with this condition. According to Almeida and Roberts (2005) MRI is more sensitive with patients where it is not suspected. With cases where it is clinically suspected, PET is only slightly less sensitive but is has a higher specificity of 93 percent compared to 81 percent with MRI.

Magnetic resonance imaging (MRI) is mentioned as a good alternative for RNI by both Dinh et al. (2008) and Bires et al. (2015) to eliminate the risk of radiation to paediatric patients. However, MRI takes time and the patient needs to be co-operative, which may not be possible with children. Additional aspect to consider is the study by Dinh et al. (2008), only included four trials using MRI which does not necessarily mean it is a reliable method.

The challenge seems to be identifying osteomyelitis with the presence of other conditions. This is the reason why clinical findings coupled with blood tests and biopsy is the gold standard for diagnosis (Almeida and Roberts, 2005). Due to the complications resulting from SCD, research is essential in improving the specificity and sensitivity of these imaging methods.

 

 

Reference List

Almeida, A., Roberts, I. (2005) Bone involvement in sickle cell disease. British Journal of Haematology [online] 129 (4) pp. 482-490 [Accessed 04 November 2017].

Bires, A.M., Kerr, B., George, L. (2015) Osteomyelitis: An Overview of Imaging Modalities. Critical Care Nursing Quarterly [online] 38 (2) pp. 154-164 [Accessed 04 November 2017].

Dinh, M.T., Abad, C.L., Safdar, N. (2008) Diagnostic Accuracy of the Physical Examination and Imaging Tests for Osteomyelitis Underlying Diabetic Foot Ulcers: Meta-Analysis. Clinical Infectious Diseases [online] 47 (4) pp. 519-527 [Accessed 04 November 2017].

National Institute for Health and Care Excellence (2016) Sickle cell disease: Summary. Available from: https://cks.nice.org.uk/sickle-cell-disease#!backgroundsub [Accessed 04 November 2017].