Obtaining a tissue sample to diagnose parenchymal lung lesions (PPL) suspected of cancerous origin is of utmost importance. Due to it's markedly favourable safety profile, a bronchoscopic biopsy method called Radial EBUS is becoming increasingly popular. However, a meta-analysis reports the success rate of Radial EBUS in diagnosis is 73%, which in comparison to CT guided biopsy which is the gold standard in diagnosing PPL (90% success rate), is sub-optimal.

There are 2 types of USS probes used in the R-EBUS procedure. Whilst the thicker USS probe (1.7mm) is capable of accommodating larger biopsy instruments, the thinner USS probe could be advanced more peripherally to obtain a biopsy.

Therefore identifying what type of USS probe is better for a given PPL will aid in improving the diagnostic yield.

In this study, investigators compare these two types of probes in the ability to diagnose a PPL.

The biopsy instruments used for both arms are forceps and cytology brush. For the thick USS arm, in addition, an aspiration needle will also be used. (The thin USS guide sheath is too small to accommodate an aspiration needle)

Inclusion Criteria:

• Patient referred for R-EBUS as per routine management.
• Patient judged to be medically stable to give consent for this study.

Exclusion Criteria:-Unsuitable for flexible bronchoscopy and biopsy

• INR>1.5
• Platelets<150.
• Hb> 80g/l
• Liver function tests (AST/ALT) <2 times upper limit of normal
• Neutrophil count >1.0
• EGFR >30ml/kg/min
• On anticoagulation, that cannot be withheld for the procedure, due to medical reasons (e.g. On-clopidogrel with recent drug-eluting stent placement.)